382 



THALLOPHYTES 



breaks through and appears on the surface of the plant body as 



a cup or disk. 



Besides being the pioneer plants on rocks and other places 



where they form soil and thus make it possible for higher plants 



to get a start, they are also of some economic importance 



in other ways. In northern re- 

 gions the Lichen known as Rein- 

 deer Moss is an important food 

 for animals. Some forms are 

 used as food by man. Although 

 not parasites, they sometimes are 

 harmful to plants upon which 

 they grow. When growing on 

 the twigs of fruit trees, they pre- 

 vent the bark from functioning 

 properly and also furnish a shelter 

 for various kinds of destructive 

 insects. 



Basidiomycetes 



General Description. — This is 

 the group of Fungi to which 

 Toadstools, Mushrooms, Puff- 

 balls, Rusts, and Smuts belong. 

 The group scarcely needs an intro- 

 duction, because such conspicu- 

 ous forms, as Toadstools, Mush- 

 rooms, and Puffballs are familiar 

 to everybody. In number of forms this group is next to the 

 Ascomycetes. Their characteristic spore-bearing structure is the 

 basidium, which is the enlarged end of a hypha with usually four 

 slender branches upon which spores are borne, one spore being 

 borne on the end of each branch. Just as the spores borne in an 

 ascus are called ascospores and are the characteristic spores of 

 the Ascomycetes, so those borne on a basidium are called basidi- 

 ospores and are the characteristic spores of the Basidiomycetes. 

 The mycelium of many is saprophytic, living in decaying wood, 

 rotten manure, and other kinds of organic matter. In others, 

 such as the Rusts, Smuts, and other forms, the mycelium is 

 parasitic, living upon the tissues of the grains and other higher 



Fig. 336. — Reproduction in 

 Lichens by ascospores. Above, 

 vertical section through a cup 

 (apothecium), showing asci and 

 paraphyses; below, asci and pa- 

 raphyses shown more enlarged. 

 Redrawn from Schneider. 



