58 UNDER THE OPEN SKY 



itself as far as it may in all directions, by 

 means of seeds or runners or by some such 

 method. If the climate of any region grows 

 warmer, inevitably those seeds which fall 

 or are carried towards the equator will meet 

 surroundings which on the average are too 

 warm for that plant; while those that are 

 carried to the northward meet, again on the 

 average, conditions a little more favorable 

 since the change. Hence it is that the line 

 of chestnuts must be moving north followed 

 slowly by the chinquapins. And such a 

 procession of wheat and corn and cotton 

 must also be moving northward. But 

 our lives and our histories are too short 

 for us to notice it in the case of our 

 cultivated plants. It is such facts as the 

 resemblance of our arbutus to its Japanese 

 relative that lead us to the conclusions I 

 have mentioned. 



THE RUN OF THE SHAD 



Not the least strange of all the spring 

 movements is the run of the fish up our 

 rivers. An odd procession too, it is. On 



