Metals and Plants. 
468 
The most interesting point shown by this table is the growth 
of the copper and cobalt cultures during the first day, before the 
solution reached a fatal concentration. Platinic chloride and 
palladium nitrate were put into the water in unmeasured traces, 
to see if they would act as stimulants; but no such effects re¬ 
sulted. One of the plants in the presence of metallic lead was. 
too vigorous to be killed by the concentration of lead ions present 
during the first three days, and grew in the whip-like form ob¬ 
served before in some toxic but not fatal solutions. A spoon¬ 
ful of carbonate of lead in a beaker of water dissolved enough 
to be deadly during the first day. Tungsten induced a similar 
brief growth in length, without branches unless at the very 
base, in this experiment; as did also selenium, indium, and 
boron; the last one (boron) produced a monstrosity. It would 
be needless to repeat here the observations on the_ roots and 
metals already given under experiment II. 
The influence of the area of exposed metal upon the time re¬ 
quired for a solution to become deadly, is shown by coating 
with paraffin all but certain a measured length of submerged cop¬ 
per wire. The first figure in each couple in the table repre¬ 
sents a root near the wire, the other being relatively far from 
it. The influence of the area of exposed metal was tested at 
another time with similar results shown in the following table, 
the plant being the same, Lupinus albus , beginning Decem¬ 
ber 6. 
GROWTH IN MM, 
Dec. 7. 
Dec. 8. 
Dec. 9. 
Dec. 10. 
Dec. 15. 
Dec. 17. 
Control ........... 
6.7 mm. 
13 
24 
26* 
49.5 
51 
1 cm. cu. wire..... 
4.7 
10.5 
19.5 
28.5 
57.5 
57 
5 cm. cu. wire..... 
4.5 
7.7 
9 
8.7 
Brown. 
The plants in pure water were distinguished from those 
grown with 1 cm. of wire exposed, by their copious develop¬ 
ment of lateral roots more than by the slight difference in color. 
