SEED OK MATUEE OVULE. 



327 



in the secundine, so tliat in the ripe seed, all that can be detected is 

 the embryo with two coverings. The general 

 coveruig of the seed is called spermoderm 

 (<S'7tsg/ji,a, seed, and S's^fj,a, covering). In 

 order to correspond with the name applied 

 to the covering of the fruit, it ought more 

 properly to be denominated perisperm {•jrigi, 

 around, and dvig/na, seed). This latter 

 term, however, has been appropriated to 

 a certain portion of the seed, to be after- 

 wards noticed under the name of albumen. 



The Speemodbem usually consists of 

 two parts an external memlrane, called the 

 episperm or testa [siri, upon, or on the out- 

 side, and (svigfia, a seed ; testa, a shell), and 

 an internal membrane, called endopleura (hSoii, 

 within, and -rXsuga, side or rib). The former 

 may consist of a union of the primine and 

 secundine, or of the primine only, when, as 

 occasionally happens, the secundine is ab- 

 sorbed; the latter, of a combination be- 

 tween the membrane of the nucleus and the 

 embryo-sac, or of one of these parts alone, 

 remains distinct in the seed, forming what has been called a mesosperm 

 (fieeog, middle) ; and when it assumes a fleshy character, it has re- 

 ceived the name of sarcosperm or sarcoderm (cajf, flesh). 



The Epispeem consists of cellular tissue, which often assumes 

 various colours, and becomes more or less hardened by depositions in 

 its interior. In Abnis precatorius and Adenanthera pavonina it is 

 of a bright red colour ; in French beans it is beautifully mottled ; iu 

 the Almond it is veined ; in the Tulip and Primrose it is rough ; in 

 the Snapdragon it is marked with depressions ; in Cotton and Ascle- 

 pias it has hairs attached to it ; and in Mahogany and Bignonia it 

 is expanded in the form of wing-like appendages. In CoUomia, Acan- 

 thodium, and other seeds, it contains spiral cells, from which, when 

 moistened with water, the fibres uncoil in a beautiful manner. Spiral 

 cells are also seen in the episperm of the seeds of Oobsea and' Calem- 

 pelis soaber. In the episperm of the seed of Ulmus campestris the 

 cells are compressed, and their sinuous boundaries are traced out by 

 minute rectangular crystals adhering to their walls. 



Fig. 676. Young seed of Nymphsea alta cut vertically. /, Fuuioulua or umbilical cord, 

 a, Arillus derived from the placenta, r, Eaphe. c, Chalaza or cotyledonary end of the 

 seed. Ji, Hilum or base of the seed, m, Micropyle or foramen. (, Testa or primine. mi, 

 Secundine. mt, Terbine or membrane of the nucleus, n, Farinaceous external perisperm 

 or albumen formed by the nucleus, and probably constituting the quartine of Mirbel. se, 

 se. Internal perisperm or endosperm formed by the embryo-sac. e. The embryo. 



Fig. sra. 

 Sometimes the secundine 



