204 Report of the Botanist of thb 



clay loam. Since tlie variety was a choice one which the owner 

 desired to propagate extensively, the trees were cut back severely 

 in the spring of 1897 to induce a vigorous growth. In August 

 of the same year all wood available for buds was cut off; and in 

 each subsequent year the trees have been cut back in August to 

 get buds for propagation. With the exception of the gumming 

 of the fruit, the trees appeared healthy although they made very 

 little growth during the past two years. 



What caused this gumming is not clear. It was certainly not 

 the work of any insect or fungus and probably not of bacteria. 

 At our request Mr. H. A. Harding, the Station Bacteriologist, 

 made Petri-dish cultures of the-diseased plum tissue on glucose, 

 lactose and peptone gelatin and lactose agar. In several of the 

 cultures no growth whatever appeared. In others, a few colonies 

 of fungi and bacteria developed, but they were of diverse kinds 

 and evidently foreign to the disease. 



We suspect that it was partly the effect of the severe summer 

 pruning. Beach ^^ has reported a case in which summer pruning 

 of a cherry tree caused a severe gumming of the trunk; and in a 

 German periodical on plant diseases^s there is given an account 

 of some experiments which indicate that summer pruning of the 

 stone fruits is favorable to the production of gum. However, in 

 the present case there is certainly another factor to be accounted 

 tor: because an unpruned tree of the same variety in the same 

 garden showed traces of the disease as did, also^ some other 

 varieties there; and the same disease occurred in a mild form at 

 Geneva on German prunes which had, not been pruned to any ex- 

 tent for at least two years. 



Miscellaneous Diseases. — Neither orchard trees nor nursery 

 stock were much injured by leaf blight {Cylindrospormm padi). 

 Black knot {PlowHghtia morhosajie a serious enemy of plums in 

 Western New York, but it did not spread much last season. 

 Double fruits of plum were common. We found a few specimens 

 of crown gall on nursery stock. No specimens of jplum pocket 



"Beach, S. A. Gumming of Stone Fruits. Am. Gardening, 19 : 606. 

 " Zeitschrift filr Pflanzcnkranklicitcn, 6 : 58-59. 



