144 Mr. Brown on some remarkable Deviations 
quires so complete and intimate a cohesion with the proper coat 
of the seed as to be no longer either separable or distinguishable 
from it. : * i 
But systematic botanists have generally agreed to term a naked 
seed not only this kind of fruit, but every monospermous pericar- - 
pium bearing a general resemblance to a seed, and whose outer. 
covering, though distinct from the nucleus, is only ruptured after 
germination commences. ; 
For the purposes of an artificial arrangement this language may 
perhaps be sufficiently accurate; but in determining, the aftini- 
ties of plants, it is necessary.to express by appropriate terms 
those differences which are no less important than real. 
Of the fruits improperly called naked seeds, there are two prin- 
cipal kinds: The first, in which the pericarpium is distinct from 
the seed, is termed Akena by Richard in his excellent Analyse du 
Fruit; the second, in which the pericarpium coheres with the 
seed, is the Caryopsis of the same author. : 
An Akena (or Achenium), even in a separate state, may in ge- 
neral be readily determined. But it is not always equally easy to 
distinguish a Caryopsis from a seed. It may indeed be done in 
certain cases, as in Grasses, by attending to its surface, in which 
two distinct and distant cicatrices are observable; the one indi- 
cating the point of attachment to the parent plant, the other 
that by which it was fæcundated. In certain other tribes, how- 
ever, this criterion cannot be had recourse to, the surface of the 
Caryopsis exhibiting but one areola or cicatrix, which includes 
the closely approximated points of attachment and i impregnation: 
in such cases, the true nature of the fruit can onl y be determined 
by its examination in an earlier stage. : 
But although it must be adiblited that an ovulum is never 
produced without a covering, through some part of which it is 
im preg- 
