1904] NEWCOMBE & RHODES: CHEMOTROPISM OF ROOTS a 
A third row of ten seedlings of the same species, set up between 
gelatin and distilled water on one side and gelatin and I per cent. 
di-sodic phosphate on the other, gave eight roots bent into the 
gelatin containing the chemical, while the other two roots were 
straight. None of the roots were dead. In the twenty-four 
hours of the last experiment, the roots had grown but about 
1o™, though the temperature was 20° to 23°. This shows a 
retardation of growth to about 50 per cent. of what it would have 
been in air or soil. 
The last series of three experiments demonstrates that by 
strong solutions of sodium phosphate the roots of this plant 
unable to turn in negative chemotropism are helplessly lured on 
to certain death. The case is similar to that of several free- 
swimming organisms, mentioned by Rothert*, which swim into 
solutions of lethal osmotic strength. 
Though the roots of Lupinus albus are positively chemotropic 
toward di-sodic phosphate, they do not display a like behavior 
toward all salts that are absorbed by plants as food. Seedlings 
of Lupinus albus to the number of thirty-seven suspended between 
blocks of 5 per cent. gelatin, one block holding only distilled 
water, and the opposing one a 0.5 per cent. solution on the 
anhydrous nitrate of ammonium, showed when the preparations 
were taken down twenty-four of the roots grown into the block 
containing no chemical, while the other thirteen roots were 
straight. 
A similar preparation with the same species was made with 
gelatin with distilled water on one side, and with gelatin and a 
0.75 per cent. solution of water-free calcium nitrate on the other 
side. At the end of the experiment twenty roots were negative 
toward the salt, and the other eight roots were straight. Still 
another set of seedlings of the same species was prepared with 
roots between gelatin and distilled water on one side and gelatin 
and a 0.375 per cent. solution of the water-free calcium nitrate 
on the other. The result turned out as before, except that a 
smaller proportion of roots bent. Of the seventeen roots, eight 
'ROTHERT: Beobachtungen und Betrachtungen iiber tactische Reizerschein- 
ungen, Flora 88: 409. I90I. 
