76 



DEVELOPMENT OF FLOWERING OK PH^NOGAMODS 



plumule, which gives rise to the first leaves that appear. As the 

 radicle itself scarcely if at all elongates, the cotyledons are not ele- 

 vated in germination but remain under ground (i. e. are hypogaous), 

 or rest on the surface of the soil. 



125. In all the foregoing illustrations the 

 nourishment provided for the growth of the 

 embryo into a plantlet is deposited in the 

 tissue of the embryo itself, i. e. in the seed- 

 leaves. In other 



cases it is depos- 

 ited around the 



embryo ; when it 



forms what is 



commonly called 



the Albumen of 



the seed. This 



makes up the 



principal bulk of 1^^ 



the seed in the' 



Buckwheat, In- 

 dian Corn (Fig. 



126, 127), and 



most other sorts 



of grain. The 



greater the quan- 

 tity of this, the 



floury part of the 



seed, the smaller 



or less developed 



is the embryo, 



or the less thick 



are its cotyledons. 



In the Morning- 121 



Glory, for instance (Fig. 122-125), where the embryo is surround- 

 ed by mucilaginous albumen, the cotyledons appear in the seed as 

 a pair of very thin and well-foiTned green leaves. These absorb 

 the nourishment required for the plantlet's earliest growth from 



FIG. 118. Embryo of a Pea. 119. The same in germination. 



FIG. 120. An acorn, divided lengthwise, showing a section of the very thick and fleshy 

 cotyledons and the very small radicle. 121. Germination of the acorn. 



