NOTES ON PONDWEEDS. 51 
The largest bribe, Ranga All the branches ultimately rise 
and float near the s e, but remain sito Make submerged, even the 
uppermost leaves ein "Cotes by a thin film of water; at the 
time of flowering numerous lateral hae start at nearly right 
angles from the fertile stems and increase their buoyancy, so that 
e 
nd s 
gare fers broad; gs midrib is always excurrent, ev sub- 
orbicular hooded examples. The hooded tip to the leaf charactesiati 
of P. prelongus also occurs in a less marked degree in some form 
of P, rufescens, and very rarely in young plants of the — ope 
cies, but in such cases the boat-shaped contraction does not o 
n all the leaves. The lowest leaves on the stem ae mae A 
reduced to a thickened, sometimes clavately rounded midrib. This 
shortly stalked, showing that the species is ard petiolate, 
athong the ordinary leaves are subsessile from the lamina being 
owly decurrent along the petiole a, it sensi the stem. 
W acuminate; this is the 0 usually, but Se 
tinuance of hot weather, when the temperature of the * pe er a 
been unusually raised ; nat enough they may then be found o 
quite ete deep- -water form 
stipules are very varge and long, 2-4 in., slightly scarious 
at the pe: but the greater part of each is herbaceous, coloured 
like the rest of the plant, yellowish olive-green. Sometimes they 
are entirely herbaceous, green, with numerous ‘Toligititanal nerves, 
_ with cross-veins anastomosing towards the tip. Two of these nerves 
are very prominent, each mounted on a fold in the stipule and 
slightly winged, forming a conspicuous two-keeled back. 
The peduncles are much stouter than the stems from which sri 
0! 
