A BOTANICAL EXCURSION IN MY OFFICE. 521 
iodine (dissolved by means of iodide of potassium) to 
flow round it. Then adda drop of sulphuric acid, and 
see! the transparent, colorless outer wall has become of a 
decided bluish or purplish tint. This is the test for Cel- 
lulose, a substance identical with starch in its constitution, 
of which the outer wall of all vegetable cells is composed. 
When a plant wishes to store up its material for future 
use, it throws it into the form of little insoluble granules 
(starch), which are deposited in the cells in various store- 
houses,—sometimes underground stems, sometimes roots, 
Sometimes leaves, sometimes other parts are selected. 
When the plant wants to move its material from place to 
place, it converts it into deztrine, which is soluble, and 
therefore capable of being transported. But when the 
material is to be finally disposed of, stored away, then it 
is made to take the form of cellulose. 
Within the cell, lying immediately against the outer 
wall, is a thin, gelatinous, scarcely perceptible layer, 
which is colored brown by iodine, and coagulated and 
rendered more apparent by alcohol, sulphuric acid, and 
Various reagents; this is the so-called primordial utricle, 
an albuminoid, homogeneous mass, in which much of the 
life-activity of the cell resides. Inside of this is a semi- 
uid mass which is very complex in its constitution, and 
different at different times. The essential parts of it are 
protoplasm and chlorophyl. The former of these is prob- 
ably identical with the primordial utricle, and shows its 
wonderful formative power. Chlorophyl is the green color- 
ing matter of plants. It is chlorophyl containing proto- 
plasm, which alone stands between all animate creation 
and death by starvation. For it is this alone which pos- 
Sesses the marvellous, almost creative power of seizing 
the inorganic siamini and opon of the earth and 
CAN NAT., VOL. 
