in the corolla, can be in any way beneficial; yet in the Umbelliferae these differences are of such apparent importance — the seeds being sometimes orthospermous in the exterior flowers and coelospermous in the central flowers — that the elder De Candolle founded his main divisions in the order on such characters. Hence modifications of structure, viewed by systematists as of high value, may be wholly due to the laws of variation and correlation, without being, as far as we can judge, of the slightest service to the species.

We may often falsely attribute to correlated variation structures which are common to whole groups of species, and which in truth are simply due to inheritance; for an ancient progenitor may have acquired through natural selection some one modification in structure, and, after thousands of