22 HANDBOOK OP BRITISH MOSSES. 



granulated. It is often perfectly straight above, but frequently 

 decidedly curved, altering occasionally its direction as the 

 sporangium swells. It is frequently twisted either to the 

 right or left, and either enters abruptly into the sporangium, 

 or gradually passes into it, forming with it or beneath it a 

 little swelling or apophysis. 



Even in such cases as Splachnum luteum (Crypt. Bot. fig. 

 106 d), where the apophysis at length acquires such an enor- 

 mous size and appears quite distinct, if we examine the stem 

 and sporangium in an early stage of growth, we shall find that 

 the apophysis belongs quite as much to the stem as the spo- 

 rangium, though the external cells in some instances are rather 

 those of the sporangium. In Sphagnum, the fruitstalk is re- 

 duced to a little bulb. 



The base of the fruitstalk, especially in Pleuroearpous Mosses, 

 and sometimes the whole fruit, is immersed in leaves very dif- 

 ferent from the rest, even from those of the perigynium, which 

 together are called the perichsetium. They are perfected at a 

 later period than those of the perigynium, and require to be 

 distinguished, because occasionally they afford good specific 

 characters. 



The sporangium in most Mosses, when ready to develope the 

 spores, consists of a central columella continued to the apex, a 

 surrounding spore-sac, the inner membrane of which adheres to 

 the columella, or is separated from it by threads as in Polytri- 

 chum, and the external wall, which may either be confluent 

 with the outer wall of the spore-sac, as in Sphagnum, or free 

 or connected by threads (Plate 1, fig. 7, 8). In Archidium 

 there is ultimately no columella, and in Sphagnum the spore- 

 sac, instead of forming a little cylinder round the columella, 

 consists of a hemispherical, or more correctly a meniscoid, 

 cyst at the top. 



