FUNGI 151 
usually the under one, groups of sporophores, each group 
surrounded by a cup-like structure; and hence these cup- 
like clusters have been called cluster-cups. In these cluster- 
cups the spores oc- : 
cur in long chains, 
and may be called 
spring spores or clus- 
ter-cup spores (Fig. 
143), 
These spring 
spores on the bar- 
berry leaves are 
scattered by the 
wind and __ infect 
young wheat plants; 
that is, germinate Fic. 143.—A cluster-cup (on barberry) of wheat-rust 
and produce myce- pn chains of spring spores.—After Srras- 
lia which penetrate 
them. These new mycelia later put forth the summer 
spores, and in this way the life cycle has returned to the 
point with which this account began. 
It will be noted that in this life-history there are four 
kinds of spores: (1) the early spring spores, produced by a 
simple saprophytic filament, and infecting barberry leaves; 
(2) the spring or cluster-cup spores, produced by a mycelium 
parasitic on the barberry, and infecting young wheat 
plants; (3) the summer spores, produced by a mycelium 
parasitic on wheat, and infecting other wheat plants; (4) 
the winter spores, produced by the same mycelium, and in 
spring producing the saprophytic filaments. In the United 
States the barberry is not widely distributed enough to play 
so important a part in the life-history of wheat-rust, and 
other seed-plants Have been found to be used as hosts for 
the cluster-cup stage of certain forms of rust. It is also 
stated that the cluster-cup stage may be omitted, in that 
11 
