5IcS NAIAI'ACE^'E 



short-Stalked spike ; carpels coniin-essed,; keeled, with a straight 

 beak— Ditches ; frequent— Fl. July, Au^'ust. rerennial. 



2 2. P. Friesii. — SUm ihread-like, compressed; leaves often in 

 tufts, linear, 1—3 in, 5-— 7-nerved ; stipules smah, acute; flowers 

 few, minute, in an interrupted spike on a slender, compressed 

 stalk ; carpels small, swollen, bluntly keeled, with short, stout 

 beak. — Ponds and ditches ; local. — Fl. J-uly, August. Perennial. 



23. P. pusillus (Small Pond-weed). — A tangled mass of thread- 

 like stems ; and dull, olive-green, narrowly-linear, i — 3-nerved, 

 acute leaves : with numerous, small, loose, long-stalked spikes of 

 brownish floivers, which are either submersed, or rise partially 

 above the sinfa' e of the water. — Ponds and lakes ; common. — 

 Fl. June— August. Perennial. 



24. P. S/iirrnckii, a very slender, delicate, and elegant form, 

 closely allied to the preceding, with bright green, pellucid, 3 — 5- 

 nerved, obtuse leaves 2 — 3 in. long ; flowers in a very small spike 

 on a \'ery slender stalk ; and carpels^ very small and shortly 

 beaked. Occurs only in Forfar and Perth. 



25. P. trichoides (Hair-like Pond-weed). — Stem thread-like, with 

 numerous spreading dichotomous branches ; leaves bristle-like, 

 spreading, stiff, acute, i-veined, dark green, 1 — 2 in. long, with 

 slender, acute stipules ; flowers 3 — 6, very minute, on a slender 

 stalk ; carpels i in each flower, compressed, with a short beak. — 

 Ponds ; rare. — Fl August — October. Perennial. 



**** Leaves all sliiular, submerged, linear, with flat margins and 

 stipules united into tr sheath 



26. P. pectindtus (Fennel-leaved Porrd-weed). — Forming dense 

 tangled masses of thread-like stems with alternate branches ; 

 leaves 3 — 8 in. long, upper i -nerved, of 2 hollow tubes, lower flat, 

 3-n.jrved ; fl,o?e>ers few, in interrupted spikes on long, slender 

 stalks ; carpels large, swollen, slightly keeled, with short beaks.— 

 .Streams ; common. — Fl. June— -August.' Perennial. 



27. P. interriiptus, a closely allied form, with flat, i — 5-nerved 

 leaves and obscurely keeled carpels, is less common. Often in 

 brackish waters. 



28. P. fiJiformis {SlendevAciWcd Pond-weed). — S/f"; thread-like, 

 witli short brani'hes below ; leaves hair-like, i-nerved, channelled : 

 flowers in dense, separate whorls ; carpels small, wiih verv slight 

 keels and beaks. — Lakes ; local. — H.» June — September. Pe- 

 rennial. 



4. Rl'ippia (Tassel Pond-weed). — Slender, aquatic heibs with 

 thread-like, sheathing leaves and an umbellate group of minute, 



