Coefficient of Conservatism:
Coefficient of Wetness:
G. E. Crow
In lakes and larger rivers, usually at depths less than 3 m.
Some specimens of P. praelongus, especially from deep water (1.5–2 m or more), may have only rounded or even somewhat tapered leaf bases, and hence could run here in the key. They may, however, generally be distinguished from P. amplifolius by their very strongly whitish stipules and at most slightly tapered subsessile leaf bases. In P. amplifolius the stipules, while also prominent, are strongly tinged with brown or green and, particularly in deep water, the leaves are strongly narrowed at the base and/or definitely petiolate. The leaves of P. praelongus tend to have fewer nerves than those of P. amplifolius and are, of course, never floating.