DISEASES OF PLANTS. 449 



various species of Macropporiiim and Alternaria are great blighters of seed, 

 and are destructive botli on the straw and on the grain, especially at germina- 

 tion time. These organisms are not only parasites in their ability to attack 

 young, growing plants, but whenever a plant tends to sicken and die, they 

 readily attack and overcome it, so that poor drainage, drought, heat, frost, 

 Jind insect injuries greatly facilitate the destruction. 



It is claimed that with the understanding and application of the proper 

 methods of selecting and disinfecting seed, rotating crops, and perfecting the 

 seed bed, it should be possible, at least on virgin soils, to maintain for many 

 years the high yields of from 30 to 60 bu. per acre, instead of dropping in a 

 few years to the low average of from 12 to 15 bu. 



On the formation of bacterial zoogloea on the roots of barley, H. Zikes 

 (Sitzber. K. Akad. Wiss. [Viouia], Math. Naturw. Kl., 119 {1910), I, No. 1, 

 pp. 11-31). — Previously noted from anotlier source (E. S. R., 23, p. 741). 



A yellows of oats, H. Clausen (Mitt. Deut. Landw. Gesell., 25 (1910), No 

 Jflf, 2W- 631-639, figs. 3 ) . — A description is given of a disease of oats which has 

 been known for many years in certain parts of Germany and Holland. In this 

 the plants look strong and healthy for a time, but later spots appear here and 

 there in the oat fields containing plants, in which the lower leaves lose their 

 chlorophyll, either entirely or only along the midrib, as well as their turgidity, 

 causing them to become wrinkled, wilted, and yellowed, while the more severely 

 attacked plants fall over on the ground. After a few weeks the disease ceases, 

 and those plants not too severely attacked recover, but the yield is always 

 reduced. 



It is claimed that the disease is not caused by dry weather, as is usually 

 supposed, nor by parasitic agencies, but is apparently due to the kinds of arti- 

 ficial fertilizers used. 



After comparing the results of several years' experiments concerning the effects 

 of fertilizers on this disease, the author draws the following conclusions: A 

 direct application of lime should be omitted ; ammonium sulphate should be 

 used in place of nitrate of soda ; the phosphoric acid should be in the form of 

 superphosphate in place of Thomas slag; and the soil after planting should be 

 thoroughly rolled dOAvn. 



Black scab or wart disease of potatoes, G. T. Malthouse {Field Expts. 

 Harper-Adams Agr. Col. and Staffordshire Joint Rpt. 1908, pp. 19, 20, figs. 5). — 

 In a brief summary of the known facts concerning this disease it is claimed 

 that the principal sources of infection are seed tubers diseased by manure con- 

 taining spores, and in some instances by poultry. Sulphur at the rate of i lb. 

 per square yard is said to be the best remedy. 



The mosaic disease of tomatoes, Johanna Westerdijk {Meded. Phytopath. 

 Lab. Willie Comtnelin Scholtcn, 1910, Mar.; ahs. in Ztsehr. Pflansenkrarik., 20 

 {1910), No. 7, pp. Ji25, 426). — From a study of the disease in the field and under 

 glass by infection and seed experiments, the author draws the following conclu- 

 sions: First, the disease is produced by an infectious virus, for which no organ- 

 Isms have yet been found; second, the virus is able to infect only embryonic 

 tissues, where it produces two different symptoms as the plants develop, one, the 

 usual mosaic markings, and the other a species of monstrosity which is found 

 only in artificially infected plants ; third, the virus when dried retains its viru- 

 lence for a long time, but is destroyed by heating at a temperature of from .50 

 to 100° C. ; fourth, the mosaic disease of the tomato, contrary to that of the 

 tobacco, is inheritable; fifth, the tomato virus is distinct from that of the 

 tobacco, and will infect only its proper host plant. 



Combating diseases and insects of the orchard, W. II. Chandler {Ann. 

 Rpt. Mo. Bd. Eort., 3 (1909), pp. S ',5-391, pis. 21).— The author gives the symp- 



