114 PATHOLOGY [Bot. Absts. 



774. Klebahn, H. Peridermium pini (Willd.) Kleb. und seiner Uebertragung von Kiefer 

 zu Kiefer. [P. pini and its passage from pine to pine.] Flora 111-112: 194-207. PI. J^-5. 1918. 

 — After a discussion of the validity of the species and the exhaustive but fruitless search for 

 an alternate host Haack's experiments on direct inoculation with aeciospores are discussed. 

 The author then outlines the problem, his own inoculation experiments, and their results. 

 Thirty per cent of the 2- to 4-year old trees of Pinus sylveslris which were dusted with aecio- 

 spores of Peridermium pini developed infection; some showing the presence of mycelium, some 

 bearing pycnia, and some bearing fully formed aecia within two years of the time of inoculation. 

 The experiments were carefully controlled and they are therefore considered conclusive enough 

 to establish the fact that Peridermium pini can spread directly from pine to pine by means of 

 aeciospores. The author discusses the general question of susceptibility and the bearing of 

 the results obtained on problems connected with the investigation of heteroecious rusts. — 

 Reginald H. Colley. 



775. Krakover, L. J. The leaf-spot of red clover caused by Macrosporium sarcinaeforme 

 Cav. Rept. Michigan Acad. Sci. 19 (1917) : 273-328. 5 pi., 2 fig. 1918.— The writer reports 

 investigation on red clover leaf spot caused by Macrosporium sarcinaeforme which attacks 

 leaves and petioles of red clover but not alsike or other legumes. The writer describes fully 

 the signs of the disease and the morphology of the causal organism. Inoculation experiments 

 indicate that 5 to 7 days are necessary for spot formation. The injury caused by the fungus 

 brings about the disintegration and collapse of the cells of the host, the fungus advancing 

 intercellularly and intracellularly. The organism grows readily in media and its appearance 

 on different substrata is described. Relations to temperature, humidity, light and dark are 

 given. Attenuation was found in old cultures and this attenuation seems correlated with loss 

 in power to produce substance toxic to the clover leaf. Wind of approximately 4 miles an hour 

 velocity carried the spores 14.6 miles. Bibliography of 23 titles is appended. — G. H. Coons. 



776. Lewis, A. C, W. W. Chase, and W. F. Turner. Spray calender. Georgia State 

 Bd. Entomol. Bull. 53. 39 p.,' 2 pi., 8 fig. 1919. 



777. Lewis, A. C, and C. A. McLendon. Cotton variety tests 1918. Georgia State Bd. 

 Entomol. Bull. 52. 40 p., 1 fig. 1919— See Bot. Absts. 3, Entry 473. 



778. Ltjtman, B. F. Osmotic pressures in the potato plant at various stages of growth. 

 Amer. Jour. Bot. 6: 181-202. 1 table, 2 fig. 1919.— See Bot. Absts. 3, Entry 800. 



779. Makemson, Walter Kenneth. The leaf mold of tomatoes caused by Cladosporium 

 fulvum Cke. Rept. Michigan Acad. Sci. 20: 309-350. PI. 23-37. 1918.— Tomato leaf mold 

 {Cladosporium fulvum Cke.), appearing as velvety, tawny-olive colored patches on the under 

 side of the leaf and as yellow spots produced in the tissue above, occurs in southern climates 

 as a serious disease of field grown plants and of plants grown under glass in northern latitudes. 

 Fruits once set escape the disease, and main stems of the vines are not often attacked. Blos- 

 soms are especially susceptible. Successful inoculation experiments are reported. Infection 

 is stomatal. The mycelium is both inter- and intra-cellular. Minimum temperature for 

 growth of fungus is 9°C, the optimum 20° to 25°C, and the maximum below 34 °C. Moisture 

 favors growth. Strong, diffuse light retards spore formation. The fungus grows best on a 

 reaction of medium varying from +10° to +15° Fuller's scale, but withstands a considerable 

 range in reaction. Translocation of starch in infected plant leaves is interfered with. Organ- 

 ism is disseminated by air currents. Period of incubation is usually from 6 to 10 days, but 

 may be longer depending on conditions of humidity and temperature. Growth as a sap- 

 rophyte may enable the fungus to exist between crops, but the longevity of the conidia prob- 

 ably accounts for its survival. Bordeaux mixture proved inefficient in the control of the 

 disease; ammoniacal copper carbonate, sulfide of potassium and sulfur dust also valueless. 

 Self-boiled lime-sulfur and concentrated lime-sulfur solution gave evidence of value, the 

 former giving results more promising in moist chamber experiments but less effective under 

 natural conditions than the latter. Sulfur fumigation, ventilation control and clean culture 

 are recommended as prophylactic measures. — L. M. Massey. 



