1019] DTSKASES OF PLANTS. 843 



centage of plants affected wiMi take-all ; also of those showing the presence of 

 hunt, loose suuit, and flag smut. 



Phyllachora as the cause of a disease of corn, and a general consideration 

 of the genus Phyllachora, N. E. Dalbey {Trans. III. Acad. Set., 10 (1917), pp. 

 230-2Ji8, pi. 1, Ji(js. 5). — An injurious disease of corn, supposedly not recorded 

 previously for Porto Rico (where nearly every field examined showed infected 

 leaves) is descrihed as studied in connection with herbarium material collected 

 in 1915 by Stevens. 



A fungus, apparently Scolecotrichuni graminis, was commonly present in 

 discolorations somewhat similar to those which are associated with the disease 

 in question. This fungus has been identified by the author as P. graminis. 



Studies on tracheomy coses: Verticilliose of cucumber, H. A. A. van der Lek 

 {Meded. LandhouwhoogscJi. [Wageningen}, 15 (1918), No. 1, pp. 1-58, pis. 6). — 

 This is a detailed account of the wilting disease of cucumber claimed to be due 

 to Verticilliiim alboulruiii. 



Frost injury of potato tubers, J. E. Kotila (Ann. Rpt. Mich. Acad. Sci., 20 

 (1918), pp. 451-460, pis. 2). — Experimentation is described as made for the 

 purpose of determining the conditions for the various spottings and internal 

 discolorations of potato tubers, also for determining the effects of chilling and 

 freezing on germinability. Two methods for chilling and freezing tubers were 

 tested, and are described. 



The results as tabulated are considered to show that it is possible to re- 

 produce various types of injury under controlled conditions. The necrosis type 

 of injui-y developed in tubers chilled from 3 to 4 hours at — 1.3 to — 17" C. if the 

 tubers were afterwards kept at room temperature for five days. The darken- 

 ing type of injury was produced in tubers kept with others for 24 hours at 

 — 5 to — 17°. Tubers kept for 5 houi's or more at — 13 to — 17° do not show 

 so marked a discoloration as do those kept for 3 to 4 hours at the same tem- 

 perature. No discoloration occurs in case of severe chilling or freezing. This 

 fact is attributed to the more complete killing of the cells and to the bacterial 

 activity. Chilling accelerates the action of tyrosinase, and also retards ger- 

 mination of tubers, sprouts being killed after exposure to — 13 to — 17° for 

 4 hours. 



Unknown corpuscles in diseased spinach roots, T. A. C. Schoevees (Meded. 

 Landhomohoogsch. [Wagcningen'\, 15 (1918), No. 2, pp. 75-84, pl- i)- — ^A disease 

 on spinach roots is noted as invariably associated with the presence of intra- 

 cellular bodies containing fat globules. These bodies, which appear at least in 

 some cases to be motile, are thought to belong to the protozoa, and have 

 been (Called, provisionally, X-organisms. 



Sugar-cane varieties and froghopper blight in Trinidad, C. B. Williams 

 (Bui. Dcpt. Agr. Trinidad and Tobago, 18 (1919), No. 2, pp. 70-83). —Based on 

 field observations, published records, and replies to circulars sent to planters 

 in 1912 and again in 1918, the susceptibility of a number of varieties of sugar 

 cane to so-called froghopper blight is briefly indicated. It is stated that no 

 variety of cane at present grown in Trinidad is immune to the disease, but that 

 Uba and Badilla are the most resistant sorts, while a few recent introductions 

 are deemed worthy of more extended trial. 



The leaf mold of tomatoes caused by Cladosporium fulvuna, W. K. Makem- 

 SON (Ann. Rpt. Mich. Acad. ScL, 20 (1918), pp. 309-350, pis. 13, figs. 2).— The 

 causation of the tomato leaf mold by C. fulvum has been shown by isolation, 

 pure culture inoculation, and reisolation. Infection occurs by way of the 

 stomata. Blooms are especially susceptible. The mycelium is found both 

 within and between the cells. Conidia arise from a stroma-like formation 



