The mutation theory; experiments and observations on the origin of species in the vegetable kingdom . of petals ofHypericum perforatum varies in this way, in this neigh-borhood, round a mean of 5; on the one side going fre-quently to 4 and rarely to 3, and on the other side rarelyto 6. The corolla of Campanula rotundifolia often variesfrom 5 to 6 and 7, and rarely from 5 to 4 and 3.^ ^ See the second part of this volume. ^ Botanisch Jaarbock, Gent, i<S94, p. 72. See also Bcr. d. d. hot. Gcs., Vol. XIT, 1894, P- 202, where furtherexamples will be found. 34 Latent and Sciin-Latoif Characters.
The mutation theory; experiments and observations on the origin of species in the vegetable kingdom . of petals ofHypericum perforatum varies in this way, in this neigh-borhood, round a mean of 5; on the one side going fre-quently to 4 and rarely to 3, and on the other side rarelyto 6. The corolla of Campanula rotundifolia often variesfrom 5 to 6 and 7, and rarely from 5 to 4 and 3.^ ^ See the second part of this volume. ^ Botanisch Jaarbock, Gent, i<S94, p. 72. See also Bcr. d. d. hot. Gcs., Vol. XIT, 1894, P- 202, where furtherexamples will be found. 34 Latent and Sciin-Latoif Characters. Selection and nutrition have as usual a great effecton half races. I shall not deal exhaustively with thjspoint until the end of this part, but will give here a briefdiscussion of the general principles underlying it in orderto prepare a proper understanding of the question. Our discussion of the phenomena of fluctuating vari-ability in the third part of the first volume led us to theconclusion that selection and nutrition usually operatein the same manner on the individual characters of 5 6 7 8 9 10 II 12 13 14 Fig. 2. Influence of selection and nutrition on the halfrace Raiinncnlus bulbosiis scmiplcnns. A, Half Curveafter several years of culture. B, Curve of the I2 bestindividuals (i. e., those richest in petals). C, Curve ofthe best plant.^ Positive selection and plenty of food enhance the devel-opment of a character, whilst selection in a minus direc-tion or defective nutriment operate in the opposite direc-tion. Polycephaly in Paparcr soinnifcrum behaves in thisway,^ and, as we shall see later on, all the other anomalieswhich have been tested do so, as well. Half curves canthereby be transformed into unilateral ones (), either ^Ber. d. d. hot. Ges., Vol. XII, 1894, Plate X, Fig. I, Part I, pp. 135-143. Half Races and Half Curve. 35 by making r. special curve from plants which exhibit thelargest number of abnormalities, or by making a curvefrom a race
Size: 1970px × 1268px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublisherchicagoopencourtpu
