14 
Colorado Experiment Station 
The Basidiomycetes do not form their spores in sacs but bear 
them externally on 
more or less club- 
shaped stalks or basi- 
dia. Each basidium 
usually bears four 
spores. Spores born 
on basidia are spoken 
of as basidiospores or 
sometimes sporidia. 
The typical basidium 
is often modified into 
Spore formation in Basidiomycetes. The successive stages a short, USUally foUP- 
of development are in order of letters. (After de Bary.) celled tube, arising 
directly from a germinating spore. This modified basidium or 
promycelium is found in the rusts and smuts. 
The Basidiomycetes also constitute a large group and include, 
in addition to the rusts and smuts, which are serious plant parasites, 
most of the common mushrooms. 
Germination of a smut spore showing a 
modified basidium. (After Harper.) 
Germination of spores 
of asparagus rust 
showing a modified 
basidium. (After 
Smith.) 
The Fungi Imperfecti, commonly spoken of as the imperfect fungi, 
constitute a grouj) of miscellaneous individuals which do not form 
the type of spores that would identify them with either of the 
preceding groups. As their name indicates they are imperfect in 
that no sexual spores are formed. The spores which are formed 
closely resemble the asexual spores of the ascomycetes and it is 
I 
