THE WIDE DISTRIBUTION OF PLANT-GERMS. 37 



isted in the ground, and, in some as yet unex- 

 plained manner, were aroused into active life by 

 the presence of the fire. 



In some parts of the United States the burning 

 over of a region is almost invariably followed by 

 a growth of what is very appropriately called fire- 

 weed, the seeds of which appear to have been 

 called into active life in some as yet unexplained 

 manner, either by something added to the soil by 

 the heat, or possibly by the heat of the fire itself. 



Cases are on record where earthquakes have 

 brought up to the surface, soil which had probably 

 been buried for ages, but which, on exposure to 

 the light and heat of the sun, gave birth to strange 

 forms of plant life. 



Possibly, in some of the cases mentioned, the 

 germs of plant life have been carried to the locali- 

 ties by one or another of the agencies already 

 mentioned. In other cases, however, the germs 

 appear to have existed in the soil, waiting to be 

 called into life by the sun's light and heat. 



Nature, therefore, has taken care that the earth 

 shall be covered with a vegetable carpet wherever 

 man does not oppose her action. If left to work 

 out her own course, she will cover the earth with 

 a dress of such vegetable forms as are best suited 



4 



