s 



— 11 - 



et chez les animaux : les exemples sont fréquents d'in- 

 dividus qui succombent rapidement à la moindre maladie 

 alors que leur vigueur semblait devoir les protéger de 

 tout mal. 



Il m'a semblé qu'il n'était pas inutile d'exposer, en 

 guise d'introduction à la présente note, ces quelques 

 réflexions, et, pour me résumer, je citerai l'avis de 

 M. Massée (*) qui, depuis longtemps, a fait des remarques 

 analogues et a attiré en ces termes l'attention des plan- 

 teurs : 



„The field of nature is one of incessant struggle. Every 

 „ plant lias to hold its own in the face of foes bent con- 

 „tinuously and relentlessly on its destruction. If it 

 „succeeds it is only because its défensive resources are 

 „on the average superior to the attacks made upon it. 

 „The final resuit is one of equilibrium, in winch foe and 

 „victim each manage to survive. This is arrived at 

 „through the interaction of conditions usually difficult 

 „to trace, but brought into adjustment after a long period 

 „of struggle. 



„When man appears on the scène and for his own 

 „purposes destroys the adjustment, the struggle begins 

 „anew with increased severity. He grows some one plant 

 „in wide stretches after clearing the ground of its com- 

 „petitors. But in so doing he relaxes the restraint of 

 „all its foes and often gives them a chance they hâve 

 7J never possessed before. 



„ Plants and their parasites hâve to live in nature as 

 „best they may. The host can do without the parasite, 

 „but the parasite cannot do without the host. A plant 

 „mav exist alone in a forest and the parasite which kills 

 „it will fi'nd its own fate sealed if it cannot transfer 



i) Massée. — Tea Blights. — Bulletin of miseellaneous information. 

 Kew. P. 105. — 1898. 



