COMPARATIVE PHYSIOLOGICAL STUDIES OF 
 STRAINS OF CORN RESISTANT AND 
 SUSCEPTIBLE TO DISEASE 
 
 BY 
 
 FREDERICK FRANCIS WEINARD 
 
 B.S. University of Nebraska, 1916 
 M.A. University of Nebraska, 1917 
 
 THESIS 
 
 SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS 
 FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN BOTANY 
 IN THE GRADUATE SCHOOL OF THE UNIVERSITY 
 OF ILLINOIS, 1922 
 
 URBANA, ILLINOIS 
 
Digitized by the Internet Archive 
 in 2016 
 
 https://archive.org/details/comparativephysiOOwein 
 


 
 
 
Table of Contents 
 
 Page 
 
 I. Introduction 1 
 
 II. Materials and methods 2 
 
 III. Experimental work 3 
 
 Absorption of water at different 
 
 temperatures 3 
 
 The effect of temperature on 
 
 germination and growth 17 
 
 Vitality as influenced by soaking 
 
 in water 22 
 
 Vitality as influenced by growth 
 
 of fungi 29 
 
 IV. Discussion 32 
 
 V. Conclusions 34 
 
 VI. Acknowledgment 35 
 
 VII. Literature cited 36 
 
 VIII. Plates 38 
 
 IX. Vita 51 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
-1 
 
 Comparative Physiological Studies of Strains of Corn 
 Resistant and Susceptible to Disease 
 
 I. Introduction 
 
 Since the work of Burrill and Barrett (5,6), corn 
 root and stalk rots have come to be generally recognized as 
 factors limiting the crop. In recent years especially, demon- 
 stration of the widespread occurrence of these diseases through- 
 out corn growing regions has served to augment their importance 
 and to turn the light of many investigations upon them. 
 
 Reduction in yield in the field has been repeatedly 
 correlated with the presence of fungi, commonly species of 
 Fusarium or of Diplodia, in the seed. As a result, germinator 
 tests designed to eliminate such infested seed have been widely 
 and more or less successfully used. 
 
 It has been observed by Holbert (9), that corn with 
 a good record on the germinator will not always show the same 
 comparative performance in the field. Marked differences may 
 be obtained in the yields of apparently disease-free ears when 
 planted in infested soil. There are apparently, resistant and 
 susceptible strains within the variety. 
 
 A physiological comparison of three such strains, one 
 

 
 
 
 
 
 
 
 
 
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 . 
 
 . 
 
 . 
 
 
 
 
 
 
 
 ' 
 
 I Jtw C* I-.' t r tu ; I ’ • "| C 6i' t tr 1 
 
 
 
 
 . 
 
 ♦ 
 
 
 
- 2 - 
 
 resistant, and two of different degrees of susceptibility, has 
 been undertaken in the present investigation. The work was 
 done in the Plant Physiology Laboratories of the University of 
 Illinois. 
 
 II. Materials and Methods 
 
 Reid’s Yellow Dent corn, supplied by Mr. J. R. 
 Holbert, Bloomington, Illinois, was used in the tests. About 
 50 ears each of "Peoria Co. Good" (PCG), "Peoria Co. Bad"(PCB), 
 and "Fox" (Fox) were available from which to obtain representa- 
 tive samples. Typical ears of each kind are illustrated in 
 Plates 1 to 4. Data on the viability, amount of fungous in- 
 festation, physical composition, and kernel indentation in the 
 three types are given in Tables 1 to 3 (unpublished notes - 
 J. R. Holbert). 
 
 Table 1. Viability and per cent of infestation. 
 Vitality Fusarium Diplodia 
 
 (PCG) 
 
 99.40 
 
 .90 
 
 0 
 
 (PCB) 
 
 99.48 
 
 3.45 
 
 0 
 
 (Fox) 
 
 96.50 
 
 13.70 
 
 1.5 
 
 Table 3. 
 
 Physical 
 
 Horny 
 
 composition. 
 
 Medium Starchy 
 
 (PCG) 
 
 70.4 
 
 28.4 
 
 1.3 
 
 (PCB) 
 
 15.5 
 
 59.3 
 
 25.3 
 
 (Fox) 
 
 7.3 
 
 79.4 
 
 13.4 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
-3- 
 
 Table 3. Indentation of kernels. 
 
 Smooth Medium Rough 
 
 pea) 
 
 PCB) 
 
 Fox) 
 
 63.5 36.4 1.1 
 
 14.3 33.6 53.1 
 
 3.1 34.7 73.3 
 
 In general, the kernels of (PCG), the "resistant” 
 
 strain, are characteristically plump, hard, smoothly dented, 
 rich orange in color, and with a bright lustre. The kernels 
 of (PCB), and of (Fox) corn, respectively "susceptible" and 
 "very susceptible", are often somewhat shriveled, starchy, 
 usually roughened at the crown, pale in color, lacking in lustre* 
 As the methods used in this investigation varied 
 with each phase of the problem, they will be referred to in 
 the order of experiment. 
 
 Absorption of water at different temperatures. 
 
 Water absorption, one of the earliest and most im- 
 portant processes in the germinating seed, offers the first 
 logical point of comparison. 50 kernels, 5 from each of ten 
 typical ears, were used in each experiment. Effort was made 
 to select only kernels with coats intact. 
 
 The kernels were placed in perforated aluminum con- 
 
 III. Experimental Work 
 

 
 
 
 
 
 
 
 ■ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 . 
 
 
 
 
 . 
 
 - 
 
 . 
 
 
 . 
 
 
 
 - 
 
 
 
 
 
 
-4- 
 
 tainers and immersed in jars containing 600 cc. of distilled 
 water at t emperat ures of 10 w C. , 15° C. , 20° C., and 35° C. , 
 respectively. These temperatures were maintained by means of 
 the large constant temperature cases in the Plant Physiology 
 Laboratories. At half hour intervals, the seeds were removed, 
 superficially dried, and weighed on a balance in closed glass 
 dishes. Data for the first 9 hours were obtained from one 
 set of kernels, and for a second 9 hours before weighing 
 commenced. The comparative rates of absorption at the differ- 
 ent temperatures are shown in Figures 1 to 8. 
 
 The velocities of absorption at points of equal in- 
 take are shown in Tables 4 to 7. The velocity at any given 
 point is represented approximately by the tangent of the angle 
 formed by the straight line between two points determined ex- 
 perimentally, with the time axis. This straight line is a 
 chord parallel to the tangent at some intermediate point on a 
 smooth curve joining the two known points. Brown and Worley 
 (4) measured the tangents by means of string and protractor. 
 Their "ideal curves” were constructed from relatively few 
 known points. Shull (16) calculated the tangents from alge- 
 braic formulae of the curves. In view of the comparatively 
 large number of known points, it is thought that fair accuracy 
 is attainable by the method employed in the present work. 
 
. 
 
 . 
 
 * ’l 
 
 
 ■ 
 
 
 
 
 . 
 
 
 
 
 
 
 
 . 
 
 
 
 
 
 
 
 
 
 ' ' 
 
 
 
 
 
 
 . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 4. Water absorption at 15 
 deg. C. 
 
(PCS) 
 


 vjn 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 o 
 
 ro 
 
 
 M 
 
 
 
 
 oi _2 
 
 .1- 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ro 
 
 o 
 
 t 
 
 ro 
 
 nji 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 V>J 
 
 O 
 
 
 VM 
 
 VJ1 
 
 ON 
 
 H* 
 
 09 
 
 Oft 
 
 <o 
 
 o 
 
 Q 
 
-13- 
 
 Table 4. 
 
 Comparati 
 
 vs velocities at 10 
 
 Per cent 
 intake 
 
 (PCG) 
 
 (PCB) 
 
 (Fox) 
 
 3.5 
 
 2.05030 
 
 2.60510 
 
 3.29980 
 
 5.0 
 
 3.05030 
 
 3. 60510 
 
 2. 29980 
 
 7.5 
 
 . 34433 
 
 .93352 
 
 .46631 
 
 10.0 
 
 .38386 
 
 .46631 
 
 .50953 
 
 13.5 
 
 .44523 
 
 .54396 
 
 .38386 
 
 15.0 
 
 . 34433 
 
 . 39391 
 
 .28675 
 
 17.5 
 
 .40403 
 
 .40403 
 
 . 36795 
 
 20.0 
 
 .36795 
 
 .15838 
 
 . 33087 
 
 Mean 
 
 . 78629 
 
 1.01354 
 
 .84311 
 
 Ratios 
 
 1.00 : 
 
 1.39 : 
 
 1.-07 
 
 Table 5. 
 
