Ch. VIII, 21 



MORPHOLOGY OF SEEDS 



375 



Fig. 209. — Grain of 

 Corn, in longitudinal 

 section ; X 3. 



At the right is the 

 embryo, showing plu- 

 mule, primary root, 

 and hypoeotyl. In the 

 latter can be seen the 



of the nucellus by the endosperm) all of the space within the 

 seed coats. Such are the albuminous seeds, in the germi- 

 nation of which the embryo absorbs the 

 endosperm through its cotyledons. In 

 the ex-albuminous seeds, however, this 

 absorption of the endosperm occurs 

 before germination, and this is the mean- 

 ing of the difference between the two 

 kinds. It is in correlation with this 

 further stage of development that ex- 

 albuminous seeds have so often a 

 plumule, while albuminous kinds have 

 only the undeveloped foundation of a 

 bud. 



Third of the parts are the seed coats. 

 Oftenest there is but one, which is thick, „, , 



' , ' nbro-vascular system 



hard, and woody, and has the obvious extending into the large 



function of protecting the embryo against scutellum which 



' " . . forms a haustonal or- 



injury during the period of dissemina- gan for absorbing the 

 tion. Sometimes there is also an inner endosperm, -«» (looser 



texture) and eg (more 

 coat, then usually compact texture). It 



membranaceous, and '^ doubtful whether the 



' cotyledonisrepresented 



less often an addi- by the scutellum, by 



tional outer coat, 

 called an aril, which 

 is generally loose 

 from the others and has obvious con- 

 nection with dissemination, as in cases 

 earlier mentioned, i.e. the Yew berries 

 Fig. 270. — Aibumi- (page 351) and the Water-lily seeds 

 nous seed, of Castor (page .361). There is .some structural 



Bean, in section; X 2. . 1,1 



The embryo Ues em- Connection, not yet luUy understood, 

 bedded in endosperm ; between these arils and the little insig- 



below is a caruncle. . , . . , 



mficant and seemingly lunctionless swell- 

 ing called the strophiole, occurring near the hilum in 

 some seeds, and the much larger caruncle (Fig. 270), an 



the sheath leaf of the 

 plumule, or by both to- 

 gether. (From Goebel.) 



