FUNGI AND FUNGOUS DISEASES OF PLANTS 259 
245. Different forms and habits of mushrooms. While the 
types of mushrooms already discussed and shown in the illus- 
trations are probably most common of all, others are almost 
of a mushroom 
Magnified 370 diameters. After 
A. H. R. Buller 
spoken of as one of the 
tree-destroying fungi. 
The mycelium is able to 
penetrate through woody 
tissues and to extend for 
great distances within 
the host plant. It may 
infect a living tree when 
a broken limb or other 
injury offers an entrance, 
live within it during the 
life of the tree, and 
thereafter help to bring 
about the decay of the 
tree. The shelf-like re- 
productive portion, in- 
stead of bearing gills 
on the under surface, 
equally abundant. A common form 
is Polyporus (many pores) (fig. 182), 
which appears in shelf-like outgrowths 
from bodies of trees within which 
its mycelium grows. It is commonly 
Fic. 202. Puffballs 
Two species of puffballs of the genus Lycoperdon 
Those above are one half natural size; that 
below is two ninths natural size 
has many small pores within which spores are formed. The 
number of these spores is very great ; one authority 1 estimates 
1 Buller, A. H. R., Researches on Fungi. Longmans, Green & Co., 1909. 