 Comparative 
 
 velocities at 15 
 
 Per cent 
 intake 
 
 (PCG) 
 
 (PCB) 
 
 (Fox) 
 
 2.5 
 
 2.34600 
 
 2.90430 
 
 2.24600 
 
 5.0 
 
 2.24600 
 
 2.90430 
 
 3.24600 
 
 7.5 
 
 .61280 
 
 .83910 
 
 .75355 
 
 10.0 
 
 .49858 
 
 .66139 
 
 . 50953 
 
 12.5 
 
 .31530 
 
 .57735 
 
 .42447 
 
 15.0 
 
 . 36397 
 
 .44523 
 
 .48773 
 
 17.5 
 
 . 61280 
 
 .53171 
 
 .48773 
 
 20.0 
 
 . 31530 
 
 .41421 
 
 .39631 
 
 Mean 
 
 .90134 
 
 1.15974 
 
 .93140 
 
 Hatios 
 
 1.00 : 
 
 1.29 : 
 
 1.03 
 
 Table 6. 
 
 Comparative 
 
 s velocities at 30 
 
 Per cent 
 intake 
 
 (PCG) 
 
 (PCB) 
 
 (Fox) 
 
 3.5 
 
 2.47510 
 
 3.07770 
 
 2.67460 
 
 5.0 
 
 2.47510 
 
 3.07770 
 
 2.67460 
 
 7.5 
 
 .83910 
 
 3.07770 
 
 .80978 
 
 10.0 
 
 .78129 
 
 1.00000 
 
 .63487 
 
 12.5 
 
 .39391 
 
 .62487 
 
 .46631 
 
 15.0 
 
 .61280 
 
 .61280 
 
 .55431 
 
 17.5 
 
 . 31356 
 
 . 67451 
 
 .53171 
 
 20.0 
 
 .30573 
 
 . 36397 
 
 . 70031 
 
 Mean 
 
 1.01195 
 
 1.56366 
 
 1.12955 
 
 Ratios 
 
 1.00 
 
 1.54 
 
 1.12 
 

 
 
 
 
 
-14- 
 
 Table 7. 
 
 Comparative velocities at 35° C. 
 
 Per cent 
 intake 
 
 (PCG) 
 
 (PCB) 
 
 (Fox) 
 
 3.5 
 
 3.07770 
 
 3.86670 
 
 3. 73310 
 
 5.0 
 
 3.07770 
 
 3.86670 
 
 3.73310 
 
 7.5 
 
 3.07770 
 
 3.86670 
 
 3.73310 
 
 10.0 
 
 1. 51080 
 
 1.80400 
 
 1.33490 
 
 13.5 
 
 .98370 
 
 1 . 80400 
 
 1.33490 
 
 15.0 
 
 1.05380 
 
 1.00000 
 
 1.33490 
 
 17. 5 
 
 1.03550 
 
 1.00000 
 
 1.19180 
 
 30.0 
 
 .78139 
 
 . 83434 
 
 . 86939 
 
 Mean 
 
 1.83465 
 
 3.35405 
 
 3.13036 
 
 Ratios 
 
 1.00 : 
 
 1.34 
 
 : 1.16 
 
 For comparison, the 
 
 relative 
 
 rates of absorption at 
 
 kernels 
 
 with coats 
 
 broken, is 
 
 shown in Figure 7 
 
 (upper curves). The corresponding velocities at points of 
 equal intake are given in Table 8. 
 
 Table 8. Comparative velocities at 35° C. (coats 
 broken) . 
 
 Per cent 
 intake 
 
 (PCG) 
 
 (PCB) 
 
 (Fox) 
 
 3.5 
 
 3.7331 
 
 4.3315 
 
 3.8667 
 
 5.0 
 
 3.7331 
 
 4.3315 
 
 3.3667 
 
 7. 5 
 
 3.7331 
 
 4. 3315 
 
 3.8667 
 
 10.0 
 
 3.7331 
 
 4.3315 
 
 3.8667 
 
 13. 5 
 
 1.3799 
 
 1.7331 
 
 1.4550 
 
 15.0 
 
 1.3764 
 
 1.7331 
 
 1.7675 
 
 17.5 
 
 1 . 0734 
 
 1.5108 
 
 1.7675 
 
 30.0 
 
 1.0734 
 
 1.5108 
 
 1.7675 
 
 Mean 
 
 3.4663 
 
 3.9765 
 
 3.6738 
 
 Ratios 
 
 1.00 : 
 
 1.31 : 
 
 1.08 
 
-15- 
 
 (PCB) and (Fox) corn show a constant higher rate 
 of water absorption than Peoria Co. Good. If the rate in 
 the latter case be taken as 1.00, then the others stand to 
 it in the mean ratios of 1.31 and 1.09 respectively. There 
 is but little variation from these ratios as the temperature 
 changes. 
 
 Kernels with broken coats exhibit, as might be ex- 
 pected, a uniformily higher rate of absorption than kernels 
 with coats intact. But the relative rates for the three 
 samples of corn remain essentially the same, regardless of 
 whether the absorption is by kernels with coats intact or 
 kernels with broken coats (Fig. 7, Tables 7 & 8). Hence the 
 differences observed between the three types of kernels may 
 not be ascribed to modifications in the coats but rather to 
 differences in the nature of the stored materials in the ker- 
 nels. The marked correlation between the percentages of soft 
 starchy kernels and absorption rates would tend to establish 
 the latter hypothesis. 
 
 In order to determine the specific effect of temperat- 
 ure on the rate of absorption in corn, the temperature coeffi- 
 cient, Q , was commuted from the data in Tables 4 to 7. The 
 10 
 
 value of Q has been calculated for different combinations of 
 
 10 
 
 temperature?, using the formula of Kanitz (11). The results 
 
 are given in Table 9. 
 

-16- 
 
 Table 9. Q 1q for different comb inati one of 
 
 temperatures . 
 
 Temperatures 
 
 (PCG) 
 
 (PCB) 
 
 (Fox) 
 
 10° C. -1 5° C. 
 
 1.31 
 
 1. 31 
 
 1.28 
 
 10° C . -20° C. 
 
 1.29 
 
 1. 54 
 
 1.34 
 
 10° C. -35° C. 
 
 1.40 
 
 1.38 
 
 1.45 
 
 15° C . -20° C. 
 
 1.26 
 
 1.82 
 
 1.47 
 
 15° C . -35° C. 
 
 1.42 
 
 1. 30 
 
 1.51 
 
 20° C . -35° C. 
 
 1.48 
 
 1.27 
 
 1.29 
 
 Mean 
 
 1.36 
 
 1.44 
 
 1.38 
 
 The mean value of the temperature coefficient of 
 water absorption is approximately 1.4 in all three types of 
 corn. Variations in the value obtained may occur according 
 to the temperatures selected. This has been previously pointed 
 out by Denny (7). Shull (15), working with corn, has reported 
 data indicating that the temperature coefficient is about 1.5. 
 Shull (16) obtained in previous experiments with Xanthium seeds 
 values of 1.55 and 1.83, and with split peas, 1.6. Brown and 
 Worley (4), working with barley seeds, obtained the relatively 
 high values of 1.8 and 2.02, which approximate the value of 
 the coefficient of chemical change. The results of the present 
 work agree with those of Shull (15,16), showing that the coeffi- 
 cient of water absorption by seeds of corn is considerably less 
 
 than 2. 
 

 
 
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 . 
 
 . 
 
 . 
 
 
 
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 ’ 
 
 
 
 
 
 
 
 
 
 
 
-17- 
 
 The effect of temperature 
 on germination and growth 
 
 The rate of germination of the three lots of corn 
 was tested at temperatures of 10° C. , 15° C. , 20° C. , 25° C. , 
 and 30° C. 5 seeds of each kind were planted in Mason jars 
 at a uniform depth of 3/4 inch in 2i inches of clean flint 
 sand, with moisture contents of 20%, 40%, and 60% of saturation, 
 respectively. Repetition yielding essentially similar results, 
 the mean figures are given in Tables 10 to 14. The time from 
 planting to appearance of the shoot at the surface of the sand, 
 and per cent of germination are shown in each case. 
 
 Table 10. Rate and per cent of germination at 30° C. 
 
 
 
 
 Soil 
 
 moisture 
 
 
 20% 
 
 
 40% 
 
 
 6 °$ 
 
 
 Days 
 
 1° 
 
 Days 
 
 1° 
 
 Days % 
 
 (PCGr) 
 
 2.6 
 
 100 
 
 2.4 
 
 100 
 
 2.0 100 
 
 (PCB) 
 
 2.7 
 
 100 
 
 2.6 
 
 100 
 
 2.4 100 
 
 (Fox) 
 
 2.8 
 
 80 
 
 2.5 
 
 100 
 
 2.4 100 
 
 Table : 
 
 LI. Rate and 
 
 per 
 
 cent of germination at 25° C. 
 
