2 26 STRUCTURE AND LIFE HISTORIES 



may be very greatly reduced, as in Sphagnum; or the 

 spore-case may not appear as a clearly defined organ, 

 but may appear to merge very gradually into the stalk, as 

 in Anthoceros. In liverworts the spore-case never opens 

 by a lid or operculum, as is universally the case in mosses, 

 but always by valves, formed by longitudinal splittings 

 of the sporangial walls. Elaters may or may not occur in 

 liverworts, but never occur in mosses. The sporogonium 

 of liverworts and mosses never possesses a leafy stem, and 

 never possesses true roots; only one case (that of the moss, 

 Eriopus remotifolius) has ever been reported where the 

 sporogonium produces rhizoids from its basal end. To 

 compare the simple sporogonium of hverworts and mosses 

 with the leafy plant of the true ferns, would be quite super- 

 fluous. It should, however, be pointed out that the sporo- 

 phyte of liverworts and mosses Hves always, throughout its 

 life, as a parasite on the gametophyte, while the sporophyte 

 of ferns always becomes established, sooner or later, as an 

 independent plant. Except for the very simple columella 

 of Anthoceros and the central strand in the seta of mosses, 

 nothing approaching a true vascular bundle occurs in the 

 liverworts and mosses; while, as stated before, the well- 

 developed fibro-vascular system of the ferns has caused 

 them to be known as vascular cryptogams. 



