Oxystegus spiralis (Grout) H. A. Crum & L. E. Anderson; O. tenuirostris var. stenocarpus (Thériot) R. H. Zander

Stem rounded-pentagonal in section. Leaves flattened, short-lanceolate to lanceolate, distal margins plane, entire, not bordered; apex acute, plane or keeled; basal cells differentiated across leaf base as a U or V, commonly running up margins, not distinctly enlarged submarginally; distal laminal cells pluripapillose with low papillae; mucro conic, of 3-6 cells. Sexual condition autoicous. Peristome bluntly lanceolate.

Capsules mature fall. Rotten wood; Ont.; Mich., Minn., Wis.; Mexico; Asia.

R. H. Zander (1982, 1994d) treated Trichostomum spirale as a variety of T. tenuirostre (as Oxystegus tenuirostris), but the autoicous inflorescence seems significant in that differences in sexuality at the level of dioicy and monoicy are commonly found at the species level in Pottiaceae; also, the plants are slightly smaller in size and the distal medial laminal cells seem smaller (8-10 µm wide). H. A. Crum and L. E. Anderson (1980-1983) provided a summary of the problems associated with T. spirale; they noted that the spiral ornamentation of the peristome of this taxon is usually basal on the peristome teeth which may be papillose distally (as in T. tenuirostre) or completely smooth, while Zander (1982) found that peristomes of the types of T. spirale and its Mexican synonym Weisiopsis stenocarpum Thériot are within the range of variation of T. tenuirostre, which has variably smooth, low-spiculose, or spirally spiculose or ridged peristome teeth.