1904 | NEWCOMBE & RHODES: CHEMOTROPISM OF ROOTS 33 
nitrate and magnesium sulfate were opposed, ten of the fourteen 
roots grew into the magnesium salt, while the other four roots 
remained neutral, 
When we remember that all of the four salts last used caused 
the lupin roots to bend negatively when these salts were severally 
opposed to distilled water gelatin, we may be certain the curves 
noted in the preceding paragraph were repulsion and not attrac- 
tion curves. The magnesium sulfate therefore repels more 
strongly than the potassium nitrate, and the calcium nitrate 
more strongly than either the potassium nitrate or the magnesium 
sulfate. Whether this repulsion is chemotropic or traumatropic 
cannot be decided at this time. 
To ascertain whether other plants are chemotropically sensi- 
tive as Lupinus albus has been found to be, seedlings of Cucurbita 
Pepo L. have been put to the test. 
Isosmotic solutions of potassium nitrate, calcium nitrate, 
and magnesium sulfate were prepared with computed pressures 
equal to 130™™ of mercury at a temperature of 15°. With 
these solutions blocks of gelatin (6 to Io per cent. of gelatin 
according to the general atmospheric temperature) were made 
up and brought against the roots of the seedlings suspended in 
rows in damp chambers. The results may be shown in tabular 
form, the chemicals in a horizontal row being in opposing blocks 
of gelatin, the column of figures to the left indicating the num- 
ber of roots curving toward the salts to the left, the figures in 
the middle column indicating the neutral roots, and the figures 
at the right indicating the number of roots curving toward the 
salts there given. 
Curved Neutral Curved 
KNO, = I 9 fe) - MgsO, 
KNO, Ms 2 16 10 o) GRENO sh 
MgSO, ee o 9 3 = Ca(NO3), 
Through an error in reading the specific gravities of solutions 
as given in Gerlach’s tables,”* the stock solution of di-sodic phos- 
phate was made with an osmotic pressure of 39°" of mercury, 
instead of the same pressure as the solutions of the three salts 
 Zeitsch. Analyt. Chemie 8: —. 1869. 
