Home Pottiaceae
Home Page
Generic List
Name Search
Rhexophyllum Herzog Search in The Plant ListSearch in Index Nominum Genericorum (ING)Search in NYBG Virtual HerbariumSearch in JSTOR Plant ScienceSearch in SEINetSearch in African Plants Database at Geneva Botanical GardenAfrican Plants, Senckenberg Photo GallerySearch in Flora do Brasil 2020Search in Reflora - Virtual HerbariumSearch in Living Collections Decrease font Increase font Restore font
 

Published In: Bibliotheca Botanica 87: 38. 1916. (Biblioth. Bot.) Name publication detailView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 11/3/2011)
Acceptance : Accepted
Project data     (Last Modified On 11/3/2011)
Nomenclature:

18. RHEXOPHYLLUM                Plate 22.

Rhexophyllum Herz., Biblioth. Bot. 87: 38, 1916. Type: Rhexophyllum laciniatum Herz.

Neocardotia Thér. & Bartr. in Thér., Smiths. Misc. Coll. 85(4): 12, 1931. Type: Neocardotia subnigra (Mitt.) Thér. & Bartr. in Thér.

Habitat:

            Known from southwestern U.S.A., Mexico, and the Andes of Bolivia and Peru, where it is found on soil, rock and trees in montane situations.

Notes:

            The genus is readily recognized by the plant coloration: blackish green above and reddish brown below; leaves lanceolate with an oblong base (Pl. 22, f. 3–4), squarrose when moist, upper margins sharply and deeply dentate (Pl. 22, f. 5); upper laminal cells bistratose in patches across the leaf (best seen in section, Pl. 22, f. 7); dorsally serrulate costa; and eperistomate capsule. It is similar to Leptodontium in the leaf shape and stance, elongate cells on the ventral costal surface (Pl. 22, f. 5), reniform costal section, and much differentiated perichaetial leaves, but differs mainly in the red color reaction with KOH, bistratose laminae and a hydroid strand (at least occasionally) in the costa.

            Thériot and Bartram (Thériot 1931) felt that the genus was related to Leptodontium because of the habit of the plant, the dentate cauline leaves, and the strongly sheathing perichaetial leaves. Hilpert (1933) placed Rhexophyllum near Leptodontium and Triquetrella, considering the eperistomate condition to be a reduction from a leptodontioid peristome structure. He suggested that the small leaf cell size, the dense papillae, and the patchy bistratose upper lamina are xeromorphic adaptations. Cladistic analysis, however, places it with the Bryoerythrophylleae.

Literature: Zander (1976).
Number of accepted species: 1
Species Examined: R. subnigrum (BUF, FH, JE, MEXU, NY, TENN, US).

 

Export To PDF Export To Word

            Plants forming a turf, green to blackish green above, reddish brown below. Stems often branching, ca. 2–4 cm in length, transverse section rounded-pentagonal, central strand present, sclerodermis strong, hyalodermis present; axillary hairs of ca. 10 cells, all hyaline or basal 1–3 cells brownish; rhizoids often present, reddish brown. Leaves conduplicate, twisted, appressed-incurved when dry, widely spreading to squarrose when moist, lanceolate, mostly 2.0–3.0 mm in length, keeled above, margins recurved in lower 1/4–1/2, sharply dentate to erose-dentate in upper 1/4–1/2; apex acute, fragile, often absent; base rectangular, somewhat sheathing, basal margins short-decurrent; costa excurrent as a sharp, smooth mucro, superficial cells elongate ventrally, 3–4 across costa at midleaf, short-rectangular to quadrate above, serrulate dorsally by projecting papillae at distal ends of cells, costal transverse section reniform, two stereid bands present, the dorsal crescent-shaped, epidermis absent or weakly differentiated ventrally, present dorsally as cells with enlarged lumens, guide cells 2–4 in 1 layer, hydroid strand sometimes present; upper laminal cells subquadrate to rounded-hexagonal, mostly 7–10 µm in width, 1:1, walls thin, superficially bulging, bistratose in patches across leaf; papillae crowded, multifid or 1–4 irregular plates per lumen, solid or hollow; basal cells differentiated across leaf base, rectangular, 8–15 µm in width 3–5:1, walls thin. Dioicous. Perichaetia terminal, inner leaves highly differentiated, long-lanceolate, 4–6 mm in length, convolute-sheathing, lower cells long-rhomboidal in lower 1/2–7/8. Perigonia terminal, leaves little differentiated from the cauline. Seta ca. 1 cm in length, 1 per perichaetium, brown, twisted clockwise above; theca 2.5–3.5 mm in length, brown, ellipsoidal to cylindrical, exothecial cells short-rectangular, 1–3:1, stomates present at base of theca; annulus of ca. 2 rows of strongly vesiculose cells, deciduous in pieces; peristome absent, operculum short-conic to conic-rostrate, 0.5–1.0 mm in length, cells straight. Calyptra cucullate, smooth, ca. 3.0 mm in length. Spores 13–15 µm in diameter, weakly papillose, brown. Laminal KOH color reaction red.

 
 
© 2024 Missouri Botanical Garden - 4344 Shaw Boulevard - Saint Louis, Missouri 63110