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A CONTRIBUTION TO OUR KNOWLEDGE OF 

 SILVER-LEAF DISEASE. 



By Ph. Dr JAR. SMOLlK (Roudnici, Bohemia). 



(From the Department of Plant Physiology and Pathology, 

 Imperial College of Science and Technology, London.) 



The etiology of Silver-leaf disease has passed through many phases 

 and has been the subject of many diverse opinions. First observed by 

 Prillieux (1885), this disease was placed by Sorauer (17, p. 285, " Milch- 

 glanz ") among the non-parasitic plant diseases. Similarly Delacroix 

 (2, p. 227) places "le plomb" among the "maladies non-parasitaires." 

 Percival (12), Gussow (3) and Brooks (1) record successful inoculation 

 experiments with the fungus (Stereum purpureum). Massee (9) rejects 

 this view of the etiology by Stereum; Blackmore ascribes the disease 

 to the action of bacteria. Though the view generally adopted seems 

 to be that of Percival, nevertheless it must be admitted that this 

 remarkable phenomenon in phytopathology is not yet completely 

 understood. Such being the case it seems that the methods of practical 

 treatment advocated by various authors have hardly an adequate 

 scientific foundation. 



The external symptoms of Silver-leaf disease are obvious. As is 

 well known, the leaves of the attacked trees show on their upper surfaces 

 an ashen-grey colour giving a "silvered" appearance to the tree. The 

 list of host trees is considerable including in particular nearly all the 

 species of Prunus. The most important works on Silver-leaf disease 

 are those of Percival (12), Gussow (3), Brooks (1) and Pickering. 

 A complete bibliography and history of the whole question will be 

 found in Giissow's work. 



My contribution concerns the cytology of the attacked leaves. For 

 the investigation I made use of the attacked and healthy plum leaves 

 of the variety Prunus domestica var. " Victoria " which is a favourite 

 in the English gardens because of its large and valuable fruit. Hand 



