462 INTRODUCTION TO CETPTOGAMIC BOTANY. 



when exposed to the sun, especially where abundant moisture 

 is present, in some genera the leaves acquire brown, red, or 

 other tints, they are by no means so subject to assume abnor- 

 mal tints as Jungervnannice. Though, again, many mosses 

 have creeping stems, they are far more apt to be erect than 

 Jungermannice, or to make pulvinate tufts. 



508. Mosses, like Hepaticce, wee propagated by gems and 

 spores. The former grow in various situations ; sometimes on 

 distinct organs, sometimes at the tips of the nerves (Fig. 

 100, h), and sometimes*they are generated on the rootlets 

 which grow in various parts of the plant, and in many species 

 form a dense woolly or silky mass, which is mostly of a bright 

 yellow brown, varying to nearly pure tints, and sometimes 

 purple. 



509. The spores of mosses on germination form a confer- 

 void mass, which has often been considered, without any reason, 

 a sort of cotyledon. This mass is very much of the same 

 nature as the mycelium of Fungi, and is called the Protonema, 

 and is always distinguished by the cells containing chlorophyl. 

 Many spores may concur in the formation of this mass ; but 

 whether more spores than one concur in the formation of a 

 single plant, is doubtful. Be this as it may, after a time a 

 little knot or swollen articulation appears upon the threads, 

 which, by cell-division, is developed into a leafy shoot, which 

 may be annual or of longer duration. Archegonia appear at 

 different points, according to the particular species, and anthe- 

 ridia, consisting of masses of cells accompanied by jointed 

 paraphyses. At the base of each archegonium is an embryonic 

 cell, which, by cell-division, gives rise, after a time, to a perfect 

 sporangium. The archegonium swells as well as the sporan- 

 gium ; but after a time, by the elongation of the peduncle, it is 

 forced from its connection with the stem, or that continuation 

 of the stem which has been called the vaginula, and is carried 

 up by the sporangium, where it forms a veil, which, if split on 

 one side, is said to be dimidiate ; if split in several points or 

 entire, it is said to be mitriform, campanulate, &c. In one or two 

 cases the calyptra bursts in the midst, as the sporangium swells, 

 without being at the same time carried upwards from the want 



