12 VEGETABLE PHYSIOLOGY 
direction of the divisions we get filaments (fig. 13), plates 
(fig. 14), or masses of cells, the latter undergoing much 
subsequent differentiation according to their ultimate 
dimensions and the nature of their habitat or environment. 
_ 
Fig. 13.—Fmaments or Nosioc. Fic. 14.—Pediastrum, consist- 
(After Luerssen.) ING OF A PLATE oF CELLS. 
The protoplasm being the living substance of the plant 
is possessed of certain properties which are not shared by 
the framework on which it rests. It is, indeed, the centre 
of all the activities which the plant manifests. It assimi- 
lates the food which the plant requires and carries out all 
Fig. 15.—VEcETABLE CELLS. 
A, very young; B, a little older, showing commencing formation of vacuole. 
p, protoplasm; 7, nucleus; 2, a vacuole, 
the chemical processes necessary for life. It. constructs 
the framework of the plant by which it is itself supported. 
It receives impressions from without, and regulates the 
responses which the plant as a whole makes to those im- 
pressions, both by internal and external movements or 
changes of position, and by modification of its metabolism. 
