Fig. 42: Potamogeton nodosus: a, submersed leaf, X %; b, rhizome and young 

 shoot, showing stipules and attenuate scales, X %; c, venation in submersed leaf blade, 

 X 2; d, upper part of stem, showing elliptic long-petioled floating leaves, X %; e, achene, 

 showing strongly developed dorsal and lateral keels and sculptured surface, X 8; f, 

 spike, X 4. (From Mason, Fig. 28). 



