The mutation theory; experiments and observations on the origin of species in the vegetable kingdom . Fig. 137. Green Dahlia. A branch whose terminal inflores-cence b as well as the lateral one b have become green,as in the remaining parts of the plant, whilst a branchhas arisen at a from an axillary bud, bearing double redinflorescences of normal structure and without a trace ofvirescence. a, flowering and a, a bud. See above, , Fig. 14 (1902). See also pp. 628-629. in the pollen- and egg-cells; and that these changes them-selves may have had their origin before the development Vegetative
The mutation theory; experiments and observations on the origin of species in the vegetable kingdom . Fig. 137. Green Dahlia. A branch whose terminal inflores-cence b as well as the lateral one b have become green,as in the remaining parts of the plant, whilst a branchhas arisen at a from an axillary bud, bearing double redinflorescences of normal structure and without a trace ofvirescence. a, flowering and a, a bud. See above, , Fig. 14 (1902). See also pp. 628-629. in the pollen- and egg-cells; and that these changes them-selves may have had their origin before the development Vegetative Mutations. 619 of the sexual cells, and perhaps even before the uri^Miiof the flower itself. In other words: Germinal variations may be regarded as a speeial easeof vegetative mutations; and this possibility always re-mains open where the contrary cannot be proved. Concluding these discussions I propose now to arlducea series of facts in which mutations have occurred vege-tatively, tliat is to say, such facts as have hitherto beendealt with as bud-variations. It will be necessary to. Fig. 138. Cryptomcvia japonica spiralitcr falcafa. with anatavistic branch (sec page 628). consider three groups of phenomena separately: first,vegetative segregation in hybrids; secondly, vegetativeatavism in eversporting varieties, especially as cxiubitedby striped flowers (Part I, Plate I), and thirdly, thetrue vegetative mutations which are usually of an atavis-tic nature (Figs. 137, 138), but sometimes may happen tobe of a progressive kind. Vegetative segregations in hybrids are rare phencnn-ena; but this may perhaps be due to the fact that in many 620 Validity of the Doctrine of Mutation. instances of bud-variations the possibility of the plantin question being- a hybrid has not been considered. Asingle case has fallen within my own experience; this isa hybrid between Veronica longifolia and its variety alba. The flowers of this hybrid are blue, and it mayeasily be kept in cultivation f
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