114 TYPE STUDIES 



THE BASIDIA EUNGI, OK BASIDIOMYCETES 



117. The smuts. The corn smut, Ustilac/o Maijdis, is excellent for demon- 

 stration, but some of the smaller forms found on oats, wheat, many grasses, 

 and Juncus are frequently more convenient for laboratory work. 



A. Study the fructification on the host. Observe the parts infected and 

 the extent of the injury. Make habit sketches. 



B. Tease out part of the fructification in water. Draw the resting cells 

 known as chlamydospores or teleutospores. Does their structure indicate 

 that they are resting spores capable of carrying the fungus over un- 

 favorable seasons of drought or cold ? Why ? Sections of the infected 

 tissue just before the formation of the chlamydospores are necessary 

 to an understanding of their development. 



C. Place some of the chlamydospores in a dilute decoction of manure, 

 previously sterilized by boiling, or make a culture in a hanging drop 

 (Sec. 204). The spores germinate better after being frozen. Observe 

 the cultures from day to day and trace the germination of the spores 

 and the development from each of a short filament, pro77iycelium, 

 which gives rise to thin-walled, delicate sporidia, or spring spores. 



118. Puccinia graminis, the wheat rust. It is somewhat easier 

 to begin the study with the stage knov/n as black rust. 



A. The black rust. Study the distribution of the black rust on 

 the stems and leaves of wheat or various grasses. Make 

 habit sketches. At what time does the black rust appear 

 on the wheat? 



1. Scrape out the contents of a spot and examine in water 

 under h.p. Note the color of the resting cells, which are 

 really chlamydospores, although generally called teleuto- 

 spores, or winter spores. These spores are always two- 

 celled. Draw in detail. 



2. Section the leaves or stem in pith (soaking dried material first in 

 potash solution), or study sections cut with a microtome (Sec. 212). 

 Note the clusters of teleutospores, each on a stalk, and the relation 

 of the latter to the mycelium within the liost. Examine the distor- 

 tion (hypertrophy) of the host tissue in the infected region. Show 

 tliese points in a large figure or series of figures. 



B. The red rust. Study the distribution of the spots of red 

 rust. Habit sketch. At what time does the red rust appear 



