1i 
solution more readily, and so have been able to keep up a slow, inward 
flow, for in proportion as it is absorbed it exerts no pressure. But the 
normal solution was sufficiently concentrated to plasmolyse all the living 
cells, after which it was possible for the solution to travel from outside of 
the root into the xylem without being compelled to pass through any of 
these. When this condition results there is no semipermeable membrane 
in its way, and, concentrated as it is, it can exert no osmotic pressure. 
If the half-normal solution were to cause general plasmolysis then it also 
would enter freely and for the same reason. 
The turgor of root VI was tested. This root had lost water to the half-normal 
solution. A few cells in its cortical parenchyma were found to plasmolyse in 
this solution, but the turgor of most of them was decidedly higher—about 0.7 
normal, Some cells which did not plasmolyse even in such a solution did so in 
a normal one. There was no active epidermis, for the hypodermis had devel- 
oped so as to be only 1.4 millimeters behind the growing point, well within the 
adherent part of the cap. The turgor of the cap was rather below 0.5 normal. 
In the meristem the limit was slightly higher, but the regulation had not kept 
pace with that in the cortex; and in the latter it was not what might have been 
expected from the observations of Stange ° on the roots of various European plants. 
My experiments on the absorption of potassium nitrate conspicuously 
show that the absorbing activity of the coconut roots is little interfered 
with by a moderate concentration of the surrounding solution (up to at 
least 0.2 normal). This obviously fits it for life in its typical habitat; 
for, while the water in the soil near the sea, and even in the beach itself, 
is not usually saline, because its mass movement is seaward, yet strand 
plants are subject to inundation during storms, which sometimes bring an 
amount of sea water about their roots which would be fatal if they were 
more sensitive. 
THE COCONUT LEAF. 
Gross morphology and growth.—Aside from the cotyledon, which is a 
very short sheath at one end with an enormous absorbing structure at the 
other, the first leaves of the coconut are mere sheaths, resembling the bases 
of later leaves, but entirely destitute of any lamina. These sheaths are 
usually 4 to 6 in number, each being longer and less scale like than its 
predecessor. In vigorous seedlings they sometimes appear at intervals of 
less than one week, but as a rule the succession is slower. Their most 
rapid measurable growth is immediately after they emerge from the nut. 
The transition from sheaths to leaves may be abrupt; or there may be one 
or two, the upper part of which, after splitting, bends outward, like the 
rachis of a leaf, but develops no blade. 
The succeeding leaves, 2 to 6 in number, do not become pinnate, but 
develop a lamina, which splits down the median line, sometimes merely 
forming a notch, but usually extending more than half of the length of the 
* Stange, B.; Beziehungen zwischen Substrat-concentration, Turgor, und Wachs- 
thum bei einigen phanerogamen ‘Pflanzen. Bot. Zeit. (1892), 50, 253, ete. 
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