TEMPERATURE AND ANTHESIS

Abstract

That there are waves of blossoming, or anthesis, in any particular locality and that such waves are more pronounced or less apparent according to the greater or the less amplitude of temperature variation, is a matter of both common experience and scientific knowledge. The seasonal succession of vegetative and reproductive periods, from quiescence during the cold or dry seasons to quiescence again, is an annual occurrence and is repeated in the same sequence and in the same order from year to year with little variation except as the is early or late. The season of vegetative and reproductive activity may be long or short according to the latitude, but even in the moist tropics, on the one hand, and the extreme arctic, on the other, there is to be found at least a slight indication of periodicity, which is usually, if properly observed, greater than might be expected. In the temperate regions, where the winter is cold (typically with ice and snow) and the summer warm (or even hot), the seasonal march from the bursting into leaf and blossom in the spring to the leaf-fall in the autumn occurs in a succession of waves, each accompanied by the anthesis of certain groups. There are a few flowering plants with an extended season of bloom, some even reasonably meriting the title of perpetual bloomers. There are others which have a short period of general or anthesis, which at certain other times may show scanty flowering or what may be designated as sporadic anthesis. Full anthesis is generally preceded by scattering, often scanty anthesis, resembling sporadic anthesis except that the latter never merges into full anthesis. Full anthesis seems to represent general optimum conditions whereas the scattering anthesis preceding full anthesis presumably represents minimum favorable conditions, while the scattering anthesis lingering after the full anthesis has passed may represent another minimum following the maximum of favorable conditions. On the other hand, sporadic anthesis (I apply the term to scattering anthesis not directly before or after full anthesis but disconnected) may mean a return of favorable conditions for anthesis but for a short period or not fully favorably connected with preliminary or accompanying conditions for flower-bud formation. For some years my attention has been turned to the relations existing between temperature intervals and geographical distribution in the case of marine algae and marine spermatophytes (cf. Setchell, I893, 19I5, I9I7, 1920a, I920b, I920 C, I922 a, I922b, I923,and I924). Theadvantageofdealing with aquatic (entirely submerged) plants is that the influence of the one