10 THE NATURE-STUDY OF PLANTS 
placed over the object on the slip. Covers can be had * 
either circular or square, and the former are the more 
useful, especially when wanted for a circular drop of 
water or other liquid. 
We shall have to choose a plant from those whose 
leaves are smooth and without hairs, and we shall 
find none better than a snowdrop, a tulip, a hyacinth, 
a narcissus, or a lettuce. 
We must have a small pair of sharp scissors handy, 
and we must take a slip and put upon it a large drop 
of water. 
The next thing is to take the leaf and break or 
cut it across, but not into two: we must not break the 
skin of the lower surface. We shall then be able, 
quite easily, to strip a piece of the colourless skin from 
the underside. 
The thinnest part of the strip will be the end 
farthest from the breakage. With a little practice 
and the help of a little more water and the pair of 
scissors we shall soon be able to manceuvre a small 
transparent bit into the water on the slip; we must 
then put another drop of water on to it and place a 
cover over the thinnest part. If we now hold the slip 
to the light and look at the strip through a lens we 
shall be able to see, not the holes themselves, but the 
places where they are and where they will be found, 
if we are fortunate enough to possess a microscope 
or a friend who will give us the necessary help with 
his own. 
With a lens, however, we can see quite plainly that 
the bit of skin has darker dots upon it. In the centre 
of each dot there is a single hole: it is not a round 
hole, but about twice as long as broad, and in the 
snowdrop it is so small that its length is hardly yoo 
