Citation: Kuo & Cambridge, Aquatic Bot. 20:277 (1984).

Synonymy: P. aft. ostenfeldii E. Robertson in H.B.S. Womersley, Marine benthic fl. southern Aust. 85, figs 21C & 22H, I, K-M (1984), partly. , Posidonia aff. ostenfeldii Hartog, Posidonia ostenfedlii, Posidonia ostenfeldii

Common name: None

Description:
Robust rhizomatous perennial marine herb; rhizomes more or less oval in cross section, 2-4 mm thick, internodes variable in length, frequently an elongate internode 1.5-6 cm long alternating with a series of short internodes 0.5-2.5 mm long; roots arising irregularly, 1 or 2 per node, frequently pale-brown to reddish-brown in colour, 1-4 mm diam., with a few fine laterals, becoming hollow with age; leaves 2 or 3 per shoot: sheath 5-20 cm long, with margins overlapping for almost their entire length; ligule c. 1 mm long; auricles 2-2.5 mm long, 2-3 mm wide, mostly dark-brown; the abscission line between the blade and the sheath usually conspicuous; after the fall of the blade the sheath disintegrates to a greater or lesser extent into numerous pale-yellow to grey hair-like fibres; blade frequently to 1 m long, 1.5-2 mm broad, biconvex in cross section; longitudinal vascular bundles 5-7 (clearly seen in cross section of the blade, but inconspicuous in surface view, except near the apex), epidermal cells in surface view appearing oval, apex somewhat flattened, usually spathulate with slightly recurved margins, occasionally rounded.

Inflorescence on a flattened peduncle 30-40 cm long, usually much shorter than the foliage leaves, subtending bracts 2, unequal; spikes 6-10, each terminating in a spur; flowers 3 or 4 per spike (seen only in bud).

Seed 8-10 mm long (seen only attached to young seedlings).

Published illustration: Robertson in Womersley (1984) Marine benthic flora southern Aust., figs 21C, 22H, 1, K-M.

Distribution:  From 5-27 m deep, mostly in areas of strong wave action. P. denhartogii occurs as small clumps mixed with other seagrasses and not in pure stands. S.Aust.: NU, EP, YP, SL, SE.   W.Aust. Conservation status: native Flowering time: Sept. (buds only seen).

SA Distribution Map based on current data relating to specimens held in the State Herbarium of South Australia

Biology: No text

Author: Not yet available