^2 Fifj "■ Canker,'' cmised by Phoma cinerescens Sacc. 



O 



One of the "cankers" which may be taken as typical of those found 

 on the larger branches is shown in the photograph at Fig, 1, Plate I, 

 where the characteristic cracking of the bark in the older portions is 

 seen. It will be observed that near the centre of 

 the "canker" is the old base of a smaller branch 

 and it is probable that that was the place where 

 the fmigus made an entrance. This particular 

 canker was evidently the result of three distinct 

 periods of. activity of the causal organism. The 

 oldest portion, recognized by the fact that the 

 bark is very much cracked and separating from 

 the wood, was elliptical and measured 16-5 x 5 cm. 

 At each end of this ellipse the canker extended 

 5 cm. upward and 2-5 cm. downward, these ex- 

 tensions corresponding to the second period of 

 activity. The check to the normal growth in 

 thickness of the branch induced by the presence 

 of the organism caused these afEected areas to be 

 depressed below the general surface of the branch. 

 The youngest portions of the canker extended 

 still further upward and downward and though 

 they were but indistinctly marked oft" from the 

 adjoining healthy portions of the branch they bore 

 numerous pycnidia. The accompanying diagram 

 of the canker shows the areas, affected during the 

 three periods of activity, numbered respectively 1, 

 2 and 3 ; this diagram should be compared with 

 Fig. 1, Plate I, which is a photograph of the same 

 canker. 



The portion of the branch bearing the " canker " 

 was placed in a damp chamber and in twenty-four 

 hours "tendrils" of conidia were issuing from 

 the youngest portions of the canker but not from 

 the rest. No conidia were obtainable from the 

 older portions and there the fungus was either 

 dead or had ceased to produce conidia, although 

 these areas were still dotted over with old pycnidial 

 pustules. The tendrils were at first of a pale 

 orange colour but when fully protruded were almost 

 or quite white. When a tendril or a portion of one is placed in a drop 



