PARASITIC FUNGI AND MOULDS. 15 
Basidiomycetes have no endogenous spores, but 
they may have as many as four forms of exogenous 
spores. This is the case with the rust of wheat, 
termed by naturalists Uredo or Puccinia graminis, 
which appears in the spring on the blades of this 
plant. The patches of rust are covered with a fine 
dust, which, under the microscope, is seen to consist 
of small elongated bodies of a reddish brown, resting 
on a filament; these are the first 
spores of the fungus, and are 
termed uredospores (Fig. 5). If 
they are scattered over a blade 
of wheat which was previously 
healthy, they germinate by means 
of a hypha of mycelium, which 
penetrates the leaf and develops 
a fresh patch of rust. In harvest- 
time the patches are of a darker, 
almost black shade, owing to the 
development of a second kind of “$.cnnat tine ect 
from a blade of wheat, and 
spore. These are pear-shaped, displaying several uredo- 
os £ . * Spores and one teleutospore 
divided in two, with an enveloping —_ much magnified). 
membrane of considerable thickness; they are called 
teleutospores (Fig. 5). 
Teleutospores cannot germinate on a healthy blade 
of wheat, and consequently do not communicate rust. 
They may remain through the winter on thatch 
or wheat straw, awaiting the ensuing spring, and 
even then they cannot be developed upon a blade 
