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NORTH AMERICAN SPECIES OF AMBLYSTEQIELLA. 
By George E. Nichols. 
The genus Amblystegium, as proposed by Bruch & Schimper 1 in 1858, 
comprised sixteen species which, up to that time, had been included under 
Hypnum and Leskea. Four of these have since been reduced to varietal 
rank. Seven years later Schimper 2 adopted the genus, excluding, however, 
three species and adding three others. The limits of the genus have been 
variously considered by later authors. De Notaris 3 , followed by Mitten, 
Lindberg and Braithwaite, extended its boundaries to include many species 
formerly referred to Hyftnum, but which bryologists of the present day tend to 
distribute among Chrysohypnum , Cratoneuron , Calliergon , Drepanocladus , 
and Hygrohypnum. The generic limits recognized by Schimper, however, 
seem to be more natural, and he has been followed by the majority of 
recent European and American writers. 
As defined by Schimper, and recently treated by Cheney 4 , the genus 
Amblystegium embraces two distinct groups of mosses. One group, of 
which A. subtile may be considered typical, comprises species of small size, 
characterized by the absence of a central-strand in the stem and by the 
greatly reduced, usually obsolete, nerve in the leaves. In the other group, 
which includes A. variujn and the allied species, in addition to the larger 
size of the plants, the stem possesses a distinct central-strand, while the 
nerve of the leaves is clearly defined, reaching to the middle of the leaf or 
beyond. 
Hampe, in T871 5 , although recognizing Amblystegium, transferred the 
species A. subtile and A. Sprucei to Leskea , giving to the group thus 
formed the subgeneric title Serpo-Leskea. Both Limpricht 6 and Roth 7 have 
recognized Hampe’s sub-genus, but place it under Amblystegium. 
Loeske, in 1903 8 , raised Serpo-Leskea to generic rank, proposing the name 
Amblystegiella for the genus and adding a third species, Amblystegium 
confervoides. Loeske’s opinion evidently changed regarding the untenabil- 
^ty of Hampe's name, for, in 1904 9 , he retracted A?nblystegiella , sub- 
stituting Serpoleskea Hampe. Warnstorf also, in 1905 10 , designated the 
genus as Serpoleskea. The application of Articles 38 and 39 of the Vienna 
Rules of Nomenclature, however, made it apparent that, as a generic 
title, Amblystegiella Loeske had priority over Serpoleskea (Hampe) Loeske, 
and, in 1907 11 , Loeske again brought forward Amblystegiella. 
Loeske’s genus is based chiefly on the absence of central-strand in 
the stem and the lack, or obscure development, of the nerve in the leaves. 
The same distinction serves primarily to separate Rhynchostegium Br. & 
Sch. and Sematophyllum Mitt. {Raphidostegium (Br. & Sch.) De Not.), 
according to the conception of these genera as given by Roth 13 and Warns- 
torf 13 . In the opinion of the writer, Ainblystegiella Loeske ought there- 
fore to be accepted. 
