and on the Structure of the Seed in the Rhamnaceae. 93 



the carpel ; the ovule was of an oval form, it had become thick 

 and opake, its foramen was closed, and it was sessile within a 

 short cup, with a lax undulating border, that was borne upon a 

 solid stipitate support, of the same length and diameter as the 

 body of the ovule. This was evidently an early stage of growth 

 of one of the two arilliform coats of the seed, but whether of 

 the inner or outer one, it is not easy to determine. 



I have here suggested the probable assumption that the hard 

 corneous seminal coating in Colletia, and the crustaceous cover- 

 ing in Rhamnus, derive their origin from a growth of the funicle 

 an assumption strengthened by the original observations of 

 Brongniart ; but it might possibly be argued that this coating 

 is developed from the primine of the ovule, simultaneously with 

 the intermediate tunic in which we find the double raphe-like 

 cord, in the same manner as has been contended, in the case of 

 Magnolia (which I have endeavoured to show has been contested 

 upon erroneous grounds), that these two tunics form a compound 

 testa, both developed from one single ovular coating, the pri- 

 mine. Against this supposition, in the case of Rhamnaceee, many 

 serious objections present themselves, in addition to those I have 

 elsewhere advanced* : 1. No trace of vessels of any kind is found 

 in the outer coating. 2. There is no scar or other mark upon 

 the apex of this outer coating, to indicate its previous attach- 

 ment to the chalaza of the intermediate raphigerous tunic ; on 

 the contrary, there is always a considerable vacant space between 

 that summit and the chalaza. 3. In many species of Rhamnus, 

 this external crustaceous covering does not form an entire coat- 

 ing, but is open from top to bottom, as an enfolded flat plate 

 would be : this could not possibly happen if it were a resilient 

 portion of the growth of the primine. 4. In the ovule, we find 

 a long funicle supporting it, which disappears altogether in the 

 seed. 4. This disappearance of the funicle takes place very 

 soon after the period of impregnation of the ovule, when it 

 becomes lost within a thickening around the micropylar extre- 

 mity of the primine, which is then enclosed by it, apparently as 

 if this thickening, and the formation of the outer crust, pro- 

 ceeded from an expansion of the funicle. We may hence draw 

 the almost certain conclusion that this external seminal tunic is 

 of adventitious origin, and of a distinct growth, subsequent to 

 the period of the fertilization of the ovule. 



In regard to the yet more external brittle covering of the seed 

 of Alphitonia, there appears no sufficient evidence to indicate 

 the precise source of its origin with any degree of certainty ; 

 but the facts I have already recorded concerning the sterile car- 



* Linn. Trans, xxii. 86 ; Ann. Nat. Hist. 3 ser. i. p. 280 ; ibid. ii. p. 185 ; 

 ibid. iii. p. 132, note, and pp. 144, 145, note. 



