164 On the Reproductive Functional [No. 3, 



contain an indefinite number of ovules. And tins tho more especially 

 if, as in my own experiments, castration and artificial impregnation be 

 performed in both pure and mixed unions. In drawing comparisons 

 between uncastrated pure unions, and castrated mixed unions, tbe 

 average of the former, with the maximum of the latter would certainly 

 be the fairer method, as affording a complement for the sterilising 

 influence of castration. 



For the following digest of Gartner's experiments I have to thank 

 Mr. Darwin, who kindly sent it to me from his yet unpublished MS. 

 illustrations of these phenomena : "To show the scale on which 

 Gartner worked, I may state that, in the genus Verbascum, he crossed no 

 less than 1085 flowers and counted their seed, and recorded the results. 

 Now in two of his works he distinctly asserts that similarly coloured 

 varieties of V. lyclinitis and Y. blattaria are more fertile together than 

 when differently coloured varieties of the same species are crossed. 

 But Gartner chiefly relied on the crosses which he made between the 

 yellow and white varieties of these two species and nine other distinct 

 species, and he asserts that the white-flowering species yielded more 

 seed than did the yellow-flowered varieties when crossed with the same 

 white varieties of these two-flowered species, and so conversely with 

 the yellow flowering varieties with the yellow species. The general 

 results may be seen in his Table. In one case he gives the following 

 details ; the white Verbascum lyclinitis naturally fertilised with its 

 own pollen had on an average in 12 capsules 96 good seeds : 20 flowers 

 artificially fertilised with the pollen of its yellow variety gave as the 

 maximum 89 good seeds. I should have thought that this slight 

 difference might have been wholly due to the evil effects of castration ; 

 but Gartner shows that the white variety of V. lyclinitis, fertilised by 

 the pollen of the white and yellow varieties of V. blattaria, in both of 

 which cases there must have been previous castration, bore seeds to 

 the white variety in the proportion of 62, to 43 when pollen of the 

 yellow variety was used." 



First then, in regard to the greater fertility of the unions of simi- 

 larily coloured varieties, relatively to that of the unions of dissimilarly 

 coloured varieties of the same species. To these phenomena I will apply 

 in the subsecjuent parts of this paper the following terms : " Homo- 

 chromatic" to the unions of similarly coloured varieties, and " hetero- 



