330 



ORGANOGRAPHY. 



Fig. 737. 



so as to form a winged margin to the seed, which is then de- 

 scribed as marginate or bordered; in the seeds of the Pinus {fig, 

 733), Catalfa, Bignonia, Stoietenia, Moringa, &c., the testa forms 

 wings, and the seed is winged. These winged seeds must be 

 carefully distinguished from samaroid fruits, such as the Ash, 

 Elm, and Maple {fig. 690), where the wing is an expansion 

 of the pericarp instead of the seed. In like manner, hairy seeds 

 should be carefully distinguished from the pappose fruits of the 

 Compositse and Valerianacese {fig. 450), &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) {figs. 737 and 747, 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 po- 

 sition. 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 {fi^. 728, 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 : this being 

 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 emhryotcgia. 



On removing the testa, we also observe 

 the raphe, which frequently ramifies over 

 the inner coat, and where it terminates, it 

 constitutes the chalaza {fig. 1Z1, ch). The 

 structure and general appearances of these 

 different parts have been already de- 

 scribed. 



b. Tegmen, endopleura, or internal 

 membrane {fig. 728, e). — The inner mem- 

 brane or integument of the seed is essen- 

 tially 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, probably from the secundine of the ovule. This 

 layer appears at times to be altogether wanting, which probably 



Fig. 737. Young anatro- 

 pous seed of the White 

 Water-Lily (Nymphcca 

 alba) cut vertically, f. 

 Funiculus, a, a. Arillus. 

 T. Integuments of the 

 seed. X. Nucleus. R. Ra- 

 phe, ch. Chalaza. M. Mi- 

 cropyle. s. £mbryo-sac. 

 e. Rudimentary embryo. 



