Juvenile Gametophyte Development in the Blasiales (Marchantiophyta; Metzgeriidae). 1. Receptacular Gemma/Gemmaling Ontogeny of Blasia pusilla

Abstract

Abstract The pattern of gemma/gemmaling ontogeny in the liverwort Blasia pusilla L. is described from its origin as a primordium within the gemma receptacle to the formation of a juvenile gametophyte. Data were obtained from herbarium specimens, field-grown and axenically cultured plants, using a combination of light and scanning electron microscopy techniques. A consistent, uniform, fundamental developmental pattern was elucidated that is characterized by the production, within the receptacle, of a discoid to ellipsoid, stalked gemma composed of distinct tiers of thick-walled cells and margined by lateral columns of thin-walled, potentially active cells. After dispersal from the receptacle, lateral growth ensues from a gemmaling initial that is produced via quadrant formation from one lateral margin cell. Ultimately, an adult cuneate apical cell is honed that generates segments the same as in the adult plant to produce the juvenile gametophyte typical of Blasia. Both the gemmaling and sporeling ontogenie...