22 Pflanzenkrankheiten. 



hibernating mycelium, and proceeds to show by means of experi- 

 ment that the evidence is faulty and the reasoning open to question. 

 He comes to the conclusion that it is a theory without scientific 

 evidence to support it, and one which is hard to reconcile with 

 well-known facts. 



With regard to the growth of diseased tubers, field experiments 

 show that when they are planted, the majority die in the ground, 

 and that if a few diseased plants do develop they die soon after 

 showing. The remainder produce strong healthy plants, which are 

 found to be uninfected and which remain free from the disease 

 unless infected b}r spores. Greenhouse experiments gave similar 

 results, and confirmed the point that (slightly) diseased tubers 

 yielded plants perfectly free from Phytophthova, and that they 

 remain free from it, even when brought into a warm and very 

 moist atmospherc. 



A number öf questions relating to the resting mycelium theory 

 are discussed, e. g. the reliability of previous experiments, the infec- 

 tion of young tubers etc. Pethybridge concludes that there is no 

 evidence at present to show that the attack of the Potato crop as 

 a whole with blight, occurs otherwise than by spores, but whether 

 the sources of spore-production at present known are sufficient to 

 account for an outbreak is a question requiring further investigation. 



A, D. Cotton (Kew). 



Pethybridge, G. H. and P. A. Murphy. A bacterial disease 

 of the Potato Plant in Ireland. (Proc. roy. Irish Acad. XXIX. 

 Sect. B. 251. 3 pl. Feb. 1911.) 



The paper deals with a bacterial disease of the potato plant 

 (including the tubers) of which no detailed study has up to the 

 present been published. The characters of the disease are described 

 in detail, the main features being discoloration and drying up of 

 the foliage, browning of the principal vascular bundles of the stem, 

 decay of the Underground portion of the stalk, and rotting of 

 the tubers. 



An account is given of the isolation of a pathogenic organism 

 from the diseased tissues, and of inoculation and re-isolation expe- 

 riments made with it on healthy plants, which prove that it is the 

 cause of the disease. The organism is described in detail both as^ 

 to its morphological and physiological characteristics. It is a multifla- 

 gellate, peritrichous bacillus, liquefying gelatine, practically non- 

 chromogenic, and evidently allied to, but not identical with certain 

 other organisms causing similar diseases. The name Bacillus melano- 

 genes is suggested. 



Although the disease may probably be contracted from the soil 

 the evidence at hand shows clearly that the planting of affected 

 tubers is mainly responsible for its spread. The disease causes loss. 

 not only in the growing crop, but also duringstorage, affected tubers 

 should therefore be excluded from the störe. 



A. D. Cotton (Kew). 



Rorer, J. B., The Green Muscadine of Froghoppers. (Proc. 

 Agric. Soc. Trinidad and Tobago. X. p. 464—482. 1910.) 



The Sugar cane in Trinidad is very susceptible to blight, 

 which is now associated with the attacks of the Froghopper( Tomaspis 

 bostica). The relation of blight to root disease, leaf spot and red-rot 



