STRUCTURE OF SEED. 189 



called the testa and the inner coat; but if I differ from 

 the nomenclature of Richard, I entirely adopt his 

 opinion upon the nature of this envelope. It is, like all 

 foliaceous organs, composed of two membranes and of an 

 intermediate tissue ; the external one bears the name of 

 Testa, the internal one that of Endopleura, and the 

 intermediate plexus that of Mesosperm ; these three 

 parts form, by their union, the close coat without valves 

 or sutures which surrounds the nucleus. 



The testa, when deprived of all the accessory integu- 

 ments, which the arillus, pericarp, calyx, or even the 

 involucrum may furnish it with, appears most frequently 

 under the form of a shining membrane ; sometimes, 

 however, it is rough as in the Tulip, or marked with 

 little tubercles or furrows, as in Oxalis. But in general, 

 it is smooth, even glossy, dry, scarious, osseous, or 

 almost petrous, as in Guilandina Bonduc. 



Notwithstanding this appearance, it is eminently en- 

 dowed with the faculty of absorbing water, and performs, 

 in this respect, an important office in germination. It 

 also presents this singularity — that although the micro- 

 scope can discover no kind of pores, it not only absorbs 

 water, but even the coloured particles of this fluid, 

 tinted, for example, with cochineal ; this progress of 

 absorption is entirely analogous to what takes place at 

 the extremities of the radicle and in the stigma, which 

 obliges me to consider the testa formed of seminal 

 spongioles ; its colour presents much variety, and affords 

 here and there, especially in the Leguminosae, the most 

 vivid and glaring tints ; for example, in Abrus, Ery- 

 t/irina, Beans, &c. 



The testa is interrupted at the point where the um- 

 bilical cord is attached to the seed; this forms the hilum, 

 to which I shall presently revert : this interruption 

 seems to indicate that this organ, like the epidermis of 



