DUFRENOY: false witches -brooms in ERICACEAE 



529 



III. Carbohydrates. The early development of false witches'- 

 brooms is certainly due to the formation of large quantities of 

 soluble osmotic substances in the infected tissues. That they 

 contain much sugar, may be deduced from the appearance of 

 anthocyan in them. 



Such a formation of soluble material might be readily ex- 

 plained by the secretion of hydrolysing enzymes b}" infecting 

 hyphae. Observation proves, moreover, that insoluble carbo- 

 hydrates are always scarce in false witches'-brooms (see table 1). 

 The Anylolencites in infected leaves of V. myrtillus do not color 



TABLE 1 

 BiocHEMY OF Leaves of V. myrtillus 



blue by I + KI, but browTi-red, and while, in October, sound 

 leaves of Arbutus are crowded with starch grains (blue with 

 I + KI), infected leaves never show this reaction. Assimilation 

 in sound leaves of A. unedo, though feeble, may still be demon- 

 strated, oxygen bubbles being evolved by immersed leaves when 

 exposed to full sunlight. 



No oxygen is evolved in the shade, where assimilation must be 

 so attenuated as to be superseded by respiration. Leaves of 

 false witches'-brooms of Arbutus, contain at least a few chloro- 

 plasts. They can assimilate in early. spring, at least when the}^ 

 are exposed to full sunlight, but in autumn, they never evolve 

 oxygen. Moreover leaves of false witches'-brooms of V. myrtil- 



