THE EED FUNGUS. 23 
Prof. H. S. Fawcett 1 has found that this fungus requires from 30 
to 40 days to mature a pustule and produce pycnidia when grown on 
a 5 to 10 per cent glucose agar in the laboratory. 
DISSEMINATION OP 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. Notwithstanding 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. While 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 white 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 drippings 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 thoroughly 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 which 
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 
i Special Studies, No. 1, Univ. of the State of Fla., p. 13, 1908. 
