530 dufrenoy: false witches'-brooms in Ericaceae 



lus do not form any starch grains after they have been severed 

 from healthy shoots. 



IV. Glucosides. Reddening of leaves of false witches'-brooms 

 is reported in most cases, the intensity increasing with the insola- 

 tion. Infected leaves of Vaccinium from sunny heaths in the 

 Pyrenees show a deep red, while infected leaves of Arbutus unedo 

 from the shaded pignada of Arcachon are scarcely tinged with 

 rose. 



TABLE 2 

 Effect of Staining with Nitric Acid 



ORGANS OF A. INEDO 



Infected cells of leaves... . 



Young leaves (hairs) 



Leaves 



Palisade cells 



Spongy parenchyma 



Stem 1 year old 



Cortex external 



Internal 



Pericyclic fibers 



Root 1 year old 



Corolla (outer and inner 



rows) 



Fruit (green or red) 



Seed coat 



Albumen and embryo 



NUMBER OF CELLS STAINING BY HNO3 





 50% 



100% (April) 80% (October) 

 80% (April) 20% (October) 



The appearance of anthocyan in sound or infected cells has 

 been found to be concomitant with abundant formation of sugar 

 or colorless glucosides (Combes, '09, '18), with the disappear- 

 ance of starch (Dufrenoy), and with the reduction of tannin. 

 This can scarcely apply however to false witches'-brooms 

 where brown rather than red pigments prove to be of interest 

 biochemically. 



These brown pigments were studied by Rayner in connection 

 with the glucosides of the arbutin group. These glucosides are 

 very widely distributed among the Ericaceous plants, though 

 they may differ somewhat with the different species. No 

 arbutin was obtained by Bourquelot ('13) from leaves of Arbutus 



