38 THE MEANING OF EVOLUTION 



pod, a total of more than six hundred and thirty thou- 

 sand seeds. If each of these could find lodgment on 

 a plot eighteen inches square, produce a similar num- 

 ber of seeds and plant them all, the result would be 

 overwhelming. The fourth generation would cover 

 land and sea, from pole to pole, one hundred layers 

 deep. But there is no such danger. Year by year 

 the mulleins hold their own and no more. Any par- 

 ticular field may have more or less, but in the long 

 run the average for a district is about the same. Some 

 of the seeds are poor and thin. These scarcely sprout. 

 Others spring up into thin-skinned plants, and the 

 first frost nips them. Still others lack the woolly 

 coating in its finest abundance, and the browsing ani- 

 mals eat these. Others lack power to put out a wide- 

 ranging root supply and the first drought kills these. 

 Still others fail to send up a vigorous stem and the 

 passing animal knocks them over and they die. Of 

 the few that are still surviving, some produce such 

 small and inconspicuous blossoms that the insects 

 scarcely see them, and they go unfertilized. In the 

 end only the aristocrats of the group are left, aristo- 

 crats in the best sense of the word. These are strong, 

 thrifty, and beautiful, and are provided with every 

 defense known to the mullein world. From these the 

 mulleins of the next generation will spring. Again 

 Nature will select the best of these, by a repetition 



