XI B OF THE, UNIVERSITY OF ILLINOIS G30.7 ho.354-3G3 cop. 2. TCRICULTURE NOTICE: Return or renew all Library Materials! The Minimum Fee for each Lost Book is $50.00. The person charging this material is responsible for its return to the library from which it was withdrawn on or before the Latest Date stamped below. Theft, mutilation, and underlining of books are reasons for discipli- nary action and may result in dismissal from the University. To renew call Telephone Center, 333-6400 UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN APR 2 8 2005 L16I 0-1096 EXPERIMENTS IN FORCING GLADIOLI By F. F. WEINARD and S. W. DECKER UNIVERSITY OF ILLINOIS AGRICULTURAL EXPERIMENT STATION BULLETIN 357 CONTENTS PAGE INTRODUCTION 345 DISCUSSION OF RESULTS 345 Comparison of Varieties 345 . Corms Forced Successfully a Second Time 347 Flower Production of Corms of Different Sizes 347 Effect of Storage Temperature 349 Varying Time of Planting 351 Chemical Treatments of Doubtful Value 352 Effect of Artificial Lighting 356 Corms Held Over in Storage for Early Forcing 359 CONCLUSIONS 359 LITERATURE CITED.. 360 Urbana, Illinois October, 1930 Publications in the Bulletin series report the results of investigations made or sponsored by the Experiment Station Experiments in Forcing Gladioli By F. F. WEINARD, Associate Chief in Floricultural Physiology, and S. W. DECKER, Associate in Floriculture GLADIOLI are being grown under glass for cut-flowers in in- creasing numbers. Generally the corms are planted in January or early in February and flower in May. Altho there is a de- mand for the flowers earlier in the season, early planting has not proved profitable on a commercial scale because of the large propor- tion of "blind" plants on which flowers fail to develop. Apparently the corms must undergo a certain period of dormancy, or rest, before they can be grown successfully with ordinary methods. Aside from the influence of variety and time of planting, growers state that size, age, and previous use of the corms, the temperature of storage, the temper- ature of the house, and the method of watering, all have considerable to do with the results obtained. Experiments were conducted at the Illinois Experiment Station over several seasons to determine the importance of certain of these factors, including previous use and size of corms, temperature of stor- age, and time of planting. Chemicals and artificial light were tried for the purpose of breaking the rest period and for stimulating growth. In all these tests the corms were planted at a uniform depth of 2 inches, 6 inches apart each way, in benches 6 inches deep. The soil was brown silt loam containing about one-fifth manure and a little steamed bone meal. Temperatures maintained were 52 F. night and 58 to 68 F. in so far as possible during the day. DISCUSSION OF RESULTS Comparison of Varieties No attempt was made to test the forcing qualities of a compre- hensive list of varieties. In most of the plantings Chicago White, Halley, Mrs. Francis King, and Mrs. Frank Pendleton, varieties well adapted to forcing, were used. Some results with certain newer varie- ties are given for comparison ( Table 1 ) . In this test Flanders, Seafoam, and Virginal were especially good, while Elsie McCormick, Lansing, L. W. Wheeler, and Princess Eliza- beth showed structural defects or appeared otherwise undesirable for 345 346 BULLETIN No. 357 [October, c tt g 5 R P as i as o 3 a M 3 W I X H O t3 C. O I es I|. lol Ir O e. * k- SI u E c : 5 : *j ' 64 " 1930] EXPERIMENTS IN FORCING GLADIOLI 347 forcing. The corms planted late in February sprouted in about two weeks and flowered in about a hundred days. Corms Forced Successfully a Second Time Flowers from forced corms were cut in May, two good leaves being left on each shoot. On June 15 the plants were lifted, tops and all, and placed in a cool room to dry before being cleaned. These corms were stored in a cool room and planted in the bench the following season on December 12 and 26 and on January 9 and 23. Corms which had not been forced were planted each time for comparison. The averages from all the plantings are shown in Table 2. The results from