THE BRYOLOGIST. 
VOL. VIII. 
March, 1905. 
No. 2. 
A LESSON IN SYSTEMATIC BRYOLOGY. 
Dr. George N. Best. 
[Read at the meeting of the Sullivant Moss Chapter, Philadelpha, Pa., Dec. 31, 1904.] 
Whilfe engaged in the study of some specimens of Thuidium abieti?ium , 
collected in Minnesota by Prof. J. M. Holzinger, I noticed that one of these 
differed from the ordinary forms of this species in that the leaves were some- 
what larger, longer and more gradually acuminate, more strongly falcate- 
secund, and that the leaf cells were narrower and more elongated. 
Recognizing in these variations, at least in part, the characters on which 
Mitten had based his Thuidium hystricosum , and having an authentic speci- 
men of this species at hand, a comparison was made, with the result of find- 
ing them nearly identical. The leaves, however, of Thuidium hystricosum 
were slighly larger and the leaf cells somewhat longer, but the differences, in 
these respects were hardly appreciable. Not being fully satisfied that the 
Minnesota moss was indeed Thuidium hystricosum , I . submitted it to Dr. 
Mitten, who considered it a form of Thuidium abietinum. Not comprehend- 
ing how it was that two mosses, so nearly identical, should be referred to 
different species, I decided on an appeal, and in this instance to my herba- 
rium, which contained about forty specimens of Thuidium abietinum from 
an extended range : that is to say, from Germany, Switzerland, France, Bel- 
gium, England, Labrador, various localities in the United States and in Can- 
ada, and as far north as the Yukon Territory. With few execeptions these 
specimens had been determined by well known bryologists. It may therefore 
be confidently assumed that they were correctly named. In fact, while 
Thuidium abietinum is but very rarely found in fruit, its specific characters 
are so well marked that no difficulty need be experienced in distinguishing 
it from all of the North American and European Thuidia, unless it be from 
Thuidium hystricosum , which I regard as simply a form of this species. 
In my examination of these specimens attention was more especially 
directed to 
1. The size and shape of the stem leaves taken from the middle third 
of the stem. 
2. The size and shape of the leaf cells of these same leaves. 
3. The presence or absence of a central strand in the stems. 
As a tabulated statement of the results obtained from the examination 
of each of these specimens would be somewhat confusing, a few representa- 
tive specimens have been selected by which it will be seen that we have here 
a series of forms, intergrading and ascending, and that the space between 
the extremes, that is between the lowest and the highest forms, is so covered 
by intermediate forms as to leave no doubt as to their being but variants of 
one specific type. 
The January BRYOLOGIST was issued December 27 th, 1904 . 
