Monographs Details: Plectonema spirale
Authority: Gardner, Nathaniel L. 1927. New Myxophyceae from Porto Rico. Mem. New York Bot. Gard. 7: 1-144. pl. 1-23.
Description:Species Description - Filaments attached at one end, erect and parallel, 125-150 µ long, variable in width at different periods of growth and in different parts of the filaments, when young tapering gradually towards the apices, later bulging in tjie middle and toward the base on account of the coiling and contortion of the trichomes, increasing the length of the diameter 2-3 times; trichomes 3-4 µ diam., tapering at the apices; cells quadrate to mostly one-half the diameter, long, pale aeruginous, homogeneous; cross-walls distinct below, obscure above; sheath very thin, about 0.5 µ diam., hyaline; branching simple or geminate.
Distribution and Ecology - Growing on an old pump, forming a dense velvety stratum, with other Myxophyceae, Maricao, no. 1276 b, type.
Discussion:It was somewhat troublesome to place this species of Plectonema. The attached and erect habit is unusual in the small species, as are also the tapering filaments, although Gomont's description provides for that character. The plants are firmly attached at their bases by thin gelatinous walls, stand very closely together, and are chiefly parallel. In the lower half or quarter of the filament the trichome seems to begin to divide actively, and, not being able to push the upper part forward, begins to form a more or less regular to distorted spiral, at the same time the sheath enlarges instead of rupturing. Nearly the whole lower part of the trichome becomes thus transformed. The trichome also enlarges somewhat in diameter in the coiled part. Branching was observed to take place usually in the upper part of the coil or just above. Eventually the coiled portion of the trichome breaks into small segments, which become more or less spherical. Whether this is a natural process of decay or represents gonidia could not be ascertained. The sheath finally dissolves, but no evidence was at hand to indicate that the fragments of the trichome germinated to form new filaments. The presence of these bodies in the lower part of the erect tapering filaments suggests the genus Leptocliaete. The gonidia in that genus, however, begin to form at the basal cells first, and no coiling of the filaments is known to occur. Again, Leptocliaete does not branch. It seems best to place the specimen in the genus Plectonema as a new species, awaiting more knowledge of its life history. In company with this species is an undescribed species ofCalotlirix, and a very slender filamentous species of another member of the Myxophyceae. The latter I forbear to place. The filaments are attached at one end and stand erect and parallel. They are about 1 µ in diameter. Possibly they represent the earlier stage of growth of Plectonema spirale.