1918.] DISEASES OF PLANTS. 645 



(Pinus eduHs) within National Forests as a source of cordwood and mining 

 timbers is justified. 



Guide book for the identification of woods used for ties and timbers, A. 

 KoEHLER {U. S. Dcpt. Agr., Forest Serv., 1917, pp. 79, pis. 31, figs. 19).— This 

 guide booli points out the differences which are of practical value in the 

 identification of various species of native woods used for ties and timbers. It 

 is intended primarily for inspectors, but since it includes most of our com- 

 mercial species it is of value to others interested in the identification of 

 woods. Keys for the identification of the wood, both with and without the 

 aid of a hand lens, are included, together with an appendix on a method of 

 distinguishing long leaf from short leaf and loblolly pine ties or timbers. 



Valuation of damages to immature timber, W. N. Sparhawk {Jour. For- 

 estry, 16 (1918), 2\^o. 2, pp. 176-191). — A comparative discussion of various 

 methods of valuing damage in immature stands of timber. 



First-aid manual for field parties, H. W. Barker {U. S. Dept. Agr., Forest 

 Scrv., 1917, pp. 9S, figs. 47). — A first-aid manual similar to that issued by the 

 American Red Cross, and prepared with special reference to its use by field 

 parties of the Department. 



DISEASES OF PLANTS. 



[Report of the department of] botany, G. M. Reed (Mi.^souri Sta. Bui. 151 

 (1917), pp. 30-33). — Brief accounts are given of investigations conducted by 

 the author on the physiological relation of the powdery mildews to their hosts, 

 forest-tree diseases, a systematic and physiological study of rusts, grain smut 

 and its control, and watermelon diseases found in southeast Missouri. The 

 last investigation was carried on by the author in conjunction with Helen 

 .lohann. 



The study of the powdery mildews has been largely to determine the sus- 

 ceptibility of oats to powdery mildews. So far no variety of common species 

 of oats has been found entirely resistant to mildew. 



The forest-tree disease investigations have consisted largely of collections 

 and studies of forms occurring on different species of trees. In addition a 

 study has been begun of fungi which attack fence posts, observations being 

 made on the durability of fence posts and on the efficiency of different mate- 

 rials used for their preservation. 



The watermelon diseases reported upon are said to occur in southeast Mis- 

 souri, where considerable damage is done to watermelons, cantaloups, and cow- 

 peas. Isolations of strains of Fusarium were made, and infection experiments 

 gave positive results for many of them. It is stated that F. tricJiothecioides, 

 which has never been known to cause watermelon wilt, may in some instances 

 prevent the appearance of seedlings above the ground. 



In the study of rusts inoculation experiments with the crown rust of oats 

 were carried out with 49 varieties and species of Avena, practically all prov- 

 ing highly susceptible and only a few showing any evidence of resistance. In 

 conjunction with this experiment oats were tested for mildew, and a striking 

 parallelism was noted between the relation of oat varieties to crown rust and 

 to mildew. Some additional data were obtained regarding the resistance of 

 wheat varieties to the black stem rust and orange-leaf rust. 



The grain-smut studies have been carried on to determine the relation of 

 wheat smut (TiUetia fceteiis) to the date of planting, and in practically every 

 instance the percentage of smut was higher on late planted wheat. Some in- 

 vestigations with the sorghum-kernel smut (Sphacelotheca sorgJii) were car- 

 ried on to determine the susceptibility of certain nonsaccharin sorghums. In- 



