NORTH AMERICAN SPECIES OF AMBLYSTEGIUM. 
LELLEN STERLING CHENEY. 
(WITH PLATES XI—XII1) 
INTRODUCTION. 
AMERICAN students of bryology have felt for several years 
that the characterization of the several species of Amblystegium 
expressed in the descriptions of them now available, are unsatis- 
factory in many respects, While I was engaged in naming 
some collections of mosses I met this difficulty and was led to 
make a closer study of the group, in order, if possible, to dis- 
cover some clearer diagnostic characters for the several species. 
To do such work in the most satisfactory manner the worker 
should have before him the plants from which the original 
descriptions were made. Had it been possible for me to pro- 
long this work indefinitely I should have endeavored to see all 
existing types, notwithstanding the fact that they are widely 
scattered, and some of them probably available only after 
months of search. But I have been compelled by circumstances 
over which I did not have complete control to bring my work 
to a close without seeing several of the types. In the absence 
of these, I selected material named by bryologists of recognized 
ability, compared it carefully with material of other authorities, 
with the original descriptions and figures, and later ones of good 
standing, and selected for my descriptions and illustrations 
those forms which agreed best with the consensus of opinion as 
expressed in existing descriptions and figures. 
In addition to the characters commonly enumerated in 
descriptions, such as color, general habit, disposition of arche- 
gonia and antheridia, | have added some structural characters 
of both gametophyte and sporophyte, and the averages of a 
large number of measurements of cells and organs in both. 
236 [ocTOBER 
seal 
To Sa eae Te 
po SS 
