DISEASES OP PLANTS. 347 



of the old sori and produce auicebfe, which come together to form Plasmodia 

 that cause secondary infections. These Plasmodia feed on surrounding tissue, 

 causing a dry rot, which is probably a mild form of the canker stage. 



The spores germinate in culture media, each producing a single uninucleate 

 amo?ba, and this body encysts, entering a resting stage, when conditions become 

 unfavorable. Apparently saprophytic Plasmodia are produced on culture media. 



A bibliography is given. 



Soil stain and pox, two little known diseases of the sweet potato, J. J. 

 Taubenhaus {Abs. in Phytopathology, Jf (IQIJ/), No. 6, p. Jf05). — Soil stain or 

 scurf, which was first described by Halsted (E. S. R., 2, p. 416), was attributed 

 to Monilochcetes infuscans, but the author has carried on some investigations 

 which indicate that the genus Monilochsetes is probably not well founded. 

 Affected potatoes are considerably reduced in value, the disease being confined 

 to the underground parts and carried with the seed. It is said that it may be 

 easily controlled by soaking the seed (roots) for 10 minutes in a solution of 

 corrosive sublimate. It may also be eliminated by growing plants from vine 

 cuttings. 



The second disease reported upon was also described by Halsted (E. S. R., 2, 

 J). 416) and attributed by him to Acrocystis batatw. During two years' work 

 of the author's on this disease this fungus has not been found associated with 

 it. A Fusarium, an Actinomyces, and a Rhizoctonia were isolated, and it was 

 found that an excess of lime favored the disease, while an acid fertilizer such 

 as acid phosphate retluced it. 



Some important leaf diseases of nursery stock, V. B. Stewart {New York 

 Cornell Sta. Bui. 358 {1915), pp. 167-226, figs. 2.9).— This is a condensed report 

 of investigations since 1909 on nursery leaf diseases and means of protection 

 therefrom. These include apple scab {Venturia incequalis), pear scab (F. 

 pyrina), apple powdery mildew {Podosphwra oxyacanthw or P. leucotricha) , 

 yellow leaf disease of cherry and plum, ascribed by Higgins (E. S. R.. 29, p. 

 349; 30, p. 750) to Coccomyces spp. (polymorphic forms of Cylindrosporium), 

 powdery mildew of cherry (/'. oryacuntlue), anthracnose of currants and goose- 

 berries {Pseudopeziza ribis, parasitic stage Glososporium ribis), Septoria leaf 

 spot of the same plants {8. ribis), gooseberry mildew {^phcerotheca mors-uvce) , 

 leaf blotch of horse chestnut {Lwstadia oesculi, conidial and parasitic form 

 Phyllosticta pavice), peach leaf curl {Exoascus deformans), leaf blight of pear 

 and quince {Fabrcea maculata [Stigmatca mespili], parasitic stage Entomo- 

 sporium maculatum), Septoria leaf spot of pear {Mycosph(erella sentina, 

 conidial stage S*. piricola), black spot of roses {Diplocarpon rosw, conidial stage 

 Actinonema rosw) , and mildew of rose and peach {Sphccrotheca pannosa, conidial 

 form Oidiuni leucoconium) . 



A promising- new fung-icide, W. M. Scott {Abs. in Phytopathology, ^ {1914), 

 No. 6, p. 412). — The author briefly reports upon some expeinments on the use 

 of barium polysulphid in crystal form for the control of apple scab. Spray- 

 ing experiments were conducted, the fungicide being used at the rate of from 

 3 to 6 lbs. to each 50 gal. of water in comparison with lime-sulphur solution. 

 No outbreak of apple scab occurred on any of the checks, so that the value of 

 the fungicide could not be determined for the control of the disease. 



In peach-spraying expeiiments the barium sulphur used at the rate of 3 lbs. 

 to 50 gal. of water controlled peach scab almost completely. 



The author concludes that this material has decided fungicidal properties 

 and is worthy of further investigation. 



Apple cankers and their control, L. R. Hesler {New York Cornell Sta. Circ. 

 28 {1915), pp. 17-28, figs. 16).—Bviet popular descriptions are given of the 

 various forms of canker of apple trees found in New York State with sugges- 



