ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 527 



should have remained almost wholly unsolved must be attributed 

 chiefly to the very great difficulties which are met in any experimental 

 investigation, but also to the fact that the few investigations published 

 have been carried out, in most cases, for the purpose of proving that 

 vegetation had been injured by metallic compounds traceable to 

 metallurgical works, and with the special purpose of founding a claim 

 for damages, rather than to solve a scientific problem. The study of 

 the influence of metallic compounds on plants has recently acquired 

 great practical importance, from the fact that many manufacturing 

 processes, more especially those employed in the smelting of lead 

 and copper, and arsenical ores of various metals, have given rise to a 

 gradual impregnation of the soil with such metals, and to the conse- 

 quent poisoning of vegetation and animals. 



The possibility of injury to plants has been denied on the assump- 

 tion that they select such elements of the soil as are nutritious and 

 reject all else. 



Mr. Phillips has therefore undertaken experiments from which it 

 seems safe to conclude : 1. That healthy plants grown under favour- 

 able conditions may absorb, through their roots, small quantities of 

 lead, zinc, copper, and arsenic. 2. That lead and zinc may enter the 

 tissues in this way without causing any disturbance in the growth, 

 nutrition, and functions of the plant. 3. That the compounds of 

 copper and arsenic exert a distinctly poisonous influence, tending, 

 when present in larger quantity, to check the formation of roots, and 

 either killing the plant or so far reducing its vitality as to interfere 

 with nutrition and growth. In the case of the heavy metals, copper, 

 zinc, arsenic, and lead, it seems to be probable that their oxides may 

 under certain circumstances become deposited in the tissues of the 

 plant. As to the manner in which this takes place, authorities differ. 



It is supposed by Freytag and others, that plants absorb all 

 soluble matters indiscriminately, through their numberless rootlets ; 

 that the absorption of poisonous metals causes no disturbance until a 

 certain degree of concentration is reached, when the plant rapidly 

 withers and dies ; that plants are therefore spared the sufferings of 

 chronic poisoning, but are very susceptible to acute poisoning, which 

 is invariably fatal ; while it is held by others that plants absorb only 

 such elements as are essential and nutritious, refusing to take up 

 what is poisonous or innutritious ; metallic compounds found in the 

 analyses are therefore to be traced to atmospheric deposit adhering 

 externally. The theory of Freytag seems to the author to have the 

 weight of facts in its favour, and if it is possible that crops may 

 become charged in this way with poisonous elements of the soil, it 

 becomes a matter of the highest importance that wherever there is 

 danger of such impregnation the most efficient means be employed 

 for its aversion ; for soil once impregnated with copper, lead, and 

 zinc, may year after year bear crops poisoned in the same manner. 



Decomposition of Calcium carbonate in the Stem of Dicoty- 

 ledonous Woods.* — H. Molisch states that the deposition of calcium 



* SB. K. Akad. Wiss. Wien, Ixxxiv. (1SS1). See Bot. Centralbl., x. (1SS2) 

 p. 161. 



