DECAY A^D DEATH. 125 



dies. This is that gradual and slow but sure inarch 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 as 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, or a 

 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- 



