1918.] DISEASES OF PLANTS. 545 



latexometers often give very inaccurate figures as to the rubber content of 

 latex, four series of experiments were conducted under estate conditions in 

 which the percentage of rubber was measured by means of latexometers of 

 different types and also by the dry weight of a slab coagulated from a 50 or 

 100 cc. sample of latex. The figures found by the latexometer measurements 

 differed from those found by the dry-weight measurements, but the relative 

 figures remained the same. 



The authors suggest that the differences may be partly due to errors in the 

 weight of the dry samples. The errors of the latexometer measurements are 

 largely explained by errors in the scale and by the influence of temperature on 

 the readings. 



Thirty-seven years of spruce selection in Austria, Reuss {Ccnthl. Gesam. 

 Forsho., 42 (1916), No. 11-12, pp. 383-417: abs. in Internat. Inst. Agr. [Rome'\, 

 Internat. Rev. Sci. and Pract. Agr., 8 (1911), No. 8, pp. 1116-1118).— In cou- 

 tinuation of selection studies reported on in 1884 the results are given in this 

 paper of .selection studies conducted to 1916. The earlier work is also sum- 

 marized. 



The experiments in pure selection were made with 21 classes of spruce seed 

 taken from parent trees ranging in age from 23 to 142 years. The influence 

 of the parent on the progeny is considered with reference to the climatic origin, 

 age, growth performance, and distinguishing characteristics of the parent. The 

 study is being continued by the Imperial Forestry Experiment Institute at 

 Mariabrunn. 



The rotation period of teak, H. Beekman (Boschhouwk. TijdscJir. Tectona, 

 10 (1911), No. 12, pp. 995-1044). — A paper on this subject delivered at the 

 P'orest-Keepers' Congress, held at Djocja, October 17-18, 1917. 



Forest terminology. — Terms used in the lumber industry (Jour. Forestry, 

 16 (1918). No. 1, pp. i-75).— This comprises an alphabetical list of terms used 

 in the lumber Industry, prepared by a committee of the Society of American 

 Foresters. A similar list of terms used in forestry has been noted (E. S. R., 

 36, p. 744). 



DISEASES OF PLANTS. 



The Michigan plant disease survey for 1914, G. H. Coons (Rpt. Mich. 

 Acad. Sci., 11 (1915), pp. 123-133, pis. 4). — This is a preliminary account of re- 

 sults obtained in a plant disease survey conducted by the department of botany 

 at the Michigan Agricultural College in cooperation with the U. S. Department 

 of Agriculture. 



The present extent of curly dwarf and that of leaf roll of potato is outlined. 

 The cucumber disease situation appears to be serious. A disease of unknown 

 causation, called white pickle, is described supposedly for the first time. A 

 very injurious stunting disease of celery is ascribed to a bacterium which 

 plugs the vascular system. A somewhat similar disease of lettuce is named 

 stunting disease of lettuce. Sclerotinia lihertimia causes a disease of green- 

 house lettuce and a trench rot of celery. Black rot of lettuce is supposedly 

 associated with a Rhizoctonia. Chestnut bark disease has not been foimd in 

 the State, Maple anthracnose and leaf scorch are contrasted. The Phyl- 

 losticta disease of horse chestnut has not proved to be serious. Certain heart 

 rots, especially of maple, though doing serious damage, have largely escaped 

 attention hitherto. 



Investigation work [on the control of plant diseases and injurious insects 

 in Ontario] (Ann. Rpt. Ontario Agr. Col. and Expt. Farm, 42 (1916), pp. 12- 

 14)- — It is stated that work during this year looking to the control of pear 

 blight was successful, and that a bulletin is to be published on the practical 

 control of that disease. 



