MOSSES. 55 



The calyptra is either simply mitre-shaped, or mitri- 

 form (PI. III. fig. 24), or it is half-cleft, or dimid'iate 

 (figs. 14, 36) . When the capsule is ripe, the upper 

 part usually separates at a circular horizontal line 

 (fig. 8) as a kind of lid, which is called the oper- 

 culum (operculum, a lid), and thus the spores are 

 enabled to escape. The rim of the capsule, from 

 which the operculum has separated, forms its mouth, 

 and this often exhibits a fringe of teeth (figs. 15, 18, 

 31), arranged in one or more rows; sometimes the 

 teeth are replaced by a membrane, or, again, both 

 teeth and a membrane may be present. This mouth- 

 fringe is iheperistome (-Trepl, around, oro/i-a, mouth). 

 In many mosses, an elastic row or ring of cells is 

 situated between the mouth of the capsule and its 

 operculum, called the annulus (figs. 18 & 39) ; this, 

 when the capsule is ripe, aids in throwing off the 

 operculum. 



It is important to become acquainted with the 

 structure and arrangement of these parts, as they 

 form characters by which the families and genera of 

 mosses are distinguished. 



The capsules of the mosses form very beautiful 

 microscopic objects, especially those furnished with a 

 toothed peristome. 



Most of the mosses produce their fructification in 

 the winter and spring. 



The class of mosses is divided into two Orders, 

 according to whether the fruit-stalk is terminal, i. e. 

 arises from the end of the stem or its branches, or 

 whether it is lateral, arising from the side of the 

 stem. Those with the fruit-stalk terminal, or the 

 end fruited (PL III. fig. 22), form the Ac'rocarpi 

 (a/cpa, summit, /capTros, fruit) ; while those with the 

 fruit-stalks lateral, or the side-fruited mosses (fig. 43), 

 constitute the Pleurocarpi (irXevpa, side). The new 

 shoots or young branches of the stems of mosses are 

 termed innovations. 



