142 On the Campus 



through our own devices ; modes of motion and of matter 

 concerning which we are ignorant absolutely, simply be- 

 cause such knowledge is not of immediate practical value 

 to our terrestrial life. What do most men know to-day 

 about Becquerel rays, or those other rays recently dis- 

 covered, not yet named? Nature is a generous mother; 

 but after all, she has put into our scrip just capital 

 enough to convey us safely to the journey's end in com- 

 fort; a little surplus perchance for hazard on the road, 

 but not one cent for luxury or spending money. Thus it 

 has happened that with all the natural forms of energy 

 about us, animals have used but few. The force that we 

 call gravitation pulls continually and every animal in his 

 every feature shows response. The winds are an un- 

 ceasing source of natural power, and animals, not a few, 

 take advantage of their moving currents. Heat, light, 

 and sound are more subtle forms of natural energy but 

 each of these has found, as we have seen, appreciation in 

 the animal's structure. The latest form of energy is 

 that developed by the animals themselves and the inter- 

 action here, t.e., between animal and animal, is a matter 

 long established. Now it will surprise you to reflect that 

 to every one of these natural agencies the plant makes 

 response with the single exception of sound, and even 

 this response has of late been strongly claimed. Plants 

 respond to gravitation, to currents of wind to the cur- 

 rents of water, to heat, light, to electricity, physical 

 change of every sort, and to the presence of animals ; in- 

 deed, plants are the natural chemists of the world and 

 their chemical responses and activities surpass all human 

 cunning. To all cosmic conditions, the structural re- 



