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PLANT STUDIES 
"cluster-cups." This mycelium on the barberry, bearing 
cluster-cups, was thought to be a distinct plant, and was 
called ^Ecidium. The 
name now is applied to 
the cluster-cups, which 
are called cecidia, and 
the conidia-like spores 
which they produce are 
known as cecidiospores. 
It is the secidia which 
give name to the group, 
and ^Ecidiomycetes are 
those Fungi in whose 
life history aecidia or 
cluster-cups appear. 
The aecidiospores are 
scattered by the wind, 
fall upon the spring 
wheat, germinate, and 
develop again the myce- 
lium which produces the 
rust on the wheat, and 
so the life cycle is com- 
pleted. There are thus 
at least three distinct 
stages in the life history 
of wheat rust. Begin- 
ning with the growing 
season they are as fol- 
lows : (1) The phase bear- 
ing the sporidia, which 
is not parasitic ; (2) the 
aecidium phase, parasitic 
on the barberry; (3) the uredo-teleutospore phase, para- 
sitic on the wheat. 
In this life cycle at least four kinds of asexual spores 
