92 Mr. J. Miers on the Tribe Colletiese, 



second tunic; along each margin, emanating from the basal 

 point of attachment, and crossing over the chalaza, there is seen 

 a prominent white cord, filled with spiral vessels, which is im- 

 bedded in the fleshy tissue of the integument, in one continuous 

 and completely peripherical line, exactly like that described in 

 Colletia and Zizyphus. Within this tunic is yet a fourth, 

 delicate integument, a thin albumen, and an embryo similar in 

 form to that of Colletia*. 



I have abstained from giving any denomination to the seed- 

 coats in the foregoing descriptions; but we may now enter 

 into this inquiry. In regard to the two inner coatings, no 

 doubt can be raised against the obvious conclusion that the 

 innermost is the tegmen produced from the secundine of the 

 ovule, and that the other, in which the raphe is imbedded, 

 is the true testa, developed from the primine, notwithstanding 

 its soft fleshy texture. What, then, is the nature of the outer 

 hard corneous coating in Colletia, the external crustaceous cover- 

 ing in Rhamnus, and the second tunic in Alphitonia ? for there 

 can be no doubt that they are all similar in their nature, and all 

 derived from the same origin. The larger size of this tunic in 

 Alphitonia, its lax condition in regard to the testa which it enve- 

 lopes, the total absence of any cicatrix or mark that could indi- 

 cate any previous connexion with the chalazal disk of the testa, 

 are circumstances that manifest a distinct and subsequent origin. 

 Indeed we have seen the proof of this in the seeds of Rhamnus 

 (ante, p. 89), where in the same fruit we have found fertile and 

 sterile carpels : in the latter case, the spiral vessels of the raphe 

 were imbedded in the substance of the outer tunic of the ovule ; 

 in the former case, this raphe was found only in the second 

 coating of the ripe seed : another adventitious coating, perfectly 

 deficient of vessels, in the interval of growth had thus manifested 

 its existence, apparently developed from the fleshy funicle which 

 had simultaneously disappeared. This adventitious coating 

 must therefore come within the category of an arillus. In such 

 case the question presents itself what is the nature of the 

 outer brittle tunic in Alphitonia ? Is it also an arillus, and have 

 we in this genus two distinct arilli enveloping its seeds ? The 

 truth of this conclusion, at first sight, appears subject to little 

 doubt. 



On the other hand, I must not omit to record an instructive 

 fact that I have observed in the fruit of Alphitonia eoccelsa. The 

 fruit consists of three carpels, and, in the instance examined, 

 only one of these contained a perfect seed; the two sterile car- 

 pels presented a single erect ovule, each being half the length of 



* The details of structure of the ovule and seed of Alphitonia will be 

 shown in plate 33 F of the ' Contributions to Botany.' 



