THE ANGIOSPERMAE 



1501 



with the cotyledons so much enlarged that they practically fill the seed, as 

 we see in peas and beans. This enlargement may lead to complex folding 

 of the two cotyledons, as in the seed of Fagiis, or the condition in species 

 of Geranium, where they are rolled together. The size of the containing 



Fig. 1375. — Capsella bursa-pastoris. Longitudinal section of 

 a seed showing the incumbent embryo. 



seed is seemingly the controlling factor, the packing of the cotyledons being 

 adapted to it, not vice versa. The paired cotyledons may be of unequal 

 development, which modifies their packing pattern, or they may both be 

 asymmetrical, which is associated with dorsiventrality of the embryo as a 

 whole, the larger side of each cotyledon lying towards the dorsal or larger 

 side of the embrvonic axis. The behaviour of the cotyledons at germina- 

 tion, which we shall have something to say about later, is naturally related 

 to their symmetry and position beforehand in the seed, which may be 

 influenced by factors that have nothing to do with germination. For 

 example, the convoluted cotyledons of the Walnut are related to the inner 

 convolutions of the endocarp wall; broad or narrow cotyledons may be 

 related to the shape of the embryo sac; divided cotyledons to their function 

 in absorbing nutriment from the endosperm, as is beautifully seen in the 

 ruminate endosperm of Myristica; or finally to difi^erences of nutrition on 

 different sides during the development of the embryo. 