corms forced for the second time were in all re- spects as good as the results from new corms. Under commercial conditions it may or may not be feasible to allow corms to ripen in the bench after forcing. Flower Production of Corms of Different Sizes First-size corms (1% inches and up) are perhaps generally pre- ferred by florists. Oven 14 * found in an experiment in the field that a considerably larger number of flower spikes were produced from 2- inch corms than from corms measuring 1% inches or less. The larger corms bloomed earlier and had a longer season of flowering. The figures shown in Table 2 are of interest in this connection. Corms being forced the second time in 1925-26 were graded into 2-inch and 1%-inch sizes. As the time of planting did not seem to give im- portant variations in results, only the averages for all plantings are shown. There were no differences in the time it took the different sizes to sprout or to flower, but higher percentages of the larger corms flowered, and likewise the total flower production of the larger corms was larger with three varieties. In the case of Halley the difference amounted to 25 percent. On the other hand, Mrs. Frank Pendleton showed no increase in flower production from the larger corms. In 1928 corms from No. 3 stock in the field were graded into 1%- inch, 1%-inch, and 2-inch sizes and planted in the bench on February 11 (Table 3). In this test the percentage of corms that flowered was in inverse ratio to the size of the corms. There appeared to be no consistent differences, however, in the total number of spikes cut from the different sizes. This experiment needs repetition with larger numbers of corms before definite conclusions can be drawn. 348 BULLETIN No. 357 [October, 1 P v 5,3 33- . , < J * Average ||i - = 2 ^0 CM** 0*00 || R e, . -, **3 2- a li n H. CS CS CS CN CS CS CSCSCS **> f*> **5 H Q " fc | 1^ Cfl II | sss S8S SS:?: SSS a a to H Q o> ^ a u |I| SiO 00 t^OOf^ OS O>O t^io 'WOO0000 O o b, en II U u, Q 1 "3, ll *% SSS S2S SSS ^SS O ! S u v-o |3 E c 3 rt sss sss sss sss 2 a Q O R | X X X X H to g NN- . C a c 1 c 'o rj c S 2 * 2 ? C B a a O U u H K K 1 J J u X S S I - f 1 | 1 |M a ;ss ?4 C *: O -rs O>OC r :- r 3 c 1 4 j 1! ^ 2 ^u,^ 5 C B a C 4) ) 3 8 S8 SRS - So So n co I 4, M ; 3. c c'S t^ O^ ^O VN w) C4 - d U : gl 5 3 5 1 3 C u M 5 .2 3 3 = 2 *fO-* *** tN tSfS SfS tS -^ < U ', : S-b XI 4> EC tsests Mtscs s a i J ^ B < - R | XX XX to 5 X 1 c .-. S "x CO >. / 2 1 1930] EXPERIMENTS IN FORCING GLADIOLI 349 Effect of Storage Temperature Boswell, 1 * working with onions, found that the development of flower primordia was hindered at low temperatures. He concluded that "bulbs which are to be planted for seed production should be stored at a temperature which will reduce to a minimum the losses from growth and decay during storage and still have no injurious effect upon floral development. This happy medium perhaps lies some- where between 40 and 45 F." Floyd 7 * reported an experiment in which gladiolus corms were stored in an open shed in Florida and also placed for periods as long as four months in cold storage at 32 to 35 F. and at 42 to 45 F. before planting in the field. Corms stored at 32 to 35 F. came up and also bloomed about a week later than did corms stored at 42 to 45 F. The length of time the corms were in cold storage seemed to make little difference in the results. There was no marked difference in results with corms stored at 42 to 45 F. as compared with corms stored in the open air. Loomis 11 * showed that the rest period of potatoes was shortened by storage at a temperature of about 86 F. in comparison with storage at lower temperatures. Also, relatively high soil temperatures seemed to aid the germination of partially dormant tubers, Loomis and Evans 12 * state that high storage temperatures and high soil temperatures were very effective likewise in forcing gladioli. Arlon, Halley, and Marshal Foch were used, and it is suggested that temperatures ranging from about 77 F. for four weeks to 102 F. for one week should prove approximately equally effective. At the University of Illinois test plantings were made under glass for several