Citation: Forster & Forster f., Char. Gen. Pl. 26 (1776).

Derivation: After Dr Henry Gahn, a Swedish botanist and friend of Linnaeus.

Synonymy: Not Applicable

Common name: None

Description:
Perennials, with short woody rhizomes, often forming large tussocks, often branching at the base, short or tall; stems leafy throughout; leaves terete and furrowed along the inside or with involute margins so as to appear terete, always ending in a long subulate point; bracts similar to the leaves, the upper ones gradually shorter.

Spikelets paniculate, rarely almost spicate, blackish or very dark-brown in most species, with 1 bisexual flower and usually 1 male flower below it; glumes spirally imbricate, 3 to many outer ones empty, the flowering glumes almost always thinner and smaller than the others; no hypogynous bristles; stamens 3-6, the filaments often lengthening and persistent so that the nut remains suspended by them after it has fallen from the spikelet; style slender, not thickened at the base, deciduous, 3-branched or 4- or 5-branched due to 1 or 2 of the branches being 2-fid.

Nut usually ovoid to obovoid, obscurely or not at all 3-angled, usually shining.

Distribution:  About 30 species from Asia to Australia and the Pacific Islands.

Biology: No text

Key to Species:

1. Spikelets c. 4 in a simple spike-like inflorescence almost hidden by the leaves; dwarf plant	G. hystrix 5.
1. Spikelets numerous, paniculate
2. Mature nut adhering to the persistent staminal filaments; culms stout, more than 120cm high; glumes broadish, never long-acuminate; nut 2-4 mm long, shining.
3. Glumes more than 12, all more or less obtuse, the lowermost without awns	G. clarkei 2.
3. Glumes up to 10, mostly acute, the lowermost with exserted awn-like midribs	G. sieberiana 8.
2. Mature nut never held by the staminal filaments; culms usually less than 120 cm high; at least the outer glumes long-acuminate; nut c. 2 mm long or less, often dull or greyish.
4. Spikelets 1-flowered, densely clustered.
5. Lower leaf-like bracts of inflorescence coarsely scabrid, green or slightly tinted below; nut 2-2.5 mm long	G. trifida 9.
5. Lower leaf-like bracts of inflorescence smooth or minutely scabrid, conspicuously reddish-purple below; nut c. 5 mm long	G. filum 4.
4. Spikelets 2-flowered, more or less loosely arranged.
6. Panicle ovate, broad	G. radula 7.
6. Panicle linear or linear-lanceolate.
7. Leaves very scabrous at least in the upper half	G. deusta 3.
7. Leaves smooth.
8. Leaves with straight tips; basal leaf sheaths bearded at the mouth	G. lanigera 6.
8. Leaves with curved or coiled filiform tips; leaf sheaths all glabrous	G. ancistrophylla 1.

Author: Not yet available