DISEASES OF PLANTS. 147 



large leaF areas are sometimes killed, iiKlic.itiug a killing of host cells by the 

 fungus and a consequent death of the mycelium itself. In this respect they 

 resemble very closely some of the rust resistant forms of wheat, and this is 

 thought to throw light on the question of the nature of resistance to P. graminis. 



In the second part of the bulletin the author discusses rust resistant varieties 

 of wheat. 



It was found that in maliing inoculations in tlie greenhouse on wheats resis- 

 tant to P. (jraminis tniki, only two. Khai)li, an Indian eramer, and Kubanka 

 2094, possessed a very marked degree of real resistance, although a number of 

 other forms were fairly resistant in the field. It was observed that the more 

 resistant a form proved, the more pronounced was the tendency of the rust to 

 kill small areas of the leaf. The length of incubation period was found to be 

 correlated to some extent with the degree of immunity, those forms being most 

 nearlj^ immune having the longest incubation i)eriod. Infection secured on par- 

 tially i-esistant varieties as a result of inoculations with aecidiospores and pri- 

 mary uredospores proved only slightly more virulent than did that secured by 

 means of inoculation with long-time uredospores. 



Experiments with drought-resistant durum wheats grown in a very dry soil 

 and with Minnesota No. 163 in wot soil indicated that normal conditions for the 

 host plant are probably the most favorable ones for rust development. The 

 presence or absence of excessive amounts of fertilizer elements was not found 

 to directly affect immunity or susceptibility of wheats. The addition of copper 

 sulphate, copper cai-bonate, and iron suliJhate to nutrient media in which plants 

 were grown did not markedly diminish the amount of rust when they were used 

 in such concentration as to permit the normal development of the host plants. 

 A comparison of the sequence of infection in susceptible and immune forms 

 showed that the fungus gained entrance into the host plant in the same manner 

 in both cases, growing readily in the tissues of the susceptible variety, while it 

 does not thrive in the immune forms. The reason for this is believed to be a 

 physiological incompatibility. 



A bibliography is appended. 



[Grain diseases] (Edinb. and Eat^t of Scot. Col. Agr. Rpt. 30 {WIS), pp. 

 15-19). — Barley leaf stripe (Hchninthosporiiim gramineum and H. teres) is 

 said to cause injury only where it is excessively abundant. Early sowing 

 favored attack, whereas late planting hindered it. The removal and destruc- 

 tion of plants attacked by leaf stripe has proved a good method of eradicating 

 the disease. Formalin and copper sulphate treatment of seeds greatly re- 

 duced leaf stripe. 



[The stem rot of cereals], L. Mangin {Jour. Agr. Prat., n. ser., 27 (1914), 

 Xo. S, pp. 236-239). — The author recognizes two forms of stem diseases of 

 cereals, one due to Leptosiih?eria and Ophiobolus, and the other to Fiisarium 

 spp., among the best known being F. nival e. All the species of the fungi 

 attack cereals near the ground, causing a weakening of the stems and often 

 resulting in very considerable losses. 



Experiments on control of loose smut of barley, and wheat, R. Schandeb 

 (Mitt. Kaiser Wilhelms Inst. Landiv. Bromhcrg, 6 (1914), No. 2, pp. 132-139, 

 pi. 1). — Regarding the plan and principle of control of loose smut as determined 

 by previous investigations (E. S. R., 28, p. 646), the author gives attention to 

 the possibility of simplifying the process, and of reducing injury caused to 

 germination and yield by such treatment. 



The work and results are exhibited in tabular form, permitting the inference 

 that the second treatment employing hot water (52 or 53° C.) can not well be 

 dispensed with or shortened from 10 to 5 minutes. Other features are dis- 

 cussed and the work is to be continued. 



