THE GEELONG NATURALIST 32 7 
a specialized portion of the protoplasm slightly differing 
from it in chemical composition. Sometimes there is a 
nucleolus, and in cell division the nucleus or nucleolus are 
always the first to show signs of the intention of the cell to 
multiply itself. 
The most striking feature of leaves is their color, which is 
almost invariably green in young growing leaves ;’ this green- 
ness is due to the presence in the cells of specialized portions 
of the protoplasm which have been told off for a very important 
duty. These green bodies are termed Chlorophyll Corpuscles, 
bodies, or grains; they can multiply by division like cells, and 
can change their shape. In these Chlorophyll bodies starch 
is formed, and starch is believed to be the basis of all other 
vegetable compounds. It is only formed in sunlight; in 
darkness it becomes soluble, and passes from the leaves to 
the buds and the roots. Potato tubers are a remarkable 
instance of this translation of starch, consisting of an 
aggregation of starch, containing cells surrounded by a corky 
protective covering. 
Physiologically, a leafis a collection of cells, containing 
Chlorophyll, and a system of conducting tubes which convey 
` to the leaves the water absorbed from the roots, and from the 
leaves the assimilated product which will provide the necessary 
plant food and a surplus of reserve material. 
Mechanically, a leaf is a frame work, or system of netting, 
supporting a vast number of cells containing Chlorophyll, 
and presenting these cells to the air and sunlight in the most 
advantageous manner. 
A study of the Anatomical structure of the leaf will show 
how beautifully the various tissues are arranged to subserve 
the purpose for which the leaf exists. Proceeding from the 
outer surface inwards, we find the following tissues :— (a) 
the Epidermis—this consists of a single layer of cells of a 
tough corky nature, often outwardly covered by a deposit of 
wax. Its cells contain red Chlorophyll, and its office is to 
protect the tender cells within against climatic influences, the 
attacks of insects, dust, gases, etc. -It is frequently covered 
with an outgrowth of hairs, which often assist the cuticle in 
its protective functions, but are frequently to be regarded as 
“ sportive excresénces.” The cuticle is only slightly attacked 
by mineral acids, and resists rotting far longer than the sub- 
. stance of the other cell walls does. 
Scattered over the epidermis, in great numbers, are the 
Stomata, openings with a power of adjustment, and which 
form a connective between the external air and the air spaces 
within the leaf; they are most abundant on the under side of 
