Hybridization 93 



latent potency in these species ; but the same may be said 

 of every species of plant and animal, even of man himself. 

 If one species of plant would overrun and usurp the land, 

 if it increased to the fullest extent of its possibilities, 

 what would be the result if each of the two thousand and 

 sixty-one plants known to inhabit Middlesex County 

 were to do the same ? And then fancy the result if each 

 of the animals from rabbits and mice to frogs and leeches 

 were to increase without check! The plagues of Egypt 

 would be insignificant in the comparison! 



Survival of the most fit. The fact is, the world is not 

 big enough to hold the possible first offspring of the 

 plants and animals at this moment living upon it. 

 Struggle for existence, then, is inevitable, and it must 

 be severe. It follows as a necessity that those seeds 

 grow or those plants live which are the best fitted to 

 grow and live, or which are fortunate enough to find a 

 congenial foothold. It would never appear, at first 

 thought, that much depends on the accident of falling 

 into a congenial place, or one unoccupied by other plants 

 or animals; but, inasmuch as scores of plants are con- 

 tending for every unoccupied place, it follows that every- 

 where only the fittest can germinate or grow. In the 

 greater number of cases, plants grow in a certain place 

 because they are better fitted to grow there, to hold 

 their own, than any other plants are; and the instances 

 are rare in which a plant is so fortunate as to find an un- 

 occupied place. We are likely to think that plants chance 

 to grow where we find them, but the chance is determined 

 by law, and, therefore, is not chance. 



Flexibility as an aid to survival. Much of the capa- 



