1867.J Relations of Verbasca. 149 



Radical leaves ovate-lanceolate, light green. Flowers white and 

 rather larger than the others, wfth a few whitish glandulose hairs 

 near the base of petals. Filaments and form of anthers similar to 

 these of V. pkamiceum, hnt beset with white instead of purple, 

 glandular hairs. Pollen similarly copper-coloured in each. 



Thus, judging from the characters of these three forms alone, there 

 can be no doubt as to their being other than conspecific. In addition 

 to this I may add, on the authority of Mr. Stirling of Edinburgh, 

 that they have been raised from pure seed of the V. phceni- 

 ceum, the rose-coloured variety frequently appearing amongst the 

 seedlings of V. phceniceum, the white presenting itself more rarely. 



In the first part of Tab. 1, the number of flowers fertilised, and 

 the simple results are shown, and in the right hand, for the sake of 

 comparison, the calculated produce of the number of seeds from 20 

 capsules of each is given.* If we compare the results, we see that 

 reciprocal unions may be effected becwecn the V. phceniceum and 

 varieties, with one exception, viz., V. phceniceum, roseum, by pollen of 

 V. phceniceum, album, in which case 1 have found that though the 

 pollen tubes are abundantly developed and freely penetrate the stigmatio 

 tissues, the capsules nevertheless drop prematurely. The goodness, 

 however, of both the male and female elements of the above varieties 

 is nevertheless shown by their reciprocal unions with V. phceniceum^ 

 The individual potency of the respective sexual elements of these 

 varieties, in their reciprocal relations, is clearly shown ; whereas by 

 those experiments given in the three last lines of the table, in which the 

 stigmas of each variety were covered by their own good pollen, no 

 unions were effected, each proving utterly self-sterile ! 



This absolute, or conditional, sterility of the three varieties of V. 

 phceniceum, when treated by their own good pollen, led me to examine 



* From Mr. Darwin's suggestion m " The Origin of species" that the decreased 

 fertility of mixed unions, as compared with that of the pure unions, might possi- 

 bly be increased by the fact, that for perfectly satisfactory results, castration is 

 necessary in the cross-unions ; whereas in the latter, in pure unions, this not 

 being necessary, we may have indiscriminate comparisons, of the two results 

 though clearly castration may have a direct sterilising influence. In view of 

 this prudent suggestion, I took the precaution to castrate every flower both of 

 the pure and mixed unions, from which I intended to draw results. The sole 

 exception to this is that given in the first line of Table 2 of V. pliosniceum 

 as I was unable to get any of the plants under me to produce seed by their own 

 pollen. Whatever be the effects of castration then on the fertility of the plants so 

 treated, in the present cases, all having undergone it, the results will be mutual. 



