v WOODS AND FIELDS 187 
the parenchyme run “ fibro-vascular bundles,” 
forming a sort of skeleton to the leaf, and 
comprising air-vessels on the upper side, rayed 
or dotted vessels with woody fibre below, and 
vessels of various kinds. The under surface 
of the leaf is formed by another layer of 
flattened cells, supporting generally more or 
less hairs, and some of them specially modi- 
fied so as to leave minute openings or 
“stomata” leading into the air passages. 
These stomata are so small that there are 
millions on a single leaf, and on plants growing 
in dry countries, such as the Evergreen Oak, 
Oleander, etc., they are sunk in pits, and fur- 
ther protected by tufts of hair. 
The cells of the leaf again are themselves 
complex. They consist of a cell wall per- 
forated by extremely minute orifices, of pro- 
toplasm, cell fluid, and numerous granules 
of “Chlorophyll,” which give the leaf its 
green colour. 
While these are, stated very briefly, the 
essential parts of a leaf, the details differ in 
every species, while in the same species and | 
even in the same plant, the leaves present 
