CONTRIBUTIONS TO BOTANY. 
247 
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 5 II 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. 244), 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 
deflcient 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 excelsa. 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 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 
