, DECAY AKD DEATH. 127 



From a physiological point of view death may result 

 from starvation or from suffocation ; the process in each 

 case may be partial and gradual or immediate and com- 

 plete. Sudden death, or death by violence, results from 

 the injuries inflicted by too high or too low a tempera- 

 ture, electric shocks, sunstroke, strong corrosives, and 

 the like. These destroy life by disorganizing the pro- 

 toplasm, breaking up the tissues, and arresting the 

 natural movements, and cause death by destroying the 

 machinery or paralyzing its action. The gradual effects 

 produced by such injurious agencies as noxious vapors 

 from kilns or factories, or as insects, or parasitic fungi 

 are the same as those produced by starvation or suffoca- 

 tion. In the neighborhood of towns it may happen that 

 the relative absence of oxygen, or, what comes to the 

 same thing, the inability to use what there is, may con- 

 duce to the death of plants quite as much as the direct 

 injury caused by noxious vapors. A perusal of the fore- 

 going -chapters as to the food and growth of plants will 

 suffice to show why plants die ; and a consideration of 

 their life-history as here set forth will show how the 

 cause that may kill at one stage of active growth may be 

 all but harmless at another stage of growth (see p. 64). 



Death beginning at the Root. When death begins at 

 the root, the supply of water and of the air and food de- 

 rived from the soil is cut off, and the plant ultimately 

 perishes of starvation. Death at the root may result 

 from injury inflicted by small parasitic worms, insects, 

 rats, or other creatures from unsuitable conditions of 

 soil, too much or too little water, deficient drainage, 

 deficient aeration, or from the presence of really poison- 

 ous ingredients. If the cause is widespread, so as to in- 

 volve a majority or the whole of the roots, the conse- 

 quences are proportionately serious ; if only a few are af- 

 fected; the plant may not be visibly or materially injured, 



