150 DEVELOPMENT OF THE OVULUM 
"This is certain, that in figure 4, which presents a section 
there is no trace of a nucleus. Indeed in the explanation 
Mirbel says, that it has disappeared, that it is doubtless in- 
timately united with the secundine, a circumstance, he adds, 
of almost universal occurrence. 
Foramen, Endostome, Exostome, Micropyle. 
By the term foramen, I mean the opening of both tegu- 
ments when two exist, this becomes mycropyle in the seed ; 
an useless discrimination. M. Mirbel adopts the term exos- 
tome for the opening of the outer integument, and endostome 
for that of the inner. But the distinction is needless, and 
the term endostome can scarcely be said to be applicable in 
those cases in which at the epoch of fecundation, it is ex- 
serted beyond the endostome. 
The existence of the foramen has not escaped its share of 
denial. Mr. Raspail’s opinion that the teguments of the seed - 
are imperforate, is worthy of one who places more reliance on 
his own observations made with an ordinary lens, than on 
those of such men as Brown, Brongniart, and Mirbel, aided 
by the best instruments. 
The foramen, after fecundation, becomes more or less 
closed up; it may however, even in the ripe seed, be very 
generally traced. 
n some few instances, as in Bucklandia, it „preserves its 
original appearance. 
Generally it is indistinct, in some cases however, by a 
fungous growth of its lips it becomes carunculiform. 
lt is generally more or less prominent, generally very 
much so in the ovulum ; it may however, owing to inequality 
of development as Mirbel has shewn in Tradescantia, even 
in the ovulum become depressed as it were, below the level 
of the other parts. Memoire p. 27, Pl. 6.— Figs. 6, 7, 8, 9. 
Mr. Brown states that in Lemna he has found ** an appa- 
rent inversion of the embryo with relation to the apex of the 
nucleus." M. Brongniart however has described and figur- 
ed the embryo of Lemna as presenting no anomaly on this 
particular point. 


