76 



DEVELOPMENT OF FLOWERING OR PH^NOGAMOUS 



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

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

 vated in germination but remain under ground (i. e. are hypog^ous), 

 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 



princiiml bulk of MJ 



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- 

 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-formed green leaves. These absorb 

 the nourishment required for the plantlet's earliest growth from 



121 



FIG. 118. Embrj'o 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. 



