280 
PLANT STUDIES 
disease with great rapidity (Fig. 250). Once it was thought 
that this completed the life cycle, and the fungus received 
the name Uredo. When it was known that this is but one 
FIG. 250. Wheat rust, showing a young hypha forcing its way from the surface of a 
leaf down among the nutritive cells. After H. MARSHALL WARD. 
stage in a polymorphic life history it was called the Uredo- 
stage, and the spores uredospores, sometimes "summer 
spores." 
L 
FIG. 251. Wheat rust, showing the winter spores (teleutospores). After 
H. MARSHALL WARD. 
Toward the end of the summer the same mycelium 
develops sporophores which bear an entirely different kind 
of spore (Fig. 251). It is two-celled, with a very heavy black 
