Xanthidium mamillosum var. mediolaeve (Grönblad) Couté & Tell, 1981

Xanthidium mamillosum var. mediolaeve (Grönblad) Couté & Tell *

( Fig. 7J View FIG )

Beihefte zur Nova Hedwigia 68: 197 ( Couté & Tell 1981). — Xanthidium antilopaeum f. mediolaeve Grönblad , Acta Societatis Scienctiarum Fennicae, Nova Series B, 2 (6): 22 ( Grönblad 1945).

DISTRIBUTION. — South America and China. Amazon Basin: as Xanthidium antilopaeum var. mamillosum f. mediolaeve : Grönblad (1945). As X. mamillosum f. mediolaeve : Thomasson (1971). Western Amazonia (lowlands): no records.

DESCRIPTION

Cells 76.4 µm long (115.0 µm with spines), 83.9 µm wide (136.2 µm with spines); isthmus 31.5µm; apex: 27.7-31.7 µm. Cell wall finely punctuated. Semicells hexagonal-pyramidal, sinus linear inwardly, outwardly greatly enlarged. The spines on each semicell are arranged apically and laterally and are strongly inflated at the base. The spines, which are strong, straight, and long, become sharper towards the ends.

REMARKS

This taxon is easily identifiable by the well-defined inflated base of spines in our specimens. Although our specimens are slightly smaller than those described by Grönblad (1945) from the Amazon, and Bourrelly & Couté (1982) from French Guyana, they are slightly larger in cells longitude than those shown by Camargo et al. (2009) for Mato Grosso, Brazil (as Xanthidium antilopaeum var. mamillosum f. mediolaeve Grönblad ). The size of our specimens falls within the wide range of variation exhibited by specimens reported by Oliveira de et al. (2011b) for northeastern Brazil. As recorded in those other works, X. mamillosum var. mediolaeve presents a high variation in size.