of the Organs of Pilularia globulifera. 489 
of the growing processes, for it is frequently in advance of them; but it is pro- 
duced by a gradual condensation, inherent to the tissue, around the cavities 
and along the radiating dividing lines, which, in fact, are nothing more than the 
result of this condensation, which at maturity is so complete, that the whole of 
the spongy tissue is condensed into four dissepiments, dividing the cavity of the 
involucrum into four equal loculi (Tas, XXXV. fig. 30.). The nipple-like pro- 
cesses are found upon a careful examination to be hollow sacs with obscurely 
cellular walls, those which occupy the lowest part of the involucram being 
considerably in advance of the upper ones. These sacs contain a quantity of 
grumous matter, and a number—perhaps about ten—of soft, rather opake 
pulpy bodies, which are evidently compounded of four closely connected parts, 
so placed on each other as to form a cone with a triangular base (Tas. XXXV. 
fip 31 & 32.). These bodies have their future development in two different 
Ways, according, in a great measure, to the position they occupy in the involu- 
crum. Those which occupy the upper portion, although not absolutely confined 
to that portion, enlarge, become pellucid, and recede from each other, but con- 
tinue to be attached to each other by four stalks as long as half their diame- 
ter, which meet in one centre (Tas. XXXV. fig. 33,). It is now evident that 
these four bodies or sporules are contained in a mother-cell, which most pro- 
bably existed before, but on account of its close approximation to the four 
united sporules could not be seen. On the surfaces of each of these sporules 
are three short lines which radiate from the insertion of the stalk. From an 
observation of the sporules of Isoëtes lacustris, I am inclined to believe that 
these lines are a slight ridge caused by the projection of the membrane into 
the interstices between the three other sporules, and that the stalk is a draw- 
ing-out, as it were, of the same membrane, some evidence of which is seen in 
the instance represented at Tas. XXXV. fig.34. At length the mother-cell is 
ruptured, and the sporules separate from each other at the point where the 
stalks meet in one centre, so that each sporule is furnished with a short tail, 
which, however, soon disappears (Tas. XXXV. fig. 34.). A deposit gradually 
takes place on the outer surface of the sporule, forming a second coat, which 
gradually becomes more and more opake, until the three radiating lines are 
quite invisible, and the sporule a perfectly opake white body (TAB. XXXV. 
fig. 35 & 36.). Until the sporules have become opake they are quite empty, 
