KIDD’S OWN JOURNAL. 3 

POPULAR SCIENCE. 
—_———_— 
VEGETABLE PHYSIOLOGY. 
No. I].—Tue Srructurs or Puants. 

THERE IS SOMETHING PECULIARLY TEMPT- 
ING to the mind in the study of the minute 
structure of organic life; to look into the 
secrets hidden from the vulgar gaze, as it 
were, in the silent counsels of the Creator. 
In the pursuit of this knowledge, the student 
feels the light buoyancy of spirits which 
characterise our earliest searches after truth. 
With genuine simplicity he feels himself a 
child again ; listening to the mysterious re- 
velations of the Father of all Truth. Aye; 
and with his microscope in his hand, he is in 
a fairer way for Heaven than the professed 
theologian with his empiric distinctions of 
doctrine and discipline. 
Simplicity is the great leading trait in all 
the works of nature; and never is this truth 
more beautifully illustrated than in the 
branch of science of which we are treating. 
So simple indeed is the structure of plants, 
and even of animals, that we might sum up 
by stating that a round little globe, a minia- 
ture bladder—a cell, represents all life, all 
action, all sensation, even the throne of in- 
telligence. To illustrate this proposition, 
let us suppose that we have a thin section of 
some succulent vegetable substance—say a 
tuberous root; and subjecting it to a magni- 
fying power of some two-hundred diameters, 
what have we then? The field of the 
microscope, which in reality does not exceed 
a pin’s head in size, is covered by a piece of 
netting about two inches across. This net- 
ting is the cellular structure of which the 
plant is composed. Each cell was originally 
separate, and had a distinct covering to it- 
self; being in fact a bladder, though so 
small, that it would require from three hun- 
dred to a thousand of them (placed in single 
file) to make up one linear inch. Cork, the 
outer bark of a species of oak, is composed 
of this tissue, and was found by Hooke to 
contain more than one thousand cells in the 
length ofan inch. Little indeed do we ima- 
gine that a piece of this substance (an inch 
each way), is made up of 1,000,000,000 dis- 
tinct cells, all possessed of individual as well 
as conjoint life. 
In the example supposed to be under our 
microscope, we see no evidence of the mass 
being made up of hollow spheres. The ap- 
pearance presented is merely that of a piece 
of net-work, exhibiting dark thread-like 
lines, crossing each other at somewhat re- 
gular angles, enclosing clear spaces—gene- 
rally six-sided. These spaces are the cells; 
the membrane of which is so delicate as to 
be invisible, unless when placed edgeways to 
the eye. So that it follows, as a matter of 
course, that we cannot see that part on 
which we look perpendicularly. This phe- 
nomenon is well illustrated by a piece of 
window-glass. We know that, as it is 
usually presented to our gaze it is invisible, 
save by reflections from its surface, or the 
occurrence of some foreign body on it; but 
turn the edge to the eye, and instead of 
being colorless and perfectly transparent, it 
becomes colored and almost opaque. 
The structure which we have just exami- 
ned is the simplest form of vegetable tissue ; 
and is supposed to be the parent of all other 
forms. It is principally found in very suc- 
culent tubers and roots, fruit, im the flower, 
pith, and bark. The original form of the 
cell is said 10 be spherical ; but from various 
causes, this form becomes changed by pres- 
sure. The cells change to square, oblong, 
many-sided; and indeed to an infinitude of 
shapes. One change, however, is more de- 
terminate than the rest, 2. e., from the spher?- 
cal to the tubular. In physiological lan- 
guage, from the cellular to the vascular. 
Let us now take as a second object, a 
fine section, cut lengthways, from the first 
year twig of a tree; and placing it under our 
microscope, we have a decided change of 
scene. True we have still the net-work of 
cells; but in addition to them, we discover a 
number of tubes running in a parallel course 
between them; some retainmg a uniform 
thickness throughout, and others gradually 
tapering down toa pointed extremity. These 
tubes, or vessels, are never found in the 
lower class of plants—as mushrooms, sea- 
weeds, and mosses; and occur most plenti- 
fully in such as form woody stems, as trees 
and shrubs. Their purpose is two-fold ; they 
serve as canals through which the fluids pass, 
and they give solidity and strength to the 
structure. Foremost among the strength- 
giving, are those which taper towards the 
extremity. They are by far the shortest of 
all the vessels; their length seldom exceed- 
ing from twelve to twenty times their 
breadth. They are called fusiform or 
spindle-shaped, from their tapering at each 
end, and make up almost the entire bulk of 
timber. 
Occasionally, both cells and vessels pre- 
sent beautiful markings on their surface. 
Sometimes, they appear as if a band had 
been carefully wrapped round their exterior, 
and then they are called spiral cells or 
vessels, as the case may be. At other times, 
this ribbon seems. broken up in pieces, and 
instead of a regular corkscrew-like appear- 
ance on a vessel, only a number of rings are 
visible. Or the breaking may go still fur- 
ther, and a few bars alone remain ; giving the 
idea, when looked at through the micro- 
scope, of a ladder. Only one step further 
is necessary, and all definite marking is lost 

