The Plant 
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get the bark of varying thickness; then we get the phloem, 
or bast — soft woody tissue — after which comes the cambium, 
or actively dividing tissue. This is the layer from which 
all the others spring and add to their growth. Inside this 
layer we have the xylem, or wood proper, and the centre 
is made up of thin-walled cells — the pith. 
Portion cut from a Branch of a Leafy Tree x about 150. Diagrammatic 
In some stems, such as that of the Elder, the pith forms 
a considerable part of the young stem; but in others, such 
as that of the Beech, it is very small indeed. We already 
know that the stem or branches bear leaves. These leaves 
are of the greatest importance to the plant. They are 
usually flat in shape and green in colour. There are 
exceptions, however, as the shape of the Onion leaf is 
round, and the colour of the Purple Beech leaf slightly 
brown. Leaves are covered with a skin or epidermis. 
This skin is perforated by large numbers of microscopic 
