32 BOTANICAL GAZETTE [JANUARY 
turned into the gelatin holding distilled water only, while nine 
grew straight. 
Used in experiments similar to the foregoing, a 0.5 per cent. 
solution of potassium nitrate caused nine roots of the lupin out 
of ten to turn slightly into the distilled water gelatin, while the 
tenth root bent into the potassium nitrate gelatin. The growth 
was good, the roots not distorted, and the curves were slight. 
A 0.6 per cent. solution of anhydrous magnesium sulfate caused 
very slight curvatures in the lupin roots, but all ten roots cer- 
tainly bent into the distilled water gelatin. 
The curves described above as following the use of ammonium 
nitrate, calcium nitrate, potassium nitrate,and magnesium sul- 
fate may have been either negatively traumatropic or negatively 
chemotropic. In view of the behavior of the roots of this plant 
toward gelatin containing 3.5 per cent. of cane sugar, the curves 
last described could not have been osmotropic. The experiments 
certainly do show that Lupinus albus is not similarly chemotrogi- 
cally sensitive to all salts that it may absorb as food. Its roots 
are positive toward all solutions of sodium phosphate tried, but 
they turn away from solutions of corresponding osmotic strength 
of the other salts used. 
During the course of the work it seemed of interest to test 
the behavior of the roots of the lupin when two unlike salts of 
the same osmotic pressure were brought at the same time against 
opposite sides of the roots. For this purpose isosmotic solu- 
tions were made of potassium nitrate (KNO,), calcium nitrate 
(Ca(NO,),), and magnesium sulphate (MgSO,). The solutions 
were made by the specific gravity method to give a pressure 
equal to 130™ of mercury, it being assumed that in these weak 
solutions ionization was complete. It was assumed also that 
KNO, gave two ions, Ca(NO,), three ions, and MgSO, two ions. 
When these isosmotic solutions of potassium nitrate and of 
calcium nitrate were opposed on the flanks of a row of lupin 
roots, nine of the eleven roots grew into the potassium nitrate, 
two roots growing straight. When potassium nitrate and mag- 
nesium sulfate were opposed, ten of the eleven roots grew into 
the potassium salt, and one into the magnesium. When calcium 
