i66 THE FLORA OF THE ALPS 



by Gremli as natives of Switzerland, all being also British 

 plants: — P. densus, L., leaves opposite; natans, L., 

 floating leaves thick, coriaceous ; fluitans^ Roth ; colo- 

 ratus, Vahl {^plantagineus ^ Ducr., Hornemanni^ Koch) ; 

 rufescenSy Schrad. {alpinus, Balb.) ; gramineus, L. {hetero- 

 phylluSy Schreb.), submerged leaves linear - lanceolate ; 

 lucenSy L., leaves very large and shining; Ziziiy Roth.; 

 crispuSy L., leaves crisp, wavy; perfoliatus, L., leaves 

 cordate- am plexicaul ; prcelo?tgus, Wulf., leaves oblong, 

 half-amplexicaul ; decipienSy Nol. ; pectinatus, L., leaves 

 very long, filiform ; marinuSy All., spikes on long stalks, 

 alpine lakes; compressus, L. {zostercefolius, Sch.), stem 

 winged, leaves linear, half-amplexicaul ; acutif alius , Link. ; 

 obtusifoliuSy M. K. ; mucronatuSy Schr. ; pusilluSy L., spike 

 very few-flowered. 



2. Zannichellia, L. 



Flowers minute, solitary or in pairs, axillary, in a 

 cuplike sheath; leaves submerged, linear. 



Z.palustriSy L. {^yLioSM^vci^ pedunculatay Rchb.), Horned 

 Pond- Weed ; stem very slender, leaves opposite ; stagnant 

 water; Switzerland, rare. 



3. Naias, L. 



Flowers unisexual, solitary or few, enclosed in sheaths ; 

 perianth o; stamen i; carpel i, with I ovule; leaves 

 linear, very narrow. 



N. majoVy All. {marinay L.) ; flowers dioecious, solitary, 

 leaves dentate-spiny ; stagnant water ; Switzerland, Pyr- 

 enees, rare. N, minoVy All. {Caulinia fragilisy Willd.); 

 flowers monoecious, solitary or few, leaves nearly entire, 



