DECAY AND DEATH. 125 
dies. This is that gradual and slow but sure march of 
destiny which comes sooner or later to all living things 
at their appointed time. That time comes when the 
tissues are—from that degeneration of their substance 
which may be a morbid process resulting from injury, 
or which may be merely the necessary result of the 
growth and maturation of the plant, or from the failure 
of supplies—no longer able to carry on their life-work. 
The period in question varies ag to its occurrence. A 
wheat plant uses up its life within a few months, an oak 
tree within a few centuries, and there is every inter- 
mediate period. 
But, in addition to changes which are the result of an 
inevitable march of events, death in plants sometimes 
comes suddenly from violence, life action is arrested in 
its full flow and tide, and by much the same essential 
causes as those which extinguish the life of animals. 
The death of plants is the death of the protoplasm. Pre- 
vent the access of oxygen to the living cell, and the 
movements of the protoplasm will be arrested and ulti- 
mately cease altogether. The properties and functions 
of protoplasm have already been explained. It is their 
destruction and their cessation which constitute death. 
But the death of a part is not necessarily the death of 
the whole, and the individual cells of plants are, as a 
rule, much more independent one of the other than are 
the individual cells of an animal. A root or a leaf, ora 
mass of roots, and a number of leaves may be injured, or 
even killed, and the plant will still live on, because there 
are more left behind uninjured; and these, relatively 
speaking, do not suffer from the damage done to their 
fellows. A tree may be stripped of its leaves and may 
still live, because there are cells which are uninjured, and 
which will do their parts towards compensating the 
injury. A felled tree by the roadside will often be seen 
pushing up new shoots in a manner that would be im- 
