1916] DISEASES OF PLANTS. 655 



Fungi attacking- cultivated and wild Orchidaceae and their control, G. 

 LiNDAU (Garten flora, 64 {1915), Nos. 21-22, 23-24; Orchis, 9 {1915), Nos. 7, 

 pp. 171-178; 8, pp. 181-203). — Descriptive lists are given including many Ure- 

 dinese, Ascomycetes, and imperfect fungi attacking orchids in many widely 

 separated regions of tlie world. 



Black canker in young chestnut trees and nurseries, G. Brigs: and R. 

 Farneti {Atti R. Accad. Lincei, Rend. CI. Sci. Fis., Mat. e Nat., 5. ser., 24 

 {1915), I, No. 2, pp. 98-105; abs. in Internat. Inst. [Rome], Mo. Bui. Agr. Intel, 

 and Plant Diseases, 6 {1915), No. 4, pp. 637, 638).— It is stated that black 

 canker may attack not only adult chestnut trees but also very young plants 

 and even germinating seed, so that a considerable epidemic of this disease may 

 occur in the nursery. The disease is said to be due to infection and not to soil 

 exhaustion. 



Studies on diseases of oak, E. MtJNCH {Naturiv. Ztschr. Forst u. Landic, 13 

 {1915), No. 11-12, pp. 509-522, figs. 6).— Previous reports (E. S. R., 24, p. 52) 

 are followed up by an account of a study of Polyporus igniarius, the cause of 

 white rot of oak, more particularly as regards its rate of progress in canker 

 formation and the different rates of progress in cambium, bast, and sapwood. 



Monograph on oak mildew, P. W. Neger {Naturw. Ztschr. Forst u. Landw., 

 13 {1915), No. 11-12, pp. 544-550, figs. 2).— The article previously noted (E. 

 S. R., 33, p. 745) is here supplemented by an account of tests with the Oidium 

 causing oak mildew on species of Rubus, from which the author concludes that 

 under appropriate conditions a fungus may flourish and even produce spores 

 on a host normally foreign thereto, and that on the basis of studies involving 

 such cases errors of identity may be promulgated. The overwintering of oak 

 mildew is also discussed. 



A new disease of walnuts, H. Memmler {Gartenwelt, 19 {1915), No. 53, pp. 

 623, 624, fig- 1). — A nut spot of walnut is described as apparently new, but the 

 cause of the trouble has not yet been determined. 



Note on western red rot in Pinus ponderosa, W. H. Long {Mycologia, S 

 {1916), No. 3, pp. 178-180). — Reporting on the study of the heart rot of western 

 yellow pine, called western red rot in order to distinguish it from a very similar 

 heart rot called red heart or red rot (Trametes pini) common in many species 

 of conifers, the author states that the western red rot has three developmental 

 stages. The first shows reddish to dark brown areas in the heartwood which 

 is still firm, the second a whitish or gray color with more or less delignification, 

 and the third a disappearance of much of the heartwood and a very brittle 

 condition of the particles which remain. 



This fungus never forms the brown, woody, perennial fruiting bodies on liv- 

 ing pine trees that T. pini does but forms annual fruiting bodies which usually 

 develop as white encrusting layers on the underside of logs. The pileate form 

 of the fungus resembles very closely Polyporus ellisianus (Tyromyces ellisianus) 

 and is thought to be specifically identical therewith. The rot is very common 

 throughout the western yellow pine regions of Arizona and New Mexico, and 

 is known to occur in Vermont, New Jersey, Washington, Idaho, and South 

 Dakota. 



The fungus enters the living tree, passing through the sapwood, then the 

 heartwood of dead branches, then down into the heartwood of the living tree. 

 During the black jack stage, i. e. when not over the age of 150 years, the trees 

 are practically free from this rot. It is, however, exceedingly common in the 

 older trees on account of the dead branches, this factor favoring a short forest 

 rotation. Thin soils on steep southern or eastern slopes, where growth condi- 

 tions are poor, seem to encourage western red rot. 



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