VERNALIZATION EXPERIMENTS WITH FORAGE CROPS 5 



With reference to conditions for growth in the greenhouse, open 

 field, and coldframes, it should be recorded that in the open field 

 conditions were less favorable for growth than in the greenhouse and 

 in coldframes where artificial watering was practiced; and in the case 

 of the greenhouse plantings, temperature conditions were more 

 favorable for rapid growth during the early period of development. 

 The effect of the vernalization is most definitely shown in the green- 

 house plantings. Only in the case of hairy vetch is the development 

 of the preliminarily moistened and then dried seed advanced and this 

 only in the coldframe and field-planted lots. 



It seems evident that lupines require a shorter period of cold to 

 induce normal development than some other winter annuals. The 



Figure 2. 



-Crimson clover. The vernalized plants (B) are in bloom and later matured while the check 

 plants (^4) never bloomed. 



intensity of the cold and the time of exposure required probably are 

 contingent on other environmental factors. The white sweet-clover 

 in this experiment showed no effect of the cold treatment and red 

 clover showed but little if any, while the hairy vetch and field pea 

 were only slightly influenced. This may have been due to insufficient 

 time or insufficient growth activity during the cold period. Johnson 5 

 reports that sweetclover seedlings 3 inches high gave greater response, 

 for the same period of cold treatment, than did three-leaf seedlings, 

 while swollen seed under the same conditions gave no response. 

 That all winter annuals may require some cold for their best develop- 

 ment and that all may differ somewhat in this requirement is at least 

 reasonably possible. 



5 Johnson, I. J. the physiological effect of low temperature on the biennial growth of sweet- 

 clover (MELTLOTUS alba). Sei. Agr. 12: 746-748, illus. 1933. 



