and serve to disseminate the fungus during the summer on other wheat plants or grasses. Late in the season, teleutospores are again produced, completing the life cycle of the plant.
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Fig. 285.—How a Parasitic Fungus works. Anthracnose on a bean pod entering the bean beneath. (Whetzel.)
Many rusts besides Puccinia graminis produce different spore
forms on different plants. The phenomenon is called heterœcism,
and was first shown to exist in the wheat rust. Curiously enough,
the peasants of Europe had observed and asserted that barberry
bushes cause wheat to blight long before science explained the
relation between the cluster-cups on barberry and the rust on
wheat. The true relation was actually demonstrated, as has since
been done for many other rusts on their respective hosts, by sowing
the æcidiospores on healthy wheat plants and thus producing
the rust. The cedar apple is another rust, producing the curious
swellings often found on the branches of red cedar trees. In the
spring the teleutospores ooze out from the "apple" in brownish
yellow masses. It has been found that these attack various
fruit trees, producing æcidia on their leaves. Fig. 285 explains
how a parasitic fungus works.
Puffballs, mushrooms, toadstools, and shelf fungi.—These represent what are called the higher fungi, because of the size and complexity of the plant body as well as from the fact that they seem to stand at the end of one line of evolution. The mycelial threads grow together in extensive strands in rotten wood or in the soil, and send out large complex growths of mycelium in con-
