216 
ORGANOGRAPHY. 
BOOK I. 
It has been remarked that the raphe or vascular extension 
of the placenta always occupies the side next the ventral 
suture of the ovary ; and that when, as in Euonymus, it is 
turned towards the dorsal suture, that circumstance arises 
from an alteration in the position of the ovule subsequent to 
its being fertilised. 
It has also been stated that the passage through the pri- 
mine and secundine is called the foramen ; or the exostome, 
when speaking of that of the primine ; and the endostome, in 
speaking of the secundine. Upon these Mirbel remarks: — 
‘‘ These two orifices are at first very minute, but they gradu- 
ally enlarge; and, when they have arrived at the maximum 
of dilatation they can attain, they contract and close up. 
This maximum of dilatation is so considerable in a great 
number of species, in proportion to the size of the ovule, 
that, to give an exact idea of it, I would compare it not to a 
hole, as those express themselves who have hitherto spoken 
of the exostome and endostome, but to the mouth of a goblet 
or of a cup. It may therefore be easily understood, that, 
to perceive either the secundine or the nucleus, it is not 
necessary to have recourse to anatomy. I have often seen, 
most distinctly, the primine and secundine forming two large 
cups, one of which encompassed the other without entirely 
covering it, and the nucleus extending itself in the form of 
an elongated cone beyond the secundine, to the bottom of 
which its base was fixed.” 
In practical botany the detection of the foramen is often a 
matter of great importance; for it enables an observer to 
judge from the ovule of the direction of the radicle of the 
future embryo : it having been ascertained by many observ- 
ations that the radicle of the embryo is almost always pointed 
to the foramen. A partial exception to this law exists, how- 
ever, in Euphorbiaceae, in many of which Mirbel has noticed 
that, after fertilisation, the axis of the nucleus and the endo- 
stome are inclined five or six degrees, without the exostome 
changing its position ; by this circumstance the foramen of 
the secundine and that of the primine cease to correspond, 
and the radicle, instead of pointing when formed to the exo- 
stome, is directed to a point a short distance on one side of it. 
