318 PRACTICAL COURSE IN BOTANY 
stage in the life cycle of the plant, and to this stage the old 
name uredo is applied, the spores being called uredo-spores. 
360. Black rust. — Teleuto stage. Next examine with a 
lens a part of the plant attacked by black rust. Do you 
observe any 
difference ex- 
cept in the 
color? Do the 
two kinds of 
rust attack all 
parts of the 
; — = plant equally? 
Fie. 452. — Uredo spores of wheat rust (Puccinia graminis), igi t hat 
magnified. (From CouLtsr’s ‘‘ Plant Structures.’’) not, wna 
77 
part does each 
seem to affect more particularly? At what season does the 
black rust appear most abundantly? Place a section of the 
diseased part under the microscope and notice that the dif- 
ference in color is due to a preponderance of long, two- 
celled bodies with very thick, black walls (Fig. 453). These 
are called teleu- 
tospores, a word 
meaning “‘ final 
spores,” be 
cause they are 
formed only 
toward the end 
of the season. 
They are de- 
veloped from 
the same my- 
celium with the 
Fic. 453. — Teleutospores of wheat rust, magnified. 
uredos pores, (From Coutter’s ‘ Plant Structures.’’) 
and are not a 
product of the latter, but collateral with them and belong to 
the same stage in the life history of the fungus. After they 
appear, the uredospores cease to be developed at all, and 
