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are made congeneric with others having a peristome, but with 
which they otherwise agree in habit and leaf-structure ; e.g., 
Grymnostomum is abolished, and its species distributed under 
Weisia and Pottia ; his principal divisions are : 
Class 1. Schistoccirpi (Andregea). 
Class 2. Cleistocarpi (the old genus Phascum). 
Class 3. Stegocarpi. 
Sub-class 1. Acrocarpi. 
Sec. 1. Distichophylla. 
Sec. 2. Polystichophylla. 
Sec. a. Leaves not papillose. 
Sec. b. Leaves papillose. 
Sub-class 2. Pleurocarpi. 
4. This was still further elaborated by Professor Schimper, 
in his valuable “ Bryologia Europaea and Synopsis Muse. 
Europ.,” 1860, by the formation of additional tribes and 
families and very many genera, some indeed on characters 
which do not appear to be sufficiently important. 
5. Mr. Mitten, in his descriptions of Indian and South 
American Mosses in the “Journal of the Linnean Society,” 
proposed a new system, which, notwithstanding its great merit, 
does not seem to have met with general acceptance, probably 
because there still lingered a strong bias in favour of Hedwig 
and his successors. He places all mosses under two sections : 
Homodictyi, having leaf cells of uniform structure, and Hetero- 
dictyi, having leaf cells of two forms and including only the 
Sphagnacese. The Homodictyi again have two divisions Schis- 
tocarpi and Stegocarpi, and the latter comprises three groups 
according to the structure of the peristomial teeth already de- 
scribed. The families also are reduced and thus brought more 
in accordance with the natural orders of flowering plants ; while 
the leaf structure receives its due importance the peristome is 
regarded as subordinate, every degree of its development being 
found in a single genus, and sometimes in a single species. 
Believing these views to be strictly in accordance with facts 
derived from a careful study of the plants themselves, and 
therefore true to nature, I feel bound to adopt it, though I 
have ventured to deviate a little from the arrangement, believ- 
ing that the retention of the acrocarpous and pleurocarpous 
sections is certainly convenient. 
