BFNA Title: Pallaviciniaceae
XX. PALLAVICINIACEAE Migula
Plants terrestrial, bright green. Thallus unlobed, unistratose except for a sharply well-defined, cordlike midrib, branching dichotomous and latero-ventral, with a well-defined central strand of narrow conducting cells, underside without scales, without Nostoc colonies. Specialized asexual reproduction absent. Sexual condition dioecious, gametangia dorsal on main thallus segments, antheridia subtended by small unistratose scales, archegonia clustered, each cluster surrounded by a ring of partially fused scales forming an involucre. Sporophyte protected by a long, cylindrical pseudoperianth surrounding an enlarged calyptra. Capsule cylindric, 2(--4)-valved, without fixed elaters. Spores unicellular when shed, their walls rather thin and delicate.
Genera 8 (1 in the flora): North America, Central America, South America, Europe, se Asia, Africa.
Gray Nat. Arr.
Brit. Pl. 1: 775. 1821* [Probably for Lazarus Opizio Pallavicini,
fl. 1719--1785, botanist and archbishop of
Plants 15--60 mm x 2--8 mm, translucent-green to deep green, without other pigments, with only old portion of thalli becoming brownish green or decolorate. Thallus branching latero-ventral, rarely furcate, thallus flattened, margin plane or lightly undulate, with well-defined biconvex costa, mostly with clearly visible (whitish or yellowish brownish) single median vascular strand; shoot apices ventrally with 2--3--celled slime papillae. Rhizoids brownish, distributed along ventral surface of costa. Thallus margin entire (except for mostly ephemeral 1(--3)-celled teeth or slime papillae) [dentate]. Thallus lamina 1 cell in thickness, laminar cells thin-walled, polygonal; along margin dentate-ciliate to virtually entire. Asexual reproduction absent. Sexual condition dioicous. Androecia dorsal; antheridia in one row on each side of midrib [irregularly scattered over midrib], each subtended by a laciniate-dentate scale. Gynoecia solitary on dorsal side of costa, outer involucre of complete ring of laciniform scales, free or united proximally; capsule surrounded by a tubular pseudoperianth. Seta 17--24 mm. Capsule wall 2-stratose. Spores 17--24 \um, areolate to papillose. Elaters ca. 150--350 x 7--9 \um, 2(--3)-spiral.
ca. 30 (1 in the flora): North America, Central America, South America,
SELECTED REFERENCE Doyle, W. T. and R. E. Stotler. 2006 Contribution toward a bryoflora of California III. Keys and Annotated species Catalogue for Liverworts and Hornworts. Madroño. 53: 89--197.
1. Pallavicinia lyellii (Hooker) Gray,
Plants 15--50 x 2--6 mm. Thallus with lightly undulate margin, with clearly visible (whitish or yellowish brownish) single median vascular strand. Thallus margin mostly entire except for regularly spaced ephemeral 1(--3)-celled teeth or slime papillae (quickly disintegrating in herbarium or in old portions of thallus). Thallus lamina with cells thin-walled, 35--100 x 24--48 \um, cells slightly elongated along margin. Oil-bodies small and numerous, in middle part of lamina 30--65 per cell, spherical to ellipsoidal, fusiform, botryoidal to granulate, small 2--6 x 2--4 \um to larger 8--11 x 2--5 \um. Androecia with antheridia and scales in one row on each side of midrib; antheridial body spherical to shortly ellipsoidal. Gynoecia with outer involucre 1.5--2 \um high in maturity, consisting of ciliate-laciniate segments; inner involucre (pseudoperianth) tubular, 5--8 mm high, ciliate-laciniate at mouth. Seta 17--24 mm. Spores 17--24 \um, areolate. Elaters 2--3-spiral.
Wet and shady places along banks of ponds, stream, lakes, or in swamps associated with flowing water, only in acidic habitats; low to moderate elevations; N.B., Nfld. and Labr. (Nfld.), N.S., Ont.; Ala., Ark., Calif., Conn., D.C., Fla., Ga., Ill., Ind., Ky., La., Maine, Md., Mass., Mich., Miss., Mo., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., S.C., Tenn., Tex., Vt., Va., W.Va.; Central America: South America; Eurasia: Africa; Pacific Islands; Australia.