TfiE RED FUNGUS. 23 



Prof. H. S. Fawcett ^ has found that this fundus requires from 30 

 to 40 days to mature a pustule and j)roduce pycnidia when grown on 

 a 5 to 10 per cent glucose agar in the laboratory. 



DISSEMINATION OF SPORES. 



Various agencies, such as rains and dews, crawling and adult white 

 flies, and other insects, have been considered as probable means of 

 spreading fungous spores. Notwitlistanding the fact that its spores 

 have been described as mucilaginous, and therefore would not seem 

 to be subject to being blown about by winds, laboratory tests have 

 shown that after water solutions of spores have been dried on a hard 

 surface the spores can be loosened and blown away by the aid of an 

 electric fan or lung power. Wliile complete success did not attend 

 these experiments, it was demonstrated that spores can be and doubt- 

 less are blown about by winds to a considerable extent after once 

 being freed from their mucilaginous matrix by rains and dews, and it 

 is believed by the authors that winds are the most valuable agents in 

 spreading the fungus from tree to tree and to the more isolated groves 

 in a fungus-infested district. However, when once the wliite flies 

 in a tree have become infected, rains and dews appear to be the most 

 valuable agents of distribution throughout the individual and closely 

 adjoining trees. The fact that the pustules are largely borne on the 

 underside of the leaves is no argument against this view. While the 

 pustules thus located are for the most part protected from the direct 

 wash of beating showers, examination of citrus trees, especially 

 oranges and tangerines, will show that many of the leaves are more 

 or less slightly curled so that their underside is easily wetted, either 

 entirely by direct rainfalls or in spots by splashing from closely 

 growing leaves, while the newer growth, upon which infestation is 

 usually very heavy, because of its more flexible nature is soon beaten 

 or weighted down by the rain so that the underside of its leaves 

 receive innumerable splashings and dri])pings from the pustule- 

 bearing leaves above. 



After several showers of moderate duration and force, an exami- 

 nation of trees in the laboratory grove showed that about 90 per cent 

 of the leaves were either thorouglily or partly wetted on the lower 

 surface, and during the progress of ordinary showers drippings from 

 leaves above have been seen to bound off from lower leaves to wliich 

 they had fallen and strike the exposed underside of leaves 3 feet to 

 one side, or to splash obliquely upward as high as 1 foot. This 

 upward spattering accounts not a little for the upward spread of 

 fungus. It requires only a microscopic examination of drippings 

 from fungus-laden trees, caught during a heavy shower, to prove that 



» Special Studies, No. 1, I'niv. of the State of Fla., p. 13, 1908. 



