THE BITTKR-ROT FUNGU8. 9 



the iipplo. An applo mux have only one diseased spot, but in a serious 

 outbreak there are usually several, and it is not uncommon to see a 

 fruit literally pep])ered with points of infection. Durinjr the past 

 season the writer coiuited 1,20(1 on a sinolr apple and i\stiniated 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 the apple, and 

 are fre(iuently 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 tlu> upper or stem end, from which 

 the specked areas extend in strips toward the calyx end. 



When a number of spots ap))ear on a single apple, they soon coalesce, 

 and three or four, gaining the asc(>ndency, envelop the others and 

 retain their circular shape, each producing its rings of fruiting pustules. 

 Finally the entire fruit is convei-ted into a dark-brown, shriveled, and 

 wrinkled mummy, which may hang on the tree a year or more. (PI. I, 

 and PI. VI, tig. 1.) However, the majority of the atfected fruits fall 

 to the ground before they are half rotten, and their decomposition is 

 hastened by scavenger insects and deca}- fungi. 



THE BITTKK-HOT FUNGUS. 



The })itter-rot disease is due to a fungus which has received the 

 botanical name (Tloinert'lla ruf()m(t<-al(iit.'< (Berk.) Spaulding & von 

 Schrenk," but which has T)eeii known until recently as (rJoifn^poriiim 

 frnctl(/<')i Kill Berk.'' 



This microscopic plant, developing fron\ a spore that has found its 

 way to the apple, penetrates the skin in the form of a minute tube, 

 which immediately begins to ])ranch and grow rapidly in every direc- 

 tion. This mycelium absorl)s its nourishment from the cells of the 

 apple, killing them and thus producing the brown sunken spots known 

 as bittei'-rot. 



The iiiycelium. — The diseased tissue is tilled in the intercellular 

 spaces with pale, delicate, much-branched threads of mycelium, which 

 are septate, slightly granular, and chietlj' -i to <> /< in diameter. (PI. 

 II, ^, <i.) Under favorable conditions the mycelium grows ver}^ 

 rapidly, killing the fruit cells almost as fast as it enters the healthy 

 tissue. It gi'ows 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 hyphas, 



« Von Schrenk and Spaulding. The Bitter-Rot of Apples, Bui. 44, Bureau of Plant 

 Industry, U. S. Dept. of Agriculture, p. 29. Saccardo (Annales Mycologici, 2, p. 19.S) 

 thinks the name should be Glomerella fruciigeua (Clinton) Sacc. 



^Berkeley, M. J. Oloeosporiuvi frudigenam, n. s.. Gardeners' Chronicle, 1H56, 

 p. 245. 



