NAIADACE^E. 63 



SPECIES I.— NAIAS PLEXILIS. Bostl. 



Plate MCCCCXXXII. 



Caulinia flexiHs, WiUd. Spec. PI. Vol. IV. p. 183. 

 Fluvialis flexilis, Fers. Syn. Vol. 11. p. 530. 



Leaves ternate or opposite, spreading, pellucid, linear, entire or 

 very finely and remotely serrate, those on the main stem with fascicles 

 of leaves on their axils ; sheaths shortly ciliate. 



In shallow water, in lakes. Discovered in Biitain by Professor 

 Oliver, in a lake near Roundstone, Connemara, between the Clifden 

 Itoad and the sea, at a mile or two from the village of Roundstone, 

 and found by Dr. D. Moore in a small lake less than a mile from 

 Roundstone, on the way to Uri-isbeg. 



Ireland. Perennial. Avitumn, 



A delicate plant, Avith fragile filiform branched stems growing entirely 

 submerged. Leaves frequently ternate on the main stems, but generally 

 ojjposite on the branches, -J- to 1 inch long, very delicate and pellucid, 

 with short dilated sheathing bases, commonly with a few short laciniate 

 ciliations on the margins; the upper part entire or with a few remote 

 serratures more marked towards the apex. Flowers dioecious (?) or 

 monoecious (?), axillary. Fruit sessile, elliptical-ovoid, -J- inch long, 

 pale brownish-olive, partly enclosed in the sheathing bases of the leaves, 

 sometimes 2 or 3 together in the axils of the leaves of the fascicles, 

 which are developed in the axils of the leaves on the main stem. 



The male plant I have not seen. Dr. Asa Gray suspects this species 

 is monoecious, but I can find no male flowers on my specimens, which 

 were collected by Mr. T. Kirk. 



Flexible Naias. 



French, Naijade marina. German, Biegsavies Nixkraut, 



EXCLUDED SPECIES. 



POTAMOGETON PLUITANS. Both. 



This plant has been frequently recorded as a native of Britain ; but 

 the statements have invariably been corrected, some other species 

 having been mistaken for it. Still it is very probable that it may 

 be a British species. In the last edition of Professor Babington's 

 " ]\Ianual " it is stated tliat a plant gathered at Hounslow, in the 

 Lambertian Herbarium at Kew, may be P. fluitans, but the Rev. "W. 

 W. Newbould informs me he led Professor Babington into an error 

 about this plant. Although I have twice carefully examined all the 



