350 ON LYELLIA, LRPTOSTOMTJM,
ing a character to comprehend both species, I entirely re- jected the outer peristomium of Hedwig ; and having also adopted his opinion respecting the middle peristomium of B. aphylla, which he has termed corona, and considered as analogous to the annnliis 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 regard- ing them as forming distinct genera.
This determination 1 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 sepa- ration ; though the two genera must always remain in the same natural section of the order.
The observations that follow belong, therefore, solely to Buxbaumia apliylla.
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 annulus existing in many other mosses ; and the 582] principal objection to this view would perhaps be obviated by rejecting the outer peristomium of Hedwig, as I have formerly proposed, and which Mr. Hooker has since done ; as there would then be nothing either in the origin or texture of this part essentially at variance with the supposition ; the principal remaining difference being its greater length ; for the cilia of the peristomium of Buxbaumia may be com- pared with the striae or divisions existing in the annnlus, which seem to be equally determinate in number, and in some cases also disposed in a double series.
On the second supposition, the peristomium of Bux- baumia originating entirely from the outer membrane, may, though consisting of several and even of dissimilar series, be regarded as analogous to that portion of the pencil of Dawsonia which arises from the same part of the capsule. This analogy is suggested by Mr. Hooker, and is confirmed
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