of the Organs of Pilularia globulifera. 485 
projection, or a general swelling of that part (Tan. XXXIV. fig. 12.). By dis- 
section, however, we can observe this process at an earlier period ; and I find, 
upon removing the conical projection, that the first evidence of germination 
having commenced is an appearance of cellularity within the unsupported or 
valved portion of the internal membrane, which is transparent; and I now 
find, for the first time, a very delicate pellucid membrane lining the whole 
cavity of the sporule, and having the cells, which give the appearance just 
mentioned, either lying on its external surface, or forming that portion of it 
which lies beneath the valves. From the appearances, and the impossibility 
of separating the cells from the membrane, I am inclined to believe that the 
cavity formed by this membrane is completed by the cells, or, in other words, 
that the sac is partly membranous and partly cellular (Tas, XXXIV. fig. 10 
& II.). It is possible that this last-described membrane may exist before ger- 
mination begins, notwithstanding the numerous unsuccessful dissections which 
I have made to discover it, the failure being owing to its extreme delicacy ; 
but I am pretty well satisfied that it is a product of germination, because I 
have not the slightest difficulty in demonstrating it after that has commenced, 
nor is there the slightest ace of it in any stage of the development of the 
sporule. However this may be, it is quite certain that fresh cells are gradu- 
ally formed on the external surface of the cellular part of the sac, and that 
the valves of the third membrane are very soon ruptured and gradually 
turned back by the growth and protrusion of this button-like cellular germ 
(Tas. XXXIV. fig. 9 & 13.). The enlarging cellular mass then distends the 
conical projection, unfolding the plicæ of that body, and at length appears 
externally with four of its cells projecting beyond the general mass, and com- 
pressed into a quadrangular form by the pressure, as [ imagine, of the apex of 
the cone, the aperture in which is quadrangular. These projecting cells soon 
harden, and acquire a reddish-brown hue, and in the advanced stage of ger- 
mination appear like a brown quadrangular space, which I should have little 
hesitation in referring to the above cause, did I not find several similar spaces 
on the germinating sporules of Isoëtes lacustris, which I could not refer to such 
an origin: it must be observed, however, that I have not seen the earlier stages 
of germination in Isoëtes. Soon after the exposure of the entire germ, Which 
is effected by the reflection of the valves and conical membrane over the side 
382 
