1917] DISEASES OF PLANTS. 845 



strains may be the result of the loss of the parasite, giving rise to varieties 

 by a process analogous to regressive mutation, or it may result from the influence 

 of prolonged or severe climatic factors, the parasite in such cases being simply 

 latent during successive generations. 



Chemotropic reactions in Rhizopus nigricans, A. H. Graves {Mem. N. Y. 

 Bot. Gard., 6 (1916), pp. 323-331; Bot. Gaz., 62 {1916), No. 5, pp. 337-369, figs. 

 4). — A study of several fungi, mainly R. nigricans, has demonstrated a negative 

 chemotropism of the fungi tov^ard their own metabolic products. A much 

 weaker positive chemotropism toward such substances as cane sugar and glucose 

 was noted. This positive response is better in case of turnip juice and may in 

 general be better in plant juices. The facts as noted suggest that the distribu- 

 tion of a parasitic fungus in a plant may be due more to negative chemotropism 

 in regard to its own staling products than to positive chemotropic stimulation. 



Discovery of internal telia produced by a species of Cronartium, R. H. 

 CoLLEY {U. S. Dcpt. Agr., Jour. Agr. Research, 8 {1917), No. 9, pp. 329-332, pi. 

 1). — The author reports the production of internal telia by C. ribicola in the 

 petioles of leaves of species of Ribes. Internal rust sori, four types of which 

 have been found developing in the host plant tissue, are regarded as rather 

 common teratological phenomena. 



Discussion of certain plant diseases, J. T. Barrett {Proc. Fruit Growers' 

 Conv. Cal., 47 {1915), pp. 216-222). — The participants in this discussion dealt 

 with prune rust (Puccinia pi'uni), two epidemics of which have occurred in 

 southern California in the last two years; apricot scab or black spot, which was 

 serious in at least two sections during the previous year ; shot hole, easily 

 confused with scab, but readily controlled with Bordeaux mixture; and brown 

 rot, which is now under investigation. 



Report of the department of plant pathology, M. T. Cook et al. {New 

 Jersey Stas. Rpt. 1915, pp. 365-374). — In these pages a report is given of the 

 activities of the department in 1915, with a list of the common diseases observed 

 during that time. 



[Investigations on plant diseases] {Wisconsin Sta. Bui. 275 {1917), pp. 

 35-40, figs. 3). — Progress accounts are given of investigations of various plant 

 diseases carried on at the station. 



In continuation of the work on tobacco diseases, J. Johnson Is reported to 

 have carried on studies of inheritance in crosses between resistant and sus-. 

 ceptible varieties of tobacco and also of the distribution of the causal organism 

 of tobacco root rot {Thielavia hasicola). In the latter investigation, he is said 

 to have found 66 new hosts for this fungus. 



In studies of inheritance of disease resistance in plants, W. H. Tisdale is 

 investigating wilt resistance in flax and also strains of cabbage resistant to 

 yellows. Resistance to wilt is considered a dominant characteristic in flax, 

 while in case of cabbage resistant to yellows, a greater degree of variability in 

 first generation seed was observed than in case of flax resistant to wilt. 



A brief account is given of a bacterial disease of barley, a preliminary note 

 of which has already been given (E. S. R., 35, p. 845). 



For the control of barley diseases through seed disinfection, A. G. Johnson 

 reports the successful use of formaldehyde for all of the three important barley 

 diseases, stripe, loose smut, and covered smut, a preliminary account of his in- 

 vestigations having been previously noted (E. S. R., 36, p. 247). In general 

 practice, he recommends controlling the stripe disease by soaking seed for two 

 or three hours in 1 pint of formaldehyde to 20 gal. of water. 



The work of G, W. Keitt on the control of cherry leaf spot is briefly outlined, 

 attention being called to the successful use of Bordeaux mixture or lime- 

 sulphur against this disease (E. S. R., 36, p. 149). 



