398 FERTILE HYBRIDS. 



the surface of the earth, which the Monocotyledons, 

 or gram-bearing plants, and the Dicotyledons, or 

 fruit-bearing make their appearance and predom- 

 inate to prepare the earth for man, by affording 

 food to the ruminating animals, which compose 

 most of his meat, and the fruit tree to tempt his 

 appetite. Instead of these different types of vegeta- 

 tion gradually succeeding and displacing one another, 

 the change has been abrupt and simultaneous, ac- 

 companied by great physical commotions. These 

 have been not a few ; but, according to some writers, 

 from sixty to one hundred. Thus the earth has 



been the theatre of a series of alterations and re- 

 ♦ 



creations, which have prepared it to become the 

 dwelling-place of intelligent man. 



Mr. Herbert asserts that hybrids between plants 

 of the same species do not always produce fertile 

 offspring ; but that it " depends upon circumstances 

 of climate, soil, and situation ;" and that " there does 

 not exist any decided line of absolute sterility in 

 hybrid vegetables ; though, from reasons which I 

 did not pretend to be able to develop, but undoubt- 

 edly depending upon certain affinities, either struc- 

 tual or constitutional, there was a greater disposition 

 to fertility in some than in others. Subsequent 

 experiments have confirmed this view to such a 

 degree as to make it almost certain that the fertility 

 of the hybrid, or mixed offspring, depends more 

 upon the constitutional than the closer botanical 



