Thelepogon elegans Roth

Global description

Thelepogon elegans is a hispid grass with lanceolate leaves broadened at the base and embracing. Stilt roots develop from the nodes of the base. The ligule is membranous. The inflorescence is composed of several whorls of linear racemes with fragile rachis. Each item includes a sessile, fertile spikelet, biflore and a pedicel without spikelet. The glumes are hard and leathery, strongly rough and denticulate. The upper lemma is bifurcated and surmounted by a long twisted and knotted awn.

Seedling

The seed is a determinant since it remains attached to the seedling for a long time by an axis 1 to 2 cm long.

First leaves

The first leaves are lanceolate oval, with a rolled prefoliation. They are 2 to 5 cm long and 1 to 2 cm wide. The base of the limb is auriculate, partially embracing the culm. The sheath is pubescent, even hispid, covered with tubercular hairs. The ligule is membranous. The limb is erect obliquely. It is strongly ciliated on the margin and both sides are dotted with tubercle hair.

General habit

Thelepogon elegans is an erect plant developing in solitary axis or in large tuft with several erect axes. The culm is little or not branched. The plant is 50 to 150 cm high.

Underground system

The roots are fasciculate. Stilt roots develop from the lower nodes of the plant.

Culm

The culm is cylindrical and dotted with stiff hairs. It is very robust at the base, with a diameter of 4 to 7 mm. The nodes are glabrous and dark in color.

Leaf

The leaves are alternate. The sheath is cylindrical and little faired. It is pubescent to hispid, covered with hairs tuberculate at the base. The margin is ciliated. The ligule is membranous, 1 mm high, barely ciliated at the top. The blade is lanceolate, at the top in broad corner and a base broadly auriculate and partially surrounding the culm. It is obliquely erect and flat, 4 to 20 cm long and 1 to 4 cm wide. The central rib forms a very marked white gutter. The margin is strongly ciliated. Both sides are more or less strewn with stiff, tubercular hairs.

Inflorescence

The inflorescence is composed of 2 to 20 linear racemes arranged in several whorls along a main axis 2 to 5 cm long. The lower whorl is formed of the largest number of racemes. These are 4 to 15 cm long, with fragile rachis having finely scabrous internodes, flattened at the base and then widened into a cup at the top. Each article of the raceme carries a sessile spikelet and a claviform pedicel, flat and scabrous, longer than the spikelet sessile but not bearing a spikelet. The base of the sessile spikelet and the pedicel is surrounded by a crown of short bristles.

Spikelet

The sessile spikelets are provided at the base of a horny patella that articulates on the previous article. This spikelet is 4 to 7 mm long and compressed dorsally. It comprises two flowers, the lower one being male and the upper one fertile. The lower glume is oval, convex, with acuminate apex. It is thick and leathery, strongly coarse and denticulate longitudinally. The upper glume is narrower and rougher. Lemmas and paleas are translucent chataceous. The lemma of the upper flower is bifid, surmounted by a twisted and knotted awn 1 to 2.5 cm long.

Grain

The grain is obovoid elongated, 3 to 4 mm long and 1.5 mm wide. It is surmounted by two short points corresponding to the base of the styles. It remains included in the spikelet, itself remaining attached to the article of the raceme that disarticulates at maturity.

https://www.gbif.org/fr/species/4126446