242 HENRY SCHMITZ 



The above observations point towards the following conclu- 

 sions. (1) They corroborate the assumption that the broom 

 manufactures a considerable amount, if not all of the food neces- 

 sary for its excessive growth. (2) The increased amount of 

 storage food and the consequent increased osmotic pressure may 

 account for the prolonged and rapid growth of the diseased parts. 

 The influence of an increased osmotic pressure and consequent 

 greater turgidity of the individual cells, if sufficient amounts of 

 water are present — as they no doubt are — may be far reaching. 

 For example it maj^ change the semi-permeability of the proto- 

 plasmic membranes and thus decidedly influence the metabo- 

 lism of the cells. It may also, by tightly pressing the proto- 

 plasm against the cell wall and by mechanical stretching, stimu- 

 late cell enlargement and division. (3) The fact that the buds 

 on the brooms open before the normal buds indicates that the 

 fungus disturbs the normal periodicity of the affected region. 

 (4) Chlorophyll is present in the leaves of the brooms but is 

 masked by the red color. (5) The red coloration of the leaves 

 is due to the acidity of the leaves, and (6) The red color disap- 

 pears when the acidity of the leaf is neutralized. 



Whether the increase in acidity of the leaves of the brooms is 

 due to the fungus causing certain hydrolytic effects on the stored 

 material, or even the cell walls themselves, is a matter to be 

 cleared up by future investigation. In this connection it is 

 interesting to note that many normal leaves in their young stages 

 have a decided red color, as for example the leaves of the rose, 

 maple, beech, cherry, etc. It may be that the fungus merely 

 prolongs the embryonic condition of the leaves and twigs, since 

 even the leaves of the brooms lose all traces of their red color 

 on becoming fully mature. 



