Fig. I. — Potamogeton praelongu-s. 



Fig. 2. — Potamogeton perfoliatus. 



Fig. 3. — Potamogeton foliosus. 



Fig. 4. — Potamogeton pusillus. 



PLATE XXXV. — WIDE-RANGING SPECIES OF PONDWEEDS. (From Morong.) 



(After Biological Survey.) 



