Ethel M. Doidge 409 



altogether destroyed. Affected leaves show a tendency to curl inwards, 

 and are more or less twisted and distorted. 



Spots on calyces, pedicels and young parts of the stem are similar 

 in character to the leaf spots. On the calyx they may be numerous, 

 but very minute and scattered, or less numerous and up to 2-3 mm. 

 diameter, forming elongated streaks up to 5 or 6 mm. long. 



Cankers are produced on older parts of the stem, especially where 

 the tissues have been somewhat injured by friction or otherwise. At 

 first there appear irregular, dark green water-soaked areas, which later 

 become corky-looking, slightly raised, roughened and with numerous 

 small longitudinal cracks. They are nearest tawny olive in colour. The 

 surface has the appearance of having become blistered or raised by 

 abnormal tissue development underneath, with subsequent cracking of 

 the blistered areas. Cankers of irregular form and 1-2 cm. in diameter 

 are not uncommon. The discoloration does not penetrate into the wood; 

 it is apparently confined to the cortex and is quite superficial. 



In the field, infected fruits are usually found immediately below 

 diseased leaves and are doubtless infected during rainy weather by 

 raindrops which fall on infected leaves and subsequently drip on to the 

 young fruit. The majority of the fruit spots are at the stalk end, but 

 they are also found scattered over the sides and, less frequently, on 

 the blossom end. 



A very minute green or brownish blister is the first indication of 

 infection: this blister may remain minute, about 1 mm. diameter, or 

 may increase in size up to about 3 mm. and become considerably raised 

 above the normal fruit tissue. Occasionally, presumably when weather 

 conditions are unfavourable, infection does not proceed further, and 

 when the fruit is ripe these minute blister-like spots have almost the 

 appearance of fly-specks (Plate XXVI, fig. 2). 



In the large majority of cases the point of infection becomes sur- 

 rounded by a dark green, water-soaked area which spreads considerably 

 and then begins to discolour from the centre. The centre becomes 

 deep slaty brown, merging into wood brown at the edges; a water-soaked 

 margin about 1 mm. wide is still apparent whilst the organism is active. 

 Finally the epidermis ruptures in the centre, showing whitish brown 

 over the discoloured tissues like the broken edges of a blister. The spots 

 are hard and scabby in texture and usually slightly convex, although in 

 mature fruit they may lie in slight depressions owing to arrested growth 

 at the point of infection (Plate XXVI, fig. 1). 



Single scabs are usuallv not more than 5 mm. diameter, but they 



Ann. Biol, vn 27 



