872 LIFK-HISTORY OF PHOMA CITRICARPA, 



again, the disease was slower in developing upon the fruit, and 

 the spots remained of a dull brown colour. Since dew would be 

 just as heavy upon one side of the tree as another, its action, 

 except in conjunction with the sun, may be left out of account. 

 As regards the wind, the prevailing winds would tend to blow 

 spores upon the east side of a tree in the Gosford district, where 

 these observations were carried out: there is very seldom a north- 

 west wind. 



The spores from infected leaves, falling upon the fruit, become 

 uniformly distributed in the dew-drops. This uniformity of dis- 

 tribution is shown in the equidistant positions that the ripe 

 spores take up, when introduced into hanging drops. 



From the foregoing considerations, it seems probable that the 

 spores distributed on the surface of the fruit effect an entrance, 

 with their germ-tubes, into the rind, when its natural inhibiting 

 power, due to physical or chemical causes, has become impaired 

 bv exposure to the heat of the sun. 



Culture op the Fungus. 



By successive transportation of groups of spores to sterile 

 drops of water, isolated spores were obtained. These were trans- 

 ferred to various culture-media, and pure cultures in Petri-dishes 

 or test-tubes, were at length obtained. These were grown in an 

 incubator at a temperature of 22''C. The media in which the 

 fungus was most successfully cultivated were ordinary nutrient 

 agar, glucose-agar, and agar impregnated with watery extract of 

 orange-peel. The growth of the fungus upon each of these three 

 media is very different. 



Upon ordinary nutrient agar, growth proceeds very slowly. 

 Little patches of dark brown hyphie arise, creep over the medium, 

 and penetrate it. But they seldom travel far from the site of 

 inoculation, and, if several spores have been intr(^uced into a 

 Petri-dish, it is possible to obtain several isolated plants before 

 the hyphse have become interlaced. 



Upon glucose-agar, the other extreme is reached. The plant 



• (M'ows so luxuriantly, that, in a test-tube, the agar quickly 



becomes a carbonaceous-looking mass, tilled with quantities of 



