28 BOTANICAL GAZETTE [JANUARY 
gelatin blocks as they came from the molds were 15™ long, 
9 wide, and 2.5™ thick. The seedhngs to be used were 
fastened in the usual way to a bar of white pine which was sus- 
pended across the damp chamber at a suitable height. In the 
bottom of the damp chamber a glass platform had been raised 
above the water, and on this the gelatin blocks were laid, each 
block with a glass plate for a backing. A little practice soon 
enables one, with a hand on each glass plate, to turn the gelatin 
blocks up against the row of roots; and while with one hand 
the two blocks of gelatin are held in place, with the other hand 
they are secured there by bringing against the glass plate sup- 
porting them bars of wood held in place by springs of rubber 
tubing. 
A row of thirteen seedlings of Lupinus albus was first used 
between the blocks of gelatin, one of which was made with dis- 
tilled water, the other with 0.28 per cent. dry salt of di-sodic 
phosphate (Na,HPO,). The seedlings were 5° to 7™ long, 
the temperature 23°, and the period twenty-four hours. The 
dry gelatin was 6 per cent. of the whole mass. 
At the conclusion of the experiment, all. thirteen roots were 
found grown into the sodium phosphate gelatin, the angles of 
curvature being 45° on the average. The roots looked healthy, 
and growth had been good. Decisive as this result was, it did 
not demonstrate the precisé cause of the curving. The result 
may have been traumatropism, or hydrotropism (osmotropism), 
or chemotropism. 
The curves could hardly be due to the presence of copper or 
other metal in the distilled water, for water from the same bottle 
was used in the gelatin on both sides of the seedlings. Yet to 
make doubly sure, the next gelatin blocks were made with water 
twice distilled in flasks of Jena glass. In this test eleven seed- 
lings of Lupinus albus were employed as in the preceding experi- 
ment. Here as before all roots turned positively into the gelatin 
containing the sodium phosphate, nearly all angles being 45° or 
over. 
It might be thought that the curves were due to the injurious 
action of the sodium phosphate on the growing zone of the root, 
