DISEASES OF PLANTS. 151 



For tho prevention of the disoaso llie author rocomnionds the frequent chiing- 

 ing of the water on the fields and deep stirring of the soil whenever possible. 



While the disease is believed to be primarily due to eonstitutional causes, yet 

 the uniform occurrence of organisms seems to indicate that it is greatly compli- 

 cated by their activity. 



On the stages of development reached by certain biologic forms of Ery- 

 siphe in cases of noninfection, E. S. Salmon (Xcir J'lnjtoL, .'/ {I'.lO.')), A o. .9, 

 /*/). 211-22.1. III. I). — Experiments were carried on with a number of biologic 

 forms of Kriisiiihc (/ram'mis. and it was determined that the failure of the conidia 

 to Infect certain hv)st species is to be attributed not to the failure of the germ-tube 

 to penetrate the leaf cells of the plant, Imt to the inability of the fungus to 

 develop the haustorium which is formed, or to the incapacity of the fully 

 formed haustorium to adaiit itself to the intracellular conditions. 



A fungus disease of alfalfa in England, E. S. Salmon (Gard. Cliroii., 3. set:, 

 39 {1906), Ao. 1000, pp. 122, 123; Jour. Bd. Agr. [London], 13 (1906), No. 1, pp. 

 51, 52). — A report is given of diseased alfalfa plants which showed several 

 superficial, warted, gall-like (mtgrowths, about f in. across, found at the crown 

 of the roots. 



These galls, upon examination, proved to be due to attacks of Urothlyctis alfaJ- 

 f(r. From the appearance of the i>lants it was evident that they had been in- 

 fested for some time, and some of the plants were almost dead. This is the first 

 i-eport of the fungus in England. It was first observed in Ecuador in 1892, 

 and later reported as occurring in (iermany (E. S. U.. 14. p. 77.3). A detailed 

 account of the disease and the results of investigations on the fungus are jirom- 

 ised at some future time. 



Potato scurf and potato scab, II. T, Gfssow (Jour. Roy. Afjr. ^oc. Enpland. 

 66 (1905). pp. ll,i-lll. p'</. 1). — An account is given of a peculiar scabbed con- 

 dition of potatoes which upon investigation was found to be due to Rhisoctonia 

 soJiuii. A comparison of descriptions of R. viohicca and R. sohini shows no mor- 

 phological differences, and from the identity of the mycelium on alfalfa and on 

 the potato there appears to be no doubt that these two species are identical. In 

 this case R. solaiii must be considered as a synonym of R. riolacea. 



The author states that the scurf appearing on the ])otatoes does little injury to 

 them either as an article of food or for use as seed, but when the disease pro- 

 gresses further so as to result in a scab-like form, while the food value of the 

 potato is not affected, such tubers should in no case be used as seed. The so- 

 called deep scab was found to be a stage of this disease, and tubers affected by 

 this have little value as food and under no circumstances should be used as seed. 



Bacterial wilt of tobacco, Y. Uyeda (Bid. Imp. Cent. Agr. Expt. 8ta. Japan. 

 1 (1905), No. 1, pp. 39-57, pis. 5). — For 20 years or more there has been known 

 in Japan a disease of tobacco variously designated as tobacco wilt, root rot, or 

 black shank. The disease has been under the author's observation for about 5 

 years and has been determined to l)e of bacterial origin. In m.iiiy w;iys it 

 resembles the wilt of the eggplant and tomato, but the organisms are not 

 identical. 



The disease may attack the young as well as the full-grown plants any time 

 from .Tune to September. The affected ])lants wilt, the leaves I)ecome yellow, the 

 stems are i)lackened, and the entire root system is destroyed. The bacteria gain 

 entrance through the root hairs, stomata, and wounds, and inoculation experi- 

 ments show that the disease can be readily transferred to sound plants, either 

 by the transfer of the plant juices or by the use of pure cultures of the organism. 

 In affected plants the bacteria are first noticed in the fibrovascular bundles of 

 the stems and leaves, which soon become blackened. Later the darkening ex- 

 tends to the larger veins of the leaves and aUjaceut tissues. 



