Pfianzenkrankheiten. 631 



Crowther, C. and A. G. Ruston. The nature, distribution 



and effects upon Vegetation ol" atmospheric impurities 

 in and near an industrial town. (Journ. Agric. Sei. IV. 1. 

 p. 25-55. 1911.) 



Experiments to test the eomposition and effeets ot" rain contain- 

 ing many impurities have been carried on for three eonsecutive 

 years at Garforth, near Leeds (Yorks.). The impurities com- 

 prised nitrogen as ammonia, nitric aeid, and as „albuminoid" ni- 

 trogen, sulphur, chlorine, and free arid; tables are given to show 

 the yearly amounts of each , whieh were relatively high when 

 compared with results obtained at Rothamsted Experimental Station. 

 Similar analyses were made of the rain preeipitated at ten repre- 

 sentative stations within the city of Leeds itself, additional deter- 

 mination being made of the total suspended matters, with the tar, 

 ash and soot contained therein. The results show the higbTy im- 

 pure character of the atmosphere over the greater part of the city, 

 especially in the industrial areas. 



The suspended matters in the air exercise a deletenous in- 

 fiuence on plant growth in that they tend to block the stomata, 

 and also to reduce the intensity of the sunlight ineident upon the 

 leaves. Some direct or indirect toxic influence is also exerted b} r 

 certain of the impurities, such as free aeid. The action of aeid on 

 the soil is detrimental both to the growth and eomposition of plants 

 as was proved by direct experiments with Timothy grass (Phleum). 

 The chemical Constitution of the soil was influenced adversely, and 

 so also was the bacteriological flora. With increasing aeidity the 

 total number of bacteria diminished rapidly, so that processes of 

 ammonia produetion, nitrogen fixation and nitrification were all re- 

 düced in activity. The Leeds rain-water exercised an inhibitory 

 effect on the soil organisms equal to that of water containing be- 

 tween 1 — 2 parts of sulphuric aeid per 100,000. 



W. E. Brenchley. 



Essed. E., The Panama disease. Parts I und II. (Ann. Bot. 

 XXV. p. 343—361. 1911.) 



Part I. The disease lirst shows itself in the Banana by a pe- 

 culiar withering of the leaves along the margins; later on develop- 

 ment stops, the leaves droop and gradually dry up, and finally the 

 pseudo stem bends down. Death is evidently caused by a fungus. 

 which seems to Start as a wound parasite or saprophyte, and the 

 damage done is not only mechanical but physiological, due to 

 plugging of cells and vessels by hyphae etc. „Sclerotia" are formed 

 which give rise to spore Clusters - chlamydospores — of a Ustila- 

 ginoid character. Conidia are also formed, crowded in pyenidialike 

 cavities. All parts of the plant are finally attacked by the fungus, 

 which encloses the tissue-remnants in sclerotia, and adapts itself to 

 a saprophytic mode of life. Various eultures were made, with the 

 final result that the disease is attributed to the attack of a new 

 species of fungus, now named as U stilaginoidella musaeperda. 



Bacteria {Micrococcus sulfureus and Bactevium fluorescens) are 

 associated with the fungus, but experiments show that neither ot 

 these are active agents in the disease. 



Part II. The „sclerotia" are designated as pegmatia-struetures 

 arising from well nourished hyphae which harden into gristly or 

 gummy bodies which can regen erate the fungus by chlamydospores 



