Origin of Species Variorum

Comparison with 1872

&c.), .. are likewise on the whole the most abnormal in their teeth; but there are so many exceptions to this rule, as Mr. Mivart has remarked, that it has little value.

I know of no case better adapted to show the importance of the laws of correlation and variation, independently of utility and, therefore, of natural selection, than that of the difference between the outer and inner flowers in some Compositous and Umbelliferous plants. Every one is familiar with the difference between the ray and central florets of, for instance, the daisy, and this difference is often accompanied with the abortion of parts of the flower. But, in some Compositous plants, the seeds also differ in shape and sculpture; and even the ovary itself, with its accessory parts, differs, as has been described by Cassini. These differences have sometimes been attributed to the pressure of the seeds in the ray-florets in some Compositæ countenances this idea; but, in the case of the corolla of the Umbelliferæ, it is by no means, as Dr. Hooker informs me, in species with the densest heads that the inner and outer flowers most frequently differ. It might have been thought that the development of the ray-petals by drawing nourishment from the reproductive organs causes their abortion; but in some Compositæ there is a difference in the seeds of the outer and inner florets differ, without any difference in the corolla. Possibly, these several differences may be connected with some difference in the flow of nutriment towards the central and external flowers: we know, at least, that with irregular flowers, those nearest to the axis are oftenest subject to peloria, that is to become abnormally symmetrical. I may add, as an instance of this fact, and as a striking case of correlation, that in many pelargoniums, the two upper petals in the central flower of the truss often lose their patches of darker colour; and

&c.), these are likewise the most abnormal in their teeth.

I know of no case better adapted to show the importance of the laws of variation and correlation, independently of utility and therefore of natural selection, than that before referred to, of the difference between the outer and inner flowers in some Compositous and Umbelliferous plants. Every one knows the difference in the ray and central florets of, for instance, the daisy, and this difference is often accompanied with the partial or complete abortion of the reproductive organs. But in some of these plants, the seeds also differ in shape and sculpture. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. These differences have been attributed by some authors to the pressure of the involucra on the florets, or to their mutual pressure, and the shape of the seeds in the ray-florets of some Compositæ countenances this idea; but with the Umbelliferæ, it is by no means, as Dr. Hooker informs me, the species with the densest heads which most frequently differ in their inner and outer flowers. It might have been thought that the development of the ray-petals by drawing nourishment from the reproductive organs had caused their abortion; but this can hardly be the sole cause, for in some Compositæ ... the seeds of the outer and inner florets differ without any difference in the corolla. Possibly these several differences may be connected with the different .. flow of nutriment towards the central and external flowers: we know, at least, that with normally irregular flowers, those nearest to the axis are most subject to peloria, that is they become symmetrical. I may add, as an instance of this, and of a striking case of correlation, that I have recently observed in many pelargoniums, that in the central flower of the truss, the two upper petals often lose their patches of darker colour; and