The Vascular Supply of the Bracts of some Species of Anemone.*

Abstract

The form and position of the bracts of various species of Anemone are described, and these are compared with the bracts of Eranthis hyemalis and with the sepals of Ranunculus Ficaria. A detailed account is given of the vascular supply of the bracts of species of Anemone and of the part played by the bract bundles on entering the axis. Where no definite involucre is formed (A. japonica), there is little fusion between the bract bundles, and on entering the axis ring, only the midrib forms a main bundle. In species resembling A. nemorosa with a leafy involucre the characteristic features are:— Division of lateral bundles, one half joining the midrib, the other half swinging over to the marginal. Fusion of marginals of adjacent bracts so that in all six large bundles enter the axis. The vascular ring on the axis below the node consists of five large bundles, all of bracteal origin, and of several smaller ones. Species with an involucre of sessile bracts with reduced lamina and broad base (A. coronaria, A. fulgens) show a tendency to parallel venation, an increase in the number of bract bundles, lack of fusion between lateral and marginal; but the vascular system of the axis is still dominated by that of the involucre. In A. angulosa and A. Hepatica, where the reduction of the lamina of the involucral leaves results in a calyx-like structure, there is no fusion between marginals of adjacent bracts; the part played by lateral and marginal in A. nemorosa is completely reversed—although the midribs still become main axis strands, the entry of the bract bundles causes relatively little disturbance of the axis ring, and peduncle bundles become main strands, while lateral bundles from the bracts show a tendency to divide. The course of the sepal bundles of Ranunculus Ficaria resembles that of the bract bundles of A. Hepatica very closely; but here all the bundles entering the axis ring play a subsidiary part, and as a rule divide. The vascular supply of the bracts of Eranthis hyemalis resembles that of A. nemorosa in all essentials. The variations in vascular anatomy are considered in relation to the difference in function of the bracts. The significance of the double ring of bundles which occurs in several species of Anemone is discussed; but the evidence obtained in this investigation is regarded as insufficient to be in any way conclusive. The vascular anatomy of the bracts and the bract node of these species of Anemone appears to support the view of the homology of the involucre of A. Hepatica and the calyx of Ranunculus Ficaria. I wish to express my thanks to Dr. H. S. Holden, who suggested this investigation, and both to him and to Miss Bexon, for their kindly help and oriticism.