210 ORGANOGRAPHY. BOOK I, 
germination, emitting the radicle, and has been named by 
Gaertner the embryotega. 
At the apex of the seed in the orange, and many other 
plants, may be perceived upon the testa a small brown spot, 
formed by the union of certain vessels proceeding from the 
hilum: this spot is the chalaza (Plate VI. fig. 11. Z>). In the 
orange it is beautifully composed of dense bundles of spiral 
vessels and spiral ducts, without woody fibre. The vessels 
which connect the chalaza with the hilum constitute a parti- 
cular line of communication, called the raphe : in most plants 
it consists of a single line passing up the face of the seed ; but 
in many Aurantiaceae and Guttiferae it ramifies elegantly in 
every direction upon the surface of the testa. 
The raphe is always a true indication of the face of the seed ; 
and it is very remarkable that the apparent exceptions to this 
rule only serve to confirm it. Thus, in some species of Euony- 
mus, in which the raphe appears to pass along the back, an 
examination of other species shows that the ovules of such 
species are in fact resupinate ; so that with them the line of 
vascularity representing the raphe is turned away from its true 
direction by peculiar circumstances. In reality, the chalaza is 
the place where the secundine and the primine are connected ; 
so that in orthotropous seeds, or such as have the apex of the 
nucleus at the apex of the seed, and in which, consequently, 
the union of the primihe and secundine takes place at the 
hilum, there can be no apparent chalaza, and consequently no 
raphe: the two latter can only exist as distinct parts in 
anatropous seeds, when the base of the nucleus corresponds to 
the geometrical apex of the seed. Hence, also, there can never 
be a chalaza without a raphe, nor a raphe without a chalaza. 
Something has already been said 
about the aril {fig. 187. and 188.) 
when speaking of the ovule; but 
it more properly comes under con- 
sideration along with the ripe seed. 
As a general rule it may be stated, 
that every thing proceeding from 
the placenta and not forming part 
of the seed is referrible to the 
aril. Even in plants like Hib- 
