Manual of Gardening

Each spot probably represents a distinct attack of the fungus, and in
this particular disease these injured parts of tissue are liable to fall
out, leaving holes in the leaf. Plum leaves that are attacked early in
the season by this disease usually drop prematurely; but sometimes the
leaves persist, being riddled by holes at the close of the season. Fig.
212 is the rust of the hollyhock. In this case the pustules of the
fungus are very definite on the under side of the leaf. The blisters of
leaf-curl are shown in Fig. 213. The ragged work of apple scab fungus is
shown in Fig. 214.

The constitutional and bacterial diseases usually affect the whole
plant, or at least large portions of it; and the seat of attack is
commonly not so much in the individual leaves as in the stems, the
sources of food supply being thereby cut off from the foliage. The
symptoms of this class of diseases are general weakening of plant when
the disease affects the plant as a whole or when it attacks large
branches; or sometimes the leaves shrivel and die about the edges or in
large irregular discolored spots, but without the distinct pustular
marks of the parasitic fungi. There is a general tendency for the
foliage on plants affected with such diseases to shrivel and to hang on
the stem for a time. One of the best illustrations of this type of
disease is the pear-blight. Sometimes the plant gives rise to abnormal
growths, as in the "willow shoots" of peaches affected with yellows
(Fig. 215).

Another class of diseases are the root-galls. They are of various kinds.
The root-gall of raspberries, crown-gall of peaches, apples, and other

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