41 6 BOTANY Ol' CROP PLANTS 



the fruit is a loment, that is, a jointed indehiscent legume, 

 constricted between the seeds. The style, calyx, and 

 withered stamens are often partly persistent in the fruit. 



Seeds. — The seeds are usually without endosperm; the 

 cotyledons are thick and full of food. 



The seeds of legumes are noted for their great longevity. 

 Some have been known to retain their viability for 150 to 

 250 years. This is correlated with their very hard, imper- 

 meable seed coats. So-called "hard seeds" are very com- 

 mon in the pea family. Such seeds are tardy in their ger- 

 mination, either under laboratory or iield conditions. As a 

 rule, only a portion of a crop of seeds is hard, although in 

 some cases the whole crop may be hard. It is claimed that a 

 larger percentage of hard seeds is produced in dry chmates 

 or when ripening takes place under dry seasonal conditions 

 than in moist climates or moist seasons. The permeabiUty 

 of leguminous seeds can be increased by "scarifying," 

 that is, passing them through a machine that abrases the 

 surfaces. The ordinary alfalfa huUer is effective as an 

 abraser, as is shown by the experiments of Harrington who 

 found that alfalfa seed, grown imder a variety of soil and 

 cHmatic conditions, had about 90 per cent, of hard seeds if 

 hulled by hand and only about 20 per cent, if hulled by 

 machine. 



Key to Principal Genera of Leguminos^ 



Plants with tendril-bearing leaves (Fig. 19). 

 Calyx lobes leafy; stipules large, rounded (Fig. ig), Pisum (pea). 

 Calyx lobes not leafy; stipules mostly small, pointed. 

 Style slender, bearded at the tip (Fig; 173, A), Vicia (vetch). , 



Style flattened, bearded along the inner side (Fig. 173, B), Lathyrus 

 (vetchling). 

 Plants without tendril-bearing leaves. 

 Leaves palmately three-foliate (Fig. 183), Trifolium (clover). 

 Leaves pinnately three-foliate, rarely five- to seven-foliate (Fig. 182). 



