344 REPORT OF THE COMMISSIONER OF AGRICULTURE. 
It is also well known that the “‘scab” fungus is most severe in its at- 
tacks in seasons when damp, cold weather prevails at the time the 
fruit is forming. In the spring of 18385 the young fruit was closely 
watched for the first appearance of the “‘scab” by my assistant, Mr. 
Galloway, then at Columbia, Mo. it was noted that e+ the time 
the young apples were about the size of peas a period of cold, damp 
weather set in. Ina few days many of the varieties showed plainly 
the minute black specks which mark the first appearance of the fun- 
gus; later these developed into the well-known “‘scab” spots. The 
spring of 1886, in the same locality, was very dry and warm, and 
there was a marked absence of the Fusicladium. — 
The character of the soil appears to have little influence over the 
disease, although in heavy sous, particularly where the subsoil is wet 
or poorly drained, it is naturally more prevalent than in light or 
well drained lands. .A damp, cool atmosphere rather than an ex- 
cess of moisture witn 22<5 appears to be most favorable for the devel- 
opment of this malauy. 
(2) BOTANICAL CHARACTERS. 
ifyceltwwm.—In thin sections the mycelium or plant body of the 
fungus—the vegetative portion—appears like a dense mass of tissue 
composed of dark brown-walied cells. It does not penetrate the tis- 
sues of the host, but grows between the cuticleand the epidermis. It 
' sometimes occupies the cells of the epidermis, especially in the fruit, 
and not infrequently the epidermal layer is entirely destroyed by it, 
the fungus resting directly on the tissues beneath. Its effects are 
confined to a few underlying layers of cells. These are shrunken 
and have their walls and contents browned. The growth of the fun- 
gus soon distends and breaks the epidermis. From the exposed sur- 
face there arise short (404 to 50) upright brown threads upon which 
the reproductive bodies or spores are borne (Fig. 3). 
Reproductive bodies.—The spores (Fig. 4) are of the same color as 
the upright threads or stalkssupporting them. Theyare usually oval 
in outline, though not infrequently egg-shaped or pear-shaped, and 
vary a good dealin size. Theiraverage dimensions are 10” by 20y. 
Generally simple or one-celled, they are occasionally divided into two 
cells by a transverse wall cr septum. Aside from the power of re- 
production which the fungus possesses in these spores, it appears that 
the individual cells composing the plant body of the parasite may 
serve asimilar purpose. These, under favoring conditions, will push 
out germ tubes, if we may so apply this term here, which develop 
into new individuals of the species. This method of reproduction 
may be roughly compared to that by root cuttings in some of the 
higher plants. 
Germination of spores.—The spores germinate rapidly in water, or 
even inan atmosphere saturated with moisture. The surface of many 
scab spots on the White Winter Pearmain, purchased in the Wash- 
ington market in December, were found to be covered with vast num- 
bers of germinating spores, the filamentous germ tubes everywhere 
covering the spots with a vigorous growth. The appearance of 
spores in germination is illustrated in Fig. 4, Plate IT. 
The germ tubes are rather thick, nearly of the same color as the 
spore, and frequently divided by cross-walls or septa. When the free 
end of the germ tube comes in contact with any obstruction it usually 
