PLANT LIFE ON THE FAEM. 



instructions here as to the way in which cross-breeding 

 may be carried out ; it is difficult with cereals, less so 

 with leguminous plants, easiest with the cabbage tribe. 

 Indeed, as growers know to their cost, it is difficult to 

 keep the races or strains of the cabbage-tribe pure and 

 uncontaminated, owing to the facility with which the 

 flowers are fertilized by insects which bring the pollen 

 from the flower of some other variety. Too high breed- 

 ing, however, often entails a delicacy of constitution or 

 a defective productiveness which may be overcome by a 

 fresh cross with a stronger strain. 



CHAPTER IX. 

 DECAY AND DEATH. 



Change, waste and repair. Disturbance of the balance. Death of the 

 protoplasm. Causes of death. Natural death. How plants die: 

 impaired nutrition, starvation, suffocation, structural injury and 

 paralysis. Death beginning at the root. Death beginning at the 

 leaf. 



Decay and Death* Life is one continual series of 

 changes 



"By ceaseless action all that is subsists." 



The result of these changes is gain or loss, waste or 

 repair, now one, now the other ; or occasionally (and 

 indeed generally) both simultaneously. While a proper 

 balance and equitable adjustment between gain and loss 

 exists, the plant lives and is healthy. Directly the bal- 

 ance is disturbed the plant may live indeed, but it be- 

 comes unhealthy; and if the disturbance continue if 

 waste overtake repair if nutrition be persistently im- 

 paired, still more if it be arrested, the plant inevitably 



