E. ;M. Doidge 57 



had gone right through the skin and penetrated into the pulp. The 

 latter was not noticeably discoloured hut looked rather dry and had 

 a pecuhar taste and odour. 



On shaddocks by artificial inoculation a number of small spots 

 were produced not exceeding 8 mm. in diameter; they were very 

 slightly sunken, and cinnamon brown rufous in colour. On cutting 

 through these spots it was found that the disease had not penetrated 

 far into the rind : the tissues were discoloured to a dirty brownish 

 yellow to a depth of 1*5 mm., i.e., just below the oil ducts. This 

 discoloured portion was bounded by a thin scarlet line which in some 

 cases marked the boundary between healthy and diseased tissues. 

 The red line is not always present, and when present is not always 

 continuous. The red colouring matter disappeared at once when 

 pieces of the rind were fixed in hot acetic alcohol. 



Grape fruit artificially inoculated developed infected areas not unhke 

 those on the lemons. They were sunken, rather irregular in outhne, 

 up to 1 cm. diameter, cinnamon colour in the centre ^vith a darker 

 rim, of Mikado or Sayal brown. Sour and sweet limes are also affected 

 in a similar way to the lemons. 



On citrons inoculation with a pure cultm'e resulted in the formation 

 of numerous reddened areas up to 12 mm. diameter, some of these were 

 slightly sunken ; the colour was at first zinc orange to apricot orange, 

 and later became cinnamon brown. 



The only variety of citrus fruit which has so far proved resistant 

 is the Seville orange, which has not been found infected naturally, 

 and which has up to the present resisted infection by artificial means. 



Affected fruit cannot be kept for any length of time ; the discoloured 

 spots readily serve as a starting point for numerous fungus infections 

 and these complete the work of destruction. Almost every fruit 

 infected ^\T.th the spot disease, if kept for any length of time, was 

 completely destroyed by PeniciUium spp. or. less frequently, by 

 Colletotrich inn gloeosporioides. 



The disease not only disfigures and destroys the fruit, but affects 

 the branches to a considerable extent. The organism seems almost 

 invariably to attack the stems just round the leaf bases ; an area of 

 about 6 — 10 mm. diameter becomes water-soaked in appearance, the 

 petiole becomes involved and sometimes the basal part of the leaf, and 

 the leaf falls. The infection then spreads to the branch in the leaf 

 axil, surrounds it at the base and it \^-ithers and dries up. The infected 

 area on the main part of the stem becomes up to 20 mm. long, and 