 
 
 
 Soil 
 
 moisture 
 
 
 20% 
 
 
 40% 
 
 
 eo $ _ 
 
 
 Days 
 
 t 
 
 Days 
 
 % 
 
 Days % 
 
 (*CG) 
 
 3.20 
 
 100 
 
 3.0 
 
 100 
 
 3.0 100 
 
 (PCB) 
 
 3.4 
 
 90 
 
 3.1 
 
 100 
 
 3.3 100 
 
 (Fox) 
 
 3.7 
 
 100 
 
 3.2 
 
 100 
 
 3.2 90 
 
-18- 
 
 Table 
 
 (POO) 
 
 (pcb) 
 
 (Fox) 
 
 Table 
 
 (PCG) 
 
 (PCB) 
 
 (Pox) 
 
 13. Rate and per cent of germination at 20° C. 
 
 . Soil moisture 
 30 $ 40 $ 60$ 
 
 Days 
 
 $ 
 
 / 
 
 Days 
 
 $ 
 
 Days 
 
 $ 
 
 7.4 
 
 100 
 
 7.3 
 
 100 
 
 7.3 
 
 100 
 
 7.6 
 
 100 
 
 7.4 
 
 100 
 
 8.4 
 
 90 
 
 7.7 
 
 90 
 
 7.6 
 
 90 
 
 8.5 
 
 80 
 
 13. 
 
 Rate 
 
 and per 
 
 cent 
 
 of germination at 15° C. 
 
 Soil moisture 
 
 30$ 
 
 Days 
 
 $ 
 
 40$ 
 
 Days 
 
 $ 
 
 60$ 
 
 Days 
 
 1o 
 
 8.0 
 
 100 
 
 7.7 
 
 100 
 
 7.4 
 
 100 
 
 8.6 
 
 100 
 
 8. 7 
 
 80 
 
 8. 3 
 
 100 
 
 9.5 
 
 100 
 
 9.6 
 
 100 
 
 8.3 
 
 70 
 
 Table 14. 
 
 Rate and per cent of germination at 10° C. 
 
 (PCG) 
 
 m 
 
 Soil moisture 
 30$ 40$ 60$ 
 
 Days $ Days $ Days $ 
 
 38.3 
 
 70 
 
 28.0 
 
 30 
 
 35.5 
 
 20 
 
 30.4 
 
 50 
 
 32.7 
 
 40 
 
 33.0 
 
 10 
 
 0 
 
 0 
 
 34.0 
 
 20 
 
 37. 5 
 
 20 
 
 It will be observed that the differences attributable 
 to soil moisture are not great. Disregarding this factor, the 
 average number of days required for germination at each temper- 
 ature, and the ratios representing the relative performance of 
 each lot of corn, are given in Table 15. 
 
-19- 
 
 Table 15 
 
 . Average periods 
 
 for germinati 
 
 
 at the 
 
 different temperatures 
 
 Temper- 
 
 ature 
 
 
 (PCG) 
 
 
 (PCB) 
 
 (Fox) 
 
 30° C. 
 
 Days 
 
 2.3 
 
 
 2.5 
 
 2.5 
 
 
 Ratios 
 
 1.00 
 
 
 1.00^ 
 
 : 1.09 
 
 25° C. 
 
 Days 
 
 3.1 
 
 
 3. 3 
 
 3.4 
 
 
 Ratios 
 
 1.00 
 
 
 1.06 
 
 : 1.10 
 
 20° C. 
 
 Day 8 
 
 7.3 
 
 
 7.8 
 
 7.9 
 
 
 Ratios 
 
 1.00 
 
 
 1.07 
 
 : 1.08 
 
 15° C. 
 
 Days 
 
 7.7 
 
 
 8.5 
 
 9.1 
 
 
 Ratios 
 
 1.00 
 
 
 1.10 
 
 : 1.18 
 
 10° C. 
 
 Days 
 
 30.5 
 
 
 32.0 
 
 35. 7 
 
 
 Ratios 
 
 1.00 
 
 
 1.05 
 
 : 1.17 
 
 Mean ratios 
 
 1.00 
 
 
 1.07 
 
 : 1.12 
 
 When the seedlings at the different temperatures had 
 grown to approximately the height of the jars, the latter were 
 opened and the roots and shoots measured with a centimeter rule 
 Since duplicate experiments gave similar results, the averages 
 are given in Tables 16 to 20. 
 
 Table 16. Comparative growth at 30° C. 
 
 Roots 
 
 Shoots 
 
 
 20 % 
 
 40% 
 
 60% 
 
 Av. 
 
 20% 
 
 40% 
 
 60% 
 
 Av. 
 
 (PCG) 
 
 12.5 
 
 15.4 
 
 10.6 
 
 12.8 
 
 9.8 
 
 14.6 
 
 14.4 
 
 12.9 
 
 (PCB) 
 
 13.3 
 
 11.7 
 
 13.5 
 
 12,8 
 
 9.9 
 
 9.9 
 
 14.9 
 
 11.6 
 
 (Fox) 
 
 15.1 
 
 10.3 
 
 11.9 
 
 12.4 
 
 10.5 
 
 9.8 
 
 14.3 
 
 11.7 
 
 
 Table 17 
 
 . Comparative growth at 25 w 
 
 C. 
 
 
 
 Roots 
 
 
 
 Shoots 
 
 
 
 30% 
 
 40% 
 
 60% 
 
 Av. 
 
 20% 
 
 40% 
 
 60% 
 
 Av. 
 
 (PCG) 
 
 14.9 
 
 14.4 
 
 14.9 
 
 14.7 
 
 12.1 
 
 15. 
 
 3 12. 
 
 0 12.1 
 
 (PCB) 
 
 12.3 
 
 16.4 
 
 11. 7 
 
 13.5 
 
 10.3 
 
 14. 
 
 0 12. 
 
 4 10.1 
 
 (Fox) 
 
 9.4 
 
 12. 7 
 
 11.4 
 
 11.5 
 
 7.6 
 
 10. 
 
 3 10. 
 
 7 10.0 
 

- 20 - 
 
 Table 18. Comparative growth at 20° C. 
 
 Roots Shoots 
 
 
 20% 
 
 40% 
 
 60% 
 
 Av. 
 
 20% 
 
 40% 
 
 60% 
 
 Av. 
 
 (PCG) 
 
 12.5 
 
 10. 3 
 
 8.5 
 
 10.4 
 
 9.0 
 
 10. 3 
 
 10.7 
 
 10.0 
 
 (PCB) 
 
 11.9 
 
 13. 7 
 
 9.7 
 
 11.8 
 
 9.5 
 
 11.6 
 
 8.9 
 
 10.0 
 
 (Fox) 
 
 11.9 
 
 10.7 
 
 8.5 
 
 10.4 
 
 9.3 
 
 9.5 
 
 9.0 
 
 9.2 
 
 
 Table 19. 
 
 Comparative 
 
 growth at 
 
 15° C. 
 
 
 
 
 Roots 
 
 
 30% 
 
 Shoots 
 
 
 
 20% 
 
 40% 
 
 60% 
 
 Av. 
 
 40% 
 
 60% 
 
 Av. 
 
 (PCG) 
 
 10.4 
 
 15.0 
 
 12.0 
 
 12.5 
 
 9.9 
 
 12.3 
 
 14. 3 
 
 12.2 
 
 (PCB) 
 
 12.1 
 
 11.3 
 
 12.3 
 
 11.9 
 
 10. 3 
 
 10. 3 
 
 10.3 
 
 10. 3 
 
 (Fox) 
 
 10.6 
 
 10.7 
 
 10.5 
 
 10.6 
 
 8.4 
 
 8.0 
 
 8.6 
 
 8.4 
 
 
 Table 30. 
 
 Comparative 
 
 growth at 10° C. 
 
 
 
 
 Roots 
 
 
 20% 
 
 Shoots 
 
 60% 
 
 
 
 20% 
 
 40% 
 
 60% 
 
 Av. 
 
 40% 
 
 Av. 
 
 (PCG) 
 
 4.6 
 
 3.0 
 
 2.8 
 
 3.5 
 
 3.6 
 
 1.8 
 
 2.3 
 
 2.2 
 
 (PCB) 
 
 2. 7 
 
 2.2 
 
 3.6 
 
 3.6 
 
 1.9 
 
 1.9 
 
 1.3 
 
 1.7 
 
 (Fox) 
 
 1.2 
 
 2.5 
 
 1.7 
 
 1.8 
 
 1.0 
 
 1.3 
 
 2.0 
 
 1.4 
 
 For ready comparison, ratios derived from the above 
 data are shown in Table 21. 
 
