452 BOTANICAL GAZETTE [ DECEMBER 
death. The strain is so gradual, however, that the changes preced- 
ing death do not differ from those which take place in a dying 
leaf after having lived its allotted time. 
SUMMARY. 
To recapitulate, the investigations here described have shown 
that: 
(1) Coleosporium pini occurs abundantly in Maryland, Vir- 
ginia, and the District of Columbia, attacking only Pinus Vir- 
(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, !s 
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 the 
stomata and may result in keeping the diseased parts alive longer 
than the healthy in case the leaf or branch is removed from the 
tree. 
(7) As soon as the fungus ruptures the tissues evaporation 
is increased about one-fifth above the normal. In consequence 
of this the reserve water in the cells is gradually used up. This 
is followed by loss of turgidity and other physiological changes 
which lead to the gradual death and casting of the leaves. 
U. S. DEPARTMENT oF AGRICULTURE, 
WASHINGTON, D.C., 
