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- 
At deer Moss is an important food 
G Ny for animals. Some forms are 
: aa a ay used as food by man. Although 
an KI Mite “4 a not parasites, they sometimes are 
aN N 7? 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. 
a Wyn 
Y, 
Basidiomycetes 
General Description. — This is 
Fic. 336.— Reproduction in the group of Fungi to which 
Lichens by ascospores. Above, Toadstools, Mushrooms,  Puff- 
vertical section through a cup balls, Rusts, and Smuts belong. 
(apothecium), showing asci and The group scarcely needs an intro- 
paraphyses; below, asci and Pa uction, because such conspicu- 
raphyses shown more enlarged. ; 
Hadeanna/itone Selmeiden 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 
