652 THE GENUS CONIOTHECIL'M. 



On the fruit the fungus produces a scurfy condition known) 

 as " russeting " (PI. 29, a). If the fruit is attacked while young,, 

 the fungus causes it to crack on expanding (Plate 29, c). These 

 cracks become deeper and deeper with the increase in size of the 

 fruit, and when the core is reached the fruit soon withers and 

 dies. 



The spores usually found on diseased material are the Conio- 

 thecium form. The ascigerous form has to the present not come 

 to my notice in South Africa. 



The disease is best controlled by the pruning back and 

 destruction of diseased parts, accompanied by cleansing sprays 

 in winter. 



2. Isolation of the Fungus. 



On 26th September, 191 3, pieces of apple bark, on which only 

 the Coniothecinm form was present, were sterilised in mercuric 

 chloride (i : 1000), washed in distilled water, then shaken up in 

 melted beerwort gelatine tubes and plates, which were incubated 

 at 20° C. poured. Seven days after inoculation the fungus was 

 evident round the ])ieces of Imrk and elsewhere, and the following 

 fruiting bodies were observed: (t) Phoma pyciiidia. with s])ores ; 

 (2) Coniothecinm spores; (3) Alt ernaria-like spores. 



Plates subsequently jwured from blisters on apple branches 

 always gave origin to the Phoma, and the same resulted in plates 

 poured from a diseased pear branch (PI. 30, c). 



3. Growth on Various Media. 



On sterilised apple plugs at 20° C. numerous Phoma pycnidia 

 were produced, and after 25 days there was a mouse-grev my- 

 celial growth (PI. 30, d) and Coniothecinm spores in^it.' The 

 fungus grows on the cotton wool, and where it comes into contact 

 with the glass, just above the cotton wool, forms a dark brown 

 rim. 



The Phoma also readily formed on sterilised apple twigs, 

 where also raised pustule-like bodies, consisting of a mass of 

 Phoma pycnidia, were observed. A thin slice off the back of the 

 plug gave numerous Coniothccium s])ores TPl. 31, a). On the 

 Hquid in which the plug stands the fungus forms a flap of growth, 

 m which were numerous resting spores {Coniothecinm), and after 

 25 days Alt ernaria-like spores (PI. 31, h) in the mole-greyish 

 growth. The pycnidia also readily formed in prune agar (PI. 32, 

 a), and on sterilised bean stalks and leaves (PI. 32, b and c). ^ ' 



On Carrot agar (PI. 32, d) it forms small colourless colonies 

 of convex elevation measuring 5 mm. across. The fungus 

 threads frequently radiate out from these colonies, which become 

 dotted over with Phoma pycnidia and thus much darker in colour. 



On treacle agar (PI. 32, c) there formed dark filamentous 

 colonies and numerous Phoma pycnidia. Here, too. Avere observed 

 a few packets of Coniothecinm spores. 



It was now left to proceed from the one kind of spores, and 

 by sowing it alone ni suitable media to produce the other. 



