746 



According to my experience with house plants, the dryness of the air 

 is primarily the chief cause of death, and manifests itself in the drying of 

 the leaf tips and edges. 



In regard to the effect of illuminating gas on roots, Bohm's experi- 

 ments', with willow cuttings in bottles of water through which illuminating 

 gas was passed, showed that the action was slowly fatal. The cuttings 

 which died after 3 months had formed new short roots at the expense of 

 the stored starch. The action was thus less intensive than it was when carbon 

 dioxid was passed through the water. In this case all formation of new 

 structures by the submerged stem was suppressed while the upper part, 

 which formed tyloses in its ducts, developed sickly shoots. Death occurred 

 after 2 months. In other experiments in which hydrogen was passed 

 through the water, development was practically normal. (Compare the 

 section on Excess of Carbon Dioxid.) 



The plants also died when illuminating gas was introduced into the 

 earth in their pots. Seeds, set in earth through which illuminating gas had 

 passed for almost 2^ years, developed more poorly. If a stream of atmos- 

 pheric air was drawn through such soils for a considerable time, the soil did 

 not lose its injurious effect entirely so that, as already stated, this effect may 

 indeed be ascribed chiefly to the tarry products which are deposited in the 

 soil in a fluid or solid form. 



Spath and Meyer^ found that even a comparatively small amount of gas 

 (25 cu. ft. distributed daily on 14.19 sq. m. at a depth of 1.25 m.) killed the 

 roots which came in contact with it. Even a greater quantity of gas was 

 found to be less injurious if it reached the trees during their winter dormant 

 period. Here too different varieties of trees display a different power of 

 resistance. 



Most expedient at present seems to be Juergens' method, as recom- 

 mended by Bohm, of laying the gas pipes through the streets, etc., in glazed 

 terra cotta pipes which have openings leading to the light standards so that 

 constant ventilation can take place within the terra cotta pipes. 



Brizi" has made experiments in regard to Acetylene poisoning. He 

 found in one Italian city that Quercus Ilex died when growing alongside a 

 pipe carrying this gas. Herbaceous plants died in pots and dried up if 

 acetylene was introduced into the soil. The nuclei disappeared in the pali- 

 sade cells of Coleus, the roots lost their hairs, the lateral roots seemed wilted, 

 crushed and brown, the bark cells lacked all fluids. In Evonymous Japonica 

 the plants in dry soil seemed perfectly normal after 7 days, while, in moist 

 earth they had all dropped their leaves after the 6th day and most of the 

 young roots had died. The laurel and the grapevine behaved similarly. 



1 Uber den Einfluss des Leuchtg-ases auf die Veg-etation. Sitzungsber d. k. 

 Akad. d. Wissench. zu Wein, Vol. LXVIII B. 



2 Spath and Meyer, Beobachtung-en iiber den Einfluss des Leuchtgases auf die 

 Vegetation von Baumen. Landwirtsch. Versuchsstat. 1873, p. 336. 



3 Biizi, U. Sulle alterazioni prodotte alle piante coltivate dalle principnli 

 emanazioni g-asose degii stabilimente industriali. Staz. sporim. agrar. ital. XXXVF; 

 cit. Zeitschr. f. Pflanzenkrankh. 1904, p. 160. 



