ee BOTANICAL GAZETTE 7 [uty 
in marine plants. I then experimented on fresh-water plants and found 
even more striking results. 
In order to make clear the nature of these results I will describe an 
experiment with Vaucheria. Zoospores which had attached themselves to 
slides were allowed to germinate and produce short tubes. The slides 
were then transferred to 0.0937 m NaCl solution. In the course of a few 
minutes the protoplasm began to contract away from the cell wall. _ The 
solution was apparently strong enough to produce plasmolysis and I pre- 
pared weaker ones. These, however, produced the same effect, taking 
more time to do so in proportion as they were weaker. It then occurred 
to me that the effect was not due to osmotic pressure but to a contraction of 
the protoplasm due to the chemical action of the salt. 
In order to test this idea I endeavored to determine how dilute the solu- 
tion could be made and still produce this effect. I found that even 0.0001 
m solution produced it, though usually only after a day or so. The experi- 
ments are repeated several times with Kahlbaum’s C. P. sodium chloride 
which I had recrystallized six times. The result remained the same.? 
I then tried to do away with this effect. This is easily accomplished by 
adding a little CaCl,. The addition of CaCl, in solid form increases the 
osmotic pressure of the solution, but in spite of this it prevents the contrac- 
tion of the protoplasm away from the cell wall. If one molecule of CaCl, is 
present for every hundred molecules of NaCl, the algae endure solutions of — 
o.1 m (that is to say, solutions with a thousand times greater osmotic 
pressure) without any contraction or apparent plasmolysis. 
I have since experimented with a great variety of salts and combinations 
of salts which produce effects similar to those just described. Ihave found — 
that all the plants with which I have experimented (algae, fungi, mosses, 
liverworts, Equisetum, flowering plants) give similar results, though : 
most of them are much less sensitive than Vaucheria. s 
After these experiments I was in no way surprised when I found that 
water distilled from a metal still could produce apparent plasmolysis within 
a few minutes, and that this could be prevented by the addition of various _ 
substances. i 
In what way is the contraction just described distinguishable from true 
plasmolysis? In many Cases it cannot be so distinguished at all> by its 
od Vaucheria from other localities and especially in later stages proved less sensitive : 
to the action of NaCl. Cf. Jour. Biol. Chem. 12363. 1906 oO 
* It is possible that the results described by Duccar (Trans. St. Louis Acad. Ste 
103473. 1906, and Taxeucut (Bull. Coll. Agri. Imp. Tokyo Univ. 71623. 1908) af 
explicable on this basis. 
