SEED OR MATURE OVULE. 275 



577. Besides being contained in a pericarp, the seed has its own 

 peculiar coverings. Like the ovule, it consists of a nucleus or kernel, 

 and integuments. In some instances, although 

 rarely, all the parts of the ovule are visible 

 in the seed, viz., the embryo- sac, or quintine, 

 the quartine, the tercine formed from the 

 nucleus, the secundine, and the primine. 

 In fig. 480, there is a representation of the 

 seed of Nymphaea alba, in which s e indicates 

 the embryo-sac, containing the embryo, e; 

 v the cellular farinaceous covering (quar- 

 tine), formed round the embryo-sac ; m t, 

 membrane formed from the nucleus (tercine); 

 m i, the secundine; t, the primine. In general, 

 however, great changes take place by the 

 development of the embryo; the embryo -sac 

 is often absorbed, or becomes incorporated 

 with the cellular tissue of the nucleus ; the 

 "same thing occasionally takes place in the 

 secundine, so that in the ripe seed, all that 

 can be detected is the embryo and two 

 coverings. The general covering of the 

 seed is called spermoderm (aveppu, seed, 48 



and tiepftu, covering). In order to correspond with the name applied 

 to the covering of the fruit, it ought more properly to be denominated 

 perisperm (wtpl, around, and o-z-g^a, seed). This latter term, however, 

 has been appropriated to a certain portion of the seed, to be afterwards 

 noticed under the name of albumen. 



578. The Spciinoderm usually consists of two parts, an external 

 membrane, called the episperm or testa (sirl, upon, or on the outside, 

 and ovigftK, a seed, or testa, a shell), and an internal membrane, called 

 endopleura (Ii/Sov, within, and TT^SV^X, side). The former may consist 

 of a union of the primine and secundine, or of the primine only, when 

 as occasionally happens, the secundine is absorbed ; the latter, of a 

 combination between the membrane of the nucleus and the embryo - 

 sac, or of one of these parts alone. Sometimes the secundine remains 

 distinct in the seed, forming what has been called a mesosperm (/twos, 

 middle) ; and when it assumes a fleshy character, it has received the 

 name of sarcosperm or sarcoderm (?P|, flesh). 



579. The .Episperm consists of cellular tissue, which often assumes 



Fig. 480. Young seed of Nymphsea alba cut vertically. /, Fnniculus or umbilical cord. 

 a, Arillus derived from the placenta, r, Kaphe. e, Chalaza or eotyledonary end of the seed. 

 h, Hilum or base of the seed, m, Micropyle or foramen, t, Testa or Primine. mi, Secundine. 

 mt, Tercine or membrane of the nucleus, n, Farinaceous external perisperm or albumen formed 

 by the nucleus, and probably constituting the quartine of Mirbel. s e, s e, Internal perisperm 

 or endosperm formed by the embryo-sac, e, The embryo. 



