436 
95. POTAMOGETOXACE.B. 
2. VroLFFiA Horkel., e.r SMeid. 
1. W. arrhiza (Wimm.) : fronds ver]i small subglobidar 
flattish above cellular beneath, solitary, young frond separating 
immediately from the old one. ,S'//. E. B. 1398. R. vii. 14. 
IF. Michelii (Schleid.). — Frond like a grain of sand, sfibglobular 
at all ages, green. Offset from within the base of the old 
frond. — Fl. not seen in Europe. Ponds near London. A. E. 
Order XCV. POTAMOGETONACE.E. 
Fl. perfect or imperfect. Perianth inferior, 4-parted, or 0. 
Stam. free, 1, 2, or 4. Ovaries 4, distinct, each with 1 ovule 
and 1 sessile stigma. Fr. a drupe enclosing a hard nut, or a 
dry nut, not burstings i -seeded. Albumen 0. Embryo with a 
thin skin having a lateral cleft. 
1. PoTAiJOGETox. Fl. perfect. Perianth 4-parted. Anth. 
4, sessile, opposite to the divisions of the perianth. Ovaries 
4. Styles 0. Drupes 4, sessile. — Fl. sessile, spiked. 
2. PiUPPiA. Fl. perfect. Perianth 0. Stam. 2, the cells 
considerably separated : filaments very short, scalelike. 
Ovaries 4. Styles 0. Nuts 4, with long stalks. — Fl. 
about 2 together. 
3. Zannichellia. Fl. monoecious, axillary. Barren with 
1 stam., and no perianth. Fertile with a bellshaped 
perianth, persistent style, and peltate stigma. Nuts 2 — 5 
or more, more or less stalked. 
1. PoTAMOGE TON ' Linn. Pondweed. 
* L. alternate, floral I. floating and sometimes opposite ; 
stipules free. 
1. r. n/'ttans (L.) ; upper 1. stalked coriaceous floating ovate 
or elliptic folded at the ha.se, petiole jointed a little below thelim/>, 
lower linear-lanceolate or setaceous, /r. (large) 7-ouv-ded on the 
back ivhen fresh keeled when dry, peduncle equal. — E. B. 1822. 
R. vii. 50. — St. creeping below, simple. Petioles plane-concave. 
1 See Mr Fryer's magnificent Potamogetons of the British Isles, now in coarse 
of publication, and his and Mr Arthur Bennett's papers in the Journal of Botany. 
Wc are much indebted to Mr Fryer for assistance with this genus and we have 
followed his views in adding several species. H. & .1. C. 
