(29) 



into bodies of various shapes. The plants vary greatly in 

 size and structure and are both parasitic and saprophytic. 

 To this group belong the yeasts and mildews. Some plants 

 grow above the surface of the ground, as in the case of the 

 morel ; while others are subterranean, as in the case of 

 truffles. Next in order are the alga-like fungi (case 32) ; 

 these vary in form from simple masses of protoplasm to sim- 

 ple or branching threads. Here belong many of the moulds 

 and similar forms which grow both on other plants and on 

 animals. The fifth and in many respects the most interesting 

 of all the groups is that consisting of the lichens (cases 33 

 to 36). The fungi thus far considered are either parasitic or 

 saprophytic in their mode of life ; the lichens form an indepen- 

 dent symbiotic group, each lichen consisting of a fungus and 

 an alga living together, the one nourishing the other. The 

 lichens are quite familiar to most people as plants of more or 

 less leathery texture growing on rocks, on poor soil or on 

 the trunks of trees. 



A step forward brings us to the Bryophyta, or seedless 

 plants with roots, stems and leaves, but without vascular tis- 

 sue (cases 37 to 48). This group is best known through the 

 mosses, which form its largest division ; but of simpler struc- 

 ture are the hepatics or scale-mosses (cases 37 to 40) ; al- 

 though they were formerly associated with the true mosses, 

 their tissues are much less differentiated than those of the 

 mosses and the structure of their various organs much less 

 complicated. 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 more simply organized plants. The 

 leaves, too, are more like scales than in the true mosses and 

 they do not have a midvein. These differences alone enable 

 one to distinguish 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 



