Chap. XI. 



OF REPRODUCTION AND VARIATION. 



389 



prof, 

 the* 



to M. Naudin's observations 90 on Mirabilis, that it would be functionally- 

 effective. The fact of the ovules of C. adami being monstrous, and the 

 pollen apparently sound, is all the more remarkable, because it is opposed 

 to what usually occurs not only with most hybrids, 91 but with two hybrids 

 in the same genus, namely in 0. purpureo-elongatus, and C. alpino-laburnum. 

 In both these hybrids, the ovules, as observed by Prof. Caspary and myself, 

 were well-formed, whilst many of the pollen-grains were ill-formed; in 

 the latter hybrid 20*3 per cent., and in the former no less than 84*8 

 per cent, of the grains were ascertained by Prof. Caspary to be bad. This 

 unusual condition of the male and female reproductive elements in 0. adami 

 has been used by Prof. Caspary as an argument against this plant being 

 considered as an ordinary hybrid produced from seed; but we should 

 remember that with hybrids the ovules have not been examined nearly so 

 frequently as the pollen, and they may be much oftener imperfect than is 

 generally supposed. Dr. E. Bornet, of Antibes, informs me (through 

 Mr. J. Traherne Moggridge) that with hybrid Oisti the ovarium is frequently 

 deformed, the ovules being in some cases quite absent, and in other cases 

 incapable of fertilisation. 



Several theories have been propounded to account for the origin of 

 0. adami, and for the transformations which it undergoes. These trans- 

 formations have been attributed by some authors to simple bud-variation; 

 but considering the wide difference between 0. laburnum and purpureas, 

 both of which are natural species, and considering the sterility of the 

 intermediate form, this view may be summarily rejected. We shall pre- 

 sently see that, with hybrid plants, two different embryos may be developed 

 within the same seed and cohere; and it has been supposed that O. adami 

 might have thus originated. It is known that when a plant with variegated 

 leaves is budded on a plain stock, the latter is sometimes affected, and 

 it is believed by some that the laburnum has been thus affected. Thus 

 Mr. Purser states 92 that a common laburnum-tree in his garden, into which 

 three grafts of the Cytisus purpureas had been inserted, gradually assumed 

 the character of 0. adami; but more evidence and copious details would 

 be requisite to make so extraordinary a statement credible. 



Many authors maintain that C. adami is a hybrid produced in the common 

 way by seed, and that it has reverted by buds to its two parent-forms 

 Negative results are of little value; but Eeisseck, Caspary, and I myself, 

 tried in vain to cross 0. laburnum and purpureus; when I fertilised the 

 former with pollen of the latter, I had the nearest approach to success, 

 for pods were formed, but in sixteen days after the withering of the flowers 

 they fell off. Nevertheless, the belief that 0. adami is a spontaneously 

 produced hybrid between these two species is strongly supported by the 

 fact that hybrids between these species and two others have spontaneously 



01' 



90 ' Nouvelles Archives du Museum,' 

 torn. i. p. 143. 



91 See on this head, Naudin, idem, 

 p. 141. 



92 The statement is believed by Dr. 

 Lindley in 'Gard. Cliron.,' 1857, pp. 

 382, 400. 