 Table 21. Ratios for roots and shoots at different 
 temperatures. 
 
 Temperature 
 
 
 (PCG) 
 
 (PCB) 
 
 (Fox) 
 
 # 
 
 o 
 
 o 
 
 o 
 
 to 
 
 Roots 
 
 1.00 
 
 1.00 : 
 
 .97 
 
 
 Shoots 
 
 1.00 
 
 .90 : 
 
 .91 
 
 25° C. 
 
 Roots 
 
 1.00 
 
 .92 : 
 
 .78 
 
 
 Shoots 
 
 1.00 
 
 .85 : 
 
 .71 
 
-31- 
 
 Table 31 (cont.). 
 
 Temperature 
 
 
 (PCG) 
 
 (PCB) 
 
 (Fox) 
 
 30° C. 
 
 Roots 
 
 1.00 
 
 1.13 
 
 1.00 
 
 
 Shoots 
 
 1.00 
 
 1.00 
 
 .93 
 
 15° C. 
 
 Roots 
 
 1.00 
 
 .95 
 
 .85 
 
 
 Shoots 
 
 1.00 
 
 .84 
 
 .69 
 
 10° C. 
 
 Roots 
 
 1.00 
 
 .74 
 
 .51 
 
 
 Shoots 
 
 1.00 
 
 .77 
 
 .64 
 
 Mean ratios 
 
 - Roots 
 
 1.00 
 
 .95 
 
 .83 
 
 
 Shoots 
 
 1.00 
 
 .87 
 
 .77 
 
 (PCG ) germinated more rapidly than the other two 
 types, at all temperatures used. The minimum time required 
 was 3.3 days for (PCG) at 30° C. , and the maximum was 35.7 days 
 for (Fox) at 10° C. The mean ratios, based on the performance 
 of (PCG), are 1.00: 1.07 : 1.12. A slight increase in the 
 rapidity of germination in each case may be noted as the soil 
 moisture is increased from 30$ to 60$ of saturation. 
 
 The discrepancies in rates of germination are reflected 
 in the results of the measurements of seedling growth. (PCG) 
 made quite consistently a greater growth of both roots and 
 shoots in a given period of time than the other two strains of 
 corn. Considering both root and shoot growth, the mean ratios 
 for the three strains of corn were 1.00 : .91 : .79. Of the 
 temperatures used, 30° gave the most rapid germination, while 
 35° C. seemed somewhat more favorable for subsequent growth. 
 
 These general results are corroborated by the exact studies of 
 Lehenbauer (14). The latter found that for periods longer than 
 three hours, the optimum temperature for growth of com is 
 

 
-23- 
 
 between 29° C. and 32° C. 
 
 Vitality as influenced by soaking in water. 
 
 The relative percentages of germination of seeds 
 not soaked, and of seeds soaked in water at several temperatures 
 for different periods of time, were determined. Some of the 
 teste were made on the rag doll germinator, and others in soil 
 cn the greenhouse bench. 
 
 25 seeds of each strain of corn were soaked in water 
 at 65° C. for 10, 20, and 30 minutes respectively. 75 seeds of 
 each kind were used as unsoaked checks. Germinations were made 
 at 30° C. on the modified rag doll (8). As used in this labor- 
 atory a wire core insures quite uniform aeration in all parts 
 of the doll. The results are shown in Table 22. 
 
 Table 22. Relative vitality after soaking in 
 
 water at 65° C. Ger^i^ated ai 3o°C-. 
 
 Time Per cent germination 
 
 
 
 
 Strong 
 
 Weak 
 
 Total 
 
 (PCG) 
 
 Not soaked 
 
 78 
 
 22 
 
 100 
 
 (PCB) 
 
 w 
 
 n 
 
 55 
 
 45 
 
 100 
 
 (Pox ) 
 
 11 
 
 n 
 
 34 
 
 62 
 
 96 
 
 (PCG) 
 
 10 
 
 min. 
 
 76 
 
 16 
 
 92 
 
 (PCB) 
 
 10 
 
 min. 
 
 64 
 
 36 
 
 100 
 
 (Fox) 
 
 10 
 
 min. 
 
 52 
 
 36 
 
 88 
 
 (PCG) 
 
 20 
 
 min. 
 
 8 
 
 52 
 
 60 
 
 (PCB) 
 
 20 
 
 min. 
 
 0 
 
 68 
 
 68 
 
 (Fox) 
 
 20 
 
 min. 
 
 0 
 
 32 
 
 32 
 
 (PCG) 
 
 (PCB) 
 
 30 
 
 30 
 
 min. 
 
 min. 
 
 0 
 
 0 
 
 12 
 
 8 
 
 12 
 
 8 
 
 (Fox) 
 
 30 
 
 min. 
 
 0 
 
 4 
 
 4 
 

 
 
 
 
 
 . 
 
 
 
 
 
 
 
 
 
-23- 
 
 The unsoaked corn gave total germination ratios of 
 1.00 : 1.00 : .96, for (PCG), (PCB) and (Fox) respectively. 
 
 The percentages themselves coincide with the data furnished by 
 Mr. Holbert (Table l). After this severe treatment, the total 
 percentages of germination were reduced 46$, 45$, and 59$ 
 respectively, the ratios remaining 1.00 : 1.01 : .76. Consider- 
 ing the quality of the seedlings, (PCG) made a somewhat better 
 showing than (PCB). The inferiority of (Fox) becomes more 
 marked as the conditions affecting growth become more severe. 
 
 In a second experiment, seeds of each strain of corn 
 were selected, (a) with coats intact, (b) with coats broken. 
 
 10 kernels of each were soaked in water at 60° C. for 10, 20, 
 and 30 minutes, and at 65° C. for 5 and 10 minutes. They were 
 then planted in soil at 1 inch intervals, on the greenhouse 
 bench. The resulting plants are shown in the plat at the right 
 of the bench (Plate 5). The average results of the treatment 
 are given in Table 23. 
 
 Table 23. 
 
 Results 
 
 of 
 
 soaking 
 
 corn 
 
 at 60° 
 
 C. and 
 
 
 (PCG) 
 
 (PCB) 
 
 (Fox) 
 
 
 (a) 
 
 (b) 
 
 (a) 
 
 (b) 
 
 (a) 
 
 (b) 
 
 Germination 
 
 
 
 
 
 
 
 Checks 
 
 100 
 
 89 
 
 100 
 
 76 
 
 100 
 
 100 
 
 Soaked 
 
 64 
 
 48 
 
 68 
 
 40 
 
 76 
 
 56 
 
 Av. heights 
 
 (in. ) 
 
 
 
 
 
 
 Checks 
 
 16.2 
 
 9.1 
 
 15.4 
 
 2.7 
 
 14.7 
 
 6.7 
 
 Soaked 
 
 14.9 
 
 6. 3 
 
 12.4 
 
 4.4 
 
 13.2 
 
 5. 7 
 

 
 . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ■ ) 
 
 
 
 
 
-24- 
 
 Table 23 (cent.). 
 
 (PCG) (PCB) (Fox) 
 
 Av. green 
 
 (a) 
 
 (b) 
 
 (a) 
 
 (b) 
 
 (a) 
 
 (b) 
 
 weights (gms. 
 Checks 
 
 ) 
 
 2.59 
 
 1.01 
 
 2.13 
 
 .28 
 
 2.08 
 
 1.02 
 
 Soaked 
 
 2.24 
 
 .58 
 
 1.69 
 
 .32 
 
 1.77 
 
 .52 
 
 Av. dry 
 weights (gms. 
 Checks 
 
 ) 
 
 .23 
 
 .09 
 
 .19 
 
 .03 
 
 .18 
 
 .10 
 
 Soaked 
 
 .17 
 
 .05 
 
 .14 
 
 .02 
 
 .14 
 
 .04 
 
 Total yields (gms.) 
 Checks 2. 30 
 
 .80 
 
 1.90 
 
 .23 
 
 1.80 
 
 1.00 
 
 Soaked 
 
 1.08 
 
 .25 
 
 1.02 
 
 .19 
 
 .95 
 
 .23 
 
 By an inspection of 
 
 Table 
 
 23 it 
 
 may 
 
 be seen 
 
 that 
 
 soaking at relatively high temperatures affected adversely, 
 not only germination, but also subsequent growth in each case. 
 
 In general (PCG) showed more resistance than (PCB). (Fox) was 
 least resistant. Kernels with coats intact gave uniformily 
 better results than kernels with coats broken. The yield from 
 kernels with broken coats averaged 69$ less than that from 
 kernels with coats intact, without soaking. When the soaking 
 treatment was applied, the reduction averaged 78$. 
 
