554 DIE-DACK OF APPLK TREES. 



mock bodies. After a month small pustules, with Cytospora 

 spores, were observed along the surface, and in places hard, 

 whitish, raised bodies. 



The mycelium is often closel}' septate ; the cells, which are 

 usually swollen at the ends, measuring 16.5 — 33.0|U, X 5-95 

 — 6.611. The cells frequently have a jointed appearance, 

 brought about bv the swollen ends. Individuallv swollen cells, 

 resembling resting cells, have also been observed. 



Apple Agar plates (PI. 24, d). — On the 17th September, 

 1914, plates of the fungus which were incubated at 20° C. and 25° 

 C. were poured. On the 19th there was a good growth at both 

 these temperatures, and on the 24th there were small bodies 

 in the medium resembling fruiting bodies, but in which no spores 

 were found. The plates were not again observed till the 20th 

 November, 1914, by which time the medium had dried up, and 

 raised greyish bodies (whitish in earlier stages) were present. 

 These bodies resemble the hummock bodies already referred to, 

 and contain pycnidia. 



Sterilised PeacJi fzvigs (PI. 24, e; 25, a-b). — Within a month 

 the fungus covers the twig as a mouse-grey mycelial growth. The 

 flap of growth over the water is of a dark, almost black, colour, 

 and where the fungus comes into contact with the glass it is a 

 dark brown. In places are raised whitish to greyish bodies 

 ( PI. 24. e ) , in which again are the pycnidia. 



The mycelium, which is richly branched, measures 4.95 — 

 13.2/Z, across. The individual cells are from 6.6 — 33.0 long, 

 are frequently swollen at the ends, giving the hyph?e a jointed 

 appearance. Cells 19.6)11 broad have also been seen, though 

 though not in quantity. 



A section through the hummock bodies (PI. 25. a-e) shows 

 them to contain numerous pycnidia. These pycnidia are situated 

 on a dense stroma, and appear frequently in a ring along the 

 rpper surface (PI. 25, c) of the hummock body, but also at the 

 sides (PI. 25 b). The walls of ])ycnidia here, too, have Ijeen 

 observed to become confluent, and the pycnidia thus become 

 united (PI. 25, a). 



The spores, which are of the typical Cytospora type, measure 

 3 . 08—4 . 64^, f . 77— 1 . 1 5 5/x. 



C. Temperature Relations. 



Experiments were not specially devised for studying the 

 relation of the fungus to different temperatures, but incidentally, 

 in the course of the work, the conclusion was arrived at that the 

 fungus has a wide range. 



Plates of Beerwort agar incubated at 20° C. and 25° C. gave 

 growths about equally strong, and the same result was obtained 

 in tube cultures at 25° C. and 30° C. No growth resulted at 

 40° C. Growth probably takes place considerably below 20° C, 

 as is evidenced by the fact that, though considerably delayed. 



