46 Principles of Plant Culture. 
formed by assimilation (59) finds its way to the growing 
parts. Soluble matters not used by the plant are not taken 
in to the same extent because their equal distribution is less 
disturbed. 
The distribution of soluble matter in the plant is also 
promoted by transpiration (75). 
Section IV. THE INNER STRUCTURE OF THE PLANTLET 
Thus far, we have considered the plantlet mainly from 
the outside. But before going farther, it is well to learn 
something of its inner structure also. We have seen (12), 
that all parts of the plant are made up of cells, and that 
these cells differ in form and office in the different parts. 
The cells of the leaf, for example, are different in shape, and 
in the use they serve to the plant, from those of the stem, 
flower or fruit. 
65. The Epidermis 
(ep’-i-der’-mis). The plant 
is covered by a thin, translu- 
cent skin that extends over 
the entire surface of the 
leaves, stem and root, called 
the epidermis (Fig. 15 Ep.). 
This skin is formed of rather 
thick-walled cells, and serves " 
to protect the more delicate SSS HL) 
I J HSOOSS Fp. 
parts within. It may be Fic. 15. Showing section through 
readily withdrawn in some leaf of Oldenburgh apple. Ep. epider- 
mis; Pal palisade cells; J. intercellular 
plants, as from the leaves of spaces. Highly magnified. See also 
the liveforever,* and echey- Figs: 18 and 20. 
eria,t and young stems of the plum. The exposed surface 
* Sedum telephium. + Cotyledon. 