 In a more extensive experiment the soaking was 
 carried on at temperatures of 10° C. and 35° C., for varying 
 periods of time. The seeds used were (a) with coats intact, 
 
 (b) with coats broken, (c) unselected. After treatment 10 seeds 
 of each strain of corn were planted in soil on the greenhouse 
 bench. The plants were harvested at the end of three weeks. 
 
 The results are presented in Tables 24 to 28. 
 
-25- 
 
 Table 24. Germination; kernels intact (a), kernels 
 broken (b), kernels unselected (c). 
 
 Treatment 
 
 (a) 
 
 (PCG) 
 
 (b) 
 
 (c) 
 
 (a) 
 
 (PCB) 
 
 (b) 
 
 (c) 
 
 (a) 
 
 (Fox) 
 
 (b) 
 
 (c) 
 
 10° 
 
 C.- 1 
 
 hr. 100 
 
 100 
 
 100 
 
 90 
 
 100 
 
 100 
 
 100 
 
 100 
 
 80 
 
 10° 
 
 C. - 6 
 
 hrs. 100 
 
 90 
 
 100 
 
 100 
 
 90 
 
 90 
 
 100 
 
 ” 70 
 
 70 
 
 10° 
 
 C. -12 
 
 hrs. 100 
 
 100 
 
 80 
 
 90 
 
 100 
 
 70 
 
 90 
 
 80 
 
 60 
 
 10° 
 
 C. -24 
 
 hrs. 90 
 
 100 
 
 100 
 
 100 
 
 100 
 
 100 
 
 90 
 
 70 
 
 60 
 
 10° 
 
 C. -48 
 
 hrs. 90 
 
 90 
 
 100 
 
 90 
 
 90 
 
 100 
 
 80 
 
 100 
 
 60 
 
 35® 
 
 C.- 1 
 
 hr. 100 
 
 100 
 
 90 
 
 100 
 
 100 
 
 100 
 
 90 
 
 90 
 
 90 
 
 35® 
 
 C. - 6 
 
 hrs. 100 
 
 100 
 
 100 
 
 100 
 
 100 
 
 100 
 
 100 
 
 100 
 
 90 
 
 35® 
 
 C. -12 
 
 hrs. 100 
 
 100 
 
 100 
 
 100 
 
 100 
 
 100 
 
 100 
 
 100 
 
 100 
 
 35® 
 
 C.-24 
 
 hrs. 100 
 
 80 
 
 100 
 
 100 
 
 100 
 
 100 
 
 100 
 
 100 
 
 100 
 
 35® 
 
 C.-48 
 
 hrs. 90 
 
 100 
 
 70 
 
 100 
 
 70 
 
 80 
 
 80 
 
 50 
 
 40 
 
 Checks 
 
 100 
 
 89 
 
 95 
 
 100 
 
 76 
 
 100 
 
 100 
 
 100 
 
 100 
 
 
 
 Table 25, 
 
 . Average 
 
 heights (in.) 
 
 
 kernels intact 
 
 
 
 
 kernel 
 
 s broken 
 
 (b), 
 
 kernels unselec 
 
 Treatment 
 
 (a) 
 
 (PCG) 
 
 
 
 (PCB) 
 
 
 
 
 (Fox) 
 
 
 
 
 (b) 
 
 (c) 
 
 (a) 
 
 (b) 
 
 (c) 
 
 
 (a) 
 
 (b) 
 
 (c) 
 
 10® 
 
 C.- 1 
 
 hr. 16.4 
 
 14.6 
 
 16.5 
 
 15.2 
 
 13.2 
 
 17. 
 
 5 
 
 16.9 
 
 12.6 
 
 15.7 
 
 10° 
 
 C.- 6 
 
 hrs. 16. 2 
 
 13.0 
 
 17.4 
 
 14.7 
 
 10.5 
 
 16. 
 
 7 
 
 17.6 
 
 15.7 
 
 15.5 
 
 10® 
 
 C. -12 
 
 hrs. 15. 8 
 
 11.5 
 
 16.3 
 
 16.8 
 
 8.7 
 
 15. 
 
 6 
 
 18.1 
 
 13.5 
 
 14.2 
 
 10® 
 
 C. -24 
 
 hrs. 16. 9 
 
 15.6 
 
 19.3 
 
 18.3 
 
 14.5 
 
 17. 
 
 1 
 
 16.2 
 
 15.3 
 
 15.0 
 
 10-s 
 
 C. -48 
 
 hrs. 16. 9 
 
 16.9 
 
 15.3 
 
 18.7 
 
 13.6 
 
 16. 
 
 8 
 
 17.7 
 
 15.5 
 
 14.3 
 
 35® 
 
 C.- 1 
 
 hr. 16.2 
 
 13.2 
 
 16.2 
 
 15.5 
 
 7.2 
 
 16. 
 
 2 
 
 15.5 
 
 14.1 
 
 14.9 
 
 35® 
 
 C.-6 hrs. 18.0 
 
 15.8 
 
 17.0 
 
 16.3 
 
 9.1 
 
 16. 
 
 0 
 
 17.4 
 
 15.8 
 
 16.5 
 
 35° 
 
 C. -12 
 
 hrs. 15. 7 
 
 16.1 
 
 16.1 
 
 14. 5 
 
 12.3 
 
 14. 
 
 0 
 
 17.8 
 
 15.9 
 
 15.9 
 
 35° 
 
 C .-24 
 
 hrs. 18. 5 
 
 12.3 
 
 19.5 
 
 17.4 
 
 10.7 
 
 16. 
 
 3 
 
 10.5 
 
 10.9 
 
 15.9 
 
 35® 
 
 C. —48 
 
 hrs. 16.4 
 
 13.7 
 
 15.5 
 
 14.9 
 
 12.0 
 
 15. 
 
 5 
 
 17.3 
 
 13.5 
 
 14.9 
 
 Checks 
 
 16.2 
 
 9.1 
 
 18.3 
 
 15.4 
 
 2.7 
 
 16. 
 
 1 
 
 14.7 
 
 6. 7 
 
 16.4 
 
-26- 
 
 Table 26. Average green weights (grams); kernels 
 
 intact (a), kernels broken (b), kernels 
 unselected (c). 
 
 Treatment (PCG) (PCB) (Fox) 
 
 
 
 (a) 
 
 (b) 
 
 (c) 
 
 (a) 
 
 (b) 
 
 (c) 
 
 (a) 
 
 (b) 
 
 (c) 
 
 10° 
 
 C.- 1 
 
 hr. 2.02 
 
 1.49 
 
 2.67 
 
 1.69 
 
 1.67 
 
 2.76 
 
 2.44 
 
 1.38 
 
 2.68 
 
 10° 
 
 C.- 6 
 
 hre. 1. 62 
 
 1.06 
 
 2.51 
 
 1.47 
 
 .94 
 
 2.66 
 
 2.27 
 
 1.91 
 
 2.24 
 
 10° 
 
 C. -12 
 
 hrs. 2. 27 
 
 1.12 
 
 2.27 
 
 2.18 
 
 .79 
 
 1.96 
 
 2.75 
 
 1.60 
 
 2.16 
 
 10° 
 
 C. -24 
 
 hrs. 2. 29 
 
 1.59 
 
 1.36 
 
 2.23 
 
 1.84 
 
 2. 65 
 
 1.85 
 
 1.85 
 
 2.14 
 
 10° 
 
 C. -48 
 
 hre. 2.06 
 
 2.23 
 
 2.25 
 
 2.29 
 
 1.57 
 
 2.62 
 
 2.73 
 
 1.92 
 
 1.80 
 
 35° 
 
 C.- 1 
 
 hr. 1.94 
 
 1.32 
 
 3.05 
 
 1.79 
 
 .75 
 
 2.47 
 
 1.78 
 
 1.85 
 
 2.49 
 
 35° 
 
 C. - 6 
 
 hrs. 2. 73 
 
 1.65 
 
 3.16 
 
 1.80 
 
 1.00 
 
 2.31 
 
 2.28 
 
 1.95 
 
 2.61 
 
 35° 
 
 C. -12 
 
 hrs. 2.94 
 
 2.06 
 
 2.44 
 
 1.56 
 
 1.56 
 
 1.56 
 
 2.85 
 
 2.09 
 
 2.46 
 
 35° 
 
 C. -24 
 
 hrs. 2. 49 
 
 1.21 
 
 3. 60 
 
 2.15 
 
 1.05 
 
 2.42 
 
 2.24 
 
 1.25 
 
 2.62 
 
 35° 
 
 C. -48 
 
 hrs. 2. 25 
 
 1.73 
 
 2.74 
 
 1.67 
 
 1.33 
 
 2. 38 
 
 2.78 
 
 1.28 
 
 2.34 
 
 Checks 
 
 2.59 
 
 1.01 
 
 2.93 
 
 2.13 
 
 .28 
 
 2.24 
 
 2.08 
 
 1.02 
 
 2.62 
 
 Table 27. Average dry weights (grams); kernels 
 
 intact (a), kernels broken (b), kernels 
 unselected (c). 
 