seasons to determine the effects, if any, of storage tem- perature on subsequent forcing qualities of gladiolus corms. In 1922-23 plantings were made from corms held in storage at 38 F. Corms planted at the same time for comparison were stored in the potting room, where the temperature was 70 to 80 F. On January 10, after five weeks in cold storage, the corms were removed to the potting room. Plantings were made on January 10, 17, 24, and 31. In a similar experiment in 1923-24 half the corms were stored for four weeks at 38 F. and the remainder in a cool basement room where the temper- ature was about 60 F. The corms were removed from cold storage on December 4 and plantings made on December 4 and 18. In 1924-25 corms were in cold storage as long as thirteen weeks, being removed as needed for planting on December 9 and 23, January 6 and 20, and February 6. The controls were stored in the potting room. 350 BULLETIN No. 357 [October, TABLE 4. EFFECT OF STORAGE TEMPERATURE ON FLOWER PRODUCTION OF GLADIOLUS CORMS Variety Storage Corms planted Days to sprout Days to flower Temper- ature Number planted Number sprouting Per- centage flowering Spikes cut per 100 corms Stored 5 weeks; planted January 10-31, 1923 America Warm 32 32 41 47 18 123 Chicago White Cold Warm 32 32 32 32 69 76 91 84 28 22 132 120 Mrs. Frank Pendleton. . . Cold Warm Cold 32 32 32 32 32 32 87 97 88 119 112 109 28 17 29 123 115 122 Stored 4 weeks; planted December 4-18. 1923 Chicago White. Cool 32 32 31 Halley Cold Cool 32 32 32 32 47 50 39 25 131 Mrs. Frank Pendleton. . . Cold Cool Cold 32 32 32 32 31 32 59 94 84 81 97 91 35 102 95 135 153 146 Stored 9 to 13 weeks; planted January 6-February 6, 1925 Chicago White Warm 96 95 90 106 27 106 Cold 96 96 68 97 32 107 Halley Warm 96 96 84 97 15 90 Cold 96 96 85 101 33 103 Mrs. Francis King Warm 96 90 92 130 20 108 Cold 96 95 88 123 32 120 Mrs. Frank Pendleton. . . Warm 96 95 92 100 20 104 Cold 96 96 96 121 33 114 As shown in Table 4, corms from warm storage sprouted 5 to 18 days sooner than did those from cold storage. Tho greater differ- ences were obtained in certain instances, this result did not vary with the time of planting. The time of flowering was affected, as was the time to sprout, by storage temperature, but the differences were as a rule considerably smaller. The results on the number of corms flower- ing and number of spikes cut were somewhat inconsistent, with the advantage, if any, in favor of the cold-storage corms. A storage temperature of 40 to 45 F. is commonly recommended for gladiolus corms. The results of these tests indicate the desirability of cool temperatures. Flower development was not markedly delayed when corms were held at 38 F. The corms do not shrivel under pro- longed storage when temperatures are low, and a minimum of "blind" shoots is obtained. At the same time storage rots are held more or less in check. No doubt the time to flowering may be shortened by ex- posure to higher temperatures for a time before planting. This treat- ment can be left, however, for the grower who forces the corras. 1930] EXPERIMENTS IN FORCING GLADIOLI 351 Prolonged storage at either temperature extreme is not to be recom- mended, and high temperatures even for short periods should be used with caution. Varying Time of Planting The effects of varying the time of planting in forcing gladiolus corms may be seen in Tables 5 to 8. The time to sprout was progres- sively shortened from about 40 days in the case of corms planted early TABLE 5. TIME OF PLANTING AS AFFECTING FLOWER PRODUCTION OF GLADIOLI UNDER GLASS, 1922-23 Variety Dates of planting Corms planted Days to sprout Days to flower Number planted Number sprouting Per- centage flowering Spikes cut per 100 corms America Dec. 13 16 16 36 Dec. 20 24 24 8 8 32 150 Dec. 27 32 32 28 28 28 145 Jan. 3 40 40 30 30 28 150 Jan. 10 80 80 37 47 30 135 Jan. 17 72 72 55 71 24 131 Jan. 24 64 64 49 78 20 121 Jan. 31 56 55 62 82 19 119 Chicago White Dec. 13 16 16 62 69 38 145 Dec. 20 24 24 67 79 .36 144 Dec. 27 32 32 75 109 34 138 Jan. 3 40 40 72 92 32 134 Jan. 10 80 80 78 107 33 129 Jan. 17 72 72 89 126 27 123 Jan. 24 64 64 95 119 22 118 Jan. 31 56 56 96 