



406 CONCLUSION AND SUMMARY Chap. XI 



In some cases this segregation of character apparently depends 

 on some incapacity of union rather than on reversion, for the 

 flowers or fruit which are first produced display by segments the 

 characters of both parents. In the Cytisus adami and the Biz- 

 zarria orange, whatever their origin may have been, the two 

 parent species occur blended together under the form of a sterile 

 hybrid, or reappear with their characters perfect and their re- 

 productive organs effective ; and these trees, retaining the same 

 sportive character, can be propagated by buds. These various 

 facts ought to be well considered by any one who wishes to 

 embrace under a single point of view the various modes of re- 

 production by gemmation, division, and sexual union, the repara- 

 tion of lost parts, variation, inheritance, reversion, and other 

 such phenomena. In a chapter towards the close of the follow- 

 ing volume I shall attempt to connect these facts together by a 

 provisional hypothesis. 



In the early half of this chapter I have given a long list of 

 plants in which through bud-variation, that is, independently 

 of reproduction by seed, the fruit has suddenly become modified 

 in size, colour, flavour; hairiness, shape, and time of maturity ; 

 flowers have similarly changed in shape, colour, and doubleness, 

 and greatly in the character of the calyx ; young branches or 

 shoots have changed in colour, in bearing spines, and in habit 

 of growth, as in climbing and weeping ; leaves have changed 

 in colour, variegation, shape, period of unfolding, and in their 

 arrangement on the axis. Buds of all kinds, whether produced 

 on ordinary branches or on subterranean stems, whether simple 

 or, as in tubers and bulbs, much modified and supplied with 

 a stock of nutriment, are all liable to sudden variations of the 

 same general nature. 



In the list, many of the cases are certainly due to reversion 

 to characters not acquired from a cross, but which were formerly 

 present, and have been lost for a longer or shorter period of 

 time ; — as when a bud on a variegated plant produces plain 

 leaves, or when variously-coloured flowers on the Chrysanthe- 

 mum revert to the aboriginal yellow tint. Many other cases 

 included in the list are probably due to the plants being of 

 crossed parentage, and to the buds reverting to one of the two 

 parent-forms. In illustration of the origin of Cytisus adami, 



