INTRODUCTION. xiii 



tains the mass of minute, generally sphserical granules, or seeds. 

 Through the centre of this capsule, however, passes a little 

 column, which is called a columella, and to which it appears that 

 the seeds may have been attached in a young state, or which 

 formed a part of that cellular substance which constituted the 

 whole of the interior of the capsule, and in the circumference of 

 which the seeds appear to have been imbedded. 



Besides the structure of the fringe, or peristome, the situation 

 of the pedicel, orfruitstalk, whether lateral or terminal, is found 

 to be of great value in denning the genera. So also is the shape 

 of the Calyptra ; which is called dimidiate, when it is cleft on one 

 side, and mitriform, when it is entire at the base. 



The number of teeth which compose the peristome of Mosses 

 is worthy of remark, being either 4, which is the smallest number, 

 or a multiplicate of 4. Tetraphis has only 4 teeth ; Octoblepha- 

 ris, a tropical genus, has 8 teeth; Grimmia, Dicranum, and 

 many others, have 16; Didymodon has often 32, and Polytrichum 

 sometimes 64 ; but no Moss is known with any intermediate 

 number. The office of these teeth seems to consist in aiding the 

 discharge of the seeds of the capsule at a proper season. 



The seeds, or organs of reproduction, are a fine dust-like sub- 

 stance ; and require a dry atmosphere to accomplish their dis- 

 persion. Such is the hygrometric nature of the peristome^ that 

 when the weather is moist, it is entirely closed over the mouth 

 of the capsule, and the seeds are prevented from escaping ; in a 

 dry season, the teeth are spread out in a radiating manner, or are 

 reflexed : the seeds, by the shrinking of the sides of the capsule, 

 flow over the margin, and are scattered far and wide by the 

 winds. 



With these seeds, or sporules, as they are called by many, Mr. 

 James Drummond, F. L. S. of Cork, occupied himself for a 

 series of years. He succeeded in raising more than 30 different 

 kinds of Mosses from seed ; and the result of his experiments he 



