1708 CXLVIII. NAIADEiE. [Aponorjeton. 



membranous, about J line long. Stamens sbortly exceeding the perianth. 

 Fruiting carpels ovoid, tapering into a short recurved beak. Seeds 2 to 6, erect, 

 narrow-oblong, the outer membrane loose and almost hyaline, the inn^r more 

 opaque, darker coloured and closely appressed to the embryo. — Thunb. Nov. Gen. 

 Pi. 78, with a figure; Roxb. Corom. PI. t. 81 ; Andr. Bot. Eep. t. 406 ; Spathium 

 monostachyum, Edgew. in Calcutta Journ. iii. 588, t. 16, corrected to Ajionogetoit 

 monostadnjus in Hook. Lond. Journ. iii. 404, t. 17. 



Hab.: Gilbert River, Gulliver; Eockhampton, Thozet, O'Shanesy; Burdekin Elver, Herbert's 

 Creek and Gainsford, Boicman. The species is widely spread over tropical Asia. 



Eoots eaten raw or baked. — Both. 



2. A. elongatus (lengthened), F. r. M. in Herb. Hook.; Benth.' Tl.' Austr. 

 ■vii. 188. Tuberous iootstock formed below the uppermost fibrous roots. Leaves 

 mostly submerged, very tender, from 6in. to above 1ft. long, and f to l|in. broad, 

 contracted at the base or very rarely produced on one or both sides into a short 

 basal auricle, with 5, 7 or 9 longitudinal nerves. Spikes simple as in A. 

 monostachyiis but more slender and the flowers not so close. Perianth and 

 stainens as in that species. Carpels of the ovary very short with scarcely 

 prominent styles and in fruit they are ovoid-globtilar, 2 to 8 lines long, very 

 obtuse, with the very short remains of the style almost lateral. Seeds usually 3 

 or 4 in each carpel, narrow-oblong, the outer membrane not striate, the inner one 

 exceedingly delicate. Embryo with a narrow groove, the small plumula at the 

 base of the groove below the middle of the embryo. 

 Hab.: Brisbane Eiver, F. v. Mueller ; Maroochie Kiver, Bailey. 



3. POTAMOGETON, Linn. 



(From potcunos, a river; and i/eitoii, a neighbour.) 



Flowers hermaphrodite. Perianth-segments 4, scale-like, small, broad, con- 

 tracted at the base or almost stipitate. Stamens 4, inserted at the base of the 

 segments and falling oft' with them ; anthers sessile, broad, the cells opening 

 outwards in longitudinal slits. Carpels 4, distinct ; -styles short, terminal or the 

 oblique stigmas sessile ; ovules solitary in each carpel, laterally attached at or 

 above the middle. Fruit of 4 nutlets or fewer by abortion, somewhat drupaceous, 

 the exocarp membranous or slightly fleshy, the endocarp rather hard, crustaceous. 

 Seed much incurved or horse-shoe shaped, round a clavate or obovoid projection 

 of the endocarp ; testa membranous. Embryo the shape of the seed. — Aquatic 

 herbs with a perennial root-stock ; stems submerged and floating usually forked 

 and often rooting at the lower nodes. Leaves alternate or rarely opposite, wholly 

 submerged or with a lamina floating on the surface, dilated at the base into 

 membranous sheathing margins or more frequently the margins more or less 

 detached from and united within the petiole into sheathing stipules often very 

 deciduous. Flowers small, sessile in dense spikes or heads on axillary peduncles. 



The genus is dispersed in the fresh or sulsaline waters of the greater part of the globe. 



Section l.—I.eiircs all alternate and petiolale icitli floating lamina:, arthe loxver onessuhmerned. 

 Slipides connate nithin tlie 2'etiole. ■ ■■i. 



Nutlets ovoid, scarcely beaked . . \. P. nataiLS 



Nutlets with 3 prominent keels 2. P. iricarinatus 



Nutlets with projecting processes on the outer angles . 3. P. Tepneri 



Floating leaves f- to ^in. long. Nutlets distinctly beaked 4. p javauicus. 



Section 11.— Leaves allgulimer<jed, /sessile or nearly so, tliose under the piiduncles and brancliei 

 opposite, the others alternate. Stipules connate within the petiole, often very deciduous 



Leaves stem-clasping, ovate or almost orbicular, many-nerved 5. p. perfoliatas 



