296 Chances of Life 



to disperse themselves, and so they may make a gradual 

 advance. 



How is it that European weeds have spread so ex- 

 tensively in the United States, while Australian seeds, 

 widely and purposely scattered in New Zealand, have 

 gained no footing ? 



First and chiefly because in tne 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 under- 

 growth, which was 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 Mississippi 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 

 now, for meantime other changes have taken place 

 which have made it easier for plants to come from the 

 west, and they do come. New western plants migrate, 

 it is said, almost every year into the eastern states. 



And how do these new plants travel ? By rail, to 

 be sure, in accordance with the spirit of the age. They 

 come in the coats or in the food of cattle going to 

 market, and they take advantage of the bared railway 

 borders, which are such excellent nursery-grounds. 

 The great railroads run east and west, and as the pre- 

 vailing winds are westerly and very strong, the plants 

 of the west are now amply provided with the means of 



