328 OEGANOGEAPHY. 



Fig. 729. Fig. 730. Fig. 731. Fig. 732. 



Fig. 129. Rounded seed of the Vf ^ter-Cr ess (Nasturtium offlcinale). The testa 



is reticulated or netted. Fig. 730. Reniform or kidney-shaped seed 



of the Poppy, with an alveolate or pitted testa. Fig. 731. Obovate 



seed of the Larlcspur (Delphiniian), the testa of which is marked v/ith 



ridges and furrows. Fig. 732. Seed of Chickweed (.Stellaria), the testa 



of which is tuberculated. 



integuments, which have been variously named by different bo- 

 tanists. The terms most frequently used, are testa or episperm 

 for the outer coat ; tegmen or endopleicra for the inner ; and 

 spermoderm for the two when spoken of collectively. Some 

 writers, however, use the word testa in a general sense for the 

 two integuments, and call the external one spermoderm. The 

 names first mentioned are those which will be used in this 

 volume. Some botanists, again, describe a third integument 

 under the name of sarcoderm ; this layer, however, is commonly 

 and more accurately considered as but a portion of the outer in- 

 tegument, in which sense we understand it here. 



a. Testa, episperm, or outer integument {fig. 728, te). This 

 integument may be either formed of the primine of the ovule 

 only, or, as is more fi-equently the case, by the combined primine 

 and secundine. The testa is generally composed of ordinary 

 parenchymatous cells, but in some seeds, as in those of Acan- 

 thodmm, we have in addition a coating of hair-like cells con- 

 taining spiral fibres ; these cells are pressed closely to the 

 surface of the seed by a layer of mucilage. If such seeds be 

 moistened with water, the mucilage which confines these hair- 

 like cells to the surface of the testa becomes dissolved, by which 

 they are set free, and then branch out in every direction. It 

 frequently happens, also, that the membrane of the cells is rup- 

 tured, and the elastic threads which they contain also uncoil, and 

 extend to a considerable distance from the testa. The seeds of 

 Collomia, and many other Polemoniaceous Plants, &c., exhibit 

 this curious structure ; hence they form beautiful microscopic 

 objects. 



Colour, Texture, and Surface of the Testa. — In colour, the testa 

 is generally of a brown or somewhat similar hue, as in the Al- 

 mond, but it frequently assumes other colours ; thus, in some 

 Poppies it is white, in other species of Poppy, in Indian Shot 

 {Canna), and Pseony blackish, in the Aruatto and Barricarri 



