June, 1920] PATHOLOGY 



and nectarines. Both materials reduced the loss from rot in transit but the natural bloom 

 of the fruit was deal royed. < lontrol of rot in the orchard is thought to be the preferable means 

 of reducing such losses. D. Reddick. 



2615. Darnell-Smith, G. P. A fungous disease of prickly pear. Agric. Gaz. New 8outh 

 Wales 29: 440-441. 1918.- Opuntia inermia was found parasitized by a species of Fusarium 



which is not named. There are indications that the fungus may be valuable in helping to 

 exterminate this "pest-pear" and experiments are projected. — D. Reddick. 



2616. Dash, J. Sydney. Quelques conseils aux producteurs de cannes de la Guadeloupe. 

 [Hints to the sugar-cane growers of Guadeloupe.] Sta. Agron. Guadeloupe Bull. 1: 11-30. 

 1919. — Observations on the Island lead to conclusion that better drainage should be provided. 

 Most soils require lime and stable manure or the use of leguminous soiling crops. — Selection 

 of varieties suitable for Guadeloupe requires more attention. Preparation of soil and general 

 cultural directions are given. — An account of the insects and diseases affecting the sugar- 

 cane in Guadeloupe is presented. It is noted that there are no diseases in Guadeloupe which 

 do not exist in the Lesser Antilles. Hoot disease, Marasmius sacchari, being by far the worst 

 in the colony, is dealt with fully and the usual methods of treatment discussed at some length, 

 viz., healthy cuttings, proper tillage, rotation, sanitation, increased use of farmyard manure. 

 use of bordeaux mixture.—/. S. Dash. 



2617. Degrtjlly, L. Action des fumures sur le mildiou. [Action of manuring on grape 

 downy mildew.] Prog. Agric. et Vitic. 69: 531-533. 1918.— Heavy applications of nitrogenous 

 fertilizers favor the development of downy mildew. — D. Reddick. 



2618. Dey, P. K. Studies in the physiology of parasitism. V. Infection by Colletotrichum 

 Lindemuthianum. Ann. Botany 33: 305-312. PL SI. 1919.— The author investigated the 

 method by which Colletotrichum lindemuthianum gains entrance into the pods of two suscep- 

 tible bean varieties (Phaseolus vulgaris). The spores germinate on the surface, sending out 

 a germ tube which forms an appressorium as a result of a contact stimulus. The appresorium 

 becomes fastened to the leaf surface by means of a mucilaginous sheath. The spore is also 

 fixed in some unknown manner, The germ tube curves upward, thus exerting some pressure 

 on the leaf surface. From a part of the appressorium in contact with the cuticle, is developed 

 a peg-like infection thread which ruptures the cuticle. According to the author the pene- 

 tration of the cuticle is effected merely by mechanical pressure but the subcuticular layers are 

 softened and disorganized, presumably by an enzyme. The infection peg swells to the size 

 of a normal hypha shortly after penetrating the cuticle, grows into the host tissues and pro- 

 duces a small vesicle from which branches ramify. The host cells do not collapse until in- 

 vaded by the fungus. According to the author C. lindemuthianum therefore gains entrance 

 into the host quite as does Botrytis cinerea. — E. C. Slakman. 



2619. Dickson, J. G., and A. G. Johnson. Studies on stem rust in Wisconsin, 1918. 

 Bienn. Rept. Wisconsin Dept. Agric. 1917-18: 50-60. 1918. Also Wisconsin Dept. Agric. 

 Bull. 23: 56-60. 1918. — Studies begun late in the winter and carried throughout the summer 

 were so conducted as to furnish data upon the role of the common barberry (Berberis vulgaris) 

 in the spread of the stem rust of grains (Puccinia graminis). Urediniospores which had 

 formed on the new fall shoots of perennial grasses and winter grains retained their ability to 

 grow until the winter covering of snow had disappeared, about March 2, after which the via- 

 bility decreased very rapidly. None retained ability to grow after March 30. Observations 

 made at seventeen definitely marked stations in the vicinity of Madison as well as a survey 

 over the southern part of the state, gave no evidence of infections on wheat in advance of 

 the time when they could have come from infected barberries. From observations made at 

 about fifty selected stations it was noted that the original infection was definitely traceable 

 directly to infections on barberries. Spring infection was noted first only in close proximity 

 to infected barberries the spread of the rust being always more abundant to the northeast of 

 the barberry planting. It was observed that the kind of grain that was commonly grown in 

 a locality was universally heavily rusted, while grains new to a locality, with the exception 

 of barley, were rarely rusted. — L. M. Massey. 



