142 BOTANICAL GAZETTE [ AUGUST 
toxic action was due to the Cu alone, the ~SOj ions and the 
Cl~ ions being without effect. Now in the case of the Re 
acetate if the C, H, OF; was poisonous we should expeat t a : 
solution would kill the seedlings at a greater dilution, ee 
would have the combined action of H* ions and C,H eo 
but the experiments show the killing point for the a ae 
the same as for the other salts. Hence we must conelt : a 
the C,H,O, ion is without any poisonous effect at this di ie 
Nageli* has shown that copper by its mere presence ee 
water in which plants were growing was able * produce filled 
effects, and Low 3 has also shown that water which was dis pe 
from a copper retort resulted injuriously to plants. Ri 
found that it was impossible to use brass pins to — a 
lings to a cork while growing in various solutions. e me 
poisonous effect was due to the Cu and Zn of the pe a ‘A 
by the fact that as soon as glass pins were a é 
plants grew without any difficulty. We ona vee 
copper as being insoluble but in the cases mentioned a a 
very certain that enough Cu-ions were formed in the 50 
to produce the toxic action. 
as one part of copper to 404,423 parts of water. “ — 
of Zea Mais were killed by the x745; gama 2 a 
which ig equivalent to one part of copper to 808,840 Pal™ — 
water. 
uld be 
Before leaving the copper salts one other fact fe: seed- 
mentioned. At the end of the experiments some of t would | 
lings were transferred to distilled water to see if the ie dling : 
revive, but in no case would the main root grow. Bec ee 
as a whole was not dead, but would continue to grow “ Pail 1 
secondary roots above the part of the root which had bee # 
* Denkschr. d, Schweizerischen naturf. Ges. 33:1. 1893. 
3 Landw, Jahrb. 20: 235. 1891. 
