55^ DIE-iiACK UF APPLE TREES. 



and there are reasons for believing that growth takes place con- 

 siderably below 20" C. 



9. The introduction contains references to previous work 

 and the distribution of the malady. 



Literature Cited. 



1. Aderhold, A. — "A Cherry Disease; its Cause and Preven- 



tion." Exp. Stn. Records, 15, 270. 



2. Ellis, J . B., and Everhari, B.M. — •" North .Vnierican Pyreno- 



mycetes " (1892J, 4S5. 



3. Mc Alpine, D. — " Fungous Diseases of Stone Fruit in Aus- 



tralia " (1902). 115. 



4. Rolfc, E. j1/.—" Die-Back of Peach Trees {J'^ilsa Icncosfoma 



Pers.J." Science, N.S. (1907J, 26, 87-89. 



5. Rolfe, E. M. — " Winter Killing of Twigs, Cankers, and Sun- 



scald of Peach Trees." Expt. Stn. Records, 24, 450. 



6. IVonnald, H. — " l^hv Cytospora Disease of the Cherry." Exp. 



Stn. Records, 30, 352. 



Explanation of Illu.s.trat]()N.s. 



The drawings were made with the aid of Edinger's drawing 

 apparatus, with wliich also the photomicrographs were taken. 



Plate 20, a. — Photograph showing silvery-capped pustules on 

 apple twig (Herb. No. 8,831). 

 b. — Pustules on stem of ai)ple tree (Herb. No. 7,734). 

 c. — Photograph showing blackish pycnidia breaking 



through in moist atmposphere. 

 d ( X 600). — Photomicrograph. Mycelium in cells of 

 host. 

 Plate 21, a ( X 600). — Photomicrograi)h. Alycelium in cells of 

 host. 

 b (X 600). — Photomicrograph indicating the dense 

 hyphal mass from and in which the pycnidia are 

 formed. At the bottom is a portion of the stroma. 

 Plate 22, a (X 600). — Photomicrograph of section through 

 pycnidia, and showing the boat-shaped spores. 

 6 (X 600). — Photomicrograi^h showing the peculiarly 

 swollen cells in the stoma of the stroma. 

 Plate 22), a. — Photomicrograph of section through j^ycnidia on 

 oatmeal agar ; 48 days. 

 b. — Growth on potato, 14 days, 25° C. 

 c. — Growth on potato, 11 days, 30° C. 

 d (X 300). — Photomicrograph. Section through 



pycnidium on potato at 30° C. 

 e (X 300) — Photomicrograph. Section through 



pycnidium on potato at 25° C. 

 Plate 24, a. — Photomicrogra])h of section through i^ustule. 



b. — Photograph. Growth on Pear agar ; 27, days at 30" C. 



