4 BOTANY. 
(e) Mount carefully in pure water a piece (2 to 4 centimetres) of one 
of the young ‘‘ silks” of Indian corn. The movement is well seen in 
the long cells. Repeat the foregoing experiments. 
(f) The following may be taken also, viz.: the stamen hairs of 
Spiderwort, the epidermis of Live-for-ever leaf, fresh specimens of 
the Stoneworts (Chara and Nitella), Eel-grass, etc. 
7. The Plant-Cell.—In all common plants the protoplasm 
is found in little masses of definite shapes, each one en™ 
closed in a little box (Fig. 1). The substance of these 
boxes was made by the protoplasm, somewhat as the snail 
makes its shell. Each mass of protoplasm with its box is 
called a Plant-cell, and the sides of the box are called the 
walls of the cell, or the cell-wall. 
8. The cell-wall is composed of carbon, hydrogen, and 
oxygen (C,,H,,O,,), and has been named cellulose. At first 
LER 
xX 
Xx 
WO 
CL) 
DOAN NNN 
yA 
Fre. 8.—Longitudinal section of a portion of the stem of Garden Balsam. v, 
annular vessel; v’, a vessel with thickenings which are partly spiral and partly 
annular; v’, uv’, v’’’, several varieties of spiral vessels; v/’’”, a reticulated 
vessel. 
it is very thin, but as the protoplasm grows older it thick- 
ens its wall by continually adding new material to it, so 
that at last it may be more than a hundred times as thick 
as at the beginning. 
9. The cell-wall may be thickened uniformly, or, as more 
frequently happens, some portions may be much more 
thickened than others, When it is uniform the wall shows 
