DESCRIPTION OF PLATES. 



Plate I. Frontispiece. Apples affected with bitter rot resulting from inoculation 

 from a canker. Two rings of spore pustules have already formed in the apple 

 shown at the top of the plate. 



Plate II. Typical examples of apples affected with bitter rot. These fruits were 

 inoculated with spores from a diseased apple. 



Plate III. A view in a Missouri apple orchard during a severe epidemic of bitter rot. 

 Almost the entire crop of apples is diseased and has fallen from the trees within 

 a few days. 



Plate IV. Figs. 1, 3, and 7. — Apples attacked by the bitter-rot fungus at various 

 stages of the disease. Fig. 7 shows an apple with a rotten spot only 2 or 3 

 days old ; fig. 3, probably four or five days after the attack ; and fig. 1, a little later. 

 They all show how the diseased area becomes sunken, and later on wrinkled. 

 They also show the rings of spore masses. Fig. 2. — An apple affected with 

 bitter rot. The small dark spots show the appearance of early stages of this 

 disease. Fig. 4. — A mummified apple which was attacked by the bitter-rot 

 fungus in summer, and remained on the tree the following winter. It is dried 

 up and shriveled. The spore masses dried, but are still present in quantities 

 in the mummy, as shown in the figure. This illustrates the necessity for 

 removing the mummies. Fig. 5. — Two pears, of which the one on the left was 

 inoculated at one point with bitter-rot spores and the other pear not inoculated. 

 After several weeks the inoculated fruit (which remained on the tree) showed 

 a typical bitter-rot spot, with w r ell-developed spores of the bitter-rot fungus. 

 Fig. 6. — A small piece of a winter squash inoculated with spores of the bitter- 



Prot fungus. The fungus grew readily on the squash, and after a brief period 

 numerous pustules with spores formed, as shown in the figure. 

 Plate V. Fig. 1. — A mass of spores of the bitter-rot fungus growing in a pure cul- 

 ture. These spores form in countless thousands in such a culture for a period 

 of 8 to 14 days. Fig. 2. — Various stages of germinating bitter-rot spores. Some 

 have but one germ tube, others have two. On some of the threads dark second- 

 ary spores form. Fig. 3. — Starch grains in various stages of solution by the fer- 

 ment given off by the fungus. The fungus threads growing in the cells of the 

 apple digest the starch grains. Fig. 4. — Peculiar spore-like bodies formed by 

 germinating spores of a cactus fungus {Glceosporium cactorum), which resemble 

 the black bodies shown in fig. 2. Figs. 5 and 7. — The perfect or perithecial 

 stage of the bitter-rot fungus as found during the winter of 1902-3 in the apple 

 cankers. Fig. 5 shows two empty perithecia from an apple canker; fig. 7 a 

 single perithecium much enlarged with some of the asci in place. Fig. 6. — A 

 group of three mature asci with ascospores of the bitter-rot fungus and one imma- 

 ture ascus. These asci were developed in a pure culture of the bitter-rot fungus. 

 The ascospores so much resemble the ordinary spores that it is difficult to dis- 

 tinguish them. 



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