THE bagireaa etry OF APPLE pombe INFECTED 
WITH GYMNOSPORANGIUM 
Howarp S. REED AND J. S. CooLey 
(WITH ONE FIGURE) 
The present paper reports the results of some studies upon the 
transpiration of apple leaves infected with the cedar rust fungus, 
Gymnosporangium Juniperi-virginianae Schw. Observation of 
trees attacked by this fungus shows that changes involving serious 
injury to the economy of the trees are produced. Such trees 
usually show characteristic dwarfing of both trunk and fruit. 
The writers have undertaken to make some quantitative 
physiological studies upon these diseased trees as a part of a general 
pathological problem. 
The study of the causative organism is highly important for 
plant pathology if any prophylactic measures are to be taken, but 
the reaction of the host is also a factor of importance if thé action 
of the parasite is to be understood, or if efficient remedial measures 
are to be applied. The interest of the cultivator is principally in 
the host, but up to the present time that of the plant pathologist 
has been chiefly centered in the parasite. It is believed, however, 
that a physiological-pathological study of the host -will yield results 
of no less interest than those of a strictly mycological nature. 
A survey of the published work upon transpiration discloses 
few studies of the transpiration of diseased plants, although the 
assumption is frequently made that the rate of transpiration is 
affected by the presence of disease. 
BLopDGEtT? has reported an observation upon the transpiration 
of excised branches of Rubus sp. infected with Gymnoconia inter- 
stitialis. In a given period (apparently shorter than 24 hours) 
the rusted branch absorbed 42 cc. of water, while a healthy branch 
possessing an equal number of leaves absorbed only 23 cc. of water 
t Paper 24 from the Laboratory of Plant Pathology, Virginia Agricultural Experi- 
ment Station. 
2 BLopcett, F. H., Transpiration of rust-infected Rubus. Torreya 1:32. 1901. 
421] . {Botanical Gazette, vol. 55 