 Treatment 
 
 
 
 (PCG) 
 
 
 
 (PCB) 
 
 
 
 (Fox) 
 
 
 
 
 (a) 
 
 (b) 
 
 (c) 
 
 (a) 
 
 (b) 
 
 (c) 
 
 $a) 
 
 (b) 
 
 (c) 
 
 10° C.- 1 
 
 hr. 
 
 .18 
 
 .14 
 
 .18 
 
 .14 
 
 .14 
 
 . 20 
 
 .21 
 
 .12 
 
 .17 
 
 10° C.- 6 
 
 hrs. 
 
 .18 
 
 .08 
 
 .17 
 
 .13 
 
 .07 
 
 .18 
 
 .20 
 
 .17 
 
 .15 
 
 10° C. -12 
 
 hrs. 
 
 .18 
 
 .09 
 
 .15 
 
 .18 
 
 .06 
 
 .13 
 
 .24 
 
 .13 
 
 .14 
 
 10° C. -34 
 
 hrs. 
 
 . 21 
 
 .15 
 
 .13 
 
 .21 
 
 .16 
 
 .18 
 
 .17 
 
 .17 
 
 .14 
 
 10° C .-48 
 
 hrs. 
 
 .18 
 
 .22 
 
 .16 
 
 .20 
 
 .15 
 
 .18 
 
 .17 
 
 .19 
 
 .14 
 
 35° C.- 1 
 
 hr. 
 
 .16 
 
 .13 
 
 .21 
 
 .12 
 
 .06 
 
 .19 
 
 .12 
 
 .15 
 
 .18 
 
 35° C.- 6 
 
 hrs. 
 
 .26 
 
 ,17 
 
 .12 
 
 .17 
 
 .09 
 
 .17 
 
 .20 
 
 .18 
 
 .19 
 
 35° C.-12 
 
 hrs. 
 
 .18 
 
 .20 
 
 .18 
 
 .14 
 
 .13 
 
 .12 
 
 .26 
 
 .20 
 
 .18 
 
 35° C. -24 
 
 hrs. 
 
 .23 
 
 .12 
 
 .16 
 
 .20 
 
 .09 
 
 • IE 
 
 .20 
 
 .11 
 
 .19 
 
 35° C.-48 
 
 hrs. 
 
 .22 
 
 .17 
 
 .19 
 
 .15 
 
 .11 
 
 .16 
 
 .25 
 
 .12 
 
 .14 
 
 Checks 
 
 
 .23 
 
 .09 
 
 .21 
 
 ,19 
 
 .03 
 
 ,16 
 
 .18 
 
 .10 
 
 .19 
 

 
 
 
-27- 
 
 Table 28. Total yields (grams); kernels intact (a), 
 
 kernels broken (b), kernels unselected (e) . 
 
 Treatment 
 
 (a) 
 
 (PCG) 
 
 (b) 
 
 (c) 
 
 (a) 
 
 (PCB) 
 
 (b) 
 
 (c) (a) 
 
 (Fox) 
 
 (b) 
 
 (c) 
 
 10° 
 
 C.- 1 
 
 hr. 1.79 
 
 1.43 
 
 1.82 
 
 1.30 
 
 1.41 
 
 1.98 2.07 
 
 1.17 
 
 1.35 
 
 10* 
 
 C.- 6 
 
 hrs. 1. 79 
 
 .74 
 
 1.72 
 
 1.28 
 
 .60 
 
 1.61 2.00 
 
 1.06 
 
 1.09 
 
 10° 
 
 C. -12 
 
 hrs. 1 . 83 
 
 .94 
 
 1.24 
 
 1.67 
 
 .53 
 
 .89 1.89 
 
 1.07 
 
 .86 
 
 10° 
 
 C. -24 
 
 hrs. 1.90 
 
 1.52 
 
 1.32 
 
 2.14 
 
 1.25 
 
 1.79 1.55 
 
 1.23 
 
 .84 
 
 10° 
 
 C • —48 
 
 hrs. 1. 62 
 
 1.96 
 
 1.60 
 
 1.81 
 
 1.49 
 
 1.84 1.40 
 
 1.86 
 
 .82 
 
 35° 
 
 C.- 1 
 
 hr. 1.56 
 
 1.29 
 
 1.88 
 
 1.23 
 
 .58 
 
 1.91^1.11 
 
 1.38 
 
 1.64 
 
 35° 
 
 C.- 6 
 
 hrs . 2. 59 
 
 1.67 
 
 1.22 
 
 1.74 
 
 .90 
 
 1.72*1.97 
 
 1.83 
 
 1.69 
 
 35° 
 
 C. -12 
 
 hrs. 1. 83 
 
 2.02 
 
 1.77 
 
 1.43 
 
 1.22 
 
 1.16 2.64 
 
 2.02 
 
 1.81 
 
 35° 
 
 C. -24 
 
 hrs. 2. 34 
 
 .93 
 
 1. 75 
 
 1.97 
 
 .95 
 
 1.84* 2.03 
 
 1.15 
 
 1.88 
 
 35° 
 
 C.-48 
 
 hrs. 1. 96 
 
 1.66 
 
 1.33 
 
 1.35 
 
 .75 
 
 1.31 2.05 
 
 .58 
 
 .55 
 
 Checks 
 
 2.30 
 
 .80 
 
 2.14 
 
 1.90 
 
 .23 
 
 1.65 1.80 
 
 1.00 
 
 1.90 
 
 Table 29. Summary of data in Tables 24 to 28. 
 (PCG) (PCB) (Fox) 
 
 (a) 
 
 Germination ($) 
 
 (b) 
 
 (c) (a) 
 
 (b) 
 
 (c) 
 
 (a) 
 
 (b) 
 
 (c) 
 
 Checks 100 
 
 89 
 
 95 
 
 100 
 
 76 
 
 100 
 
 100 
 
 100 
 
 100 
 
 Soaked 97 
 
 96 
 
 94 
 
 97 
 
 95 
 
 94 
 
 93 
 
 86 
 
 75 
 
 Av. Heights(in.) 
 
 Checks 
 
 16.2 9.1 
 
 18. 3 
 
 15.4 
 
 2.7 16.1 14.7 6.7 16.4 
 
 Soaked 
 
 16.7 14.3 
 
 16.9 
 
 16.1 
 
 11.2 16.3 17.0 14.3 15.3 
 
 Av. green 
 
 weights (grams 
 
 i) 
 
 
 
 Checks 
 
 2.59 1.01 
 
 2.93 
 
 2.13 
 
 .28 2.24 2.08 1.02 2.62 
 
 Soaked 
 
 2.26 1.55 
 
 2.60 
 
 1.88 
 
 1.242.38 2.40 1.71 2.35 
 ) 1 
 
 Av. dry weights (grams) 
 
 
 
 Checks 
 
 .23 .09 
 
 .21 
 
 .19 
 
 .03 .16 .18 .10 .19 
 
 Soaked 
 
 .20 .15 
 
 .16 
 
 .16 
 
 .11 .17 .20 .15 .16 
 
 Total yields (grams) 
 
 
 
 
 Checks 
 
 2.30 .80 
 
 2.14 
 
 1.90 
 
 .23 1.65 1.80 1.00 1.90 
 
 Soaked 
 
 1.92 1.42 
 
 1.56 
 
 1.59 
 
 .97 1.60 1.87 1.33 1.25 
 
 The outstanding fact to be noted from Table 29 is 
 the reduction in yields when kernels with broken coats are used 
 in contrast to kernels with coats intact. This holds true 
 

 
 
 
 
 
 I ' I 
 
 
 
 <• 
 
 
 
-28- 
 
 quite consistently for germination, average heights, average 
 
 green and dry weights, and the expression of all of these in 
 
 were 
 
 the total yields. There apparently no significant differ- 
 ences in this respect between the three strains of corn. Con- 
 sidering all the plantings, the use of kernels with seed coats 
 broken resulted in a reduction of 44$ in the average dry weight 
 of the plants, and a reduction of 48$ in the total yield. 
 
 Brown (3), comparing the field performances of entire and broken 
 seeds obtained an average reduction in yield with broken kernels 
 of 11$. In other experiments (2) with dehulled seeds, a reduc- 
 tion in yield of 12$ was noted. 
 
