no William Seifriz 
and establish a second and independent rotating circle within the 
former outer one. 
Another interesting type is that in which the stream of chloro- 
plasts proceeds part way up the side of a cell and then turns, crossing 
the cell diagonally back to the corner opposite that from which it 
started, then across the end, thus leaving about one-half of the cell, 
in which chloroplasts are also present, in an inactive state. One of 
the most interesting features of a strontium treated cell is this very 
tendency of the salt apparently to affect one region of the cell more 
than another. 
The chloroplasts may also be arranged in the form of a large disk 
which slowly turns. 
One unique arrangement observed was that in which there was 
a broad belt of chloroplasts revolving in a plane perpendicular to the 
surface of the leaf, and another group arranged in a large disk at one 
end of the protoplast turning in a plane parallel to the surface of the 
leaf. 
In one leaf which was treated in a 2 per cent, solution of strontium 
chloride for seventy-two hours (a number of cells succumb to so long 
a treatment in so high a per cent, of this salt) the individual lines of 
movement of the chloroplasts were in many cells so numerous and 
so indefinite in their directions that all the chloroplasts of the cell 
seemed to wander about aimlessly. 
The fourth substance which was found to arouse the cells to 
abnormal activity was copper. 
That copper in exceedingly minute quantities is highly toxic to 
protoplasm is now generally known. Nageli did the first thorough 
piece of work on the poisonous effect of copper, and termed the action 
an “oligodynamic” one. Copper-water suitable for stimulating 
streaming in Elodea cells can best be prepared by placing several 
copper coins in a small quantity of water for a few days (one or two 
pennies in 50 c.c. of water for two days). Distilled water from a 
copper still will serve equally well: if too toxic it should be diluted. 
Of all the reagents employed to arouse protoplasm to streaming 
“oligodynamic” water proved to be the most certain. Elodea 
studied in London as compared with that worked upon in Geneva 
was found to be much less responsive (as regards streaming) to 
alcohol and strontium, slightly less responsive to saponin, but equally 
responsive to copper. 
Considerable variability in the reaction to the various reagents 
used was found in different cells of a leaf, in different leaves of a 