111 19 114 Mrs. Frank Pendleton. . . Dec. 13 16 16 94 138 42 152 Dec. 20 24 24 100 112 42 149 Dec. 27 32 32 94 106 35 140 Jan. 3 40 40 97 110 31 136 Jan. 10 80 80 96 111 31 129 Jan. 17 72 72 94 107 24 124 Jan. 24 64 64 95 108 19 118 Jan. 31 56 56 96 111 15 111 TABLE 6. TIME OF PLANTING AS AFFECTING FLOWER PRODUCTION OF GLADIOLI UNDER GLASS, 1923 Variety Dates of planting Corms planted Days to sprout Days to flower Number planted Number sprouting Per- centage flowering Spikes cut per 100 corms Chicago White Dec. 4 Dec. 18 Dec. 26 Dec. 4 Dec. 18 Dec. 26 Dec. 4 Dec. 18 Dec. 26 80 80 32 80 80 52 80 80 32 80 80 32 80 80 52 79 80 32 4 31 16 77 84 91 96 100 5 34 17 95 92 106 105 112 39 30 30 35 28 25 55 41 35 143 145 138 129 126 155 144 138 Halley Mrs. Frank Pendleton. . . 352 BULLETIN No. 357 [October, TABLE 7. TIME OF PLANTING AS AFFECTING FLOWER PRODUCTION OF GLADIOLI UNDER GLASS, 1924-25 Variety Dates of planting Corms planted Days to sprout Days to flower Number planted Number sprouting Per- centage flowering Spikes cut per 100 corms Chicago White Dec. 9 Dec. 23 Jan. 6 Jan. 20 Feb. 6 Dec. 9 Dec. 23 Jan. 6 Jan. 20 Feb. 6 Dec. 9 Dec. 23 Jan. 6 Jan. 20 Feb. 6 Dec. 9 Dec. 23 Jan. 6 Jan. 20 Feb. 6 64 64 64 64 64 64 64 64 64 64 64 64 64 64 64 64 64 64 64 64 64 63 64 64 64 64 64 63 64 64 62 61 64 63 63 64 64 64 64 63 22 58 62 89 84 51 70 75 89 92 72 80 84 94 91 95 84 94 91 97 26 73 80 106 119 58 84 84 103 109 96 111 113 136 131 105 108 106 116 109 38 38 32 30 27 31 30 27 24 22 36 31 28 25 25 46 38 28 26 24 136 127 119 107 93 131 122 113 103 91 142 132 126 114 103 144 128 122 110 95 Halley Mrs. Francis King Mrs. Frank Pendleton. . . in December to about 20 days when the corms were planted the last of January. The time to flower was similarly shortened in the same period from about 140 days to about 120 days. About 30 percent or less of corms planted before the middle of December produced flowers. The percentages flowering in the early and late January plantings were about 70 percent and 80 percent re- spectively. Counting all spikes cut from the same plantings, the per- centages were about 35, 85, and 105 percent respectively. Results varied to a considerable extent with the variety. Mrs. Frank Pendle- ton, for example, gave comparatively good results even in early De- cember plantings. With Halley and other varieties much better yields were obtained from plantings made along in January. Chemical Treatments of Doubtful Value Various chemicals, including ethylene, ethylene chlorid and ether, have been used for breaking the rest period of tubers, bulbs, and the like. Out of 224 different chemicals tried with potato tubers, Denny 2 ' 8> 4 * obtained especially marked results with ethylene chloro- hydrin, sodium and potassium thiocyanate, ethylene dichlorid, and several other materials. Thiourea forced the development of more than one sprout per eye and more than one eye on each tuber. Results with ethylene were unsatisfactory. 1930] EXPERIMENTS IN FORCING GLADIOLI 353 stem length 1 5? t : lu'S J 10 II = = 2= "22* 2 "^^^ c *-" " c~ ^ ~ : i/- ^- __ -3 S ^ ^ **> (S CS ^ r*5 cs ^< lO f*> **5 fS IO ^" fS C4 O 1 O c a Q S 5^ i : ! B SSSS SS22 gSQSS 5SSS I fa o 3 fe fc " ^OO QOQOOO OOt^OOv OOOOvO^ .-sS 1^ *+ V* H CX^^ (A Q Sao I 1 ZZZS 22ZZ gSS SSSS s* a ft." 5 !? "a S o 55 U il || rfTf"*CC T)T5^ S f^fo 5 < j- I I 2 : a I* O fN ^00 l/l^f *O **> OO OOO <*"* !P U 5* O ^ O 'O ^ **> 00 O 'fOO *O O> OMO O O O O IO 00 4)O *5 ^ ^H ^H rt ** *~' f * ** ft- Cfl rcentage jwering ^ 8S ss 2$ o *-s E S ** \O O p* (N CO 5 c MfS f * W \O*O 1 -OO ests f^ * O J 2 i c 9 CD Ja wJ >> 9 9 a a 8 II SQ 44 >> >> do OO ee OO OO & VOJ 5rf > > 00 ^ j ZZ QQ >^^ Is o : o : o : o J3 -2 -J3 -2 il :| :! i| i| '3 : 2 ^2 I x 1* ^ l^ 1 ^ :=5 :'-5 P |1 |1 zu zw zw Zw zw ZM Z W Z W p oo I 2 1 o> .2 ss "-' s h V 1 1 13 "3 s s 356 BULLETIN No. 357 [October, On the other hand, in both seasons the percentage of corms flowering and the total spikes cut were about 40 and 30 percent lower respectively on the treated as compared with the untreated corms. With Maiden's Blush there was little or no difference in results from the treated and untreated corms. These results show