DISEASES OF PLANTS. 151 



only about 21 per ceut of that from the sound tubers. The weather was abnor- 

 mally (lamp during the experiment. 



The factors governing germination and infection with Phytophthora 

 infestans, I. E. Melhus (Abs. in Phytopathology, 2 (1912), No. 1, p. 4ff). — 

 In experiments involving about 300 tests at temperatures ranging from 8 to 

 14° C, 96 per cent of the spores germinated, wbile at 21 to 25° only 20 per 

 cent germinated, indicating that comparatively low temperatures favor germi- 

 nation with P. infestans as well as with Cystopus (E. S. R., 26, p. 342). The 

 optimum temperature for oospore germination was found to lie between 10 

 and 13°, the minimum between 1 and 2°, and the maximum between 21 and 

 24°. Field observations showed oospore germination to occur freely on potato 

 plants at temperatures between 8 and 15°. 



Inoculation experiments showed that temperatures of 10 to 13° produced 

 higher percentages of infection than 21 to 25°, and that the upper surface 

 of the potato leaf is less easily infected, than the lower. 



The effect of Bordeaux mixture and various polysulphids on the germination 

 of P. infestans and Plasmopara viticola was investigated. Varying the amount 

 of lime in Bordeaux mixture did not affect the toxicity. None of the con- 

 stituents of the polysulphids was found toxic at the proportion occurring in 

 the polysulphid. The most nearly toxic agent, however, was the alkaline 

 constituent. 



Hypertrophy-structure in potatoes, M. FrcsK6 {Bot. Kozlem. [Budapest^, 

 11 (1912), Xo. 1, pp. lJ,-20 (3)-ill), figs. 10).— This is a study of the struc- 

 ture of the abnormal developments resulting from an oversupply of water in 

 contact with tubers. These are figured and described. One result is the 

 formation of abundant starch in the sublenticular cells. This, however, seems 

 to be transitory, A regular periodicity is said to be apparent in the forma- 

 tion of these excrescences. 



Relative merits of lime sulphur, lead benzoate, and Bordeaux mixture 

 for spraying potatoes, F. C. Stewart and G. T. French (Ahs. in Phyto- 

 pathology, 2 {1912), No. 1, pp. J/o, .}5). — In 1911 the authors made a comparative 

 test of lime-sulphur, lead benzoate, and Bordeaux mixture for spraying potatoes, 

 the mixtures being thoroughly applied 6 times at intervals of 2 weeks. Tip 

 burn was the only important disease involved. Bordeaux mixture checked this, 

 prolonged the life of the plants, and increased the yield at the rate of 100.3 bu. 

 per acre ; lead benzoate was found to neither benefit nor injure the plants ; while 

 those sprayed with lime-sulphur were smaller than the checks, as much affected 

 by tip burn, and yielded 39.5 bu. less per acre than the checks. 



The conclusion reached is that neither lime-sulphur nor lead benzoate can be 

 profitably substituted for Bordeaux mixture in spraying potatoes. Both lack 

 the stimulating influence possessed by Bordeaux mixture, while lime-sulphur 

 tends to dwarf the plants and lower the yield. 



Nematode disease of the sugar beet, B. NSmec {Ztschr. PflanzenkranJc., 21 

 (1911), No. 1-2, pp. 1-10, figs. 6; abs. in CentU. Bakt. [etc.'l, 2. Aht., 82 {1912), 

 No. 6-12, pp. 311, 312; Bot. CentbL, 116 {1911), No. 2k, PP- 623, 62//).— This is a 

 study of the anatomical changes observed in roots of the sugar beet as the re- 

 sult of attacks by eelworms. 



Most noticeable are the so-called giant cells which develop by growth and 

 fusion of cells in the vascular bundles, sometimes closing the channels com- 

 pletely. Such giaat cells have thick walls and abundant cytoplasm, sometimes 

 with several large nuclei. They are said to hinder or interrupt transportation 

 of wnter and other materials along the roots attacked, and by checking root-tip 

 growth they lead to the development of new lateral roots and the impoverish- 



