642 EXPERIMENT STATION RECORD. 



Heterodera radicicola attacking the Canada thistle, L. E. Melchees (Sci- 

 ence, n. ser., 40 (1914), ^o. 102fi, p. 2^/).— The author notes the occurrence, on 

 the roots of the Canada thistle, of the nematode H. radicicola, thus adding 

 another host plant to the long list already known. 



Spore germinations of cereal smuts, E. C. Stakman (Minnesota Sta. Bui. 

 133 (1913), pp. 52, pis. 25). — ^This is a technical bulletin in which the author 

 gives results of observations on the germination of spores of Ustilago tritici, 

 U. nuda, U. hordei, U. avence, U. zew, and Tilletia fcetens. 



These smuts are found to fall into two classes as far as germination is con- 

 cerned, U. nuda and U. tritici producing no sporidia, while the others produce 

 Bporidia. The period of germination was found to vary considerably in dif- 

 ferent forms, U. hordei germinating most readily, only 6^ hours being required 

 in some cases, while T. foetens required the longest time, the minimum for 

 germination of these spores being 48 hours. The germination characteristics 

 are said to be quite closely connected with the life history of the parasite, 

 those forms which live over in the seed producing no sporidia, while those 

 which live over in the soil or on the kernels produce sporidia which help to 

 insure their chances of persistence. Differences are also noted In the behavior 

 of the promycelium of the different species. The siwres of all forms were 

 exposed to winter conditions in Minnesota and all germinated readily In the 

 spring, demonstrating that smuts may survive the winter in the spore form 

 under field conditions. 



A bibliography of the subject is given. 



Studies on club root. — I, The relation of Plasmodiophora brassicee to its 

 host and the structure and growth of its Plasmodium, B. F. Lutman (Ver- 

 mont Sta. Bui. 175 (1913), pp. 21, pis. 4, figs. 6).— The results of a study of the 

 relation of the fungus causing the club root of various cruciferous plants to 

 the host plant Is given, together with a summary of earlier work. 



It is stated that the parasite enters the host either through the epidermis 

 or root hairs, and once within the plant It spreads from cell to cell, either 

 through penetrating the cell walls or through host cell divisions. It is found 

 present In the cortex, but sometimes the organism makes Its way into the cells 

 of the central cylinder. The infected host cells become hypertrophled, but 

 nuclear and cell division Is not seriously interfered with In the earlier stages. 

 In advanced cases both processes are entirely suspended and the nucleus under- 

 goes degeneration. The phismodlum of the fungus Is said to be clear and 

 almost transparent at first and Is distinguished with difficulty from the pro- 

 toplasm of the host. The nuclear divisions In the Plasmodium are both vegeta- 

 tive and reduction. In the study reiwrted most of the material was taken 

 from cabbage plants. 



A brief bibliography is appended. 



Occurrence of bacterial blight of alfalfa in the Salt Lake Valley, Utah, 

 P. J. O'Gara (Science, n. ser., 39 (1914), A'o. 1016, pp. 905, 906).— The author 

 reports the occurrence of the bacterial blight of alfalfa, due to Pseudomonas 

 medicaginis, in Utah, and he states that the alfalfa weevil is a factor in the 

 distribution of the disease. It Is said that the disease sometimes destroys 80 

 per cent of the first cutting of alfalfa, and while the chief damage Is usually 

 done at the first cutting, the plants may be so seriously injured In the crown and 

 roots as ultimately to cause their death. 



The cob rot of corn, E. G. Arzbergeb (Ohio Sta. Bui. 265 (1913), pp. 69-82). — 

 Attention was called In 1911 to a disease of corn in which the cob of the ear 

 was infected by a fungus. This appeared abundantly In 1911 and again in 

 1912. and an invostiyjation was undertaken to determine whether the fungns, 

 Coniosporiuni yccvvi, was parasitic or only present as a saprophii:e. 



