630 Validity of the Doctrine of Mutation. 
may conclude that this green Dahlia had arisen from the 
corresponding double-flowered variety. 
I do not propose to adduce any further instances; 
those which I have given show that varietal characters 
may disappear in a vegetative way, the original char- 
acters becoming active again. For such a mutation 
neither the formation of sexual cells nor fertilization 
is necessary. Therefore the possibility that seed-varia- 
tions may ultimately be derived from bud-variations can- 
not be denied ; but many more experimental data will have 
to be collected before a final judgment based on a suffi- 
cient foundation of facts can be given. One of the best 
methods is that which T have already mentioned, as 
adopted by BEYERINCK, of artificially inducing bud-varia- 
tions by pruning. 
