CHAPTER V. 
THE CHEMISTRY AND PHYSICS OF PLANTS. 
124, The Water in the Plant.—All living parts of plants 
are abundantly supplied with water. It is always present in 
living protoplasm, and the greater its activity the more 
watery is its composition. The cell-walls of living tis- 
sues also contain large quantities of water ; and in plants 
composed of many cells (as the larger flowering plants) 
even those cells and tissues which have lost their activity 
generally have their walls saturated with water. In ordi- 
nary herbaceous land-plants the amount of water is not far 
from 75 per cent of their whole weight. In aquatic plants 
the percentage is much higher, often exceeding 95; it is 
so abundant in many of the simpler forms that upon dry- 
ing nothing but an exceedingly thin and delicate film is 
left. 
125. Water in the Protoplasm.—As explained in para- 
graph 4 (page 2), living protoplasm has the power of im- 
bibing water and thereby of increasing its fluidity. Even 
after it has imbibed all the water which it can retain it 
continues the process, and separates the surplus in drops in 
its interior—the so-called vacuoles. Now an examination 
of the cells of rapidly growing tissues shows that their 
protoplasm is much more watery than that of living but 
dormant tissues—e.g., those of seeds—and one of the first 
signs of activity in the latter is the imbibition of water. 
