ON THE TAXONOMIC POSITION OF STRUCKIA C. MÜLL.

抄録

  Taxa of Struckia C. Müll. are similar to members of the Plagiotheciaceae (e.g., some Plagiothecium species) in having rhizoids growing from the abaxial leaf nerve insertion, or from the lower nerve back or from other parts of the basal leaf back, in that the rhizoids are sometimes purplish, and sometimes granular-papillose. This combination of rhizoid character states does not occur outside the Plagiotheciaceae among the pleurocarpous mosses. Other features found in Struckia and in the Plagiotheciaceae, but which are relatively rare outside this family are easily detached branches and narrow angles between the stems and the branches. In the strongly specialised sporophyte of Struckia, the long-pored stomata indicate relatively few possible familial positions, including the Plagiotheciaceae. Based on these characters, Struckia is moved to the Plagiotheciaceae. Contrary to earlier observations an endostome was found in Struckia, consisting of a low basal membrane. Finally, it is suggested that two of the taxa belonging to Struckia should be treated at the species level rather than as subspecies. Struckia argentata (Mitt.) C. Müll. (including its var. enervis (Broth.) Tan, Buck & Ignatov) has ovate to broadly ovate stem leaves, denticulate upper leaf margins, narrow cells (7.5-14.0μm) in the middle of the stem leaves, strongly branched rhizoids, and is mostly found on stems of trees and shrubs. Struckia zerovii (Lazar.) Hedenäs, comb. nov. (S. argentata ssp. zerovii (Lazar.) Tan, Buck & Ignatov), has ovate to ovate-lanceolate stem leaves, entire leaf margins, wide cells (10.5-19.0μm) in the middle of the stem leaves, slightly branched rhizoids, and is found on rocks.