. Heredity and evolution in plants . 9.—Yellow daisy, or cone-flower (Rudbeckia 5/>.), showing varia-tions of the character of mutations in the ray- and disc flowers. At dthe normally ligulate corollas are tubular; at / they have all aborted,except two; at h many of the normally tubular disc-flowers have becomeligulate, making a nearly double flower. (Photo by E. M. Kittredge.) lieving that any given species is at some periods in itshistory more labile or changeable than at other a long search he found, in an abandoned potato fieldat Hilversum, near Amsterdam, a large number o
. Heredity and evolution in plants . 9.—Yellow daisy, or cone-flower (Rudbeckia 5/>.), showing varia-tions of the character of mutations in the ray- and disc flowers. At dthe normally ligulate corollas are tubular; at / they have all aborted,except two; at h many of the normally tubular disc-flowers have becomeligulate, making a nearly double flower. (Photo by E. M. Kittredge.) lieving that any given species is at some periods in itshistory more labile or changeable than at other a long search he found, in an abandoned potato fieldat Hilversum, near Amsterdam, a large number of plantsof Lamarcks evening-primrose (CEnothera Lamarckiana)(Fig. 61). EXPERIMENTAL EVOLUTION 115 That I really had hit upon a plant in a mutable periodbecame evident from the discovery, which I made a yearlater, of two perfectly definite forms which were immedi-ately recognizable as two new elementary species. One ofthem was a short-styled form: O. brevistylis, which at firstseemed to be exclusively male, but later proved to have. FIG. 60.—A plant of the evening-primrose ((Enothera biennis) which,by bud sporting, has given rise (at the left) to a branch having thecharacters of another species. the power, at least in the case of several individuals, ofdeveloping small capsules with a few fertile seeds. Theother was a smooth-leaved form with much prettier foliagethan O. Lamarckiana, and remarkable for the fact thatsome of its petals are smaller than those of the parent type,and lack the emarginate form which gives the petals of n6 HEREDITY AND EVOLUTION IN PLANTS Lamarckiana their cordate character. I call this formO. IcevifoHa. When I first discovered them (1887) they were repre-sented by very few individuals. Moreover each formoccupied a particular spot on the field. O. brevistylisoccurred quite close to the base from which the (Enothera
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