2§2 The Great World's Farm 



ville, Indiana, though they have borne seed, have never 

 succeeded in sowing themselves till within the last few 

 years, as a single day's exposure to the hot sun is fatal 

 both to seeds and seedlings, and even daily watering often 

 proves insufficient to keep the latter alive. In the wild 

 state they spring up only in very moist or watery places, 

 though later on they will bear transplanting to dry soil. 



One year, however, there was a storm which shook 

 down such a quantity of seed that the streets of Rockville 

 were yellow with it. Then followed several days' rain, 

 with sunny intervals, and the seeds sprouted everywhere, 

 all over the streets, in the yards and the gardens, as thick 

 as weeds — a sight never seen before. 



How is it that European weeds have spread so exten- 

 sively in the United States, while Australian seeds, widely 

 and purposely scattered in New Zealand, have gained no 

 footing.^ 



First and chiefly because in the one case there was a 

 vacancy, and in the other there was none. The vacancy 

 in America was not natural, but caused by the cutting 

 down of forests and the dying off of the undergrowth, 

 which vvras killed by sudden exposure. Of course, there 

 were plenty of plants in America which would have 

 stepped in and taken possession in time, but they were 

 too far off, on the plains and prairies of the great Missis- 

 sippi Valley, to do it quickly enough, and meantime the 

 foreigners arrived. Weeds from Europe were introduced 

 with grass seed and corn seed, and in other ways, and 

 when the forest lands were turned into pastures and 

 fields, these weeds had as good a chance of thriving as 

 they had at home. 



It would be a different matter if they were to arrive 



