ANATOMY OF TISSUES. SE 
what is known as secondary growth, it will be considered under 
this subject. The primary epidermis is said to be simple or 
compound according as it consists of one or several layers 
of cells. 
The simple epidermis covers the entire plant in the early ~ 
stages of its growth, and certain organs are never provided with 
Fie. 24. 
A cross-section through the under epidermis and the mesophyll m of leaf of Hartwegia 
comosa. aepidermal cells. s stoma with guard cells. rair space. v outer court. 
x 300. — ( Wiesner.) 
any other kind. Different names have been given it according 
to the different parts of the plant which it covers. On leaves 
and stems, it is called simply epidermis, on flower leaves, 
epithel, and on the root, epiblem. The classification may be 
tabulated as follows: 
Epidermis. 
Simple < Epithel. 
G Primary ] Epiblem. 
Epidermal System Compound 
| Secondary { Periderm. 
