II. Longitudinal symmetry in Phanerogamia

Abstract

Although the transverse symmetry of Phanerogamia, as revealed by measurements of the angles of divergence of vegetative and floral leaves, has been very amply investigated, the subject of longitudinal symmetry has scarcely been touched. The reason for this is not far to seek. Early in the history of botany it was discovered that the successive leaves of a flowering plant are separated in a transverse plane by angles that are more or less equal, measurable, and constant under varying conditions; but that the longitudinal distances apart of successive leaves are obviously unequal and affected by external conditions, so that their measurements often seem to form an irregular series. The first object of this paper is to demonstrate agraphic methodof recording, in an easily perceptible manner, the quantitative relations existing among the longitudinal distances apart of successive leaves.