DISEASES OF PLANTS. 863 



Destruction of prickly pear {Queensland Agr. Jour., 9 {1001), No. 5, pp. 

 460-46'2). — An experiment is reported in whicli an attempt whh made to clear 145 

 acres of land infested with a dense growth of prickly pear. The plants were cut 

 down and afterwards sprayed with a number of solutions, the best results being 

 obtained where sodium arsenite was used at the rate of 5 to 8 oz. per gallon of water. 

 Ordinarily the cutting of this plant does not destroy it, but 3 or 4 days after spraying 

 the green succulent stems had wilted and turned brown and were drying up. Not 

 only were the so-called leaves destroyed but the spray penetrated the stumps to the 

 ends (if the roots, causing them to rot. The application of this herbicide, while very 

 destructive to the cactus, had no effect on the grass, and in a comparatively short 

 time the area was covered with an excellent stand of pasture grasses. The other 

 materials experimented with were iron sulphate, hydrochloric acid, coal tar, creosote 

 oil, ammonium sulphocyanid, calcimu sulphid, and solutions of copper sulphate, 

 sodium nitrate, and potassium chlorate. None of these gave results at all compara- 

 ble to those secured by the use of sodium arsenite. 



DISEASES OF PLANTS. 



An attempt to secure immunity of plants to fungus diseases, J. Beauverie 

 ( Compt. Rend. Acad. Sei. Paris, 133 {1901), No. 2, pp. 107-110). — An account of experi- 

 ments with Botrytis cinerea is reported, in which a form of the fungus was sought 

 which would secure various plants immunity from attacks by the fungus. This 

 fungus, which is said to be very common in greenhouse soils, exists in 3 forms. The 

 ordinary form exists as a saprophyte developing upon decomposing plants. This 

 form is the well-known normal conidial stage of the fungus. The parasitic form of 

 the fungus is said to be completely sterile, and a third form between the two, which 

 appears to be a sort of a transition stage, is also recognized. The author claims that 

 by sowing sterilized soil with the spores from the conidial stage of the fungus and 

 allowing them to grow for some time, it is possible to produce a growth of the fungus 

 in the soil which will not interfere with the growth of seeds or cuttings, and espe- 

 cially with cuttings of begonia, which is ordinarily quite subject to attack by the 

 sterile form of the fungus. In this way he claims to have secured immunity from 

 attack. By extending this method of culture to the soils of greenhouses the author 

 says it will be found possible to secure immunity from the very common and some- 

 times destructive occurrence of the sterile form of the fungus. 



Cultures and attenuated forms of fungi which cause diseases of plants, 

 J. Ray {Compt. Rend. Acad. Sci. Paris, 133 {1901), No. 5, pp. 307-309).— A. summary 

 is given of recent investigations relative to attenuated cultures of fungus parasites 

 of plants, with studies of rusts and smuts of cereals and other plants. The author 

 claims to have been successful in obtaining pure attenuated cultures of the smuts of 

 wheat and oats, and rusts of eglantine and Euonymus europxus. By using these arti- 

 ficial cultures it is believed possible that immunity to disease caused by them may 

 be secured. 



A bacterial disease of the tomato, F. W. T. Hunger {Meded. 'S Lands Plan- 

 tenttiin, 1901, No. 48, pp. 57, pis. 2). — The tomato disease caused by Bacillus solanace- 

 arum (E. S. R., 8, p. 895) is reported as prevalent at and about the botiinic gardens 

 at Buitenzorg, Java. The diagnosis of the disease is given for the parts of the plants 

 above as well as for those below ground. The author describes the germ and its 

 behavior on different culture media, and records a number of experiments with pure 

 cultures to determine the method of infection. In connection with the diseased con- 

 ditions produced by the germ, the normal anatomy of Lycopersicum esculentum is 

 described. Under the discussion of species of Solanacese suscei)tible to this disease, 

 the writer expresses the belief that the slime disease of tobacco is caused by the same 



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