^91^1 DISEASES OF PLANTS. 849 



have occurred. The Important new fact considered as established is the occur- 

 rence of leaf lesions, the evidence so far as obtained apparently favoring the 

 view that the epidermis is penetrated by the bacteria. 



A study of the brown rot fungus in northern Vermont, H. E. Babtram 

 (Phytopathology, 6 {1916), No. 1, pp. 7i-78).— As a result of a study of the 

 common brown rot of stone fruits as found in Vermont, the author claims that 

 the fungus causing the disease is that known in Europe as Sclerotinia cimrea. 

 He arrived at this conclusion not only by measurements of the conidia, absence 

 of disjunctors, and the gray color of the conidial tufts, but more especially by 

 the persistent vitality of the conidia through the winter. The conidia, both 

 those already present as well as those produced from the dormant mycelium in 

 mummied fruits, are said to present a danger of early spring infections that 

 has not been generally recognized. 



Gummosis in the fruit of the almond and the peach almond as a process 

 of normal life, M. W. Beuerinck (A". Akad. Wetemch. Amstei-dam, Vcrsl. W»« 

 en Natuurk. Afdeel., 23 (1914), pt. 1, pp. 531-542, pis. 2; also in ditto, Proc. 

 Sect. Set., 17 (1914), pt. 1, pp. 810-S21, figs. 3).— Studies previously reported by 

 the author with Rant (E. S. R., 17, p. 1146), and by the latter (E. S. R., 19, 

 p. 449), have been followed up by the author, who states that mechanical 

 wounds in growing tissues of Amygdalaeeie are sometimes healed directly, 

 sometimes after developing gummosis. 



The chief tissue which is transformed into gum is the young undifferentiated 

 secondary wood. A network of gum canals forms around the wound as a result 

 of stimulus. The network in the large branches is elliptical in outline, the 

 wound being at the lower focus. If the wound is healed the cambium con- 

 tinues to produce normal secondary wood. Continued stimulus continues gum 

 formation. The stimulus spreads from cells dying slowly after being wounded, 

 poisoned, or parasitized, a cytolytic agent passing therefrom into young wood 

 or procambium which may retain this substance and liquefy. It is considered 

 that gummosis is caused by necrobiosis. Young medullary rays and phloem 

 bundles are converted less readily. In the fleshy part of the fruit the gum 

 arises from the conversion of the phloem, the protophloem remaining unchanged. 



It is held that although gummosis in these fruits is a part of the normal 

 development, a wound stimulus is nevertheless active as a normal factor. 

 This arises from the tension in the parenchyma of the fruit wall leading to 

 tearing, necrobiosis, and gum formation in the delicate tissue of the phloem 

 bundles. In one view the almond and the peach almond may be considered 

 as pathological species. 



Report of the plant pathologist, H. E. Ste\-ens (Florida Sta. Rpt. 1915, pp. 

 LXXVII-XCIII, figs. 2). — The work here reported covers some investigations 

 of citrus diseases and a pecan disease. The citrus disease investigations have 

 been principally on citrus canker, gummosis, and melanose, the major part of 

 the work having been confined to citrus canker. 



In continuation of an investigation of gummosis, inoculation experiments 

 Avith different organisms have been undertaken, but from six series of these 

 experiments negative results have been obtained. There appears to be some 

 evidence that the disease spreads in the grove under natural conditions. Some 

 experiments for control of gummosis are briefly reported upon, In which the 

 value of Bordeaux paste, lime and sulphur paste, and commercial lime-sulphur 

 solutions were tested, the diseased areas being scraped and covered with the 

 disinfectant, or completely cut out and painted over with it. The results from 

 the treatment, while somewhat favorable, are considered to be only tentative 

 and are to be repeated. 



