Monographs Details: Symbiezidium dentatum Herzog
Gradstein, S. Robbert. 1994. Lejeuneaceae: Ptychantheae, Brachiolejeuneae. Fl. Neotrop. Monogr. 62: 216. (Published by NYBG Press
Synonyms:Symbiezidium transversale (Sw.) Trevis.
Description:Species Description - Autoicous or dioicous. Plants usually robust, 3-6 cm long × 3.5-4.5 mm wide, olive-green to brown, creeping to pendent. Frullania-type branches common, long and vegetative. Stems 0,2-0,3 mm in diam., in cross section with 20-25 epidermal cells surrounding 50-70 smaller medullary cells; ventral merophyte 6-8 cell rows wide. Leaves oblong to ligulate, 2-2.5 × 0.9-1.3 mm, 2-2.5 × longer than wide, apex broadly rounded, denticulate by 4-10 teeth, each tooth 1-3 cells long; median cells 30-45 µm in diam.; oil bodies not observed. Lobules globose, very small, 1/10× leaf length. Underleaves imbricate, elongate to broadly ovate to reniform, (3-)5-10x stem width, bases long decurrent. Androecia: on short or long branches, occasionally on innovations, bracts in 4-25 series. Gynoecia on a very short branch, with or without one short, vegetative or male innovation, bracts and bracteoles as in the genus. Perianths flat, oblong, narrowed to base, 1.2-1.8 × 0.6-0.7 mm, ca. 2-2.5× longer than wide, lateral keels finely ciliate in the upper half, cilia 5-35 cells long, uniseriate from a two cells wide base, ventral perianth surface smooth. Sporophyte not observed.
Conservation. Because of its restricted occurrence in undisturbed Choco rain forests and its very limited range, Symbiezidium dentatum is considered a threatened species (Gradstein, 1992c).Symbiezidium dentatum resembles S. transversale var. transversale by its smooth perianth sur-
faces, but is readily recognized by its denticulate leaf apices. As the difference between the two taxa is based on only one morphological character (plus geography), Gradstein and van Beek (1985) treated Symbiezidium dentatum as a subspecies of S. transversale. In this treatment, however, I have decided to accept S. dentatum as a good species, as it is the only neotropical taxon of Symbiezidium which can always be identified when sterile.Symbiezidium dentatum is usually fertile and sex distribution is variable like in the other species of the genus. The majority of the species studied were dioicous and female, one was purely male and one was autoicous. The dioicous male plant had long male spikes whereas in the autoicous plant they were quite small and occurred on short, specialized branches or on short innovations.
Herzog, Feddes Repert. Sp. Nov. 57: 173, Fig. 10f-l. 1955.
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