ORGANS OF REPRODUCTION. 



339 



manner, hairy seeds should be carefully distinguished from the 

 pappose fruits of the Compositae and Valerianacere (figAo2), &c., 

 •where the hairy expansions proceed from the calyx. 



Beneath the testa, the raphe or vascular cord connecting the 

 hilum with the chalaza is found, (this is only clearly distinguish- 

 able in anatropous seeds) (fig. 734, r); its situation is frequently 

 indicated by a projecting ridge on the surface of the seed, as in 

 the Orange, while at other times, it lies in a furrow formed in 

 the substance of the testa, so that the surface of the seed is 

 smooth, and no evidence is afforded externally of its position. 

 The testa is also usually marked externally by a scar indicating 

 the hilum or point by which it is attached to the funiculus or 

 placenta. The micropyle may be also sometimes seen on the 

 surface of the testa, as in the Pea (Jig 725, m), but in those 

 cases where no micropyle can be detected externally, its 

 position can only be ascertained by dissection, when it will be 

 indicated by the termination of the radicle: that is directed (as 

 already noticed) towards the micropyle. In some seeds, as in 

 the Asparagus, the situation of the micropyle is marked by a 

 small hardened point, which separates like a little lid at the 

 period of germination. This has been termed the embryutegia. 



On removing the testa, we also observe 

 the raphe, which frequently ramifies over 

 the inner coat, and where it terminates, it 



constitutes the chalaza. The structure 



and general appearances of these ditferent 



parts have been already described. 



b. Tegmen, endopleura, or internal 



membrane (figs. 725, e, and 734). — The 



inner membrane or integument of the 



seed is essentially parenchymatous like 



the outer. This coat may be either 



formed from the tercine only, as is usually 



the case ; or of the latter combined with 



the embryo-sac ; or, in some cases, pro- 

 bably from the secundine of the ovule. 



This layer appears at times to be alto- 



gether wanting, which probably arises ^.j^, 734. young anatro- 



from its complete incorporation or ad- rous seed of the white 



herence to the testa. Sometimes the 



embryo-sac in the ripe seed remains dis- 

 tinct from the albumen of the nucleus 



(fig. 739), and remains ir the form of a 



bag or sac which envelopes the embryo, 



as in the Nymphseaceae, Piperaceae, and 



Zingiberaccffi. To this distinct membrane the name of vitellus 



has been given. 



z2 



Water-Lily (XympJicea 

 alba) cut vertically, r. 

 Funiculus, a, a. Arillus. 

 T. Integuments of the 

 seed. Jf. Nucleus, k. Ra- 

 phe, ch. Chalaza. M. Mi- 

 cropyle. s. Embryo-sac. 

 e. Rudimentary embryo. 



