DISEASES OF PLANTS. 553 



Attention is called to the supposition that the fungus may have been intro- 

 duced from Japan or from Europe, but the author maintains that it is a native 

 species, which, liecause of peculiar conditions detrimental to the host, has 

 assumed unusual virulence and widespread prominence. The unfavorable con- 

 ditions are believed to be the unusual severity of the winter of 1903-4, followed 

 by a series of years in which summer droughts were exceptionally severe. 



A bibliography of the subject is given. 



Cultural characters of the chestnut blight fungus and its near relatives, 

 C. L. Shear and N. E. Stevens {U. S. Dept. Agr., Bur. Plant Indus. Circ. 131. 

 pp. S-IS). — The results of a study carried on to determine methods of separat- 

 ing the different species of fungi associated with the chestnut blight are given. 

 The chestnut blight fungus Endothia parasitica is said to have three rather 

 close relatives, E. radicalis, E. radicalis mississippiensis, and E. gyrosa. In 

 their pycnidial condition these species are said to be difficult to distinguish 

 either by macroscopic or microscopic examination. 



Studies of more than 2,000 pure cultures of these fungi, to test their relation 

 to light, moisture, and temperature, and their behavior on different culture 

 media, have been made. It was found that they possess constant and easily 

 recognized cultural characters on several culture media, of which potato agar 

 and corn meal are the best that have been tried. 



The resistance of the Japanese chestnut to black root rot, R. Farneti, 

 E. G. LissoNE, and L. Montemartini {Riv. Patol. Veg., 6 (1913). No. 1, 

 pp. 1-7). — From this study the conclusion is reached that while the Japanese 

 chestnut does not enjoy absolute immunity as regards black root rot in Italy, 

 it does possess a considerable degree of resistance thereto at present. The pos- 

 sible bearings of this are discussed. 



Oi'dium of oak, L. A. Haitch and F. K. Ravn (Forstl. Forsogsv. Danmark, If 

 (1913), No. 2, pp. 57-115, figs. 5). — This is a report on the appearance, progress, 

 and effects of Oi'dium in the oak forests of Denmark. 



Reported first in 1904, it was found in all parts of the country by 1908 and it 

 continues to increase in importance. The attack is said to present much the 

 same aspects as in central Europe, the second year's growth showing the effects 

 in marked degree. The leaves are lost in an early stage of development. Both 

 Quercus pedunoulata and Q. sessiliflora are severely attacked, Q. rubra and 

 Q. palustris very slightly if at all. In some localities Fagus sylvatica was 

 attacked by the same fungus. No perithecia were found, but the authors favor 

 the view that the fungus passes the winter in the oak buds. A small per- 

 centage of the oaks appear to enjoy immunity, due to some cause at present 

 unknown. Those attacked showed inferior growth, bud formation, and lignifi- 

 cation along with alterations in structure and nutrition. It is said that the 

 attack does not prevent absorption of nutritive material from the soil, but that 

 it does prematurely arrest the assimilation of carbon dioxid in the leaves; the 

 lack of nonnitrogenous organic materials accounting in large part for the 

 pathological changes observed, which seem to be closely associated with insuf- 

 ficient regulative power during the second period of growth, during which starch 

 production is quite low. The power of resistance to cold is lessened and winter 

 killing of branches or their tips is common. Growth is checked, a diseased oak 

 of 8 or 10 years showing about the same height as a normal growth of 5 or 6 

 years. 



It is stated that spraying with potassium poly.sulphid solutions checks the 

 propagation of oak Oidium, but that this treatment is probably too laborious 

 and expensive to be successfully applied to forest trees. The work concludes 

 with a bibliography. 



