368 .. REPORT OF THE COMMISSIONER OF AGRICULTURE. / 
in the loose parenchyma (Fig. 3). Below the epidermal cells it is 
rarely visible, since it is so transparent that it is easily concealed by 
the cell contents ; but when the cells are dead and shrunken it can 
be seen between them (Fig. 3). It penetrates the tissues very slowly, 
and reaches the loose parenchyma only in the last stages of the dis- 
ease. This second portion of the mycelium absorbs nourishment for 
the entire fungus. 
Spores.—The spores are borne upon the superficial layer. Short 
vertical branches may arise upon any of the strands ; these branches 
force the cuticle apart from the epidermis and soon form colorless 
two-celled spores upon very short basidia. When the spores are 
nearly full-grown the pressure upon the cuticle becomes great enough 
to rupture it irregularly (Plate LX, Fig. 2, b), allowing the spores to 
escape (Plate IX, Fig. 2). The mature spore is deeply constricted 
at the union of the two cells. The cells are oblong, nearly twice as 
long as broad, sometimes larger at the ends than in the center, and 
contain two nuclei. Sometimes the two cells fall apart; and before 
they become free from their basidia, the lower one frequently has 
the appearance of a pedicel (Fig. 4). 
The effect of the parasite upon the leaf tissues is at first apparent 
in the shape of a dark yellow mass, evidently composed of the trans- 
formed cell contents that collect in the upper part of the epidermal 
cells. The upper row of palisade cells next become discolored, and | 
the etore shy il bodies disorganized, and this process slowly extends 
through the leaf. it is this discoloration of the cell contents that 
gives the dark color to the spot. In some species of Actinonema 
the mycelium itself is dark colored ; but on the rose it has little or 
no color, and the fringed appearance of the spots is due to the fact 
that a few discolored cells follow the mycelium where single strands 
project beyond the others. Just underneath the fruiting spots the 
mycelium seems to have some color (Fig. 2, d), and these spots look 
blacker than the surrounding surface. , 
(a) TREATMENT. 
Owing to the hardy nature of the fungus and to the fact that the 
mycelium develops within the leaf tissues, the disease is very diffi- . 
cult to deal with. Although the fungus does not live over winter in 
the woody portions of the plant, the disease, having once entered a 
garden, is sure to re-appear for successive seasons, for the spores are 
lodged upon the buds at the basgs of the petioles by water trickling 
down the leaf-stalk, andthe shoot springing from these the following 
season is necessarily tainted. For the same reason cuttings from dis- 
eased bushes will spread the fungus. Unless some plan can be 
adopted by which the spores can be destroyed early in the season, 
before they have germinated and produced a mycelium within the 
leaves, a garden once infested by the parasite is beyond recovery, and 
a new site must be selected in which no roses must be planted that 
are not perfectly healthy. 
It is probable, however, that we may succeed In saving roses once 
attacked. For this purpose all the leaves should be carefully burned 
in the fall, andthe bushes and ground carefully sprayed with some 
fungicide before the buds start in the spring. Much may also be 
done by picking and burning every leaf as soon as it shows the 
faintest trace of disease. 
A solution of copper sulphate may be used for spraying the bushes, 
but should not be used upon the leaves, as it willbe apt to burn the 
