A Method for Inducing Protoplasmic Streaming 109 
from Panama wood (Quillaria saponaria) which is usually to be had 
at a chemist’s. Five grams of the wood may be boiled in 100 c.c. of 
water for fifteen minutes. (Spring water is preferable to distilled 
water, unless the latter is absolutely pure. Water from a copper still 
will kill the majority of the cells in an Elodea leaf over-night.) The 
extract obtained from Panama wood will, in 100 c.c. of water, be of 
the desired strength for treating the cells for one or two days. If 
chemical preparations of these glucosides are used the most satis¬ 
factory per cent, of solution is 2 where brief treatment is desirable. 
In the case of senegin a weaker solution (1 per cent.) is preferable, 
owing to the greater toxicity of senegin. 
The time of treatment again, as in alcohol, varies with the physio¬ 
logical condition of the leaves. Eighteen to twenty-four hours is 
usually sufficient in a 2 per cent, solution of saponin, or 1 per cent, of 
senegin. Abundant and very active streaming of a great variety of 
types results from such treatment. 
The third chemical which proved to be so strong an activator to 
protoplasmic streaming was strontium chloride—also barium chloride 
which is very similar to strontium chloride in its effect on such 
physical properties of protoplasm as viscosity, permeability, osmotic 
pressure, and streaming. 
Both strontium and barium are highly toxic to protoplasm; but 
barium more so than strontium, therefore, a lower concentration of 
barium than that which is isosmotic with the maximum per cent, of 
usable strontium chloride should be employed. The usable concen¬ 
tration of any salt for long treatment must, of course, be slightly 
below the critical concentration of that salt, i.e. below the concentra¬ 
tion which will just cause plasmolysis. For strontium chloride this 
is about 2 per cent., for barium 27 per cent. Owing to the greater 
toxicity of barium a 1 per cent, solution is more satisfactory for 
inducing streaming. 
The length of treatment varies with the sensitivity of the leaves, 
from one to three days usually being necessary. Eighteen hours is 
sometimes sufficient to arouse the cells to moderate activity in stron¬ 
tium, and often to pronounced activity in barium. 
All the types of streaming so far described are to be seen in stron¬ 
tium chloride and barium chloride treated cells. There may be a 
stream of chloroplasts moving around a group of quiescent chloro- 
plasts, the latter showing no tendency to be drawn into the stream 
even when the moving chloroplasts rub against them; yet later these 
same quiescent chloroplasts may of themselves commence streaming 
