412 Mr. Robert Brown on the Structure of the 
called, though merely the termination of the raphe, affords a 
less certain character, for in many plants it is hardly visible 
on the inner surface of the testa, but is intimately united with 
the areola of insertion of the inner membrane or of the nu- 
cleus, to one or other of which it then seems entirely to belong, 
In those cases where the testa agrees in direction with the 
nucleus, I am not acquainted with any character by which it 
can be absolutely distinguished from the inner membrane in 
the ripe seed; but as a few plants are already known, in which 
the outer membrane is originally incomplete, its: entire ab- 
sence, even before fecundation, is conceivable ; and some pos- 
sible cases of such a structure will be mentioned hereafter. 
There are several cases known, some of which I have for- 
merly noticed*, of the complete obliteration of the testa in 
the ripe seed; and on the other hand it appears to constitute 
the greater part of the substance of the bulb-like seeds of many 
Liliacese, where it no doubt performs also the function of al- 
bumen, from which, however, it is readily distinguished by its 
vascularity +. But the most remarkable deviation from the 
usual structure and economy of the outer membrane of the 
ovulum, both in its earliest stage and in the ripe fruit, that I 
have yet met with, occurs in Banksia and Dryandra. In these 
two genera I have ascertained that the inner membrane of the 
ovulum, before fecundation, is entirely exposed, the outer mem- 
brane being even then open its whole length; and that the 
outer membranes of the two collateral ovula, which are ori- 
ginally distinct, cohere in a more advanced stage by their cor- 
responding surfaces, and together constitute the anomalous 
dissepiment of the capsule; the inner membrane of the ovulum 
consequently forming the outer coat of the seed. 
The znner membrane of the ovulum, however, in general ap- 
pears to be of greater importance as connected with fecunda- 
tion, than as affording protection to the nucleus at a more ad- 
vanced period. or in many cases, before impregnation, its 
perforated apex projects beyond the aperture of the testa, and 
in some plants puts on the appearance of an obtuse, or even 
dilated stigma; while in the ripe seed it is often either en- 
tirely obliterated, or exists only as a thin film, which might 
readily be mistaken for the epidermis of a third membrane 
then frequently observable. 
This third coat is formed by the proper membrane or cuti- 
cle of the nucleus, from whose substance in the unimpreg- 
nated ovulum it is never, I believe, separable, and at that pe- 
riod is very rarely visible. In the ripe seed it is distinguish- 
able from the inner membrane only by its apex, which is never 
* Linn. Soc. Transact, xii, p. 149, + Ibid. 
perforated, 
