16 VEGETABLE PHYSIOLOGY 
sufficiently coarse to be visible under a comparatively low 
power of the microscope, and to need hardly any special 
preparation (fig. 18). 
It will no doubt have been noticed that the term ‘ cell’ 
is somewhat loosely used. A typical cell of a multicellular 
plant consists of three parts—the protoplast, the cell-wall, 
and the vacuole (fig. 6); of these the first is the most 
Fig. 17._ConvinvuiTy OF THE PROTOPLASM Fic. 18.—SEMI-D1aAGRAMMATIC Lon- 
OF CONTIGUOUS CELLS OF THE ENDOSPERM GITUDINAL SECTION OF AN OLD 
or A Patm Seep (Bentinckia). Highly AND STOUT PORTION oF Cera- 
magnified. (After Gardiner.) mium rubrum, SHOWING Con- 
TINUITY BETWEEN THE Proto- 
PLASMIC CONTENTS OF THE AXIAL 
OR CENTRAL CELLS, @ @, AT THEIR 
ENDS, AND LATERALLY WITH THE 
CorTicaL CELLS 0, BY MEANS OF 
ProropLasmic THREADs. (After 
Hick.) 
a, contracted protoplasm of a cell; b, a 
group of delicate protoplasmic filaments 
passing through a pit in the cell-wall. 
important, being the living substance. A protoplast which 
has no cell-wall and contains no vacuole is still called a cell. 
The term is again often applied to a cavity which contains 
no protoplast, as in the ease of old wood or cork. In such 
cases a protoplast once occupied the cavity, but it has been 
removed by death. These cells are consequently only the 
skeletons of dead protoplasts, 
