Mr. Brown on Lyellia, Leptostomum, and Buxbaumia. 577 
sence of the annulus; and the insertion, form and relative position 
of the male flowers, which, though always considered of import- 
ance by Hedwig, many of the most distinguished muscologists 
of the present day entirely exclude from the characters of their 
genera. 
With respect to the principal source of generic distinctions, the 
Peristomium, in addition to the circumstances generally attended 
_ to, namely, the origin, number, direction, form, and actual divi- 
sion of the teeth, it may be of some importance to ascertain their 
æstivation, which, though very generally, is not always valvular: 
and especially to mark the existence or want of the longitudinal 
strie or semi-pellucid lines: for these, if they do not prove the 
compound nature, at least clearly indicate a tendency to division 
in the teeth where they are found; division being always in the 
course of the striæ, and in no instance taking place unless where 
they are present. 
But in considering them, which I am inclined to do, as proving 
composition or confluence of the teeth, it would appear that there 
is a much greater uniformity in the structure of the simple or outer 
peristomium, at least, than is generally admitted ; and that the 
prevailing number of teeth in this series is thirty-two ; though by 
a coalescence, more or less complete, they are frequently reduced 
to sixteen, in some cases to eight, and in a few even to four. 
3 According to this view, a single longitudinal line in the axis of 
a tooth indicates the confluence of two teeth; three equidistant 
lines, one being central, the coalescence of four; and seven lines 
similarly disposed that of eight. 
_ Nearly the whole of these modifications exist in that natural 
subdivision of the order, which may be named Splachnee, consist- 
ingof Splachnum, Systylium, Tayloria, (Hookeria of Schwaegrichen,) 
Splachnum squarrosum of Hooker, and Weissia splachnoides. 
The 
