256 Pflanzenkrankheiten. 



with storage rots were inoculated into living sweet potato plants in 

 the field, but without success: F. oxysporinn , F. orthoceras, F. caii- 

 datiun and F. radicicola. Inoculations with Gibberella saubinetii and 

 Nectria ipomoeae were also unsuccessful. 



Infection is more likely to take place and the disease progresses 

 much more rapidly when the organisms are cultivated on media 

 where there is a maximum amount of septate conidia and a mini- 

 mum of hyphae and one-celled conidia. Wollenweber suggested 

 the use of stems or potato C3'linders for most species as the best 

 media on whigh a high culture, i.e. a culture with a maximum of 

 septate spores might be obtained. Indeed steamed or autoclavcd 

 sweet potato and Melilotus stems were found to be excellent media 

 for the growth of the sweet potato Fiisaria. The stemrot organisms 

 are vascular parasites, invading the bundles of all parts of the 

 plant, producing a brown discoloration. 



From stored sweet potatoes, on which field inoculations were 

 made, a number of organisms was isolated, among others Penicil- 

 liiun sp., Diaporthe hatataiis, Rhisopus sp., Macrosporiuni sp., Pesta- 

 lossia sp., Alternaria sp., and a many Fiisaria. Nectria ipomoeae is 

 also commonly found on rotting sweet potatoes in storage. Within 

 the limitations of the experiments, made by the writers to investi- 

 gate the relations between stemrot organisms and storage rots, the 

 results indicate that the stemrot organisms do not cause storage 

 rots or at least only rarely so, and then only under most favorable 

 conditions. 



The majority of infections take place in the field, though the 

 organisms may grow from diseased potatoes into the slips produced 

 therefrom. The organisms may be distributed with seed potatoes 

 and Slips, and by wind, insects, farm implements etc. Remedial 

 measures should consist in the careful selection of seed in the fall 

 from healthy vines. When selecting seed it is advisable to split open 

 the stem, and if the fibro-vascular bundles are blackened, the plant 

 is probably diseased and no potatoes should be taken from the hill. 

 Selected seed potatoes should be disinfected before bedding by 

 soaking for two minutes in a Solution ofcorrosive Sublimate (1 : 1000). 

 Disease-free soil should be used in the hotbed and the material 

 used in its construction should be previously sprayed with Bordeaux 

 mixture or some good disinfectant. B}'' practising such remdial 

 measures the writers have been able to materially increase the 

 yield even on badly infected soil. M. J. Sirks (Haarlem). 



Heald, F. D., M. W. Gardner and R. A. Studhalter. Air and 



wind dissemination of ascospores of the chestnut- 

 blight fungus. (Journ. agr. Res. Washington. III. p. 493—526. 

 1915.) 



The conclusions, drawn by the authors from their researches 

 about the dissemination of Endothia parasitica (Murr.) And., are the 

 following ones: 



As a result of 756 exposure plates made in or near the badh' 

 diseased chestnut coppice at West Chester Fa., it can be defini- 

 tely stated that ascopores of E. parasitica (Murr.) And. are prevalent 

 in the air and after expulsion are carried for varying distances 

 from their source. 



As shown by the same exposure plates, the period of prevalence 

 of ascospores varies with the conditions following the cessation of 



