222 THE " SHOT-HOLE " FUNGI OF STONE-FRUIT TREES, 



of the leaf, producing large indefinite patches which bear innumer- 

 able fructifications of the fungus. Here there is no formation of 

 callus, and this following upon the stoppage of the vital activities 

 of the leaf, leads to the conclusion, that the callus-formation or 

 separation layer is a special character possessed in particular by 

 the living leaves of the stone-fruit trees and designed to minimise 

 or localise the attacks of the fungus. 



The bearing of this on the treatment of the disease is obvious. 

 It has been recommended to give the first spraying to Apricot 

 trees badly affected with shot-hole as soon as the leaves turn 

 colour, because when the}^ fall they deposit the spores in the soil. 

 But before this happens innumerable minute round portions of 

 the leaves have ali-eady fallen to the ground, bearing with them 

 the seeds of the disease, which will be read}^ to germinate at least 

 when the buds burst. 



Fungi producing " Shot-hole " generally. 



Quite a number of fungi act in this way, at first producing 

 sharply defined blotches, usually circular in outline, brown in 

 colour and surrounded by a red margin, then finally causing 

 perforations in the leaf. Bacteria are often found on the " shot- 

 hole " spots, without any other fungus being present, and they 

 are probably active agents in their production. 



There are at least twenty species of fungi at present known to 

 produce or to be associated with ''shot-hole" eftects in the leaves 

 of Prunus, and two of these are new species determined for 

 Victoria. The following attack the various cultivated plants as 

 well as other species of Prunus : — 



* 1. Ascochyta clilorospora, Sacc. — V. 

 2. Cercospora cerasella, Sacc. 



■^ 3. C. circu7)isclssa, Sacc. — Q. 



4. C. 2^^'unicola^ E. k, E. 



5. Cladosporium carpopliilum^ Thuem. — N.S.W. 



* 6. Clmterosporium amijgdaJearum, Sacc. — V., S.A., IST.Z. 



7. Cylindrosporium padi , Karst. { = Sepfori(f cerasina, Peck). 



* 8. Exohasid'mm vitis, Prill, k Del. — Y ., Q. 



