Monographs Details: Acromastigum
Authority: Fulford, Margaret H. 1966. Manual of the leafy Hepaticae of Latin America--Part II. Mem. New York Bot. Gard. 11: 173-276.
Description:Species Description - Plants of small to medium size, prostrate to ascending, loosely branched in apparent dichotomies; vegetative branches lateral, leafy, of the Frullania type, with the dorsal ovate half-leaf subtending the stem and branch, or ventral flagelliform, of the Acromastigum type, with the ovate half-underleaf adjacent to the base of the branch on either side: sexual branches very short, ventral intercalary, in the axils of the underleaves (rarely on flagelliform branches) ; stem in transverse section with one layer of large cortical cells with thicker walls surrounding the medulla of m a n y smaller cells; leafy branches with a unistratose cortex of only seven large cells with thick walls, surrounding the medulla of many smaller cells. Rhizoids colorless, with branched tips, from the bases of the underleaves, the scales of the flagelliform branches, and the base of the female inflorescence. Line of leaf insertion transverse to oblique, the leaves incubous. Leaves rectangular to ovate in outline, undivided, bidentate or bifid, with the segments unequal or rarely equal, in some species vittate, the cell-walls thickened. Underleaves transversely inserted, undivided, bifid or trifid. Plants dioicous; male branches short, catkin-like, often curved, the bracts smaller than the leaves, usually bidentate, concave, of delicate texture, monandrous, the bracteoles similar, smaller, less concave, without antheridia; female branches without innovations, the bracts and bracteoles different from the leaves, in three or four series, ovate, with two main divisions, variously laciniate, lobate, or dentate, the innermost series the largest. Perianth unistratose (usually), terete below, trigonous above, the keels broad, with the third keel ventral, the mouth more or less plicate, 3-lobed, with marginal laciniae and cilia. Shoot/sporophyte relationship a shootcalyptra. Capsule oval, the wall of four layers of cells, the outermost layer with brown knot-like thickenings most numerous on the longitudinal radial walls, the innermost layer with crowded brown semi-annular thickenings as bands on the inner tangential walls; elaters bispiral; spores brown, minutely verruculose. Sporophyte stalk of eight longitudinal rows of large cells surrounding many rows of smaller cells.
The species belong to the section Inaequilaterae, in which the cortical cells of the leafy branches are in seven longitudinal rows, the leaves are bifid, and the underleaves trifid.
Mastigobryum ß p.p., G. L. & N. Syn. Hep. 218. 1845.
Mastigobryum [sect.] III. Inaequilaiera Stephani, Hedwigia 25: 245. 1886.
Bazzania sec. III. Inaequilaterae Schiffner in Engler & Prantl, Nat. Pflanzenfam. 1: 101. 1893.
Mastigobryum [subg. Inaequilatera] Stephani, Bull. Herb. Boissier II. 8: 404. 1900
Type species: Mastigobryum (?) integrifolium Austin.