22 THE BITTER ROT OF APPLES. 



properly belonged to this particular species. Alwood (1894) was able 

 to produce in the same culture spherical, dumb-bell-shaped, oblong, 

 ovoid, and cylindrical conidia. Although such extreme forms were 

 not found by the present writers, they agree with Alwood and others 

 that the form variation is certainly large. The general form of the 

 conidia developed on fruits and in cultures may be characterized as 

 oblong or cylindrical, sometimes slightly curved (PI. V, fig. 1). 



Extremes in sizes, gathered from all other writers, were from to 

 40 jj. in length and from 3.5 to 7 /< in width. The dimensions given 

 by some may be mentioned. Alwood gives 10 to 12 ju X 4 to 6 /<. 

 Saccardo's measurements, 20 to 30 ju X 5 to 6 yw, are probably of 

 exceptionally large spores. The average size, as determined by the 

 writers, is 12 to 16 /< X 4 to 6 /<. 



Miss Southworth says of the conidia: "They are apt to be shorter 

 and thicker on the apple [than in cultures], and in dry than in moist 

 surroundings." 



The spores can not and should not be taken as a criterion in deter- 

 mining whether any particular fungus is Glceosporium frxtctig&ium 

 Berk., since the spores of other species of Glceosporium closely 

 resemble those of the bitter rot. The great variability in size and 

 form of many fungi of a more or less saprophytic nature is coming to 

 be more widely recognized, and the former method of lumping or 

 separating many forms simply by spore characteristics is rapidly giv- 

 ing way to a clearer conception of the relationship based upon more 

 constant characters. 



The ripe conidia are filled with a finely granular protoplasm. Near 

 the middle and usually a little to one side a clear hyaline area is gen- 

 erally visible (PI. Y, fig. 1). It is at this point that the septum forms 

 during germination. Normally, the conidia are one-celled until they 

 germinate. They resemble the ascospores of this same fungus, and 

 the two can hardly be distinguished. As a rule the ascospores are 

 slightly curved, while the conidia are straight. 



GROWTH IN CULTURES — CONIDIAL AND ASCUS STAGES. 



Freshly-formed conidia of the bitter-rot fungus germinate in three 

 or four hours when put in water at room temperature. Just before 

 germination a septum frequently forms at or near the middle of the 

 spore, thus making a two-celled spore (PI. V, fig. 2). A spore may 

 produce one, two, or more rarely three, germ tubes (PI. V, fig. 2). 

 Where a wall forms, these two germ tubes start, one from each end of 

 the spore. Short spores generally have but one tube. When the 

 spores germinate in drops of water they become vacuolated after a 

 few hours, and after five or six hours they become entirely empty. 

 When germinated in bouillon or on agar, the protoplasm remains 

 finely granular for some time and the cells rarely become entirely 

 emptied. 



