A Light and Scanning Electron Microscope Study of Seed Morphology in Agalinis (Scrophulariaceae) and its Taxonomic Significance

Abstract

Seeds of 33 species of Agalinis were examined with the scanning electron microscope and the light microscope. Thin sections were cut of resin-embedded seeds from 11 taxa. The outer cells of the seed coats of all taxa form a reticulum. Thickenings (lignifications) are present on the inner tangential walls of cells making up the reticulum. The radial walls of the outermost cells of the seed coat and the thickenings on the inner tangential walls of these cells are smooth or variously or- namented. The seeds of Agalinis are classified into five major types based on seed shape, size, and color; cell shape and ornamentation; and pattern and ornamentation of thickenings. Species in certain previously recognized sections and subsections of the genus have seeds of a single type. In other cases the occurrence of species with dissimilar seeds within a section or subsection adds support to other morphological evidence that indicates a reclassification is warranted. While many species have char- acteristic seed patterns, infraspecific taxa cannot be differentiated on the basis of