IV EFFECTS OF CLIMATE ON PLANTS 93 



through several thousands of years does not produce constant 

 characters in a species of plant, so that the species could no 

 lono^er exist if brought asjain under conditions more unfavour- 

 able to nutrition. 



The directly modifying influence of climate is exhibited 

 most distinctly in our common plants. The resistance, for 

 example, of the plants of a single species to the influence of cold 

 or warmth is very variable. It is very surprising at what differ- 

 ent times trees of the same species in a wild state under the 

 same conditions develop their foliage in spring — for instance, 

 beeches growing close together in a wood. Years ago this 

 struck me particularly in the garden of the castle of Veit- 

 shochheim, near Wiirzburg, which is laid out in the rococo 

 style. The straight walks are there enclosed between hedges 

 of cut beeches like walls. In the spring, parts of the hedges 

 formed by certain beeches are already green, while parts 

 formed of others which stand between the former, and are 

 even mingled with them, have not begun to open their buds. 



Every gardener knows that individual plants are more able 

 to endure cold than others of the same species under the same 

 conditions. Darwinism is satisfied with makiug use of such 

 differences to explain how they render selection possible, and 

 how they are increased by its means, but does not inquire into 

 their causes. Yet these differences cannot be due to chance. 

 There must be a peculiar condition of the tissues underlying 

 them, which peculiarity must ultimately depend on external 

 influences which have acted on the plants themselves or their 

 ancestors. For that such powers of endurance are inherited 

 no one, in the face of so many facts known to every fruit- 

 grower, will deny. 



Perhaps the above difference in beeches, considering that 

 nearly every beech-wood with us is more or less artificially 

 planted, is due to the fact that the ancestors of the trees which 

 come into leaf at different times were derived from different 



