lyil.j PUBLIC DOCUMENT — No. 31. 153 



gis,^ Cziii)ck,- Stone/' Atkinson'* and others have dealt wilh 

 various physiological troubles more in detail. 



From our observations and experiments in the field and green- 

 house we have come to the conclusion that it is a well-developed 

 form of malnutrition, using malnutrition in its broadest mean- 

 ing, i.e., to include any physiological ti'ouble which is causetl 

 by an excess or lack of any one or more nutritive substances 

 necessary for the normal metabolism of a plant^ and is allied 

 to the phenomena exhibited in a severe case of overfeeding. 



Logically it is what one would expect when a large tree is 

 suddenly cut off or the top killed, and practically all transju ra- 

 tion, respiration, or, in short, all photosynthesis and leaf metab- 

 olism, is suddenly arrested. We have a violent disruption of the 

 normal metabolism of the tree. The balance bet^yeen root ab- 

 sorption, photosynthesis, etc., and the metabolic processes of 

 the leaves is suddenly broken, and we have the roots, which are 

 still alive, attempting to do their normal work without the aid 

 of the leaves ; starch formation is arrested and carbon assimila- 

 ti(m cannot take place. In the roots there remains a great re- 

 serve store of food and during the winter no root pressure. As 

 most woods are cut in the fall and winter, the trees are dormant, 

 and forest fires also occur largely in fall and spring during this 

 dormant period. Xow, when spring comes and circulation 

 starts, the adventitious buds are called upon to produce new 

 shoots for the utilization of the reserve food in the roots. This 

 they try to do in the manner we have described, by producing 

 abnormally large leaves or a great number of small and dis- 

 torted leaves. This distortion will be discussed later. 



Of the trees which have come under our observation, maples, 

 oaks and chestnuts seem to be the most susceptible to leaf dis- 

 tortion, while such trees as the ash, poplar and plane usually 

 have abnormally large leaves with very little distortion. IL)W- 

 ever, in some cases both conditions are observable. 



The theory which has been advanced above as to the canse of 

 the disease has been borne out by experiments carried on in the 



' Conn. Agr. Exp. Sta., 1808, and others. 



2 Biochemie der Pflanzen (general). 



' Mass. Agr. Exp. Sta. reports. 



* N. Y. (Cornell Univ.) Agr. Exp. Sta., Bui. No. 53. 



