BY D. McALPINE. 229 



of the atmosphere. P. prunicola and E. vitis also occurred in 

 Queensland. 



It is interesting to notice that C. amy(jdalearum was found in 

 the Auckland district of New Zealand as well as in Victoria and 

 South Australia, but P. prunicola has not been recorded yet, 

 although it probably occurs there. 



I am not aware of any of these "shot-hole" fungi having been 

 definitely determined for New South Wales, although some of 

 them are almost sure to occur there. Dr. Cobb has indeed 

 referred to the "Shot-hole disease of the Apricot and other Stone- 

 fruit trees" as being due to P. cirmmiscissa,* but the drawing- 

 given there in illustration of his remarks only shows a Hypho- 

 mycete and probably a form of Torula which has nothing to do 

 with the production of the disease. 



Shot-hole effects in relation to the Host-plant. 



It is a question for consideration whether such effects are due 

 to the nature of the fungus or the nature of the host-plant, and 

 the prevalence of shot-hole effects in the genus Prunus would 

 seem to indicate that the reaction of the host-plant has a con- 

 siderable influence on the result. 



Tubeuf in his " Diseases of Plants induced by Cryptogamic 

 Parasites," devotes a chapter to the reaction of host to parasitic 

 attack, and concludes that while the reaction is fairly constant 

 for the same host and fungus, yet different hosts behave differ- 

 ently in attacks of the same fungus. In the case of many leaf- 

 spot diseases, he assumes that the mycelium excretes a ferment 

 which causes the immediate death of any cell it may touch. The 

 death of the cells would soon prevent the further extension of 

 the parasitic fungus, and in this way the area of the disease 

 would be circumscribed. Duggarf in -his paper on "The shot- 

 hole effect on the foliage of the genus Pru?ius,'' states his belief 

 that from the number of species of fungi producing this effect, it 



* Ag. Gaz. N.S.W. Vol. iii. p. 289 (1892). 

 t Proc. Soc. Prom. Agr. Sci. pp. 64-69 (1898). 

 16 



