CL. IV.] TETRANDRIA TETRA0YNIA. 107 



Nearly as large as the preceding, the largest British species. Pe- 

 rennial : flowers in July : grows in pools and lakes in Scotland: rare. 

 Berwickshire; Moss of Litie, Nairnshire; Lochleven. Brit. Ft. 4th ed. 

 p. 70. 270. 



8. P. lanceoldtus. Lance-shaped Pond-weed. Leaves lance-shaped, 

 membranous, tapering at the base, sessile ; spikes dense, few-flowered. 



Leaves marked with chain-like reticulations near the ribs : spike 



small, short. Perennial: flowers in July and August: grows in pools 

 and slow streams : rare. Eng. Bet. vol. xxviii. pi. 1985. Eng. Ft. vol. 

 i.p. 233. 271. 



9. P. crlspus. Curled Pond-weed. Leaves lance-shaped, three-nerved, 

 waved, serrate, alternate, the upper opposite. Leaves sessile, bright- 

 green : flowers yellowish-green, in short, loose spikes. Perennial : flowers 

 in June and July: grows in ditches, pools, and rivulets: common. 

 Eng. Bot. vol. xv. pi. 1012. Eng. Fl. vol. i. p. 233. 272. 



10. P. gramin'eus. Grassy Pond-weed. Leaves linear, tapering to- 

 wards the base, alternate, sessile ; stem round, forked ; flower-stalks 



little longer than the spikes. Leaves bright-green, grassy-looking : 



spikes egg-shaped, dense. Perennial : flowers in July : grows in ditches 

 and streams: rare. Eng. Bot. vol. xxxii. pi. 2253. Eng. Fl. vol. i. 

 p. 235. 273. 



11. P.pusiClus. Small Pond-weed. Leaves linear, three-ribbed, op- 

 posite and alternate, spreading at the base ; stem round ; flower-stalks 



many times longer than the spikes. Leaves very narrow, pointed, much 



expanded at the base : spikes nearly globular. Perennial : flowers in 

 July : grows in ponds, ditches, and slow streams : not uncommon. Eng. 

 Bot. vol. iii. pi. 215. Eng. Fl. vol. i. p. 236. A variety with broader 

 leaves and interrupted spike is the P. compressus, Flat-stalked Pond-weed. 

 Eng. Bet. vol. vi. pi. 418. Eag. Fl. vol. i. p. 234. 274. 



12. P. pectinatus. Fennel-leaved Pond-weed. Leaves bristle-shaped, 



one-ribbed, parallel, closely set in two rows ; spikes interrupted. 



Leaves alternate, bright-green : spikes few, with interruptions. Perennial : 

 flowers in July : grows in ditches, pools, and rivers : rare. Eng. Bot. 

 vol. v. pi. 323. Eng. Fl. vol. i. p. 237. 275. 



13. P. acutifolius. Sharp-leaved Pond-weed. Leaves linear, taper- 

 pointed, with three principal and numerous close parallel intermediate 

 nerves, occupying the whole surface : spikes oval, compact, about 

 equal in length with the short panicle. Perennial : flowers in July. 

 Found by Mr. Borrer, in marsh-ditches at Amberley, Henfield, and 

 Lewes, Sussex. Eng. Bot. Suppl. pi. 2609. Brit. Fl. 4th ed. p. 69. 276. 



14. P. zoster afolius. Graw-wrack-like Pond-weed. Leaves broadly 

 linear, acute, with three principal and numerous close parallel interme- 

 diate nerves, occupying the whole surface : spikes cylindrical, upon long 

 peduncles. Perennial: flowers in July : grows in ditches: rare. Rivulet 

 at Hovingham, Yorkshire; Lakes of Rescobie and Forfar. Eng. Bot. 

 Suppl. pi. 2685. P. cuspidatus. Eng. Fl. vol. I p. 234. 277. 



18. RU'PPIA. TASSEL-GRASS. 



Calyx none. Corolla none. Anthers four, sessile, equal' 

 roundish. Germens four, egg-shaped, close together. Styles none? 



