1896 | TOXIC EFFECT OF ACIDS AND SALTS UPON PLANTS 143 
so that when it has been stated that the seedling was killed only 
the root has been referred to. 
5. NicKEL AND COoBALT. 
A series of experiments were carried out with two nickel 
salts, NiSO, and Ni(NO,), and two cobalt salts, CoSO, and 
Co(NO,),. The same two seedlings, Pisum sativum and Zea 
Mais were used. First as to the results obtained with the seed- 
lings of Pisum sativum. Seedlings were placed in the dilutions 
shown in the following table and the growth recorded for periods 
of twenty-four hours. 
PISUM SATIVUM. 
1 
Nickel and Cobalt. 6L00 T2800 25600 Biz00 | 102400 
mol, mol. mol mol, mol. 
NiSO 4 Ist24 hours se loa 1.5 mm r.750™ to ™m 13 6g 
* 2d 24 hours s a ed 65 5 
Ni(NO.), J Ist24hours} 1 « Mra tas 225° 7 ea 13.25" 
ee ( 2d 24 hours a ah ae = 1¥.75** 
CoSO, $18t24hours} 1 « poe 7 eases 6,25" ne 
2d ours ce rf 3.5.0 Cy Be 
CoNG,), 4 2abours; 1 | 3 | 45! 78 
( 2d 24 hours io. ‘75 
He AED Re aa aaa to 
First as to the nickel salts. In the eaten reteo 20d xst00 
8ram-molecule solutions a small amount of growth was observed 
for the first twenty-four hours but no further growth resulted. In 
the 57359 and + 55'y)9gram molecul lutions i | pags 
occurred for the entire period, except in the 5,49, nickel nitrate, 
in which solution the normal conditions were not fulfilled, since 
the plants suffered from a copious growth of bacteria. At the 
end of the experiment the roots which were killed were not soft 
— flabby as in the acid or copper poisoning, but were extremely 
rigid. The roots were so rigid and brittle that if the seedlings 
Were dropped on the table they would snap in pieces almost like 
“© much glass. For'the cobalt salts growth was observed in the 
id and +51. gram-molecule solutions for the first twenty-four 
Sabet but no growth afterwards, while in the two next weaker 
Solutions growth continued for the entire period. The roots 
