Chap. XVII. 



EVIL FROM INTERBREEDING. 



129 



fertilised plants were only a quarter of an inch high. But this inequality 

 did not continue, for, when the crossed plants were four and a half 

 inches high, the self-fertilised were three inches; and they retained the 

 same relative difference till their growth was complete. The crossed 

 plants looked far more vigorous than the uncrossed, and flowered before 

 them ; they produced also a far greater number of flowers, which yielded 

 capsules (judging, however, from only a few) containing more seeds. As 

 in the former case, the experiment was repeated in the same manner during 

 the next two generations, and with exactly the same result. Had I not 

 watched these plants of the Mimulus and Ipomoea during their whole 

 growth, I could not have believed it possible, that a difference apparently 

 so slight, as that of the pollen being taken from the same flower, and 

 from a distinct plant growing in the same small pot, could have made so 

 wonderful a difference in the growth and vigour of the plants thus pro- 

 duced. This, under a physiological point of view, is a most remarkable 

 phenomenon. 



With respect to the benefit derived from crossing distinct varieties, 

 plenty of evidence has been published. Sageret 43 repeatedly speaks in 

 strong terms of the vigour of melons raised by crossing different varieties, 

 and adds that they are more easily fertilised than common melons, and 

 produce numerous good seed. Here follows the evidence of an English 

 gardener : 44 "I have this summer met with better success in my culti- 

 vation of melons, in an unprotected state, from the seeds of hybrids 

 " (i.e. mongrels) obtained by cross impregnation, than with old varieties. 

 " The offspring of three different hybridisations (one more especially, of 

 " which the parents were the two most dissimilar varieties I could select) 

 " each yielded more ample and finer produce than any one of between 

 " twenty and thirty established varieties." 



Andrew Knight 45 believed that his seedlings from crossed varieties of 

 the apple exhibited increased vigour and luxuriance; and M. Chevreul 46 

 alludes to the extreme vigour of some of the crossed fruit-trees raised b Y 

 Sageret. 



By crossing reciprocally the tallest and shortest peas, Knight v says 

 I had m this experiment a striking instance of the stimulative effects 

 ^ol crossing the breeds; for the smallest. variety, whose height rarely 

 ^ exceeded two feet, was increased to six feet; whilst the height of the 

 large and luxuriant kind was very little diminished." Mr. Laxton gave 

 me seed-peas produced from crosses between four distinct kinds; and the 

 plants thus raised were extraordinarily vigorous, being in each case from 

 one to two or three feet taller than the parent-forms growing close along- 



m ' M f7 SUr leS C ™*bitacee S ,' 46 'Annal. des 8c. Nat.,' 3rd series, 



VV . 36, 28 60 Bot., torn. yi. p. 189. 



i«*9 tT S g,/ V ° L Vili " 47 'Philosophical Transactions,' 1799, 



45 ' Transact. Hort. Soc.,' vol. i. p. 25. 



VOL. II. 



K 



