Potamogelon.\ FLUVIALES. 205 



with considerable interruptions, rising just above the surface, seldom 

 produced but in still waters. FL two or three together, dull green. 

 Seeds scarcely more than one or two from each flower, gibbous. Few 

 plants vary more in the size of its herbage, which is most considerable 

 in rivers and rapid streams, where the flowers seldom appear. It 

 flowers more freely in salt-water ditches, where it grows less luxuriantly. 



* * * Leaves alternate, all linear, submersed; stipules free. 



3. P. pusillus, Linn. Small Pond-weed. Leaves narrow, 

 linear, 3 — 5-nerved, with obscure connecting veins ; peduncles 

 elongated. Br. Fl. 1. p. 73. E. Fl. v. i. p. 235. E. Bot. t. 

 215. — ft. major; stem more compressed; leaves broader; 

 spike somewhat interrupted. — P. compressus, Linn. E. Bot. t. 

 418. E. Fl. v. i. p. 233. 



Ditches and still waters, not uncommon. (3. In Ballypheane bog ; 

 Mr. J. Drummond. In the Bann river ; Mr. Templeton. In a 

 pond at Florencecourt. Fl. July. If.. — The stem is here, as in all of 

 this division, more or less compressed. The leaves are more or less 

 acute ; the spike oblong, compact, or a little interrupted. 



4. P. gramineus, Linn. Grassy Pond-weed. Leaves broadly 

 linear, obtuse, three-nerved, with few and obscure connecting 

 veins ; peduncle scarcely longer than the oblong-oval spike. 

 Br. Fl. 1. p. 14,. E. Fl. v. i. p. 235. E. Bot. t. 2253. 



Ponds and bog-drains. Drains at Portmore, County of Down ; Mr. 

 Templeton. Bog-drains at Enagh-Lough, County of Derry ; Mr. D. 

 Moore, 1834. Near Youghal ; Mr. E. Ball. Fl. July. TJL— Nearly 

 allied to the last, but stouter, darker coloured, and with short pedun- 

 cles, scarcely longer than the stipule of the leaf, from the axil of which 

 they spring. 



5. P. acutifolius, Link. Sharp-leaved Pond-weed. Leaves 

 linear, acuminate, with three principal and numerous close 

 parallel intermediate nerves occupying the whole surface; 

 spikes oval, compact, about equal in length with the short 

 peduncle. Br. FL \. p. 74. Hook, in E. Bot. Suppl. t. 2609. 



River Shannon, at Plassey and Castle-connel, near Limerick, (with 

 leaves only) ; Mr. W. H. Harvey. Fl. July. If. — The leaves in 

 Mr. Harvey's specimens are longer and broader than those repre- 

 sented in the figure in E. Bot. Suppl., but exactly correspond with 

 the description in having the leaves linear, acuminate, with numerous 

 parallel nerves. 



jjj * # * Leaves alternate, ovate, or lanceolate: all submersed ; 

 stipules free. 



6. P. crispus, Linn. Curled Pond-iveed. Leaves lanceo- 

 late, waved and serrated, 3-nerved ; fruit beaked. Br. Fl. 1. 

 p. 74. E. Fl. v. i. p. 233. E. Bot. t. 10 J 2. 



Ditches and rivers, frequent. Fl. June, July. If.. — Whole plant 

 immersed, bright green ; leaves obtuse, crisped at the edges. 



K K 