inconsistencies in certain plantings and they are not in entire agreement with other work. There evidently is con- siderable to be learned in regard to the action of chemicals on corms. Denny 6 * showed, for example, that the temperature at time of treat- ment is important. Below 68 F. a dipping solution of ethylene chloro- hydrin was only partially effective in breaking the rest period of potato tubers, while above 90 F. injury and rotting resulted. It is probable that variety or condition of the corms may likewise affect the results. In these experiments corms of Arlon treated with ethylene dichlorid and planted on November 2 rotted in the soil, while two other varieties similarly treated were uninjured. At the present time chemical treatments for gladiolus corms can- not be unreservedly recommended. In the majority of cases in these experiments the percentages of flowers from treated corms were con- siderably lower than those from untreated corms. Effect of Artificial Lighting Corms of Virginia, harvested in California in April and June, 1927, were planted on October 1, half under 500- watt Mazda lamps and the remainder on the opposite bench. The lamps were spaced about 6 feet apart and raised 3 feet above the plants. A muslin curtain was drawn between the two benches at night. The lights were turned on from 5 o'clock in the evening until midnight. In a similar experiment the following season, June-harvested Virginia and Souvenir from Cali- fornia were used. In both experiments the lights were turned on all night, from the time the plants were a few inches high until flowering began. The results are shown in Table 10. In 1927-28 the time to flower was reduced about ten days by the use of artificial light and the percentages of corms flowering and total flowers produced were more than doubled. In the second season there was no significant difference in the time to flower. Virginia under the lights gave increases of 8 and 12 percent respectively in corms flowering and total spikes cut, while the corresponding increases with Souvenir were 17 and 19 percent. The curtain separating the plantings was not entirely opaque, however, and with overnight illumi- 1930] EXPERIMENTS IN FORCING GLADIOLI 357 * 1 i * P c J ^^ ^.p, J5Q R f i 1 number o buds a spil ^ I s * t^ r^ t* oc 1 \ J| S2 SS S55 5* 1 1 i 1 5& SS 22 3 E S8 ss Bg : 5- CD B _e3 Percentage flowering ff>-H IOO t^f*5 fj t^ 00 O ** 00 1 Number sprouted Number planted ** ^^ >** 1 ! i 1 v -g a c. aa g 2 2 * O.M o.JJ O.M i B - 1 -. r^ 00 00 gj N (S a" !~ "s" B 5 '& 5 <8 .5 358 BULLETIN No. 357 [October, 4 stem length J, :,* oo N S! 1 \ < number of buds a spike ;. -; .ej .- X 1 W ll o .g aog 9 g 2S 55 o U U K B X I U $% OC X O ^*(S t^OO ^* (N 1 5 a Spikes cut per 100 corms a- -s S5 S s; w o (K a! I 1 c "S. Percentage flowering OO^H OOOO ^H^< ^t 1 * ^H t^ <*<* \OOO O U D3 in U Number sprouting U W K Number planted O>O>O 00 |I > > > > o o o o o ; o 222 2 ^ 2 ^ 2 ^ Y. /. XZ 1930] EXPERIMENTS IN FORCING GLADIOLI 359 nation the control bench may have received sufficient light to stimulate flowering somewhat, for the yields on the untreated bench seemed un- usually high for early planted stock. Corms Held Over in Storage for Early Forcing Pridham 15 * states that corms held over the summer in cold storage produced normal plants from fall plantings, and that early California grown bulbs were used with comparable results. Jones 9 * held corms over summer in cold storage and planted them in October. The plants made good growth but gave practically no blooms. In 1927 Halley corms were planted which had been held over from the previous season in storage at about 50 F. By the planting time the corms were considerably shrunken. Some flowers were obtained from an August planting, but plantings made in September, October, and November were unsuccessful. About 40 percent bloomed when planted in December, and about 70 percent of the January planting bloomed. New corms planted for comparison in November, December, and January flowered from 49 to 26 days later than the corms held over, the time of flowering depending on the time of planting. The new corms, however, flowered more freely than the held-over corms (Table 11). CONCLUSIONS 1. Young corms 1% inches and more in diameter (No. 1's) are desirable for forcing purposes. Corms between 1% and 1% inches in diameter (No. 2's) may give as good results as the larger corms tho these experiments were not extensive enough to justify the belief that they would consistently give as good results. 