ORGANS OF REPRODUCTION. 



335 



by a short raphe, ?•. In the semi-anatropous oviile the relative 

 position of the parts is the same {fiy. 723), but the funiculus 

 f, is here parallel to the ovule, instead of being at right angles 

 to it. 



The further development of the ovule, and the distinctive 

 characters it presents in Gymnospermous Plants, will be de- 

 scribed under the head of Eivibryogent. 



Fig. 725. 



2. The Seed. 



The seed is the mature or fecundated ovule. It consists essenti- 

 ally of the young plant or embryo, enclosed in integuments, of 

 which there are usually two. Like the ovule, it is either attached 

 directly to the placenta, in which case it is sessile, or by means of 

 a stalk, called the funiculus (Jig. 725,/); its point of attachment 

 is also termed the hilum or umbilicus. 

 The position of this hilum may be com- 

 monly seen on seeds which have separated 

 from the funiculus or placenta, bythe pre- 

 sence of a scar, or in a difference of colour 

 to the surrounding integuments. The hi- 

 lum varies much in size, being sometimes 

 very minute, while in other cases it extends 

 for some distance over the surface of the 

 integuments, as in the Horse-Chestnut, 

 Muciina, &c. The centre of the hilum, 

 through which the nourishing vessels Fig. 72.5. The seed of a 

 pass, has been called the ompkalodium. ^^oTidVni'ir^"^! 

 The hilum as in the ovule, indicates - 



the base of the seed, while the apex is 

 represented by the chalaza. This chalaza 

 (fig 12f), ch) is generally more evident 

 in the seed than in, the ovule, and is 

 frecjuently of a different colom*. It is 

 well seen in the Orange, and commonly 

 in anatropous seeds, in which case also, 

 the raphe may be generally noticed form- 

 ing a projection on the face of the seed. 



The micropyle also, although smaller and less distinct owing 

 to a contraction of the surrounding parts, may be observed on 



Placenta. /. Funiculus. 

 rcq). Raphe, ck. Clialaza. 

 m. Micropyle. te. Testa 

 or episperm. e. Endo- 

 pleura. The part -within 

 the endopleura is the 

 nucleus of the seed, and 

 is formed of cotyledons, c, 

 gemmule or plumule, g, 

 radicle, r, and t stalk be- 

 tween gemmule and ra- 

 dicle. 



the seed (fig. 



m). The detection of this micropyle is 



of some practical importance, as the radicle, r, of the embryo, 

 with a few exceptions, is directed towards it. It should be 

 noticed, that while the micropyle constitutes the organic apex 

 of the ovule, the chalaza indicates that of the seed. 



The tenns orthotropous, campylotropous, anatropous, &c., 

 arc applied to seeds in the same sense as to ovules; conse- 

 quently the hilum, chalaza, and micropyle, have the same 



