The Earliest Known Land Flora¹

Abstract

THE vegetable kingdom is made up of plants of most varied size, character, and habitat. Comparing those various types, the view becomes ever more insistent that dependence on water is the master-factor determining their existence. As We range their diverse forms according to probable sequences of descent, those which we regard as the most primitive according to their structure and mode of reproduction are those which are habitually the most dependent upon constant water supply. It is the same with the animal kingdom. These broad results were summed up by Weismann some forty years ago in the statement that the birth-place of all animal and plant life lay in the sea. If this be true, it follows that all life on exposed land-surfaces has been secondary, and derivative.