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SECTION OF VEGETABLE PATHOLOGY. 359 
cane are prevented from properly performing their work, and asa re- 
sult the canes become sickly; the leaves do not attain more than 
half their normal size, and if fruit is formed at all it never 
reaches its full development, but ripens prematurely or simply dries 
up and is worthless. If the young canes are not killed the first year 
the continued action of the fungus on the leaves and branches pre- 
vents theformation of fruit the succeeding year. 
On the petioles and veins of the leaves.—Soon after the appear- 
ance of the fungus on the canes the petioles of the oldest leaves are 
also attacked. ‘There appears near the base of the petiole the pur- 
plish spots which always mark the first development of the fungus. 
These are similar in appearance to those on the canes already described. 
Gradually the disease spreads along the petiole toward the leaf, and 
soon the frame-work of the latter shows the whitish, blister-like 
spots. 
PThe parasite usually confines its attacks to one side of the petioles 
and veins, which results in an unequal development, the leaves be- 
come distorted, and their edges rolled inwards towards the midrib. 
Frequently the pedicels of the fruit are attacked, and this is usually 
followed by the complete drying up of all the berries. 
On the parenchyma of the leaves.—The fungus produces spots on 
the leaves similar to those on the canes, excepting that they are much 
smaller (scarcely exceeding 1"™ in diameter) and moreclosely approx- 
imated, but rarely coalescing. The injury extends through the en- . 
tire thickness of the leaf, and frequently the diseased tissue separates 
ie the surrounding healthy part and the leaf becomes riddled with 
oles. 
(c) BOTANICAL CHARACTERS OF THE FUNGUS. 
About 60 species of the genus (Gleosporiwm) to which the fungus 
of Anthracnose of the raspberry and blackberry belongs are known 
to occur in the United States. They are all true parasites, but very 
little is known respecting their development. The species attacking 
the raspberry and blackberry consists of three parts, namely, (1) the 
mycelium or body of the fungus, composed of very slender, colorless 
threads ; (2) slender stalks, called basidia, and (3) reproductive bodies, 
called spores, that are borne upon the tips of the basidia. 
The mycelium creeps between the cells of the host and obtains its 
nourishment at the expense of the latter. As a first result there is 
simply a slight discoloration of the cell contents ; later the ceils lose 
their shape, and very soon they eollapse entirely, leaving nothing 
but a mass of dead and dry tissue. Just as far as the fungus threads 
extend the tissues of the host are destroyed (Fig. 2). As already 
stated, the injury rarely reaches to the pith ; for the most part it is 
confined to the bark and cambium layer. Near the center of the 
diseased spot the ends of many of the creeping threads unite and 
form a dense tuft, which, as seen under the microscope, resembles a 
mass of short, slender, club-shaped bodies ranged side by side. 
These bodies are the basidia ; they are formed beneath the cuticle, 
which they soon rupture, and appear on the surface in the form of 
a minute globule, being covered with a clear gelatinous substance. 
Upon the tips of the basidia the spores are borne (Fig. 2, a) ; these 
are colorless, oval or oblong, and very minute one-celled bodies. 
Each basidium develops but a single spore, and the entire mass of 
spores and basidia are held together in the gelatinous substance, 
which, however, readily dissolves in water. 
