SEKD. 



95 



the distinction of the two great classes of flowering plants, on the 

 fact that the radicles of one were inclosed within a sheath, while 

 the radicles of the others were destitute of such a covering. 



Y' 165. The embryo of the Pine, although reckoned among the 

 dicotyledons, has several cotyledons ; but these are opposite, 

 forming a whorl. (Fig. 163.) The distinction made by this 

 arrangement of the cotyledons, being alternate in Endogens, and 

 opposite or verticillate in Exogens, will always be a guide in de- 

 termining to which an individual should belong. An equally 

 sure mark of distinction is the mode of germination, whether of 

 the endorhizal or exorhizal manner. 



,^ig. 163. 



Fig. 164. 



cot. 



A Seed with Albnmen. 

 e, embryo ; aJ, albumen. 



Embryo of the Pine. 



166. The albumen', when present, is a substance surrounding 

 the embryo, and is supposed by some to be the solidified amnios. 

 (Fig. 164, al.) It varies remarkably in consistence and appearance ; 

 sometimes it is farinaceous, consisting of cells filled with starch, 

 as in our common grains, wheat, oats, corn, &c. Sometimes 

 abundant and fleshy, as in the cocoanut, and often contains oil, 

 as in the castor-oil plant. At other times it is hard and bony, 

 as in coffee and the vegetable ivory-nut, which is the albumen 

 of the seed of the Phytelephas. The albumen is the store of 

 food laid up for the nourishment of the embryo, which it con- 

 sumes in the early development of the plant. In size it varies 

 from an exceedingly small, quantity, as in the grasses, to the 

 amount of several ounces in the cocoanut. It is sometimes 

 perforated by dry cellular tissue, in which state it is said to be 

 ruminated. 



167. To determine the several parts of the seed which we 

 have above defined, and the position they occupy in reference to 



16o. How is the embryo of tho pine? How arc the cotyle(lon3 ar- 

 ranged in the two great classed of plants?— 106. What is the albumen? 

 What are some of its varieties ? AVhat is vegetable ivory ? What is the al- 

 bumenfor? Whatof its size?— 167. What is of great practical importance* 



