(n5) 



A step forward brings us to the Bryophyta. These are 

 seedless green plants, most of which possess roots, stems, 

 and leaves, but have no vascular tissue (cases 41-50). This 

 group is best known through the mosses, which form its 

 largest division. Of somewhat simpler structure are the 

 hepatics or scale-mosses (cases 41 to 43). The stems and 

 leaves of the hepatic plant are sometimes combined into 

 a flat thallus-like body which creeps closely on the ground or 

 other objects and resembles in aspect some of the lichens. 

 The leaves, when present, are usually more delicate in 

 texture than in the true mosses and they do not have a 

 midvein. These differences alone enable one to distin- 

 guish a hepatic from its relatives by the unaided eye or at 

 most by the use of a lens. In addition to these characters, 

 the capsule or the receptacle which bears the spores, or 

 reproductive bodies, usually splits into four valves when 

 full-grown and the spores themselves are accompanied by 

 spiral threads called elaters. The favorite habitat of 

 hepatics is wet places, and mountains continually steeped 

 in clouds yield a surprising variety of forms. Closely re- 

 lated to the hepatics, and commonly included with them, 

 is the group Anthocerotes; these plants may, however, be 

 distinguished by the presence of a central axis or column 

 (columella) in the capsule, and there are several other im- 

 portant structural differences in their tissues. 



The mosses (cases 44 to 50) follow the hepatics in order 

 of development and complexity; they differ from them, 

 however, in many respects. The stem and leaves have 

 more differentiated tissues, and the leaves usually have a 

 midvein. The moss capsule generally opens by a lid under 

 which there are commonly appendages to aid in scattering 

 the spores, which in this case are not accompanied by 

 spiral threads as they are in the hepatics. The mosses 

 fall into three primary groups: First the "peat-mosses" 

 (Sphagnum), which differ from the rest of the mosses in 

 the development of the tissue-structure of the capsule and 

 in the spores; they grow in swamps and other wet places, 



