. Carnegie Institution of Washington publication. 90 VARIATION AND DIFFERENTIATION IN CERATOPHYLLUM. The diagram brings out very sharply a number of points. In the first place we see that, whatever the part of the plant, first whorls con- tribute proportionately very largely towards the frequencies on the low leaf-numbers. As we go out towards the distal end of the branch or the main stem the proportionate frequency of 9 and 10 leaved whorls increases. Thus if we compare the rectangle representing 7-leaved whorls with that for 10-leaved whorls we see at once that the sub- divisions of the firs
. Carnegie Institution of Washington publication. 90 VARIATION AND DIFFERENTIATION IN CERATOPHYLLUM. The diagram brings out very sharply a number of points. In the first place we see that, whatever the part of the plant, first whorls con- tribute proportionately very largely towards the frequencies on the low leaf-numbers. As we go out towards the distal end of the branch or the main stem the proportionate frequency of 9 and 10 leaved whorls increases. Thus if we compare the rectangle representing 7-leaved whorls with that for 10-leaved whorls we see at once that the sub- divisions of the first decrease for each division of the plant as we go towards the top of the diagram, while the subdivisions of the latter increase. This means of course that the skewness of the distributions is changing in the manner schematically indicated in the following diagram:. Small leaf-num- ber per whorl Proximal whorls, ") Positive ) â j skewness. C Leading through var- ious inter- mediate stages, Including symmetry, to extreme. Positive r High leaf- âi,«^v,^.,o â ^ number per skewness. I^j^^^l_ Tistal whorls. A and C would represent the extreme conditions of proximal and distal whorls, while B would represent one of a whole series of inter- mediate stages passed through as we go from A to C. It will be under- stood that this diagram is purely schematic, but fairly represents the essential facts very closely. The same stages as those indicated may indeed be seen in plate ll, or in the correlation tables (cf. supra) on which it is based, while a careful examination of the data will leave no doubt in the mind of the reader that the general trend of the frequency distributions in respect to skewness is fundamentally that indicated. We see, then, that homologous organs on the same individual plant run through the whole gamut of skewness from positive (A), through perfect symmetry* to negative (C). The phenomenon of skew variation stands forth in this case, free of doubtful inter
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