A Key to the Tropical African species of Leptodontium

J.L De Sloover

Extracted from: Bull. Jard. Bot. Nat. Belg. 57:425-451 (1987)

Translated by C.R.Stevenson

1	Stem channelled towards the base. At stem apices the epidermal cells are inflated in cross section; lower down the stem they are collapsed, and this gives the stem its channelled appearance. Epidermal cells thin walled	3
1	Stem not channelled. Epidermal cell walls thickened	2

2	A short, slender plant, generally less than 3cm tall. Leaves ligulate / oblong / lanceolate, generally less than 3mm long	*L. flexifolium*
2	Robust plant; stem generally more than 3cm tall. Leaves lanceolate to ovoid-lanceolate, generally more than 3mm long	*L. viticulosoides*

3	Leaf margin often denticulate to near base, where it may be eroded (?). Leaf apex obtuse. Sheath often a quarter to a third of the total leaf length. Plant yellowish; stem long, little branched	*L. luteum*
3	Leaf margin denticulate only towards apex, rarely to the sheath, and never to near the base	4

4	Leaf lamina with sharply pointed, sometimes papillose, teeth on both surfaces. Leaves longitudinally wrinkled. Stem long,little branched. Endemic to Reunion	*L. longicaule subsp. stellatum*
4	Lamina unistratose throughout, ocasionally with some more or less protuberant papillose cells towards the apex	5

5	Basal cells of leaf, near nerve, hyaline, thin walled, forming a distinct zone	6
5	Basal cells not clearly hyaline; walls thin or thick, not forming a distinct zone	7

6	Leaves ligulate - lanceolate, with obtuse tip. Upper cells 14-19µm wide. Basal marginal cells narrow and elongate; thick walled. Nerve circa 130µm wide at leaf base. Leaves widely spaced, squarrose, with a well marked sheath	*L. latifolium*
6	Leaves lanceolate, tip acute. Upper leaf cells 11-15µm wide Marginal cells of leaf base hardly ever longer than internal cells. Walls scarcely thickened. Leaves approximate, squarrose, scarcely sheathed	*L. capituligerum*

7	Stem rigid, often short, forming yellowish brown dense tufts. Leaves curved in an arc, with a poorly differentiated sheath. Leaf apex made up of more elongated, non-papillose cells. A single row of lower marginal cells enlarged. Basal median cells forming a yellowish-orange band of variable shape	*L. pungens*
7	Stem soft and flexuous, often long, forming loose tufts. Green, yellowish-green or brownish. Leaves squarrose, with distinct sheaths. Apical cells of leaf papillose, scarcely differentiated. Several rows of marginal cells at leaf base more-or-less differentiated from internal cells. Basal medial cells not forming a yellowish-orange band	8

8	Stem moderately stiff, long, flexuous. Leaf sheath well marked, reaching at least one third of the total leaf length.. Marginal cells of sheath larger and thicker than those internally, forming a well marked band. Inrolled. Nerve, at top of sheath, semi-circular in cross section, with two or three rows of ventral stereids	*L. wallisii*
8	Stem generally soft, of variable length, non-flexuous. Leaf sheath moderately distinct, reaching at most one third total leaf length. Marginal cells of sheath scarcely differentiated, forming a poorly defined band. Recurved. Nerve in cross section at top of sheath, kidney shaped, with occasionally two rows of stereids	*L. longicaule var. longicaule*

TBG28/lepdt Issue 1 - 18.09.93