326 
POTAMEJE CYPERACEiE. 
E. B. 323. P. marinus Fries, Koch. — L. like those of the pre- 
ceding but longer. Nuts smaller and rounded on the back with- 
out keel or ridges. Whorls very distant on the spikes. Peduncles 
very long. — Rare ? Lakes in Forfarshire. P. VI. VII. E. ? S. 
***** L. all opposite, stibmersed ; stipules none. 
19- P- densus (L.) ; I. all opposite pellucid clasping elliptical- 
lanceolate or lanceolate, spikes shortly stalked ultimately reflexed. 
— E. B. 397- — L- crowded, rather recurved. Spike 4-flowered. 
—Ditches. P. VI. 
2. Ruppia Linn. 
1. R. maritima (L.) ; cells of the anthers oblong. — R. Icon. 
f. 307. — Whole plant stronger than the next. L. very narrowly 
linear. Sheaths large inflated. Nut ovate, obliquely erect. — 
Salt marshes. Guernsey. P. VII. VIII. O. 
2. R. rostellata (Koch) ; cells of the anthers nearly round. — 
E. B. 136 ? — Whole plant very slender. L. rather filiform than 
linear. Sheaths small, close. Nut very obliquely ascending but 
less so than in continental specimens. — Salt marshes. P. VII. 
VIII. 
3. Zannichellia Linn. 
1. Z. palustris (L.) ; style at least half as long as the nut. — 
E. B. 1844. — Floating. L. slender, opposite, filiform. Fl. ax- 
illary, sessile. Anth. 2 — 4-celled. Stigma generally notched at 
the margin. Nuts very shortly stalked. — (i. pedunculata ; clus- 
ter of fr. stalked, nuts with elongated stalks. Z. pedunculata R. 
— Z. polycarpa (Nolte) is distinguished by its very short style 
scarcely a sixth of the length of the nut. — Stagnant water. A. 
or P. VII. VIII. Horned Pondweed. 
4. Zostera Linn. 
1. Z. marina (L.) ; 1. obscurely 3-nerved, nuts striated. — 
E. B. 467. — Fl. hidden m a long sheathing portion of the leaf. 
— Two forms are distinguished by continental botanists: 1. Z. 
marina (L.) ; 1. 3-nerved, peduncle of the spath swelling upwards, 
stem terete. 2. Z. uninervis (R.) ; 1. 1 -nerved, peduncle equal, 
stem compressed. — In sea-water. P. VII. VIII. 
Subclass II. GLUMACE.E. 
Floral envelopes imbricated. 
Order XC. CYPERACEiE. 
Fl. perfect or unisexual, each with a scale or glume imbricated 
on a common axis. Perigone 0, or rarely membranous. Stam. 
