SECT. I 



CRYPTOGAMS 



439 



sporogonium outside tlie spore-sac, a well -developed assimilating 



tissue is present ; this is bounded by water-storage tissue and an 



epidermis. In most Mosses stomata are 



found on the lower part of the capsule. 



Distinctive variations in the mode of 



development and structure of the capsules 



are exhibited by the four orders of th& 



Musci : Sphagnaceae, Andreaeaceae, Phas- 



caceae, and Bryinae. The Si)hagnaceae and 



Andreaeaceae are nearest to the Liverworts. 



Order I. Sphagnaceae (^-°) 



The order of the Sphagnaceae, or Bog Mosses, 

 includes only a single genus. Sphagnum, containing 

 many sj^ecies. The Bog Mosses grow in swampy 

 places, and form large tussocks saturated with 

 water. The upper extremities of the stems con- 

 tinue their growth from year to year, while the 

 lower portions die away and become eventually 

 converted into peat. Of the numerous lateral 

 branches arising from each of the shoots, some grow upwards and form the apical 

 tufts or heads at the summits of the stems ; others, which are more elongated and 



Fig. 382. — Schistostega osmmulacca. 

 A, Sterile; C, fertile plant, (x j.) 



Fif!. 383. — Mnium undulatmn. Orthotropoiis 

 shoot terminating in a male receptacle sur- 

 rounded by involucral leaves. The lateral 

 shoots are plagiotropous. (After Goebel.) 



Fid. 384. — Hypnnm ]in rum. (Nat. size.) 



flagelliform in shape, turn downwards and envelop tlie lower portions of tlie stem 

 (Fig. .378, jI). Every year one branch below the apex develops as .strongly as the 



