628 Validity of the Doctrine of Mutation. 



hereditary properties of the seeds which they produce; 

 as, for instance, in Chclidoniiun niajiis fiore plcno (p. 

 336). 



In the majority of cases a more detailed examina- 

 tion is urgently needed, before the true nature of even 

 the commonest bud-variations can be properly under- 

 stood. This is particularly the case in variegated plants, 

 amongst which every one is familiar with the phenom- 

 enon, on shrubs and trees at anv rate ; but even here the 

 ]>rocess has not yet been exhaustively studied. On the 

 one hand, some of these cases consist of bud-atavism, 

 wh(>le branches of a variegated variet}^ reverting to the 

 normal type of the species in their color as well as in 

 their secondary characters (Fig. 141).^ On the other 

 hand, sometimes halves of leaves become green, or occa- 

 sional branches with usually slightly, but sometimes 

 finely, variegated leaves arise on green individuals (Figs. 

 142 and 143). On a large tree of Moms nigra in our gar- 

 den the latter phenomenon occurs almost every year. 



It is not until all these and similar cases have been 

 excluded that bud-variations may be regarded as true 

 cases of vegetative mutations. Even then we should 

 require the proof that the deviating branches will re- 

 produce their type from their seeds, after pure self-fer- 

 tilization. In manv cases, however, this is not possible 

 because the bud-variations in question often bear no 

 seeds, even when they occur regularly, as in Cephalo- 

 fariis pediinculata fasti r/ia fa (p. 109. Fig. 16) and in 

 numerous other conifers, the bud-variations of which 

 have been described by Betssner: as, for instance, in 

 Cryptonicria japonica spiraliter falcata (Fig. 138, p. 619). 

 Even from the i^Teen Dahlia I was, unfortunatelv, unable 



^ See above p. in and pp. 272-277. 



