40) TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 
wooden mould, and with a very sharp, square, iron-soled plane, shave 
off a number of thin slices; placing the slices in pure alcohol, in 
order to free the tissue from air and water. After a few hours’ 
soaking, they may be removed and put between blotting-paper to 
dry, applying pressure to keep the sections flat and free from 
ripples. The slices or sections should not exceed 53, of an inch 
in thickness. When they are thoroughly dry, the slices may be 
stained. Any colour will do, but violet is best adapted for the 
purpose. The stain is prepared from the ordinary aniline dyes, a 
small quantity of which is dissolved in pure alcohol. The sections 
should be placed for about a minute in the dye, then removed and 
again placed between blotting-paper to remove any superfluous 
dye. When they are dry, place them in pure benzole. This will 
remove the last trace of water and air from the cells. 
The section is now ready for mounting between the glasses of 
the slides. This is best done with a mixture of Canada balsam, 
eight parts, and pure benzole one and a half parts. Mix thoroughly, 
and be certain that there are no air-bubbles in it. Place a little of 
the mixture on the main glass, and then take the section, now soaked 
and wet with benzole, and place it on the balsam; press down the 
cover-glass tight upon it, so as to squeeze out all air-bubbles, and 
then set it aside to dry. 
The main glasses should be of a uniform size, not larger than 
34 by 2 inches. The cover-glass should be at least half an inch 
shorter, and a quarter of an inch narrower than the main glass. 
After the balsam is set and perfectly dry, which will be in about 
two months, the slides should be bound with slips of gummed paper. 
This will prevent the glasses from slipping past one another. 
This form of slide is only of use for the microscope, and for 
lanterns with micro-fronts. 
If a transverse section of the stem of any hardwood tree, and of 
any poplar, willow, or conifer, be examined with a microscope of 
even a low power, the great differences in their structure will be 
seen at a glance. The oak stands out distinctly in its structure 
from all the other broad-leaved trees, and the latter from the conifers, 
which in themselves form a distinct group, differing, however, more 
or less, in every genera and species. Generally speaking, every 
species of wood differs in the number, size, or position of the vasa, 
and the compactness of the vascular tissue ; the number and size 
of the medullary rays; and in the pines, the more or less frequency 