 Considering all the plantings, the total yields of 
 (PCB) averaged 26$, and of (Fox), 9$, below those of (PCG). The 
 data obtained with composite samples would in general indicate 
 some decreases in yield due to soaking at medium temperatures. 
 The apparent exception in the case of the plantings with broken 
 kernels, is quite possibly explained by the position of the 
 ohecks adjacent to a row of kernels intact which had been soaked 
 for 48 hours. The latter germinated somewhat more rapidly, 
 and possibly exerted an undue influence through competition, 
 in view of the close planting in the plat. (See Plate 5, first 
 row in second plat from the left). 
 
 Kidd and West (12) on the basis of their own work 
 and that of previous investigators, draw the conclusion that 
 presoaking, particularly in an excess of water, is generally 
 harmful. Considering all the plantings, and having in mind 
 
-39- 
 
 the total yields, it appears that the soaking at 10° C. may 
 be somewhat more injurious than soaking at 35° C. No signifi- 
 cant differences were observed between the three strains of 
 corn in this respect. 
 
 Vitality as influenced by the growth of fungi 
 
 Study was made of the effects of superficial fungi 
 on germination in the three strains of corn. The fungi used 
 were ieolated from corn on the germinator, and included strains 
 of Fusarium moniliforme, Penicillium, Rhizopus, and Aspergillus. 
 Fusarium moniliforme is recognized as a very active parasite 
 on corn. ■Pwai-giilim Aspergillus may cause considerable 
 losses in the field (18). Rhizopus is commonly present, and 
 has been noted as a weak parasite on the germinator (l). 
 
 This investigation however, did not involve primarily 
 any comparisons of relative pathogenicity of the fungi employed. 
 They were used as a means of measuring the relative resistance 
 of the three kinds of corn under test. Untreated seeds, as 
 well as others which had been subjected to presoaking treatments 
 designed to reduce their vitality, were used. In order to in- 
 eure a uniform distribution of the spores, the seeds were soaked 
 for 15 minutes in a spore suspension. They were then placed 
 on blotters above plaster of paris blocks in germinator pans, 
 under favorable temperature conditions. As the interiors of 
 the germinators were scalded before use, the various fungi grew 
 

 
 
 
 
 
 
 
 
 . 
 
 . 
 
 . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 - 
 
 
 ■ 
 
 
 
 
 
 
 . 
 
 . 
 
 
 . -<»«r 
 
 
 
 
 
 
 
-30- 
 
 in fairly pure cultures. A series of checks and a series of 
 kernels covered with spores were placed in each pan, 20 to 25 
 seeds being used in each case. Typical cultures are shown in 
 Plates 6 to 12. The average results for a number of experiments 
 are shown in Table 30. 
 
 Table 30. Vitality as affected by fungi 
 
 Treatment Per cent germination 
 
 (PCG) (PCBj (Fox) 
 
 
 Str. 
 
 Wk. 
 
 Tot. 
 
 Str 
 
 . Wk. 
 
 Tot. 
 
 Str. 
 
 Wk. 
 
 Tot 
 
 Not soaked 
 
 No spores 
 
 81 
 
 18 
 
 99 
 
 68 
 
 32 
 
 100 
 
 57 
 
 38 
 
 95 
 
 Fusarium 
 
 78 
 
 15 
 
 94 
 
 71 
 
 13 
 
 84 
 
 33 
 
 6 
 
 39 
 
 Penicillium 
 
 74 
 
 23 
 
 97 
 
 70 
 
 29 
 
 99 
 
 40 
 
 44 
 
 84 
 
 Rhizopus 
 
 56 
 
 44 
 
 100 
 
 58 
 
 38 
 
 96 
 
 34 
 
 60 
 
 94 
 
 Aspergillus 
 Soaked at 10° 
 
 76 
 
 C., 
 
 23 
 
 99 
 
 79 
 
 21 
 
 100 
 
 49 
 
 48 
 
 97 
 
 24 hrs. 
 
 No spores 
 
 93 
 
 5 
 
 98 
 
 71 
 
 21 
 
 96 
 
 53 
 
 30 
 
 83 
 
 Fusarium 
 
 75 
 
 35 
 
 100 
 
 35 
 
 65 
 
 100 
 
 5 
 
 60 
 
 65 
 
 Penicillium 
 
 85 
 
 10 
 
 95 
 
 75 
 
 30 
 
 95 
 
 50 
 
 40 
 
 90 
 
 Aspergillus 
 Soaked at 10° 
 
 60 
 
 c. 5 
 
 40 
 
 100 
 
 70 
 
 25 
 
 95 
 
 30 
 
 50 
 
 80 
 
 48 hrs. 
 
 No spores 
 
 90 
 
 10 
 
 100 
 
 65 
 
 30 
 
 95 
 
 50 
 
 32 
 
 82 
 
 Fusarium 
 
 30 
 
 70 
 
 90 
 
 55 
 
 45 
 
 100 
 
 0 
 
 30 
 
 30 
 
 Aspergillus 
 
 100 
 
 0 
 
 100 
 
 55 
 
 35 
 
 80 
 
 35 
 
 35 
 
 60 
 
 In another series, kernels with coats intact, and 
 kernels with coats broken, were used. The results may be seen 
 in Table 31. 
 
-31 
 
 Table 31. Comparative vitality of kernels with 
 coats intact and coats broken. 
 
 Treatment Per cent germination 
 
 Str. Wk. Tot. Str. Wk. Tot. Str. Wk. Tot. 
 
 Kernels intact 
 
 No spores 
 
 100 
 
 0 
 
 100 
 
 95 
 
 5 
 
 100 
 
 55 
 
 30 
 
 85 
 
 Fusarium 
 
 90 
 
 10 
 
 100 
 
 90 
 
 5 
 
 95 
 
 45 
 
 35 
 
 70 
 
 Kernels broken 
 
 No spores 
 
 90 
 
 10 
 
 100 
 
 90 
 
 5 
 
 95 
 
 45 
 
 35 
 
 70 
 
 Fusarium 
 
 55 
 
 30 
 
 75 
 
 60 
 
 35 
 
 85 
 
 55 
 
 10 
 
 65 
 
 \ 
 
 In the above experiments, it may be noted in general 
 that the germinating spores of Fusarium, Penicillium, Rhizopus, 
 and Aspergillus were effective in reducing the germination of 
 the corn in the order named. The effect of the fungous mycelium 
 was most marked on (Fox) in every case, and in general, the 
 least impression was made on (PCG). There may be seen in general 
 a direct correlation between the severity of soaking and injury 
 attributable to the fungi. 
 
 Fusarium produced the more severe effects on the 
 kernels with broken coats. Miss Hurd (10) has shown a direct 
 relation between seed-coat injury and susceptibility to molds 
 and fungicides, in the casefof wheat and barley. 
 

 
 
 - 
 
 
 
 
 
 ' 
 
 ■ 
 
 
 
 
 
 •• . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 . 
 
 
 
 
 
 . 
 
 
 
 
 ■ 
 
 
 
 
 
 
 
 
 
 
 
 
 
-32- 
 
 IV. Discussion 
 
 The corn used in the present investigation showed but 
 slight differences in vitality in ordinary germinator tests. 
 
 But when adverse conditions are encountered, more marked differ- 
 ences are to be seen. Strain (PCG) is most resistant, and (Fox) 
 the most susceptible to injury. 
 
 The constant differences in the rates of water absorp- 
 
 are 
 
 tion improbably to be explained on the basis of physical compo- 
 sition of the kernels. The percentages of starchy kernels in 
 the three types of corn may be correlated directly with the 
 relative rates of water intake. Leaching was also apparently 
 somewhat greater in the cases of the (PCB) and (Fox) strains, 
 although attempts to measure these differences with the refract- 
 oroeter were not successful. Kidd and West (12) would attribute 
 injury by soaking to the leaching of soluble food reserves to- 
 gether with an accumulation of carbon dioxide in the seed. 
 
 Results obtained in the present work, and those of 
 Brown (2,3) clearly indicate that broken kernels exhibit a 
 relatively lower vitality than entire kernels. Cracked or 
 abraded kernels due to injury in handling, shelling, or planting 
 by machinery are common. This is doubtless true to a greater 
 extent with the rougher types of corn. For example, the percent- 
 ages of broken kernels to be found in composite samples of the 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 . 
 
 
 
 
 
 
 
 
 
 
 - 
 
 . 
 
 
 
 
 
 
 
 
 
-33- 
 
 corn used in this investigation are as follows: (PCG) 8.8$, 
 
 (PCB) 21.0$, (Fox) 36.5$; this in spite of the fact that 
 thi^ corn had not been handled by machinery, and the rougher 
 ears had been wrapped in paper to prevent damage. Under ordinary 
 conditions the discrepancies in percentages of broken kernels 
 would probably be even greater. 
 