2. Corms which have been properly ripened off after forcing may be forced successfully a second time. 3. Corms from cold storage come into growth somewhat slower than corms kept in a warm place. When held in a warm place the corms may show a greater tendency to produce "blind" shoots, but there seems to be no marked advantage in storing corms at tempera- tures below 40 F. Storage at temperatures of 40 to 45 F. early in the season, with perhaps 70 F. or higher for a short time previous to planting, is suggested as likely to be most effective in promoting the healthy development of the corms. 4. Flowering of early planted corms may be stimulated by the use of artificial light. This suggests that the short days of winter are responsible for the slow growth and the high percentage of "blind" 360 BULLETIN No. 357 [October, shoots normally found in winter plantings. The use of artificial light is not recommended for commercial plantings at present on ac- count of the cost. 5. In plantings made before the first of the year, there will be a relatively large proportion of "blind" shoots, the number depending to a certain extent upon the variety. Under ordinary conditions, early planting of fall-dug corms will not insure flowers either proportion- ately early or in paying quantities. 6. Corms may be forced into early growth with certain chemicals such as ethylene dichlorid or ethylene chlorohydrin. Such treatments are not yet standardized, however, and may be ineffective or injurious. They are not recommended, therefore, as a regular commercial prac- tice. 7. The holding-over of corms for early planting the following season was not a practical success in these experiments. LITERATURE CITED 1. BOSWELL, V. R. Influence of the time of maturity of onions on the behavior during storage, and the effect of storage temperature on subsequent vegetative and reproductive development. Amer. Soc. Hort. Sci. Proc. 20, 234-239. 1924. 2. DENNY, F. E. Hastening the sprouting of dormant potato tubers. Amer. Jour. Bot. 13, 118-125. 1926. 3. Second report on the use of chemicals for hastening the sprouting of dormant potato tubers. Amer. Jour. Bot. 13, 386-3%. 1926. 4. Effect of thiourea upon bud inhibition and apical dominance of potato. Bot. Gaz. 81, 297-311. 1926. 5. Chemical treatments for controlling the growth of buds of plants. Indus, and Engin. Chem. 20, 578-581. 1928. 6. The importance of temperature in the use of chemicals for hastening the sprouting of dormant potato tubers. Amer. Jour. Bot. 15, 395-404. 1928. 7. FLOYD, W. L. Storage experiments with gladiolus in Florida. Gladiolus Rev. 5, (3), 99. 1928. 8. HABER, E. S. A preliminary report on the stimulation of bulbs and seeds with ethylene. Amer. Soc. Hort. Sci. Proc. 23, 201-203. 1926. 9. JONES, L. H. The rest period of gladiolus. Mass. Agr. Exp. Sta. Bui. 247, 310. 1929. 10. LAURIE, ALEX. Breaking the rest period of the gladiolus. Florists Exch. 68. 510. 1928. 11. LOOMIS, W. E. Temperature and other factors affecting the rest period of potato tubers. Plant Physiology 2, 287-302. 1927. 12. LOOMIS, W. E., and EVANS, M. M. Experiments in breaking the rest period of corms and bulbs. Amer. Soc. Hort. Sci. Proc. 25, 73-79. 1928. 13. MILLER, D. R. Gas treatment of bulbs. Gladiolus Rev. 5 (7), 244. 1928. 14. OVEN, H. C. The relation of size of bulbs to flower production. Gladiolus Rev. 5 (4), 150. 1928. 1930] EXPERIMENTS IN FORCING GLADIOLI 361 15. PRIDHAM, A. M. S. The culture of the gladiolus as a greenhouse crop. Gladiolus Rev. 6 (9), 333. 1929. 16. Rhode Island Agr. Exp. Sta. 41st Ann. Rpt., 51. 1929. 17. VACHA, G. A., and HARVEY, R. B. The use of ethylene, propylene, and similar compounds in breaking the rest period of tubers, bulbs, cuttings, and seeds. Plant Physiology 2, 187-192. 1927. UNIVERSITY OF ILLINOIS URBANA