THE GENERA OF MOSSES. 
447 
When the dens Jissus is cleft to the base, or nearly so, it 
becomes difficult to distinguish it from two teeth per paria 
approximati ; and it is not improbable that the latter ^re, 
in some instances, nothing more than denies Jissi ; but little 
or no confusion can arise from using two names to denote 
different states of the same structure. 
Weber and Mohr (Handbuch, p. 10.) have some ob- 
servations under Splachnum, much to our purpose. " Hu- 
jus et Orthotrichorum quorundam dentes non tam per 
paria approximati, sed principio adglutinati observantur. 
Posthac, imprimis si dentes reflectantur, nexus inter gemi- 
nos tollitur, et tum primum 16 distinctos reperis. Hae 
'dentium cohaesione et in sicco statu reflexilitate maximopere 
jam hi musci a Didymodontibus peristomio semi-completo 
gaudentibus, quorum e numero in nostra Flora est inclina^ 
fum, discrepant, quippe quibus dentes ab initio omnes inter 
se liberi sunt, et nunquam reflexi. Quare Splacknorum et 
horum Orthotrichorum dentes 8 geminati, Didymodontmm 
per paria approximati dicuntur.*" 
We have now^ finally, to remark, that, in our opinion, it 
will always be found, when a gemination of the teeth ac- 
tually takes place, that the peristome, in the young stated- 
forms one uniform undivided, but longitudinally striated, 
submembranous substance *, which is usually arched over 
the orifice of the theca ; the tendency to split into a definite 
number of teeth being afterwards developed and regulated 
by the laws of nature. This idea appears to be corroborated 
by the fact, that, in the same tuft of specimens, we have re- 
peatedly observed peristomes with six, eight, or twelve teeth,. 
• This structure, which we attribute both to the Splachnoidece and Ortko- 
trichoidecB, will certainly exclude from these orders any of the other species 
to which Bome have attributed a geminating line down the teeth. 
