and on the Structure of the Seed in the Rhamnaceae. 79 



Within this shell, and adhering to it, is a second tunic, which 

 is membranaceous, and agglutinated to it by means of a thick 

 layer of cellular deposit of spongiose texture, brittle when dry, 

 aud so loosely aggregated that, when removed and soaked in 

 water, and then slightly touched, these cells separate into di- 

 stinct globules of a hexagonoid shape, and of a deep crim- 

 son colour. In the substance of this second membranaceous 

 tunic is observed a white cord, which rises from the bottom, 

 originating in one of the angles of the basal pervious chink, 

 runs up one side of the tunic, crosses its summit without inter- 

 ruption in its course, and passes down the contrary side, termi- 

 nating in the opposite corner of the basal perforation, and thus 

 making a complete peripherical circuit round the inner surface 

 that lines the shell. This cord is composed of a number of 

 delicate spiral threads, so free that each fibre is easily drawn out 

 separately. In some genera of the Rhamnacea (as in Zizyphus, 

 Alphitonio, &c.), this second tunic is perfectly free from the 

 outer corneous shell, a considerable space existing between them, 

 in which is generally found a small quantity of very lax white 

 cellular tissue. A third integument, although free from it, fills 

 the space in the upper moiety of the last-mentioned coating in 

 Colletia, but a little below the middle it becomes gradually 

 narrower, more opake, and of a thicker texture, until it 

 tapers into a short stout thread, that terminates in the basal 

 perforation of the outer shell. The opposite extremity, or sum- 

 mit, is marked with a dark fleshy disk, like a chalaza, of nearly 

 its own diameter. These integuments closely invest the albu- 

 men, which is fleshy, homogeneous in texture, and of consider- 

 able thickness on the ventral and dorsal faces, but becomes 

 very thin round the margins of the cotyledons, the whole 

 mass being of a roundish oval shape, suddenly contracted at its 

 base into a prominent nipple, which is enclosed within the ros- 

 tellated neck of the investing integuments before described; the 

 embryo is nearly the size of the albumen, and much flattened, 

 the cotyledons being oval, foliaceous, and fleshy, slightly cordate 

 at the base, where they are united by a short cylindrical radicle, 



ence of a small thickening or chalazal spot on the summit of the inner 

 integument, and of another round its contracted basal neck, are constant 

 in all the seeds I have examined. The raphe is invariably peri])herical, and 

 undisturbed in its course by the apical chalaza, which it crosses : it is also 

 free from the shell in all parts, except at its two basal extremities, which 

 are both imbedded in channels formed in the crustaceons thickening of the 

 shell around its base ; but one of these extremities only, as just said, ap- 

 pears to be a continuation of the cord of the funicle. The imbedding of 

 the two extremities of the raphe in a cruntaceous deposit in the base of the 

 shell is analogous to the structure observed in many genera of the Rkaui- 

 naceee. 



