1897 j CURRENT LITERATURE 305 
a considerably more marked response to changes of temperature than is dis- 
played by the latter. This being so, it is unnecessary to refer the difference 
to the vitality of the protoplasm. 
Essentially the same phenomenon described by Krabbe is that of bleeding, 
decreasing rapidly as it does with falling temperature, and usually ceasing 
some degrees above zero. 
While in the life of the plant the protoplasm must permit the wandering 
of various food matters from cell to cell, and, therefore, be permeable to them 
under circumstances which we do not sufficiently understand, it is extremely 
doubtful if perfectly healthy cells ever permit exosmosis of anything except 
water when immersed at room temperatures. Determinations of turgor are ordi- 
narily made at such temperatures, and though Krabbe does not carry his point 
so far, their accuracy would at least be shaken by the possibility of such a pro- 
cess. And as plants live and grow at such temperatures, what is to limit the 
filtration of the sap from the cells? That this does not occur so as to be appre- 
ciable by any test of plasmolysis, or measurement, unless by fine chemical reac- 
tions, needs no argument. That it does begin with injury to the protoplasm 
is a matter of common experience receiving critical attention from De Vries.” 
Last year the writer had occasion to determine very carefully the turgor 
of leaves of several mosses, and of the roots of Vicia Faba and other phanero- 
gams at temperatures from o° to 37°C., and while the temperature appreciably 
affected the time required for plasmolysis, it had not the slightest discernible 
influence on the ultimate result. These experiments covered a wider range 
of temperature than Krabbe’s. The conditions were different in that practi- 
cally all the cells were in immediate contact with the plasmolysing solution- 
And while the results confirm Krabbe’s conclusion that the combined resist- 
ance of many layers of protoplasm is responsible for the difference of tension 
_ in cold water between the axis and periphery of pith cylinders, and for their 
failure to plasmolyse completely at o°C., they are unfavorable to the idea of 
the filtration from the healthy cell of any of its turgor-producing contents. 
Any such action was a stage of death. 
Finally the statement that pith in cold water does not stretch beyond its 
__ limit of elasticity holds good according to Kolkwitz” only when the time of 
; immersion, does not exceed four to six hours.- —E. B. COPELAND. 
Bot. t Zeit. 42 :289. 
7 Fiinfstiic k's Beitrige zur wiss. Botanik, eae 
