Flora of North America species comparison

leaves to 1.7 × 1 mm, occasionally longer; rarely hemiisophyllous;

hyaline cells non-ornamented, nonseptate.

leaves triangular-ovate, more than 1.2 mm, usually appressed;

apex acute to apiculate, hyaline cells rarely septate or porose, apical region often fibrillose.

long and tapering, leaves ± imbricate to spreading in shade forms.

mostly unranked to weakly 5-ranked, often conspicuously falcate, leaves greatly elongated at distal end.

broadly ovate, 2.2 × 1.3 mm, hyaline cells non-ornamented, convex surface with elliptic pores along the commissures, chlorophyllous cells isosceles-triangular to ovate-triangular in transverse section and just enclosed to just exposed on the convex surface;

end wall not thickened.

ovate-lanceolate to lanceolate, 1.6–5 mm, falcate toward branch tips, when dry often undulate and recurved, rarely weakly serrulate along the margins in submerged forms, leaves from middle of spreading branches with length to width ratio less than or equal to 1:0.28;

hyaline cells length to width ratio in apical convex surface region 8:1 or more, convex surface with 0–1 small round pores at apex, concave surface with faint round wall thinnings in cell apices and angles; chlorophyllous cells triangular to trapezoidal in transverse section, broadly exposed on the convex surface and exposed slightly on the concave surface.

dioicous.

dioicous.

with numerous pseudostomata.

24–33 µm, surface finely papillose to smooth, distal surface with distinct bifurcated Y-mark sculpture;

proximal laesura more than 0.6 spore radius.

29–38 µm; covered with large papillae on both surfaces, appearing pusticulate;

proximal laesura less than 0.5 spore radius.

fascicles with 2 spreading and 2 pendent branches.;

branch stems with hyaline cells non-ornamented;

no or weak funnel-like projections on the interior end walls, often with 1 large pore per cell on superficial cell walls.

fascicles with 2 spreading and 2–3 pendent branches.;

branch stems green, but often pinkish at the proximal ends, with cortex enlarged with conspicuous retort cells.