•Potamogeton.] CXLVIII. NAIADE^B. 1709 



jLeaves naiTOw-oblorit^ or rarely linear, usually 3-nerved, very obtuse, ttje- 



margins often undulate-crisped , 6. P. crUpii^. 



-Leaves narrow-linear, obtuse or scarcely aeute, 1-nerved. Spikes Jin. long 



or more 7. P. ohtiisifalins. 



Section III. — Leaves all submerycd, «cs.s(7f <ir nearly so icilli sheathing margins lut no distinct 

 stipules. 

 Leaves narrow-linear, 1-nerved. Stems repeatedly dichotcmous .... 8. P. pectiiialiis. 



1. P. natans (floating), Linn.; Kitnth, F.nvm . iii. 127; Benth. Fl. Awtr. 

 vii. 170. Upper leaves or often the whole of them on long petioles, floating on 

 the surface of the water, of a thick opaque texture, ovate or oblong, 2 to 4in. long 

 ■by 1 to liin. broad, or rarely in small varieties about half that size, usually 

 rounded at the base, but sometimes cordate or tapering, marked by several (5 to 

 9 or rarely 11) longitudinal nerves with a few cross veins often branched or 

 slightly netted ; lower submerged leaves usually few or often wanting, rarely all 

 submerged thin and narrow but always tapering at the base into a stalk and 

 several-nerved. Stipules closely sheathing, connate, free from the petiole except 

 at the very base. Spike dense and cylindrical, often lin. long or more, on a stout 

 peduncle. Nuts ovoid, above 1 line long, slightly compressed, nearly straight, 

 with 1 or 3 dorsal ribs, obtuse or acute, quite entire or more or less denticulate or 

 muricate.— E. Br. Prod. 348 ; Hook. f. Fl. Tasm. ii. 41 ; F. v. M. Fragm. viii. 

 217; Eeichb. Ic. Fl. Germ. t. £0; P. Jicter^phyllus, Hook. f. Fl. Tasm. ii. 41, 

 ■and of some authors, but not the true plant of Schreber. 



Hab.: Eockhampton, O'Shanesy, Bowman. A ecmmon species of the southern still waters. 

 The species is one of the most conmion over the greater part of the area of the genus.'" " 



2. P. tricarinatus (3-keeled), F. r. Jl/. ined. in Herb. Kev ; A. Bonnet 

 ■in Journ. of Bot., June, 1887. 



The Queensland specimens referred to by Mr. Bennett were collected at Aramac some years 

 ago by Mr. C. W. De Burgh Birch, and -were placed by me at the time with P. natans, I only 

 noticed then that the plant had a more robust habit and larger leaves on shorter petioles ; the 



-nuts also were prominently 3-keeled, the middle one almost wing-like and more decidedly toothed 

 on its undulate edge. This species seems not to have been further dfescribed, and the specimens I 



■now have are not suitable for the purpose of diagnosing the species. 



3. P. Tepperi (after J. G. 0. Tepper), A. Bennett, Journ, of Bot., June, 1867. 

 ■Stems lengthening as in P. nutans. Submerged lower leaves 4in. long by ^in. 

 wide, the lamina tapering at either end ; upper leaves ovate-lanceolate ; floating 

 leaves from oval with subcordate bases- to ovate with tapering bases ; 21 to 

 23-\eined, Sin. long by 1-J-in. broad, coriaceous, on long letioles enlarged 

 gradually upwards. Spikes f to lin. long, dense in fruit. Fruit nearly.straight 

 on the inner face, rounded, with three angles on the outer face, half-obqvate, with 

 a short beak forming a continuation of the inner face, with projecting processes 

 irregularly distributed on the outer angles ; embryo with its upper part incurved 

 to half its depth. — A. Benn. l.c 



Hab.: Tooloomba Creek, Bailey. 



Mr. Bennett points out that this species is allied, to P. natans, Linn., and in European herbaria 

 rbas been mixed with specimens from Australia of P. tricarinatus and P. natans. 



4. P. javanicus (of Java), llassk. in Verh. Natuurl<. Ver. ■ A'frf. Ind. i. 

 Perhaps a variety of '.Z'. jmtafls, with which it is closely connected through the 

 small Tasmania!! variety of that species. Stems ahiiost filiform. Floati!ig 

 leaves -oblong-elliptical or lanceolate, f to 1-^in. long, acute at the base, few- 

 nerved. Stipules very thin. Submerged leaves few, linear. Spikes dense, 

 4 to 6 lines long. Nutlets smaller tlian in P. natans, more distinctly rostrate 

 and the ribs often but not always denticulate.' — P. tenuicauHs, F. v. M. Fragm. 

 i. 90, 244, viii. 217 ; Benth. Fl. Austr. vii. 171. 



• Hab.: Gulf of Carpentaria, F. v. Mueller ; Brisbane Eiver, Bailey ;■ Moreton Bay, Ltichhardt ; 

 Eockhampton, Powmaji, O'Shanesy- Rockingham Bay, DaZiac/iJ/ ; Mount Elliot, FHialan.; also 

 in Java, India, and tropical Africa. 



