DISEASES OF PLANTS. 845 



Forest Products Laboratory of the U. S. Department of Agriculture, has shown 

 that the size of the pith in conjunction with the diameter of the second annual 

 ring furnislies a reliable guide for determining the above species of wood 

 without the aid of a microscope. This method of identification is described 

 and a chart is given showing the relation of tlie pith diameter to the diameter 

 of the second annual ring. 



Strength tests of structural timbers treated by commercial wood-preserv- 

 ing' processes, H. S. Betts and J. A. Newlin (L^ .S'. Dept. Ayr. Bui. 286 (1915), 

 pp. 15, figs. 7). — This bulletin describes experimental tests made by the Forest 

 Service in cooperation with the Illinois Central Railway and one eastern and 

 two western wood-preserving companies to determine how the strength of bridge 

 stringers is affected by commercial creosote treatment. An account is given 

 of the materials tested, methods of treatment, method of testing, and the results 

 of tests. A bibliography of publications relating to strength tests of various 

 woods is also given. 



The tests have shown in general that timber may be very materially weakened 

 by preservative processes, although creosote in itself does not appear to weaken 

 the timber. A preservative process which may seriously injure one timber may 

 have little or no effect on the strength of another. A fair comparison of the 

 effect of a preservative process on the strength of different species can not be 

 made unless it is the common or best adapted process for all the species com- 

 pared. The same treatment given to a timber of a particular species may have 

 a different effect upon different species of that species, depending upon the 

 form of the timber used, its size, and its condition when treated. 



The artificial preservation of mine timbers, F. Moll {Forestry Quart., 13 

 {1915), No. 3, pp. 308-316). — An account of various European methods of 

 preserving mine timbers, abstracted from the German by F. W. Haasis. See 

 also a previous note (E. S. R., 30, p. 647). 



Study on vegetable ivory, F. Vignolo-Lutati {Ann. R. Accad. Agr. Torino, 

 57 {1914), pp. 137-U8, pi. i).— A short comparative study of vegetable ivory 

 derived from different plants. 



DISEASES OF PLANTS. 



Annual report of the botanist and plant pathologist, F. Stowaed {Dept 

 Agr. and Ifulus. West. Aust. Ann. Rpt. 1914, PP- 2i-^2) .—Sprain, a potato 

 disease thought to be of physiological nature and not hereditary, appears to be 

 accentuated by dry-soil conditions. Heterodera radicicola has been discovered 

 attacking potatoes for the first time in this region. Potato blight {Phytophthora 

 infestans) reappeared after the lapse of a year, being reported from numerous 

 points in several districts. 



Premature shedding of blooms by tomato, which could not be associated with 

 any organism, was ascribed to conditions of cultivation and season. Tomato 

 wilt was almost invariably associated with Fusarium spp., which may constitute 

 normally a portion of the fungus flora of the soil in this region. No case of 

 tomato blight could be ascribed to P. infestans, and if such a disease is present 

 it is thought to be rare. 



Studies on cereals are briefly reported. Copper sulphate used alone for wheat 

 smut was shown to cause loss, or more particularly abnormality in germination, 

 in a large percentage of wheat seed tested. 



Vine mildew {Oidium tuckeri) and anthracnose {Olwosporium ampeloph- 

 agum) were the most prevalent of the vine diseases noted. The former was 

 controlled by several dressings of finely powdered sulphur, beginning as soon as 

 the foliage is formed. The latter yielded to preventive treatment, a precaution 



