FROST RESISTANCE. 15 



very pale, especially when old, and are sometimes erroneously called 

 white, but no truly white seeds are known in soy beans. In several 

 varieties with straw-yellow seeds, like the Mammoth, the seeds have 

 a greenish tinge if harvested before full maturity, making it difficult 

 to distinguish them from varieties whose fully mature seeds are 

 greenish yellow. The latter again merge by very fine gradations 

 into olive and from this into brown. 



Bicolored seeds occur in but few varieties. The commonest are 

 green or yellow with a saddle of black, the latter not sharply de- 

 limited. Two varieties have their seeds brindled brown and black, 

 the two colors somewhat concentrically arranged. One variety has 

 black seeds faintly marked with minute brown specks. On heter- 

 ozygote plants the seeds are often irregularly bicolored, as discussed 

 on another page. 



The hilum or seed scar is pale in some varieties and dark in others 

 and therefore often of value to distinguish varieties. In a few 

 varieties, as in Ito San, there is a minute brown spot on the micropyle 

 which is diagnostic. 



The germs or embryos of soy-bean seeds are yellow, except in the 

 green-seeded and part of the black-seeded sorts, in which they are 

 green. 



FROST RESISTANCE. 



Soy beans will withstand considerable frost, both in the spring, when 

 young, and in the fall, when about mature. The trials at the Arling- 

 ton Experimental Farm, near Washington, D. C, indicated that 

 varieties vary to a considerable degree in this respect. The first 

 frost in the fall of 1909 at this farm came on October 13, the mini- 

 mum temperature being 31° F. The top leaves of nearly all varieties 

 were slighty touched by this frost. The varieties from India were 

 injured to a greater extent than any of those previously grown. The 

 first killing frost occurred on October 29, 1909, the minimum tem- 

 perature being 27° F. In the majority of the late and very late 

 varieties the plants were killed. However, several varieties still 

 retained a fair percentage of green leaves, and the pods were but 

 slightly touched. The Riceland and Barchet varieties showed con- 

 siderable frost resistance, about 50 per cent of the leaves and all the 

 pods remaining green after this later frost. The most resistant 

 variety in the trial was No. 20798E, a selection from No. 20798, 

 Barchet, this variety still having about 70 per cent of green leaves 

 and no pods injured. Those varieties showing any degree of resist- 

 ance still retained green leaves and pods on November 15, the tem- 

 perature meantime not reaching the minimum of October 29. 



In a variety trial at Muskegon, Mich., in 1909, the Guelph, Ito San, 

 and Ogemaw varieties were found to be quite frost resistant and the 

 58576°— Bui. 197—10 2 



