730 



In regard to the forest trees, wliich come most under consideration, we 

 find it stated that the spruce, even one day after artificial smoking, shows 

 some shoots with a whitish gray discoloration ; in fact, they had wilted. 

 After a second smoking the little trees were set out of doors, where the color 

 tone, which originally had been a whitish, yellowish gray, passed through all 

 the gradations from yellow and yellowish red to the "characteristic red of 

 injury from acids." 



Pines, larches, and acacias, like the spruce, were found to be discolored 

 in the vicinity of a phosphate factory where hydrofluoric vapors were devel- 

 oped in the removal of phosphorite containing the calcium-fluorin by the 

 use of sulfuric acid^ Mayrhofer- was able to prove a strikingly high 

 content of fluorin in the needles and leaves at a distance of 500 to 600 m. 

 from the factory. The effect of such an exhalation may be absolutely 

 destructive to grain. Thus Rhode^ observed that in sortie plots rye devel- 

 oped no kernels at all, or only deformed ones. 



My own investigations were made only on preserved material of dead 

 spruce needles which I had received from Professor Ramann, but, what is 

 most important, the condition found in them agreed with the effects obtained 

 with sulfurous acid. Only, in the needles affected by the hydrofluoric acid, I 

 found, however, a wrinkling of the tissues as a result of the shrivelling of 

 the cell walls. It must be concluded from this that the drying of the needles, 

 which appears so quickly with the use of sulfurous acid, takes place only 

 after the direct action of the acid has already produced a change in the form 

 of the tissues. The contents, however, had not dried against the walls as in 

 the action of sulfurous acid, and, on this account, could not have contributed 

 to the stiffening of the walls themselves. 



Nitric Acid. 



We find only one note by Konig* on the influences of nitric acid (or 

 nitrogen tetroxid). With 5 grains nitric acid (reckoned on nitrogen 

 tetroxid) to 100,000 1. of air or 0.05 g. of nitrogen tetroxid in one cubic metre 

 of air, he found characteristics occurring in trees which resembled those 

 appearing after the action of sulfurous acid and hydrochloric acid. The air 

 generally contains only 0.00003 g. of nitric acid in one cubic metre. 



Ammonia. 



Ammonia and ammonium carbonate in quantities far beyond that of the 

 usual content of the air, which at most may be assumed to be 0.056 mg. per 

 cubic metre, were found to favor growth. In general manufacturing pro- 

 cesses, however (ammonium sodium processes, etc.), such large amounts 



1 Allgem. Forst. u Jagdzeitung- 1891, p. 220. 



2 Mayrhofer, J. tJber Pflanzenbeschadigung, veranlas-st durch den Betrieb 

 einer Superphosphatfabrik. Freie Vereinigung d. Bayr. Vertreter fiir angewandte 

 Oliemie. Vol. X, p. 127. 



•^ lihode, A. Schadigung von Roggenfeldoi-n diirch dio pincr .Siipeiphos- 

 phatfabrik entstromenden Ga.se. Zeitschr. f. PflanzcMikiankli. ISlt.''), p. I'ir,. 

 ■» KiJnig, Denkschrilt lSt»6, p. 202. 



