To recapitulate, the investigations here described have shown that: (1) Coleosporium pini occurs abundantly in Maryland, Virginia, and the District of Columbia, attacking only Pinus Virginiana. (2) It requires twelve months to complete the development of this fungus, and during a large part of that time it does not seriously interfere with the functions of its host. (3) The fungus is disseminated by means of sporidia, which develop only during wet weather. (4) From the leaves on which they are borne the sporidia are washed or drop to the young needles just showing their tips, which they infect. No evidence of this infection, however, is apparent for two or three months. (5) Regardless of the season, there is a marked similarity in the time of the appearance of the sporidia and the time of the appearance of the young leaves. (6) Before the fungus ruptures the cortical tissue evaporation from the diseased areas is less than that from healthy parts of the same leaf. This is due to the permanent closing of th...