142 INBREEDING AND OUTBREEDING 



inclined to acknowledge and discuss the matter, although 

 they had an excellent example before them in the mule 

 an animal known and appreciated for over four thousand 

 years. But the necessity of their following the custom of 

 maintaining breeds true to certain fixed standards prob- 

 ably accounts for their conservatism in estimating the 

 importance of the phenomenon. 



Kolreuter, 125 the first botanist to study artificial 

 plant hybrids, made many interspecific crosses in the 

 genera Nicotiana, Dianthus, Verbascum, Mirabilis, Da- 

 tura and others, which astonished their producer by their 

 greater size, increased number of flowers and general 

 vegetative vigor, as compared with the parental species 

 entering into the cross. He gives many exact measure- 

 ments of his hybrids and speaks with some awe of their 

 " 'statura portentosa" and "ambitus vastissimus ac alti- 

 tudo valde conspicua." Later, after some observations 

 on certain structural adaptations for cross-pollination 

 which he interpreted correctly, he made a passing re- 

 mark which plainly showed he thought Nature had 

 intended plants to be cross-fertilized and that benefit 

 ensued therefrom. 



Some forty years after, Thomas Andrew Knight, 122 a 

 horticulturist who was a very keen observer, noticed sim- 

 ilar instances of high vigor in his crosses : in the descrip- 

 tion of these experiments we note the following remarks 

 concerning a cross between two varieties of peas : 



By introducing the farina of the largest and most luxuriant kinds 

 into the blossoms of the most diminutive and by reversing 1 the process 

 I found that the powers of the male and female in their effects on the 

 offspring are exactly equal. The vigor of the growth, the size of the 

 seeds produced, and the season of maturity, were the same, though the 

 one was a very early, and the other a very late variety. I had, in this 



