LEGUMINOUS FORAGE CROPS 123 



are single. The seeds all have the general structure described 

 in the common field bean. (255) The legumes differ from 

 the cereals and other seeds of the grass family in that the 

 seeds of the latter have a small embryo, most of the seed con- 

 sisting of endosperm, while the seed skin of the legumes is 

 completely filled by the large embryo. This accounts for the 

 highly nitrogenous character of the legumes and for the high 

 percentage of starch in the cereals. 



There is one tap root with many lateral branches, the latter 

 mostly near the surface of the soil. So far as known, all 

 leguminous plants bear root-tubercles or nodules on their roots 

 under suitable conditions, from which it is inferred that all 

 possess, with the aid of bacteria, the power of assimilating the 

 free nitrogen of the air. 



130. Variations. Great variations in botanical characters 

 and in habits of growth exist among the different species of 

 legumes, and considerable variations are often found among 

 different individuals of the same species. 



In general, the plant varies in size, shape, and hairiness of 

 the parts, and in proportion of main stem, branches, and leaves. 

 The stems may be erect, decumbent, spreading, or trailing. 

 Some species are strongly stoloniferous, as white clover; some 

 slightly so, as alsike clover; and others not at all, as alfalfa. 

 The leaflets may radiate from a common center, palmately 

 lobcd, as in clover; the side leaflets may be arranged along the 

 side of the midrib, pinnate, as in alfalfa; and may have an 

 even number of leaflets, pari-pinnate , or an odd number, impart- 

 pinnate. When there is an even number of leaflets the midrib 

 may end in a tendril, as in vetch. The stipules may be attached 

 to the petioles or may be free. The variety of forms of the 

 stipules constitutes one of the most distinguishing vegetative 

 characters of the legumes, especially in the clovers. 



The flowers may arise singly or may be distributed along 



