TAXONOMY 267 
ruptures, are discharged and are carried by the wind to other fields 
of grain, there to begin over a new life cycle. 
Class III.— Basidiomycetes, or Basidia Fungi 
This large class of fungi, including the smuts, rusts, mushrooms, 
gill and tooth fungi, etc., is characterized by the occurrence of a 
basidium in the life history. A basidium is the swollen end of a 
hypha consisting of one or four cells and giving rise to branches called 
sterigmata, each of which cuts off at its tip a spore, called a basidio - 
spore. In addition to the basidiospores, some forms also produce 
spores termed chlamydospores. 
Sub-class A.— Protobasidiomycetes 
(Basidium four-celled, each bearing a spore) 
Order 1. —Ustilaginales, the smuts. Destructive parasites which 
attack the flowers of various cereals, occasionally other parts of these 
plants. Example: Ustilago Maydis, the corn smut. The basidio¬ 
spores in this group are borne on promycelia. 
Ustilago Maydis (Ustilago Zese) (Corn Smut).—Corn smut is a 
destructive parasite which for a long time was supposed to be con¬ 
fined to the Indian Corn, but which now is known to occur on 
Mexican Grass. It is the only smut useful in medicine. The 
mycelium of the fungus extends through all parts of the infected 
host through the intercellular-air-spaces and produces large tumor¬ 
like masses on the ears, tassels, husk, leaves and stem. Each mass is 
filled with spores'and covered with a tightly appressed membrane 
which has a whitish appearance like German silver. The spores 
are at first a dark olive-green, but on maturity are dark brown. 
They are sub-spherical and show prominent spines. They arise 
by the division of the septate mycelium into, thick-walled echinulate 
resting spores called chlamydos pores or brand spores. These spores 
fall to the ground and pass the winter. In the spring each germi¬ 
nates into a three- or four-celled filament called a promycelium, from 
the cells of which basidiospores arise. The basidiospores develop a 
mycelium which penetrates the seedling of the host plant. 
