Chap. XVI. 



THE CROSSING OF VAEIETIES. 



85 



by its own pollen (eight capsules), and by that of the yellow variety 

 (five capsules), yielded seed in the proportion of 100 to 79. So that 

 in every case the unions of similarly-coloured varieties of the same 

 )^pecies were more fertile than the unions of dissimilarly-coloured 

 varieties ; when all the cases are grouped together, the difference of 

 fertilitv is as ICO to 86. Some additional trials were made, and 

 altogether thirty-six similarly-coloured unions yielded thirty-five 

 good capsules ; whilst thirty-five dissimilarly-coloured unions yielded 

 OFily twenty-six good capsules. Besides the foregoing experiments, 

 the purple V. phoeniceum was crossed by a rose-coloured and a white 

 variety of the same species ; these two varieties were also crossed 

 together, and these several unions yielded less seed than V. phoe- 

 niceum by its own pollen. Hence it follows from ]\Ir. Scott's experi- 

 ments, that in the genus Yerbascum the similarly and dissimilarly- 

 coloured varieties of the same species behave, when crossed, like 

 closely allied but distinct species.^^ 



This remarkable fact of the sexual aflSnity of similarly-coloured 

 varieties, as observed by Gartner and Mr. Scott, may not be of very 

 rare occurrence; for the subject has not been attended to by others. 

 The following case is worth giving, partly to show how difficult it 

 is to avoid error. Dr. Herbert ^^ has remarked that variously- 

 coloured double varieties of the Hollyhock (Althea rosea) may be 

 raised with certainty by seed from plants growing close together. 

 I have been informed that nurserymen who raise seed for sale do 

 not separate their plants ; accordingly I procured seed of eighteen 

 named varieties; of these, eleven varieties produced sixty-two 

 plants all perfectly true to their kind ; and seven produced forty- 

 nine plants, half of which were true and half false. Mr. Masters of 



** The following facts, given by 

 Kclreuterin his ' Dritte Fortsetzung,' 

 ss. 34, 39, appear at first sight strongly 

 to confirm Mr. Scott's and Gartner's 

 statements ; and to a certain limited 

 extent they do so. Koh-euter asserts, 

 from innumerable observations, that 

 insects incessantly carry pollen from 

 one species and variety of Yerbascum 

 to another ; and I can confirm this 

 assertion ; yet he found that the 

 white and yellow varieties of Verbas- 

 cum lychnitis often grew wild mingled 

 together : moreover, he cultivated 

 these two varieties in considerable 

 numbers during four years in his 

 garden, and they kept true by seed ; 

 but when he crossed them, they pro- 

 duced flowers of an intermediate tint. 

 Hence it might have been thought 

 that both varieties must have a 

 stronger elective affinity for the pollen 



26 



of their own variety than for that of 

 the other ; this elective affinity, I 

 may add of each species for its own 

 pollen (Kolreuter, 'Dritte Forts.' s. 

 39, and Gartner, ' Bastarderz., ^jass/m) 

 being a perfectly well-ascertained 

 power. But the force of the fore- 

 going facts is much lessened by 

 Gartner's numerous experiments, for, 

 dirtierently from Kolreuter, he never 

 once got (' Bastarderz.,' s. 307) an 

 mtermediate tint when he crossed the 

 yellow and white flowered varieties 

 of Verbascum. So that the fact of 

 the white and yellow varieties keep- 

 ing true to their colour by seed does 

 not proA'-e that they were not mutual- 

 ly fertilised by the pollen carried by 

 insects from one to the other. 



18 ' Amaryllidaceee,' 1837, p. 366. 

 Gartner has made a similar observa- 

 tion. 



