Mr. Brown on Lyellia, Leptostomum, and Buxbaumia. 581 
bly, in some degree, prevent dispersion, while the unequal di- 
stances of the teeth might either produce a deviation from the 
regular figure, or an early rupture, of the tympanum, which forms 
an essential part in this economy. 
BUXBAUMIA. 
In my former paper I have proposed to preserve the genus 
Buxbaumia, as established by Schmidel; and in constructing a 
character to comprehend both species, I entirely rejected the 
outer peristomium of Hedwig; and having also adopted his opi- 
nion respecting the middle peristomium of B. aphylla, which he 
has termed corona, and considered as analogous to the annulus in 
many other mosses, it became unnecessary to advert to this part 
in defining the genus. 
Mr. Hooker has since published an excellent analysis of both 
species, and has followed Ehrhart and Mohr in regarding them 
as forming distinct genera. | 
"This determination I have now no hesitation in adopting ; for, 
whatever the nature of Hedwig's corona may be, it affords at 
least an obvious character, and is connected with other differences 
of sufficient importance to justify the separation ; though the two 
genera must always remain in the same natural section of the © 
order. T | | 
"The observations that follow belong, therefore, solely to Buz- 
baumia aphylla. | ! 
"My first remark on this plant relates to its peristomium, on the 
nature of which, as compared with that of other mosses, at least 
two different opinions may be formed. | 
According to one of these, the outer peristomium of Hooker 
may with Hedwig be considered analogous to the fimbria or an- 
nulus existing in many other mosses ; and the principal objection 
4r2 to 
