CHEMICAL COMPOSITION. 251 
it assumed in this liquid a deep yellowish color, and the appearance of 
the very rough bark of a tree, marked with black spots and streaks. 
By the addition of a drop of anhydrous alcohol, there was immediately 
formed, in the liquid, a movement of oscillation; the fragment of 
epidermis was borne by the current in the liquid from left to right. 
At the end of some minutes the yellow color had entirely disappeared, 
but the piece preserved the original appearance. Submitted, then, 
to the action of tincture of iodine, the epidermis preserved its trans- 
parency ; except that the more dceply tinted parts assumed a very 
light blue color, surrounding plates and cells which were completely 
white. Ata magnitude of one hundred diameters the objects of our 
previous study can be seen, but in this case the piece of epidermis 
looks like the bark of the plane tree. 
It is difficult, at this magnitude, to recognize the details above 
mentioned ; still with a great experience in microscopic study it may 
be done. 
If the piece of epidermis belongs to a cane long time previously 
ripened, or the experiments be made with the knots nearest the ground, 
it will be found that the cerosie always will adhere to the epidermis, 
even though it may have been scraped to remove the former; the ad- 
dition of sulphuric acid can determine the yellow color ; but anhydrous 
spirit of wine subsequently added, does not produce so strong a sudden 
oscillatory movement as in the former experiment. The decoloration 
of the tissues docs not take place; they always preserve the yellow 
color, and the disposition of the fibers is the same, except that the 
most prominent tubes are particularly distinct. The tincture of iodine 
added to the solution docs not give any color changes, except that the 
deep color of the epidermis becomes clearer. Some fragments of cells 
are visible. 
The epidermis is now removed. We next come to the dermis, or 
inner coating.* Submitted to a glass of five hundred diameters, it pre- 
sents an assemblage of tubes all disposed side by side in manner accord- 
ing to the height of the plant. Submitted to the action of pure 
sulphuric acid, the deep color soon passes into a red brown; numerous 
* This piece of derma was taken from the last joint of a cane of large size, and it had 
remained on the stalk after its ripening. 
