DISEASES OF PLANTS. 643 



the upper branches, particularly in damp weather and in sheltered localities, 

 and entirely preventing the formation of bolls. 



Potato diseases and seed potatoes, D. C. Babcock (Mo. Bui. Ohio Sta., 1 

 {1916), No. 1, pp. 10-14, figs. 3). — A popular description is given of a number 

 of diseases of potatoes, and spraying, seed selection, and seed treatment are 

 suggested for tlieirt.control. 



[Diseases of prickly pear], T. H. Johnston and H. Tryon (Rpt. Prickly-Pear 

 Travel. Com., Queemland, 1912-19U, pp. XIII, 18-20, 28, 34, 35, 43, 49-51, 59, 

 63-65, 84. 86, 90, 91, 92, 93-95, 96, 98, 100, 101, IO4. 105, 109, 110, 111, 115-125, 

 pis. 3). — Such parts of this report are noted herein as refer to diseases and con- 

 ditions tending to destroy prickly pear or to reduce injury therefrom, as ob- 

 served or reported at various points visited in both hemispheres by the com- 

 mission between November 1, 1912, and April 30, 1914. 



The commission is led to conclude that disease does not play a very important 

 part anywhere in checking the growth of prickly pear when growing under 

 normal conditions. Observations and studies have been made on several abnor- 

 malities due to parasitic agency, and others due to environment, including cli- 

 matic conditions, which appear to be nowhere of considerable importance in 

 this connection. 



Only one prickly pear disease is regarded as of sufficient value to warrant Its 

 introduction, namely, anthracnose, shot hole, or black rot, due to Gloeosporium 

 lunatum. This is common in Texas, and on warm, moist days causes rapid and 

 considerable destruction of young segments and of older joints if previously 

 attacked. 



Another fungus, Selerotiton (Selejotinia) opiintiarum, causes a disease 

 which is somewhat serious in Argentina. 



A bibliogi'aphy is appended containing a few references to diseases of prickly 

 pear. 



Blister disease of fruit trees, G. Massee {Roy. Bot. Gard. Kew, Bui. Misc. 

 Inform., No. 3 {1915), pp. 104-107, pi. 1). — The three stages of the organism 

 causing blister disease of the apple, pear, and cherry are discussed. The some- 

 what rare ascigerous form {Diaporthe ambigua) and the spore-bearing form 

 {Phoma malt) are said to be pure saprophytes, the only parasitic form being 

 that previously known as Coniothecium chomatosporum. This, it is held, 

 should hereafter be retained only as a form-genus until its components are 

 correlated with their respective Phoma forms. 



Frequent spraying with Bordeaux mixture is thought to be sufficient to pre- 

 vent infection of fruits and young shoots, but the most reliable method is the 

 removal of dead twigs and spurs bearing the fungus. 



Outbreaks of grape diseases in 1914, J. Capus {Rei\ Tit., 42 {1915), No. 

 1088, pp. 382-384). — This is an account of the several appearances, in parts of 

 France, of downy mildew and black rot of grape, the dates of which agree in 

 part, and of the several outbreaks of Oidium as related to weather conditions. 



Employment of hot water against grape parasites, L. Ravaz {Prog. Agr. 

 et Vit. {Ed. VEst-Centre). 36 {1915), No. 18, pp. 4 1 4-4 16). —This is mainly a 

 statement, with a brief discussion, of the conclusions of Semichon as already 

 noted (B. S. R., 34, pp. 50, 243). 



Notes on black rot and downy mildew, L. Ravaz {Prog. Agr. et Vit. {Ed. 

 VEst-Centre), 36 {1915), No. 22, pp. 505-508, pi. 1).— The development of black 

 . rot is described. The mycelium arises in early spring, about the same time as 

 that of the downy mildew, and is able to penetrate the leaf cuticle. 



The receptivity of the plant to black rot appears to be related to the nature 

 and character of the material which unites and embeds the epidermal cells. It 

 is thus, apparently, more dependent on the conditions prevailing in the plant 



