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PHARMACEUTICAL BOTANY 
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 chlamydospores or brand spores. These spores 
fall to the ground and pass the winter. In the spring each germinates 
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. 
Order 2. — Uredinales, the rusts. Obligate parasites possessing 
a septated branched mycelium which ramifies through the inter- 
cellular-air-spaces of the host and sends haustoria into the cell 
cavities. The different stages of their life cycle are either restricted 
to one host or distributed between two or more hosts. An outline 
of the life history of the wheat rust will give an idea of the peculiari- 
ties of the group. ' 
The Wheat Rust (Puccinia Graminis). — If we examine the wheat 
plant just before harvest we will find on the stems and leaves 
some rust-red lines. The presence of the mycelium of the fungus in 
the intercellular spaces of the host does not kill the host directly 
or appear to stunt its growth, but the effect of the parasite on the 
host is seen when the grains mature. The grains are small and 
mushy, due to the fact that the nutrition of the host had been dis- 
turbed and the formation of starch in the grains inhibited. The 
mycelium is localized and gives rise underneath the epidermis to 
rounded egg-shaped spores attached to it by short pedicels. The 
spores are produced in such numbers that the space beneath is too 
confined. As the long epidermal cells of grasses run longitudinally, 
the pressure of the spore masses from within causes the epidermis to 
crack and its edges become turned back. Through the resultant 
cleft the summer spores or uredos pores are thrust out. These uredo- 
spores are orange-brown in color and covered with minute spines. 
The mass of them has been called a uredinium. These spores are 
