182 
ORGANOGRAPHY. 
BOOK I. 
ever, in Euphorbiaceae, in many of which Mirbel has 
noticed that, after fertihsation, the axis of the nucleus and the 
endostome is inclined five or six degrees, without the exos- 
tome 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 exos- 
tome, is directed to a point a short distance on one side of it. 
Besides the two external integuments, Mirbel has re- 
marked the occasional presence of three others peculiar to 
the nucleus, which he calls the tercine, quartine, and quintine. 
The former is the external coat of the nucleus, and is very 
generally, if not universally, present. As I am almost unac- 
quainted either with it or the two latter, I can add nothing to 
the following remarks of Mirbel upon the subject: — "The 
quartine and quintine are productions slower to show them- 
selves than the preceding. The quartine is not very rare, 
although no one has previously indicated it ; as to the quin- 
tine, which is the vesicula amnios of Malpighi, the additional 
membrane of Brown, and the sac of the embryo of Adolphe 
Brongniart, I am far from thinking that it only exists in a 
small number of species, as Brown seems to suppose. If no 
one has noticed the quartine, it is, no doubt, because it has 
been confounded with the tercine ; nevertheless these two en- 
velopes differ essentially in their origin and mode of growth. 
I have only discovered the quartine in ovules of which the 
tercine is incorporated at an early period with the secundine ; 
and I think that it is only in such cases that it exists. At its 
first appearance it forms a cellular plate, which lines all the 
internal surface of the wall of the cavity of the ovule ; at a 
later period it separates from the wall, and only adheres to 
the summit of the cavity : at this period it is a sac, or ratlier 
a perfectly close vesicle. Sometimes it rests finally in this 
state, as in Statice ; in other cases it fills with cellular tissue, 
and becomes a pulpy mass ; under this aspect it is seen in 
Tulipa gesneriana. All this is the reverse of what takes place 
in the tercine ; for this third envelope always begins by being 
a mass of cellular tissue, (and at that time it has the name, as 
we have seen, of nucleus,) and generally finishes by becoming 
a vesicle. 
