THE BITTER-ROT FUNGUS. 9 
the apple. An apple may have only one diseased spot, but ina serious 
outbreak there are usually several, and it is not uncommon to see a 
fruit literally peppered with points of infection. During the past 
season the writer counted 1,200 on a single apple and estimated 1,000 
on each of several others. When so numerous, these spots are at first 
raised, appearing as small brown blisters on the skin of theapple, and 
are frequently so arranged as to suggest that the points of infection 
had followed drops of water trickling down the sides of the apple, the 
specks being distributed evenly over the upper or stem end, from which 
the specked areas extend in strips toward the calyx end. 
When anumber of spots appear ona single apple, they soon coalesce, 
and three or four, gaining the ascendency, envelop the others and 
retain their circular shape, each producing its rings of fruiting pustules. 
Finally the entire fruit is converted into a dark-brown, shriveled, and 
wrinkled mummy, which may hang on the tree a year or more. (PI. J, 
and Pl. VI, fig. 1.) However, the majority of the affected fruits fall 
to the ground before they are half rotten, and their decomposition is 
hastened by scavenger insects and decay fungi. 
THE BITTER-ROT FUNGUS. 
The bitter-rot disease is due to a fungus which has received the 
botanical name Glomerella rufomaculans (Berk.) Spaulding & von 
Schrenk,” but which has been known until recently as Glocosporiwin 
Sructigenum Berk.’ 
This microscopic plant, developing from a spore that has found its 
way to the apple, penetrates the skin in the form of a minute tube, 
which immediately begins to branch and grow rapidly in every direc- 
tion. This mycelium absorbs its nourishment from the cells of the 
apple, killing them and thus producing the brown sunken spots known 
as bitter-rot. 
The mycelium.—The diseased tissue is filled in the intercellular 
spaces with pale, delicate, much-branched threads of mycelium, which 
are septate, slightly granular, and chiefly 4 to 6 “ in diameter. (PI. 
Il, 4, a.) Under favorable conditions the mycelium grows very 
rapidly, killing the fruit cells almost as fast as it enters the healthy 
tissue. It grows toward the center of the apple at a rate about equal 
to its lateral progress. After a time these threads become congre- 
gated just beneath the surface at certain points almost equidistant from 
the point of infection, forming stromata, which give rise to upright 
bundles of interwoven branches. These are the spore-bearing hyphe, 
«Von Sehrenk and Spaulding. The Bitter-Rot of Apples, Bul. 44, Bureau of Plant 
Industry, U.S. Dept. of Agriculture, p. 29. Saccardo (Annales Mycologici, 2, p. 198) 
thinks the name should be Glomerella fructigena (Clinton) Sacc. 
b Berkeley, M. J. Gloeosporium fructigenum, n. s., Gardeners’ Chronicle, 1856, 
p. 245. 
