Monographs Details: Riccia ekmanii S.W.Arnell
Bischler, Hélène, et al. 2005. Marchantiidae. Fl. Neotrop. Monogr. 97: 1--262. (Published by NYBG Press
Description:Species Description - Thalli in gregarious patches; lobes 2-3 times forked, 8-10 mm long, 1.5-3 mm wide; dorsal side greenish, flattened and slightly concave when dry, rounded apically, margins acute, slightly undulate, hyaline and dotted with pink-violet. Median groove deep apically, shallower and vanishing below. Epidermal cells disintegrating except apically, convex. Ventral scales imbricate, entire, hyaline, dotted with pink-violet near margins, or entirely pink-violet, reaching or extending beyond lobe margins. Cross section of lobes 4-4.5 times as wide as high; dorsal edge acute laterally; flanks obliquely ascending, outer layer of larger cells than those of ventral tissue, tinged with pink-violet, with 1-2 hyaline cells apically; ventral edge convex; dorsal tissue in 3-5 cell layers, cells with 2 thickened, longitudinal strips. Monoecious. Antheridial necks colorless. Archegonial necks long, violaceous. Sporangia bulging mainly on ventral side. Spores tetrahedral, 90-120 |im diam., red-brown, wingless, margins weakly crenulate; distal face with (6-)8-9 areoles across diam., with thick, red-black ridges and large tubercles; proximal face with short ridges and tubercles of varying size and shape, ridges of triradiate scar discontinuous.
Discussion:Riccia ekmanii is close to R. weinionis and R. ridleyi. It is characterized by hyaline lobe margins, dotted with violet at level of insertion of the scales. Its spores have 6-9 areoles across the diam, on the distal face, as in R. weinionis (not 10-12 as in R. ridleyi). The facets of the proximal face show 10-12 areoles in R. weinionis, whereas in R. ekmanii they are more numerous and ill-delimited, with short, discontinuous ridges and tubercles of variable size and shape.
Distribution:Cuba South America
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