THE OCCURRENCE,EVOLUTION, AND PHYLOGENETIC SIGNIFICANCE OF PARENCHYMA IN COLEOCHAETE BRÉB. (CHLOROPHYTA)

Thalli of four species of the charophycean green alga Coleochaete Bréb.; C. irregularis, C. soluta, C. orbicularis, and C. scutata, were examined using light and electron microscopy. The parenchymatous nature of the plant bodies of C. orbicularis and C. scutata became apparent when the degree of cellular association in these species was compared with that of parenchymatous land plant tissues, the pseudoparenchymatous thalli of C. soluta, and the branched filaments of C. irregularis. Coleochaete soluta was shown to be morphologically and phylogenetically transitional between the more primitive branched filamentous species (C. irregularis) and the more advanced discoid species (C. orbicularis and C. scutata). The branching patterns observed in C. soluta suggested a possible pathway for the evolutionary development of land plant parenchyma from branched, filamentous charophycean green algae.