No. 4.] CKOSSING OF PLANTS. 21 



THE PHILOSOPHY OF THE CROSSING OF PLANTS, 



CONSIDERED IN 



REFERENCE TO THEIR IMPROVEMENT UNDER CULTIVATION. 



BY PROF. L. II. BAILEY, ITHACA, N. Y. 



It is now understood that the specific forms or groups of 

 plants have been determined largely by the survival of the 

 fittest in a long and severe struggle for existence. The proof 

 that this struggle everywhere exists becomes evident upon a 

 moment's reflection. We know that all organisms are emi- 

 nently variable. In fact, no two plants or animals in the 

 world are exactly alike. We also know that very few of the 

 whole number of seeds which are produced in any area ever 

 grow into plants. If all the seeds produced by the elms 

 upon Boston Common in any fruitful year were to grow into 

 trees, this city would become a forest as a result. If all the 

 seeds of the rarest orchid in our woods were to grow, in a 

 few generations of plants even our farms would be overrun. 

 If all the rabbits which are born were to reach old age, and 

 all their offspring were to do the same, in less than ten years 

 every vestige of herbage would be swept from the country, 

 and our farms would become barren. There is, then, a 

 wonderful 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 full 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 1 The plagues of Egypt would be 

 insignificant in the comparison ! 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 



