the Development of the Theca, and on the Sexes of Mosses. 501 
to the mother-cells, except that they are more adherent to each other, it is fair 
to presume that it is by a secretion of granules in their cavities that the addi- 
tional sporules are formed. I have not been able to find a theca in an inter- 
mediate state between the formation of the first layer of sporules and the 
complete conversion of the yellow tissue into sporules. I am not at all cer- 
tain by what means the four masses of granules in each mother-cell acquire 
each a separate envelope. It is certain, however, that they gradually become 
more and more distinct, and their enveloping membrane becomes more opake 
by a gradual deposition of a granular matter on its surface, which at maturity 
is completely covered. This granular deposit has but a loose connexion with 
the membrane, and is easily rubbed off in little grains, which are of a brownish 
colour when mature, and are individually transparent, although when crowded 
over the surface of the sporule they obscure its contents. The contents of the 
sporules gradually become less and less granular, the smaller grains being 
apparently absorbed by the larger one, which at length fills the entire cavity 
of the sporule*. 
The four sporules in each mother-cell are piled on each other, so as to form 
a cone with a triangular base (Tan. XXXV. fig. 12.), and they appear to be 
connected with each other in the young state by a very minute stalk which is 
situated at the conjunction of three radiating lines (Tas. XXXV. fig. 13, 15 
T * 1 ‘have described- the contents of the sporules as they appeared at the time; it did not occur to 
me, until I had no longer the power of applying it to this species, that sulphuric acid might perhaps 
have some effect on the sporules of Mosses. From its effects on Gymnostomum truncatulum and several 
other species, I am now certain that these large apparent granules are globules of fluid surrounded 
by a thicker grumous viscid fluid, or I believe I may say, in other words, that they are particles of 
that fluid separated from its more solid constituents, which separation takes place gradually ; and the 
globules thus formed, as they increase in size, combine with each other until there is but one large 
globule remaining, which occupies the entire cavity of the sporule, and is surrounded by the viscid 
matter of the fluid, which is consolidated into a most delicate translucent pellicle, that forms an elastic 
internal lining to the sporule. In the cavity thus formed is finally secreted the slimy granular matter, 
which in Gymnostomum truncatulum consists of a few granules only; in Tortula ruralis var. levipila, 
the granules and globules of fluid are in about equal proportion ; in Orthotrichum striatum the granules 
predominate; and in Jungermannia complanata I cannot discover any traces of fluid, the cavity being 
filled with granular matter. ‘This fluid is easily observed on account of its immiscibility with water 
or sulphuric acid. This account of what I conceive to be the modus operandi is of course quite hypo- 
thetical. 
3 62 
