582 



SCIENCE 



[N. S. Vol. XLII. No. 1086 



Some New and Old Methods in Plant Pathol- 

 ogy: J. Franklin Collins, TJ. S. D. A., 

 Washington, D. C. (Eead by title.) 

 Citrus Oummosis and Melaxuma: H. S. Faw- 

 OETT, Whittier, Cal. 



These diseases were illustrated by means of 

 lantern slides and brief explanations, together 

 with a set of specimens and photographic en- 

 largements in the laboratory. The former is 

 caused by the fungus Pythiacystis citrophihora 

 S. and S., and the latter by a fungus which is 

 probably a Dothiorella. 



Fruit Stain and Wither Tip of Citrus: J. T. 

 Barrett, Riverside, Cal. 

 Effects of the fungus Colletotrichum gloeo- 

 sporioides were illustrated on twigs and fruit. 

 Dr. Barrett stated that he did not yet have 

 evidence that the fungus is capable of infecting 

 thoroughly sound and healthy tissue of leaves 

 and twigs, but infection of the fruit through 

 germination from appressoria, killing small 

 areas of rind, and later development of the 

 fungus cause serious fruit rotting in addition 

 to the tear-stain marks upon the surface. 

 Oiservations on Prune Rust (Puccinia Pruni- 

 spinosce Peis.) in Southern California; J. T. 

 Barrett, Riverside, Cal. 

 This fungus has become serious at times in 

 southern California on apricots and peaches. 

 The characteristic spots and injury to the 

 orchard by defoliation were shown by lantern 

 slides. In some eases early fall pruning has 

 stimulated fall growth in which foliage re- 

 mains alive through the winter and rust devel- 

 oped in this has caused early spring infection 

 with very detrimental effects to the orchards. 

 Coryneum Fruit Spot of Apricots: J. T. Bar- 

 rett, Riverside, Cal. 



Characteristic spotting was illustrated by 

 lantern slides. This disease is not of so wide 

 distribution in apricots as has been supposed. 

 Accordingly, spraying operations carried out 

 for this trouble have not given satisfaction in 

 all cases. 



Walnut Blight and Croivn Gall: C. O. Smith, 

 Whittier, Cal. 



The symptoms of this disease were illustrated 

 by means of lantern slides and specimens were 

 shown in the laboratory. 



August 5, 2 P.M. The program was continued 

 in the laboratory of plant pathology. 



Peridermium MarTcnessii Moore, and Cronar- 

 tium Quercuum (Berle.) : E. P. Meineoke, 

 U. S. D. A., San Francisco, Cal. 

 The results of extensive observations on these 



rusts and inoculation experiments with the 



different spore forms were given. 



An Estahlished Asiatic Oymnosporangium in 

 Oregon: H. S. Jackson, Corvallis, Oregon. 

 Results of careful studies and cross inocu- 

 lations with a newly imported Oymnospo- 

 rangium discovered on Oriental pears in Ore- 

 gon were given. 



The Need of a Pure Culture Supply Laboratory 

 for Plant Pathology in America: C. L. 

 Shear, U. S. D. A., Washington, D. C. (To 

 be published in full in the October number of 

 Phytopathology.) 



Studies of the Rhizoctonia Disease of Potatoes: 

 J. H. CoRSADT, Corvallis, Oregon. 

 On account of the seriousness of potato 

 troubles due to Rhizoctonia in the state of 

 Oregon, studies on this disease were under- 

 taken. Affected plants and tubers were secured 

 from different localities and a large number of 

 different strains of the causal organism were 

 isolated from sclerotia on the tubers, from 

 sterile mycelium on the underground parts of 

 the plant, from basidium-bearing mycelium, 

 and from individual basidiospores. The cul- 

 tural characters of these strains were similar, 

 but showed some variation. A splendid devel- 

 opment of the typical Corticium (Hypochnus) 

 stage appeared on the stems of young plants 

 grown in sterilized soils from sterilized seed 

 pieces which had been inoculated with pure cul- 

 ture of the organisms isolated from sclerotia, 

 sterile mycelium, and single basidiospores. A 

 number of different varieties of potatoes were 

 inoculated with Rhizoctonia grovni under sim- 

 ilar conditions and the effects noted. Some 

 varieties proved extremely susceptible, while 

 others were rather strongly resistant. It was 

 also found that when grown on sterile raw 

 plugs cut from different varieties of potatoes 

 the fungus developed rapidly on certain vari- 

 eties and but slowly on others. By artificial 



