CV. NAIADACEJE. 



483 



!*' 



PotamogetonJ] 



r 



leaves sessile lanceolate attenuate at both ends aplculate den- 

 ticulate or entire membranaceous, floating ones elliptical stalked 

 slightly coriaceous, stipules strongly ribbed, peduncles thickened 

 upwards. E. B. t. 1285. 



Pools and ditches, in various parts of the country. 1/.. 6 7 



Mr, Wilson finds this sometimes without floating leaves^ when it seems 

 intermediate hetween P. lanceolatus and P, rtifescens, " The stipules 

 which are not dorsally winged, are short and broad, yet with 2 stout 

 principal ribs, ovate and bhnit ; both they, and the leaves subtendino- 

 the flower-stalk, are widely spreading. Leaves distantly inserted on 

 the stem ; upper ones considerably larger than the rest. Distin- 

 guished by these marks, and the clavate flower-stalk from P. rufescens 

 and lanceolatus ;" Wilson, Wahlenberg, Hartmann, and Fries are of 

 opinion that this is the true P. (jraminens of Linnaeus • but Lin- 

 naius adopted that name from Ray, and Ray's P. gramineus is the 

 species commonly so called in this country, 



15. P. lanceolatus Sm, (la^iceolate P.) ; submero*ed leaves 



Anglesea. 



lanceolate ".not apiculate" tapering at the base entire mem- 

 branaceous with about 5 — 7 nerves and transverse veins 

 . floating leaves elliptic-lanceolate subcoriaceous many-nerved 

 petiolate, peduncle about as long as the leaves not thickened 

 upwards, spikes elliptical. — /3, floating leaves none. P lanceo- 

 latus E, B. t. 1985. 



Pools and ditches,^ — a. and j8. growing together in a rivulet in 



Angus-shire ; Kincardineshire ; in the Lossie, by Elgin. 

 ^- V; — This plant had been very little understood till Mr, Wilson 

 found it growinc^c in a small rivulet in Anglesea, having a moderately 

 swift stream. Floating leaves are always found where the current is 

 slow.^ Small chain-like reticulations are distinguishable near the 

 midrib on the submerged leaves, but not on the floating leaves, which 

 are elegantly overspread by them : " Wilson in Hit. This remark is 

 quite correct, and the portion of chain-like reticulations increases 

 gradually upwards. The diflSculty is now to distinguish this plant 

 from the preceding, than which, however, it is much smaller and more 

 delicate in all its parts. Sir J. E. Smith considered the P. setaceus of 

 Lmn. and Huds. and FL Brit, to be probably the same as the pre- 

 sent, which can hardly be correct. 



16. P. riffescens Schrad. {reddish P.); submerged leaves 



lanceolate attenuate at both ends "not apiculate" entire 



membranaceous many-nerved with connecting veins and many 



linear reticulations at the midrib, floating ones subcoriaceous 



oblong or obovate rather longer than their stalks, stipules not 



jvinged, peduncles not thickened upwards. P. fluitans E. B. 

 t. 1286. 



Anglesea. 



Ditches and slow streams, m many parts of England, /ingiesea. 

 ^ear Glasgow and Forfar; in the Gaddie, at Fremnay. Aberdeenshire 

 4. I. -.» This does, in some situations, much resemble P. lucens 

 ihe coriaceous floating leaves are nearly as acute as the lower ones, 



