870 LIFE-HISTORY OF PHOMA CITRICARPA, 



"The round, sunken, conspicuous spots are generally of a 

 ruddy-brown tint, and paler in the centre where the pustules are 

 seated." 



" This is a distinctive species in the small size of the perithecia, 

 as well as in the size and shape of the sporules." 



N. A. Col)b(5), in 1904, described some attempts to germinate 

 the spores of Phoma citricarpa. He states that -" The spores 

 of this disease do not germinate under the laboratory conditions 

 ordinarily brought to bear in their examination, and, in this 

 respect, they differ from most spores found in connection with 

 prevalent fungus diseases. The following observations, though 

 they are inconclusive, are inserted here out of regard to the 

 rarity with which I have observed these spores to germinate. . . . 

 Spores of this fungus were ringed in a small supply of water and 

 numerous air-bubbles. After twenty-four hours, the spores had 

 failed to germinate in those parts where they were completely 

 surrounded with water. Spores located at the edges of air- 

 bubbles where, on one side, they had access to air, each sent out 

 into the air a single very fine unbranched mycelial thread about 

 one micromillimetre wide, though slightly wider at the free end. 

 The mycelium was colourless, and so fine as, under the circum- 

 stances, to preclude observation as to septa; none were seen. At 

 the end of twenty-four hours, the length of these hyphje averaged 

 several times the length of the spores." 



General Symptoms of the Disease. 

 The disease, which is now commonly known in New South 

 Wales as Black Spot or Anthracnose of Citrus Fruit, appears as 

 minute black spots upon the foliage throughout the year. Upon 

 the fruit, it is seldom seen till the beginning of August. In 

 September, particularly after hot westerly winds, it may quite 

 suddenly make its appearance upon the fruit throughout an 

 orchard. Dark brown, irregular spots first make their appear- 

 ance upon the skin. The spots vary in size from one-eighth of 

 an inch or less to half an inch or more in diameter. Later, these 

 become depressed, and some may become confluent. The inner 

 part of the spot next becomes of a light cream-colour, and some- 



