502 Mr. VALENTINE's Supplementary Observations on 
X 18.). This connexion is, perhaps, in most instances dissolved at an early 
period, and the sporules recede a little from each other, but are still kept in 
the triangular form by the mother-cell (Tak. XXXV. fig. 13.). It is not un- 
common, however, to find the connexion unbroken after the sporules have 
arrived at maturity; and in these instances there seems to be a general adhe- 
sion at the opposing faces of the sporules (Tas. XXXV. fig. 17.). When 
these adhesions are broken by violence, the adherent surface of the sporule is 
seen to be transparent, and altogether deficient of the granular deposit which 
covers the rest of the sporule, and the three radiating lines are most easily 
seen in this state of the sporule (Tas. XXXV. fig. 18.). The mother-cell 
remains entire until the sporules haye nearly arrived at maturity, but as to 
what finally becomes of it I have no evidence. When it is ruptured by ex- 
ternal violence it assumes a shrivelled appearance, as if it had been on the 
stretch and had contracted on the removal of the distention (Tas. XXXV. 
fig. 15.). I have observed several instances in which the mother-cell contained 
but one sporule, which was in all the cases round, and did not exhibit any 
signs of a stalk or of radiating lines on its surface (Tak. XXXV. fig. 16.). 
I shall conclude this paper with some observations on the analogy that 
exists between sporules and pollen, which is so remarkable, and the particu- 
lars so numerous, that the essential identity of the two can, as I conceive, be 
scarcely a matter of opinion. In the first place, the sporules are formed in 
thecæ which have a great resemblance to some anthers. They are in most 
instances surrounded by a perichætium, which is a collection of modified 
leaves analogous to the perianth. They are either sessile, or seated on a stalk 
or seta, which may be named the filament. In Sphagnum the theca is elevated 
on a pedicel or leafless prolongation of the axis, of which peculiarity the anther 
of Euphorbia is a parallel instance. The thecze are one-celled, yet they have 
a columella, which may be likened to the connectivum ; and although the 
connectivum usually divides the anther into two cells, Callitriche is an in- 
stance in which there is but one cell; and there are examples in which the 
cavity is spuriously divided into four cells, as in Tetratheca, which in this 
respect resembles the theca of Polytrichum; and in the fact of evacuating its 
contents by a single pore, resembles the general structure of thecæ. All thecze 
are lined by a distinct membrane, and so nearly does this resemble the endo- 
