464 THE UNIVERSE. 



Lastly, Brugmans, i3rofessor at the university of Leyden, 

 pushed the matter still further. Having collected this 

 substance from the roots of violets which he had placed 

 in pure fine sand, he found that it acted like poison upon 

 other plants. 



Thus the cause of those curious instinctive mutual 

 advances, already perceived by Mathiolus, who called 

 them the friendships of plants, is demonstrated. Indeed 

 the old botanist, in his work, says that there is so much 

 affection between the reed and the asparagus, that if we 

 plant them together both will prosper marvellously. 



In Germany agriculture, guided by science, has learned 

 to profit from these mutual affections, and Schwerz, in 

 his learned works, points out how cereals should be allied 

 in order to augment the i^roduce of our fields. 



CHAPTER VII. 



THE SLEEP OF PLANTS. 



The deeper we search into the mysteries of vegetable 

 life the closer relation do we find with animal existence. 

 Exhausted by the functional labour of the day, many 

 plants, when the evening arrives, assume a particular atti- 

 tude, which they preserve through the night; this is their 

 sleep. 



This curious phenomenon, Avhicli a fortunate accident 

 revealed to Linnseus, was carried by him to demonstra- 

 tion. He first observed it in a Bird's-foot Lotus growing in 



