THK ALBUMKN AND KMBKYO. 



323 



the Barberry, &c. ; when it chiefly consists of mucilage or vegetable 

 jelly, as in the Morning-Glory and the Mallow, it is said to be muci- 

 laginous ; when it hardens more, and becomes dense and tough, so 

 as to offer much resistance to the knife, as in the Coffee, the Blue 

 Cohosh, &c., it is corneous, that is, of the texture of horn. Between 

 these all gradations occur. Commonly the albumen is a uniform 

 deposit. But in the nutmeg, as also in the seeds of the Papaw (Fig. 

 658), and of all plants of the Custard-Apple Family, it presents a 

 wrinkled or variegated appearance, owing to numerous transverse 

 divisions, which are probably caused by inflections of the innennost 

 integument of the seed : in these cases the albumen is said to be rumi- 

 nated. The albumen may orighiate from new tissue formed either 

 within the embryo-sac (579), which is probably the more common 

 case ; or in the nucleus of the ovule exterior to the embryo-sac, 

 which is certainly the case in the Water-Lily and its allies, and in 

 Saururus ; for here the thickened embryo-sac persists within or at 

 one extremity of the copious albumen ; or both kinds may coexist. 

 When this is the case, the outer albumen may be distinguished as the 

 perisper7n, and the inner as the endosperm. 



G34. Seeds provided with albumen (as in Fig. 599, 600, 605, 606, 

 609, 610-616, 622, &c.) are said to be albuminous; those destitute 

 of it (as in Fig. 607, 629, 110, 120, &c.) are exalbuminous. The 

 comparative amount of the albumen, and its relation to the embryo 

 in various seeds, may be seen on inspection of many of the subjoined 

 fljrures. 



635. The Embryo, or Germ, being an initial plantlet or individual, is 

 of course the most important 23art of the seed : to its production, protec- 



FTG. 604. Seed of a Violet (anatropoua), enlarged: a, hilum or acar j &,rhaphe; c, chalaza. 



FIG. 605. Vertical section of tlie same, showing tlie straight embryo in the axis of the mealy 

 albumen. 



riG. 606. Vertical section of the (orthotropous) seed of Buckwheat, showing the embryo 

 folded round in the mealy albumen. 



FIG. 607. Vertical section of the (anatropous) seed of Elodea Virginica, the embryo com- 

 pletely filling the coats. 



FIG. 608. Seed of Delphinium tricome (anatropous), enlarged ; a, the hilum ; J, the 

 rhaphe ; c, the chalaza. 609. Vertical section of the same : c, the chalaza ; d^ the testa j e, 

 the tegmen i /, the albumen ; g*, the minute embryo near the hilum, a. 



