2-42 FIELD CROP PRODUCTION 



ferent from the grasses is in the structure of the seed. 

 The seeds of the grasses have a relatively small embryo, 

 and a large endosperm, while those of the legumes have a 

 very large embryo, which completely fills the seed coat. 

 It is due to the absence of the endosperm and to the large 

 proportion of embryo, which contains a high percentage 

 of nitrogen, that the legumes are so highly prized for 

 their nitrogenous feeding value. 



242. Pollination. — Unlike most members of the grass 

 family in which the pollen is spread by the wind, the flowers 



Fig. S5. — Legume flower. Fig. 86. — Cross section. 



of the legumes are so constructed that they require the 

 services of certain insects to carry the pollen for them. 

 The following quotation from Percival tells how, with 

 their conspicuous flowers, they attract the insects, and 

 in return for the nectar given them in payment for their 

 visit, they unwittingly extract from them a friendly 

 service. " The flowers of the Papilionaceae are all 

 specially adapted for insect pollination. The ' standard ' 

 acts as a conspicuous attractive banner. The ' wings ' 

 and ' keel ' petals are often interlocked near their bases 

 in such a manner that when an insect of sufficient weight 

 alights on the ' wings,' the latter are pressed downwards 



