DECAY AND DEATH. 133 



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 intermediate 

 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 hy much the same essential causes 

 as those which extinguish the life of animals. The death 

 of plants is the death of the protoplasm. Prevent the 

 access of oxygen to the living cell, and the movements of 

 the protoplasm will be arrested and ultimately '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 impossible in the case of an 

 analogous injury done to one of the higher animals. The 

 lower the organism, the less special in its conformation and 

 construction, the more independent are its constituent 

 cells. The higher the organism, and the more specialised 



