THE FLORA OF THE NORTHERN TERRITORY. 21 



APONOGETONACEiE. 



1. APONOGETON, Thunb. 



Bulb-shaped rootstock covered with filamentous remains of leaf-sheaths, 

 and emitting roots from the base. Leaves under 6 in. long. Fruit carpels 

 tapering into a short recurved style. — 2. A. monostachyus. 



Bulb-shaped rootstock without filaments, emitting fibrous roots from the 

 apex. Leaves above 6 in. long. Fruit carpels obtuse with the rudimentary 

 style, almost lateral. — 1. A. elongatus. 



1. A. dongattis, F. v. M. — Roper and Van Alphen Rivers, F. v. Mueller. 



2. A. monostachyus, Linn. — Gilbert River, Gulliver. 



JUNCAGINACEffi. 



1. TRIGLOCHIN, Linn. 

 Arrow-grass. 



1. T. procera, R.Br. — ^Islands of the Gulf of Carpentaria, R. Brown. 



ALISMACE.X. 



1. ALISMA, Linn. 



Water Plantain. 



Carpels, about 3 fines long, hard, often muricate. — 1. A. acanthocarpum. 

 Carpels under 2 lines long, smooth or tuberculate, the pericarp not very 

 hard. — 2. A. ofigococcum. 



1. A. acanthocarpum, F. v. M. — Lower Victoria River, F. v. Mueller; 

 Gulf of Carpentaria, Gulfiver. 



2. A. oligococcum, F. v. M. — Upper Victoria River, F. v. Mueller ; Port 

 Darwin, Schultz. 



BUTOMACEa:. 



1. TRENAGOCHARIS, Hochst. 



1. T. cordofana, Hochst. — (Butomopsis lanceolata Kunth.) Lagoons on 

 Gilbert River, Armit. 



HYDROCHARITACEiE. 



Tufts of radical leaves and scapes fixed to the bottom of the water. 



Leaves with a broad lamina. Flowers hermaphrodite, soUtary. 



Ovary partially 6-celled. — 4. Ottefia. 

 Leaves elongated without any lamina. Flowers unisexual. 



Male flowers several in a spathe, exserted. Perianth of 6 



segments. — 3. Blyxa. 

 Male flowers numerous, crowded in a head shorter than 

 the spathe. Perianth of 3 segments. — 2. VaUisneria. 



Leaves small, verticellate along the floating stems. Spathes sessile, both 

 males and females 1- flowered. — 1. HydriUa. 



1. HYDRILLA, Rich. 



1. H. verticillata, Casp.^ — Gilbert and Roper Rivers, F. v. M.. A trouble- 

 some water -weed, blocking watercourses.. 



B2 



