654 EXPERIMENT STATION EECORD. [Vol. 43 



In the teleutospore germination studies reported, P. graminis on quack grass, 

 wlieat, and volunteer oats germinated best when allowed to remain attached 

 to the straw. A relative humidity of at least 95.6 per cent is required for 

 teleutospore germination and .sporidia production, the sporidia production taking 

 place at temperatures between 5 and 25° C, but most profusely at 20°. The 

 teleutosporos were found to germinate in the open following a rain, and those 

 developed on volunteer grain in the late fall germinate more readily than 

 those maturing in summer or early fall. 



In studying infection, sporidia were placed on barberry leaves under green- 

 house conditions and Infections secured with the production of mature secidio- 

 spores in 12 days. When the barberry leaves had become green and crisp infec- 

 tion apparently did not take place, due possibly to the increased thickness of 

 the cuticle and walls of the epidermal cells. Both surfaces of the barberry 

 leaves are susceptible to infection, although the stomata occur only on the 

 lower surface. The germ tubes of the sporidia enter directly through the 

 cuticle and epidermis. 



A survey was undertaken to locate European barberry bushes in Iowa, and 

 although incomplete, 132,673 bushes were found on private and public grounds 

 in 300 cities, towns, and surrounding country of the State. The barberry was 

 found to have escaped from cultivation in several localities, but in no case 

 was the plant far from the original planting, the farthest distance observed 

 being about one mile. 



The authors have traced a number of local epidemics of rust, not only on wild 

 grasses, but also oats, wheat, barley, etc., and found that the rust spreads 

 in concentric zones in the direction of the prevailing wind. Infection center? 

 vary from 5 to 320 rods in diameter. When near barberry bushes infected witli 

 secidia, stem rust was found on Ilordeum jubattuu, Agrostis olba, Agropyron 

 repens, and A. tenerum. On account of their universal presence and long grow- 

 ing period, the authors consider these wild grasses important factors in starting 

 and aiding the spread of local epidemics of stem rust. 



Blackleg disease of cabbages, T. G. B. Osborn {Jour. Dept. Agr. So. Aust., 

 23 (1919), No. 2, pp. 107-110, fig. 1). — Observations made at Summertown on 

 plants grown in South Australia are said to be in full agreement with those 

 of Henderson (B. S. R., 40, p. 846), regarding the causation, character, and 

 course of the cabbage blackleg disease due to Phoma lingam. 



Seed transmission of cucurbit mosaic by the wild cucumber, S. P. Doo- 

 LiTTLE and W. W. Gilbert {Phytopathology, 9 {1919), No. 8, pp. 326, 327).— In a 

 previous article (E. S. R., 39, p. 853) the authors reported the occurrence of 

 the cucurbit mosaic on the wild cucumber {Micrampelis {Echinocystis) lohata). 

 In order to determine the possibility of this plant acting as an overwintering 

 host, seed was collected from wild cucumber plants and tested under green- 

 house conditions. It seems possible that a certain percentage of the seed from 

 mosaic plants of the wild cucumber may produce diseased plants the following 

 season. In this way the first mosaic centers could be established, from which 

 the disease is later carried to cultivated cucumbers by the striped cucumber 

 beetles or other insects. 



Onion smut, R. E. Vaughan {Canner, 51 {1920), No. 4, pp. 51, 52, fig. 1).— 

 Formaldehyde solution, prepared as outlined and applied as a drip with the 

 seed at planting time, is said to have given satisfactory control of onion smut 

 (Urocystis cepuKe) under Wisconsin conditions. Ti-eatment of 11 acres at 

 Racine, Wis., in 1917, at an expense of $55 increased returns more than .$3,000. 



Studies on the viability of the potato blackleg organism, G. B. Ramsey 

 {PhtjtopathoJoyy, 9 {1919), No. 7, pp. 2S5-28S).—lu order to secure data regard- 



