DISEASES OF PLANTS. 545 



DISEASES OF PLANTS. 



The symbiosis of bacteria with plants, H. Miehe (Biol. Centbl., 32 (1912), 

 No. 1, pp. .'i6-50). — The author describes bacterial tumors foimd. on the leaves 

 of Ardisia crispa and Pavetta spp. in addition to those recently reported by 

 Boas (E. S. R., 26, p. 451) on 2 species of Psychotria. There do not appear 

 to be any symptoms of parasitism on the part of the bacteria, and the author 

 believes the relation is one of symbiosis. 



Patholog'ical fungus forms, E. Voces (Ztschr. Pflo/nsenkranlc., 21 (1911), 

 No. Ji, pp. 207-213, figs. 5). — The author describes and discusses certain abnor- 

 malities of form and habit observed in the development of certain cultures of 

 Septoria apii and Marssonia potentilUe gi'own on substrata of plum and straw- 

 berry decoction and of gelatin. He considers the peculiarities as pathological 

 and accidental, being expressions of the artificial nature of the substratum. He 

 does not explain the fact that he found abnormalities resembling some of these 

 in Marssonia growing naturally on leaves of its proper host, Potentilla anserina. 



Intumescences in Araliaceas, P. Soraueb (Ztschr. Pflanzcnkranlc, 21 (1911), 

 No. 6, pp. 336-3-'tl, fig. 1). — The author made a careful study of the distortions, 

 discolorations, and cell changes in the leaves of Aralia sieboldi, A. palnutta. 

 Panax arborcus, and Hedera helix, but was not able to state any regular re- 

 lation between these abnormalities and the organisms found in connection 

 therewith. 



Study of fungi on Lolium, J. FucHs (Hedivigia, 51 (1911), No. 5, pp. 221- 

 239). — The author gives an account of his investigations on the relations of 

 Lolium as host to certain fungi parasitic or symbiotic thereon. 



Attempts to obtain the fungus from the host directly by means of cultures 

 from small portions of the mycelium-containing aleurone layer of infected 

 embryos resulted in the separation of 2 different fungi, a Pleospora and a 

 Fusarium. By utilizing the fact pointed out by Stingl that an embryo of one 

 species can be made to grow on the endosperm of another, it was found that 

 in almost every case where the transferred embryo failed to grow, Fusarium 

 developed, apparently of the same species that had already been obtained 

 by the separating pi'ocess mentioned, but now living not as a parasite but 

 saprophytically. 



The author holds that these results support the view that the normal life 

 of the fungus is here really symbiotic rather than parasitic. Fungus-free 

 Lolium seeds inoculated with the fungus separated as above appeared after 

 from 2 to 4 weeks to have been penetrated by the fungus. 



Combating stalk disease of rye (Tylenchus dipsaci) in Westphalia, A. 

 SniXKERMANN (Luudio. Jalirh., J/O (1911), No. 3-.'i. pp. Ji75-515; abs. in Centhl. 

 Bald. [etc.'\, 2. Abt, 31 (1911), No. 23-25, pp. 600-603) .—AUer giving a brief 

 history of this nematode disease the author presents an account of the investi- 

 gations carried on looking to its control. The experiments were conducted 

 mainly in sandy soils, more or less loamy, and of vai'ying fertility in a region 

 where rye is the leading crop, especially on the lighter soils. 



The industrious removal of the infected plants produced but little improve- 

 ment in seriously infected fields. Disinfection was found practicable only on 

 small spots of recent infection. Carbon disulphid, mixed carbolic and sulphuric 

 acids, and in a degree petroleum, have been fovmd efficacious in this connec- 

 tion. On weak soils the improvement of nutrition on application of proper 

 fertilizers, si>ecifically nitrate of soda, has been found to check the disease. 

 No marked iufiuence of seed time on the disease can be stated, except that early 

 plantings following mild winters suffer more than late sowings, while late seed- 



