DISEASES OF PLANTS. 873 



DISEASES OF PLANTS. 



Recent researches on the parasitism of fungi, II. MARSHALL WARD | Inn. 

 Hot., in i 1905), Vo. 7..'. /<//. / 54; <H,s. in Bot. Centbl., 98 i 1905), Vo. 16, p. \19). - 

 This is .-in address delivered by the author before the British Association for 

 the Advancement of Science, in which he reviews the literature relating to 

 parasitism of fungi, paying particular attention to the parasitism of cereal 

 rusts. 



The author in concluding his paper rejects the mycoplasm hypothesis of 

 Eriksson, and states thai inasmuch as uredospores can be found almosl con 

 tinuously the year round, and thai they may develop on tufts of grass here 

 and there during the winter and retain their germinating power for at least 

 2 or ."'. months and perhaps longer, and, further, thai specialized forms can 

 occasionally infest races of wheal which normally prove immune, there is qo 

 necessity for explaining parasitism by any mycoplasm theory. 



He lias been unable to find any trace of mycoplasm, and from the present 

 facts regards the revision of the hypothesis as accessary. He predicts thai if 

 infesting spores are soughl for bj means of serial sections they will ultimately 

 be found. 



A bibliography of mere than 200 papers relating to parasitism of fungi is 

 appended to the address. 



Some recent observations on plant diseases, P. Rjppert (Fuhling'8 handle. 

 Ztg., ■',) (1905), Vos. I), pp. \81 \81 ; 15, pp. 513 516).— A summary is given of 

 the present status of knowledge regarding a number of diseases of economic 

 plants, and means are suggested for their control. 



Among the diseases described are the blackleg of potatoes due to Bacillus 

 phytophtkorus, rusts of cereals and grasses caused by different species of Puo 

 • inia, cereal smuts, blights of cereals due to Helminthosporium gramineum and 

 //. lacs, and the gummosis and canker of fruit trees. For the prevention of 

 cereal smuts the author rec mends the formalin treatment of the seed. 



On endophytic adaptation shown by Erysiphe graminis under cultural 

 conditions, E3. S. Salmon i Ann. Bot., I!) (1905), Vo. 75, /</'• /// //'»'>■ In other 

 papers (see below) the author has pointed oul the fad th.it certain species of 

 Erysiphe under cultural conditions are able to infest their host plants when 

 their COnidia or asCOSpores are placed on the cells of the internal Tissues exposed 



by wounds, etc. 



In the present paper an abstract is presented of a longer report, giving the 

 results ( >f experiments carried on with the conidial stage of /:. graminis, a strict 

 ectoparasite under normal conditions. The author shows thai this mildew is 

 not so highly specialized as an ectoparasite ;is t.. he restricted for its food supply 

 to the cells of the epidermis, hut is capable of adaptation to conditions closely 

 resembling those obtaining in endophytism. 



This suggests the possibility that under some circumstances the mycelium of 



species of 1 -]y\ siph.-iee.-e ni;iy penetrate into the internal tissues of their host 



plants exposed through wounds caused by the attacks of animals or by physical 

 agency. It is pointed out. however, that the entry of the byphse mighl probably 

 he prevented to ;i considerable extent by the drying up of the superficial layers 

 of cells or by the healing processes which take place with greal rapidity in the 

 leaves. 



Further cultural experiments with " biologic forms " of the Erysiphaceae, 

 E. s. Salmon (Ann. Bot., /'■> i 1905), Vo. 7.;. pp. I !■'» i )s .- abs. ;,, Bot. Centbl.. 98 

 (1905), No, iu. t>i>. U s - //•'"• — in the present paper experiments are described 



