400 FIRST FORMS OF VEGETATION. 
aggregation of club-shaped bodies, their thicker 
end being divided into two chambers, each filled 
with minute sporules, and 
their lower end tapering 
into a fine stalk connect- 
u ing them with the stem 
: of the corn (Fig. 46, 4). 
These different forms were 
supposed to be distinct 
Fic. 47.—Puccinia GRAMINIS. species, but they abe LOW: 
(a) Diseased chaff-scale. (4) Spores. ascertained to be dimor- 
phic forms of the same fungus, produced by the 
modifications of growth. Attention has already 
been directed to the relationship between this 
species and the Berberry-rust, which is supposed 
to be only another form of it. When this disease 
is very prevalent, the juices of the corn are inter- 
cepted, the stimulating effects of light and air are 
prevented, and the grain in consequence becomes 
shrivelled and defective, yielding at the same time 
a superabundant quantity of inferior bran. 
One of the most remarkable diseases affecting 
the cereals is ergot, already slightly alluded to. 
Though found in various kinds of grasses, such as 
Agrostis, Festuca, Elymus, and Dactylis, this 
disease is most frequently produced in rye, and 
hence it is commonly known as ergot of rye. It 
is not very common, although diffused in greater 