 In view of the facts presented thus far it seems 
 probable that broken kernels play a considerable part in deter- 
 mining the results obtained with apparently disease-free com 
 in field experiments. Holbert (9) for example, obtained with 
 (PCG) and (PCB), both practically disease-free, differences in 
 yield of 20 bushels or more per acre, in infested soil. The 
 differences obtained on clean soil were less marked. Again, 
 four years’ trial at Nebraska with smooth and rough selections 
 within the variety resulted in an average decrease in yield of 
 3.5 bushels per acre, or 7$, when rough corn was used. 
 
 Reductions in yield of 12$ to 40$, due to broken 
 kernels, indicate that Holbert’s results in the field may be 
 due at least in part, to a similar cause. The greater differ- 
 ences obtained on infested soil are of interest in connection 
 with the demonstrated effects of fungi on broken kernels. It 
 has been shown in the present investigation, and likewise by 
 M iss Hurd(lO), that kernels with broken coats are more suscep- 
 tible to injury by fungi present superficially, than are kernels 
 

 
 
 . . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 . 
 
 
 . 
 
 
 
 
 . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
-34- 
 
 with coats intact. The work of Richey (15) indicates that 
 spores carried externally on the seed may ordinarily be a 
 factor of considerable importance in the field. This chain 
 of evidence is to say the least, most suggestive. 
 
 V. Conclusions 
 
 1. The rate of water absorption is greatest in the 
 types of corn containing the higher percentages of starchy 
 kernels. The rate is least with (PC G) , a comparatively horny 
 type of corn. 
 
 2. The temperature coefficient of absorption is 
 about 1.4 in all three strains. 
 
 3. Strain (PCG) exhibits slight though constantly 
 higher rates of germination and growth at various temperatures 
 in comparison with the other two strains. 
 
 4. Entire kernels show greater vitality than broken 
 kernels, under all conditions. 
 
 5. Soaking is in general, apparently injurious to 
 the subsequent growth of corn. 
 
 6. Superficial fungi are detrimental to germination, 
 especially in the case of (Fox) corn. This effect is heightened 
 by presoaking treatments. 
 
 7. The higher percentages of broken kernels obtaining 
 in the rougher types of corn is offered as the most probable ex- 
 planation for the poor showing often made by such types in the 
 field. 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 . 
 
 
 
 
 
 
 
 
 
 
 
- 35 - 
 
 VI. Acknowledgment 
 
 The author wishes to express his appre- 
 ciation of the assistance extended by Dr. C. F. 
 
 Hottes, Professor of Plant Physiology in the Uni- 
 versity of Illinois, under whose direction the 
 work was carried out. By inspiration and advice 
 he has contributed largely to the success attained. 
 
 Thanks are also due him for the use of 
 the constant temperature cases in the Plant Physiology 
 Laboratories. 
 

 . - - 
 
 - 
 
 ' 
 
 t it 
 
 
 
 
 
 
 
-36- 
 
 VII. Literature cited 
 
 (1) Adams, J. F. & Russel, A. M. Rhizopus infection of corn 
 
 on the germinator. Phytopath. 10:535-543. 1920. 
 
 (2) Brown, E. B. Effects of mutilating the seeds on the growth 
 
 and productiveness of corn, U. S. Dept. Agri Bull. 1011. 
 1922. 
 
 (3) Brown, E. B. Relative yields of broken and entire kernels 
 
 of seed corn. Jour. Am. Soc. Agron. 12:196-197. 1920. 
 
 (4) Brown, A. J. & Worley, F. P. The influence of temperature 
 
 on the absorption of water by seeds of Hordeum vulgare 
 in relation to the temperature coefficient of chemical 
 change. Proc. Roy. Soc. Lond. B85:546-553. 1912. 
 
 (5) Burrill, T. J. & Barrett, J. T. Dry rot of corn. 111. Circ, 
 
 117. 1908. 
 
 (6) Burrill, T. J. & Barrett, J. T. Ear rots of corn. 111. 
 
 Exp. Sta. Bull. 133. 1909. 
 
 (7) Denny, F. E. Permeability of certain plant membranes to 
 
 water. Bot. Gaz. 63:373-397. 1917. 
 
 (8) Duddleston, B. H. The modified rag doll and germinator 
 
 box. Purdue Exp. Sta. Bull. 236. 1920. 
 
 (9) Holbert, J. R. Address, Corn Growers and Stockmens' 
 
 Convention, Urbana, 111. Jan., 1922. 
 
 (10) Hurd, Annie M. Seed-coat injury and viability of seeds of 
 
 wheat and barley as factors in susceptibility to molds 
 and fungicides. Jour. Agr. Res. 21:99-122. 1921. 
 
 (11 ) Kanitz, A. Temperatur and Lebensvorgange. 1915. 
 
 (12) Kidd, F. & West, C. Physiological pre-determination: the 
 
 influence of the physiological condition of the seed 
 upon the course of subsequent growth and upon the yield. 
 I. The effects of soaking seeds in water. IV. Review 
 of literature. Ann. Appl. Biol. 5:1-10, 220-251. 1918 - 
 1919. 
 
-37- 
 
 (13) Kiesselbach, T. A. & Ratcliff, J. A. Freezing injury of 
 
 seed corn. Nebr. Exp. Sta. Res. Bull. 16. 1920. 
 
 (14) Lehenbauer, P. A. Growth of maize seedlings in relation 
 
 to temperature. Physiological Researches 1:247-288. 1914. 
 
 (15) Richey, F. D. Formaldehyde treatment of seed corn. 
 
 Jour. Am. Soc. Agron. 12:39-43. 1920. 
 
 (16) Shull, C. A. Address, A. A. A. S., Chicago. Dec., 1920. 
 
 (17) Shull, C. A. Temperature and rate of moisture intake in 
 
 seeds. Bot. Gaz. 69:361-390. 1920. 
 
 (18) Taubenhaus, J. J. A study of the black and yellow molds 
 
 of ear corn. Texas Exp. Sta. Bull. 270. 1920. 
 
-38- 
 
 VIII. Plates 
 Explanation of plates. 
 
 Plate 
 
 I. 
 
 Ears 
 
 of 
 
 "Peoria Co. 
 
 Good" (PCG). 
 
 Plate 
 
 II. 
 
 Ears 
 
 of 
 
 "Peoria Co. 
 
 Bad" (PCB). 
 
 Plate 
 
 III. 
 
 Ears 
 
 of 
 
 "Fox" (Fox) . 
 
 
 Plate 
 
 IV. 
 
 Ears 
 
 of 
 
 (PCG), (PCB) 
 
 , (Fox ) . 
 
 Plate 
 
 V. 
 
 Results 
 
 of soaking corn. Left 
 
 Plate VI . 
 Plate VII. 
 Plate VIII 
 Plate IX. 
 Plate X. 
 Plate XI. 
 
 Plat 1. Kernels intact, 10° C. and 35° C. 
 
 Plat 3. Kernels broken, 10° C. and 35° C. 
 
 Plat 3. Kernels intact and broken, 60° C. and 65°C 
 
 Penicillium; no presoaking. 
 
 Penicillium; 24 hrs. at 10° C. 
 
 Penicillium; 48 hrs. at 10° G. 
 
 Fusarium; no presoaking. 
 
 Fusarium; 34 hrs. at 10° C. 
 
 Fusarium; 48 hrs. at 10° C. 
 
 From left to right: (PCG), (PCB), (Fox). The checks are 
 in the foreground in each case. 
 
Plate I 
 

 
 
 
 
 
 
 
 
 
 
Plate III 
 
Plate IV 
 


Plate VI. 
 
~ 4 &- 
 
 Plate VII. 
 
- 46 - 
 
 Plate VIII. 
 

- 47 - 
 
 1 
 
 Plate IX. 
 
Plate X. 
 
- 49 - 
 
 Plate Xt. 
 
-50- 
 
 IX. Vita 
 
 Frederick Franci3 Weinard was born at Lincoln, 
 Nebraska, December 2, 1893. He attended the public and 
 parochial schools of the City, graduating from the Lincoln 
 High School in the year 1912. In the autumn of 1912 he 
 entered the University of Nebraska, which he attended for 
 the ensuing five years. He received the B. S. degree in 
 1916, and was elected to active membership in Sigma Xi the 
 same year. He was granted the M. A. degree in 1917. 
 
 The months of June to December, 1917, were spent 
 as Field Assistant in the Office of Forest Pathology, U. S. 
 Department of Agriculture. The time from December, 1917, 
 to August, 1919, was spent in the U. S. Army (Medical Depart- 
 ment ) . 
 
 Since September, 1919, the author of this thesis 
 has been a graduate student and Assistant in Botany in the 
 University of Illinois. In 1920 he received the honor of 
 membership in the Gamma Alpha Graduate Scientific Fraternity.