xxii INTRODUCTION. 



ments of Botany. The Muscologist needs not to wait for the 

 heralds of spring to announce to him the time when he may set 

 out, with a prospect of success, upon his excursions. With the 

 Mosses it is a continual spring ; a very great number of them, 

 especially in the plains, are in the highest state of perfection in 

 the middle of winter ; and there is no season but which will afford 

 some or other of them, in a state for examination and study. 



We must now say a few words on the Genera of Mosses, 

 which, since the time of Linnaeus, who established only six, have 

 been varying as the species have been multiplied, and as the time 

 and attention of Botanists have been more closely directed to them. 

 Hedwig increased the number of genera to 33, including the 

 exotic kinds. From them we have removed those whose charac- 

 ters depend solely on the situation of the male flowers, and have 

 founded our characters, in the first place, upon the absence or presence 

 of the fringe of the peristome, a peculiarity which Hedwig employed 

 to so much advantage, and, following him, Turner and Smith ; 

 secondly, on its simple or double nature ; thirdly, its configuration 

 and direction ; fourthly, upon the lateral or terminal situation of 

 the frnitstalk ; and fifthly and lastly, upon the form of the Calyp- 

 tra, whether dimidiate or entire, (mitriform) a character we think 

 of great importance, to which Mr. Turner has long had recourse, 

 but which was first publicly brought into use by that eminent 

 German Cryptogamist, Mohr. By means of this, we see many fami- 

 lies formed which are also grouped by natural habit. Thus is Hed- 

 wig's Anictangium kept separate from Gymnostomum, Grimmia from 

 Weissia, Trichostomum from Didymodon, Zygodon from Ortho- 

 trichum, and Hookeria from JJypnum. We think, likewise, that 

 scarcely a less degree of importance is to be given to the lateral 

 and terminal situation of the fruitstalk ; by the aid of which 

 natural groups, (and these last should never be lost sight of, 

 although in the present imperfect state of the science they must 

 occasionally yield to more precise artificial characters,) are often 



