Spore size and germination in Fosliella, Pneophyllum and Melobesia (Rhodophyta, Corallinaceae)

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Abstract
Spore size and germination were investigated in four epilithic species (Pneophyllum myriocarpum, P. lobescens, P. plurivalidum and P. zonale) and four epiphytic species (P. lejolisii, P. limitatum, Fosliella farinosa and Melobesia membranacea) of crustose Corallinaceae (Rhodophyta). Within any one species, tetraspores were usually the smallest spore type; bispores were largest and carpospores slightly smaller than bispores. The spores are among the smallest recorded in the Corallinaceae. Released spores were deep red and surrounded by a clear halo; on settling they secreted an adhesive substance. Calcification probably started at an early stage in sporelings of epilithic species but at a later stage in epiphytic species. The spores divided within the confines of the original spore wall (Dumontia-type segmentation) and produced a characteristic four-celled central element in Fosliella, an eight-celled central element in Pneophyllum and a many-celled central element in Melobesia. Within a species, all spore types germinated in a similar manner. Previous systems of classifying spore segmentation are assessed in relation to these results and the taxonomic implications are considered.