Victorian Plants. 441 



All leaves membranous. 



Leaves all scattered and short- stalked ; floating leaves from 

 cordate- to elliptic-ovate ; submerged leaves almost lanceo- 

 lar ; stipules blunt ; stalks of the spikes slender ; fruitlets 

 comparatively small, when fresh at the outer margin blunt, 

 their style obliterated. P. plaiitagineus. 



1880. Leaf-stalks none or unclasping ... ... ... 1881 



Leaf-stalks elongated, almost cylindrically clasping... 1885 



1881. Leaves much crisped. 



Branches compressed ; leaves all submerged, membranous, 

 transparent, from linear- to oval-elliptical, the upper 

 opposite ; flowers few in the spikes ; fruitlets compressed, 

 terminated by the conspicuous style, when fresh at the 

 outer margin blunt. P. crispus. 



Leaves almost flat 1882 



1882. Leaves distinctly stalked. 



Leaves all submerged, rather large, membranous, trans- 

 parent, shining, from ovate- to elongate-lanceolar, pointed, 

 slightly serrulate ; stipules conspicuous ; stalks of the 

 spikes thickened upwards ; fruitlets when fresh slightly 

 angular at the outer margin. P. lucens. 



Leaves quite sessile ... ... ... 1883 



1883. Leaves from ovate- to orbicular-cordate. 



Leaves all submerged, membranous, transparent, clasping 

 at the base, slightly rough at the margin, the upper 

 opposite ; stalks of the spikes hardly thickened upwards ; 

 fruitlets compressed, when fresh blunt at the outer 

 margin. P. perfoliatus. 



Leaves elongate-linear ... ... ... ... 1884 



1884. Leaves rounded-blunt. 



Branches considerably compressed ; leaves all submerged, 

 scattered except the uppermost, membranous, transparent ; 

 their longitudinal venules three to five ; stipules obtuse ; 

 flowers usually several in the spike ; fruitlets curved- 

 attenuated at the summit, bluntly angular at the outer 

 margin, their style almost straight. 



(P. ochreatus.) P. obtusifolius. 



