POND-WEED TRIBE 25 
2. Oblong-leaved Pond-weed (P. obléngus).—Leaves all stalked, 
upper ones leathery, floating, oblong-elliptical, lower ones linear-lanceolate , 
fruit small, with the back blunt and rounded; spike slender, cylindrical, 
densely flowered, upon a long rounded flower-stalk. This species, which is 
thus described by Mr. Babington, is by him considered as distinct from the 
last, of which some botanists consider it but a variety. This author remarks 
that it is far from uncommon in wet ditches, small streams, and bogs in 
Britain, but rare in Ireland. Its fruit is about half as large as that of 
P. natans, and differs in form. It bears in July short spikes of greenish 
flowers. It is of a more membranous character than P. natans, and the sub- 
merged leaves are well developed. It is also known as P. polygonifolius. A 
plant considered by Sir Joseph Hooker to be a form of this species, has been 
described by Boswell under the name of P. kirkii. It has been found at 
Galway in Ireland, and is distinguished by its very long floating leaves of a 
somewhat leathery consistence, and by the submerged leaves being long and 
linear like those of P. lanceolatus. 
3. Plantain-leaved Pond-weed (P. plantagineus).—Leaves all long 
stalked, membranous, and _ pellucid, upper ones elliptical, opposite, floating, 
lower ones submersed, and oblong; stipules short, broad. This Pond-weed 
has a creeping stem, which throws out long running shoots. It is a beautiful 
plant, with clear bright netted green leaves, and reminds one of some of the 
sea-weeds which rise so gracefully in the salt-water pools. It bears long 
greenish dense spikes of flowers in June and July, and is found in stagnant 
ditches and bogs in several counties. Also known as P. coloratus. 
4. Reddish Pond-weed, or Long-leaved Floating Pond-weed 
(P. ruféscens).—Upper leaves oblong, or inversely egg-shaped, tapering into a 
short stalk, somewhat leathery ; lower leaves linear-lanceolate, and tapering 
at both ends, sessile. In this plant the floating leaves are somewhat tough, 
and the lower thin and membranaceous. The plant is of a dull olive-green, 
more or less tinted with a dingy red colour. It bears its spikes of greenish 
flowers in July, and is found in still waters and ditches in various parts of 
the kingdom. Also known as P. alpinus. 
5. Lanceolate Pond-weed (P. lwnceoldtus).—Floating leaves stalked, 
somewhat leathery, many-nerved, sometimes wanting; submersed leaves 
sessile, lanceolate, tapering at the base, membranaceous. This plant bears 
its small, short, dense spikes of greenish flowers in July and August. It is 
a rare species, inhabiting rivers; it has been recorded from Anglesey, Cam- 
bridge, and County Down. It has very slender stems. 
6. Various-leaved Pond-weed (P. heterophillus).— Upper leaves 
elliptical, stalked, slightly leathery, but not thick, often wanting; sub- 
mersed leaves lanceolate, sessile, and membranaceous. In this plant the 
flower-stalks are enlarged at the upper part, and the spikes are dense. It 
flowers in July and August. It is a common species in pools, canals, ditches, 
and rivers generally, but rare in Ireland. 
7. Lance-leaved Pond-weed (P. lonchites).—Stem stout, longer and 
less-branched than in P. heterophyllus, floating leaves usually wanting, if 
present oblong lance-shaped, long-stalked, opposite ; submerged leaves strap- 
shaped, long and straight, alternate, translucent, with 7 to 9 ribs; flowers in 
ive 
