OEGAXS OF EEPEODrCTION. 



329 



(Adenantkcra) red, in French Beans and the seeds of the Castor 

 Oil plant it is beautifully mottled, and in the seeds of other 

 plants various different tints may be observed. 



The testa also varies in texture, being either of a soft nature, 

 or fleshy and succulent, or more or less spong}-, or membranous, 

 or coriaceous, or when the interior of its cells is much thickened 

 by secondary deposits it assumes various degrees of hardness, 

 and may become -noody, crustaceous, &c. 



The surface of the testa also presents various appearances, 

 and is often furnished with different appendages. Thus it may 

 be smooth or glabrous, as in Adenanthera ; or wrinkled, as in 

 Nigella ; striated, as in Tobacco ; marked with ridges and fur- 

 rows, as in Delphinmm {fig. 731) ; netted, as in Nashirthim{fig. 

 729) ; alveolate or pitted, as in the Poppy {fig. 730) ; tuberculated, 

 as in Chickweed {fig. 732) ; spiny, as in the Mulberry, &c. The 

 testa of some seeds is also furnished with hairs, which may 

 either cover the entire surface, as in various species of Gossypium 

 where they constitute the material of so much value, called Cot- 

 ton, and in the Silk-cotton tree {Bombax) ; or they may be con- 

 fined to certain points of the surface, as in the Willow {fig. 

 736), Asclepias {fig. 735), Apocynum and Epilobmm {fig. 741); 



Fig. 733. Fig. 734. 



Fig. 735. 



Fig. 736. 



Fig. 733. Seed of a species of Pinus, with a winged ap- 

 pendage, vj. Fig. 734. Marginate or bordered seed of 



Sandwort (^re?iar((i). Fig. 735. Comose oval seed of 



Asclepias. Fig. 736. Comose seed of a species of 



"Willow. 



in the latter cases the tufts of hairs thus formed constitute what 

 is called a coma, and the seed is said to be comose. The hairs 

 thus found upon the surface of seeds facilitate their dispersion 

 by the wind. 



Other seeds, again, have winged appendages of various kinds, 

 which also render them buoyant and facilitate their dispersion ; 

 thus in the Sandwort {Arenaria) {fig. 734), the testa is prolonged. 



