1867.] Relations of Verbasca. 151 



element with respect to its own female element. I have also to remark, 

 that the ultimate conditional sterility of these plants is not, relatively- 

 considered, an absolute but a graduated quantum ; this is shown 

 by the different degrees of development the embryos had undergone, 

 thus illustrating a most interesting, though as yet imperfectly known 

 fact, namely, that the male element, even though reaching the female 

 element, may nevertheless fail to communicate that amount of' vital 

 stimulus necessary to the complete development of the embryo. 

 Furthermore, I may in passing briefly refer to the perfect parallelism 

 between these phenomena, and those occasionally observed in hybridi- 

 sation, at least in the zoological kingdom, for unfortunately we are as 

 yet nearly void of information on this point in the vegetable kingdom, 

 hybridists having, in most instances, satisfied themselves by attending 

 to the ultimate results, without troubling themselves to examine into 

 the nature or degree of embryonic sterilisation. From the published 

 papers of the Hon'ble and Rev. W. Herbert, we find, as might 

 indeed be expected, that 'this point did not escape observation : thus 

 in one case he remarks, " It has, I believe, not been duly considered, that 

 the fecundation of the ovules is not a simple, but a complicated process. 

 There seems to me to be three or four several processes : viz., the 

 quickening of the capsule of the fruit, of the outer coats of the seed 

 itself, of the internal parts or kernel, and lastly, the quickening of the 



embryo." " It is further to be observed," he continues, "that there 



is frequently an imperfect hybrid fertilisation, which can give life, but 

 not sustain it well. I obtained much good seed from Hibiscus palustris 

 by H. speciosus, and sowed a little each year till it was all gone, the 

 plants always sprouted, but I saved only one to the third leaf, and it 

 perished then." 



To recur, however, to the above parallelism, of which we have here 

 additional and important illustrations : it has been stated by Mr. Darwin* 

 on the authority of Mr. Hewitt, that in the hybridisation of gallinaceous 

 birds a frequent cause of sterility in first crosses is the early death 

 of the embryo. Again Mr. Salter records similar results from 

 his experiments on the fertility inter se of several hybrid Galli,f thus 

 concluding, " the one striking point of these experiments (which I 

 believe has never been noticed before) is that a large proportion of 



* loc. cit. p. 286. 



t Nat. Hist. Kev. 1863, p. 276. 



