520 A BOTANICAL EXCURSION IN MY OFFICE. 
they are the same. That scarcely perceptible speck on 
the quartz is a vast assemblage of little plants, composed 
each of but a single vesicle or cell; whilst the oak that 
towers above is nothing but a vast assemblage of such 
cells united into a single plant. 
All plants, from the lowest to the highest, then, consist 
of cells, which are essentially the same throughout the 
_ whole vegetable kingdom. Let us take a cell of the plant 
before us, and examine it as a specimen of the vegeta- 
ble cell. 
Tn the first place, on its exterior we find a dense, but 
transparent coating, resistant to external force, and appa- 
rently structureless. Examine it with our highest pow- 
ers, and still it is structureless, a homogeneous, perfect 
membrane, without pores or any interruptions whatever. 
Yet it is easy to prove that water and various fluids can 
pass through it. Place the cell in a dense syrup, and the 
water will be drawn out of it so rapidly, that the contents 
will shrivel up. Again; the contents of the cell are, as 
we shall know directly, composed largely of a substance 
which shrinks and hardens under the action of various 
substances. Put a plant in diluted acid, or strong alco- 
hol, and see how the contents gather themselves together ; 
or surround it with a solution of iodine, and see how soon 
the change of color in the most central part betrays the 
presence of that element. Such experiments as these 
prove that although the cell wall is absolutely homoge- 
neous, destitute of all pores, yet fluids can pass through 
it. You see how, in the very onset, we are led into one 
of life’s processes, osmosis, as it is technically called ; but 
we must pass it by. 
Let us try a little microscopic chemistry. Put a fila- 
ment on a clean slide, and allow a watery solution of 
