Potamogeton crispus & Potamogeton perfoliatus Thomé-033, Otto Wilhelm Thomé, 1885
:33. A. Potamogeton crispus l. - curly pondweed
a part of the plant;
flower;
stamen with petal;
fruit;
individual fruit cut lengthwise to show the curved embryo. 4x. 34. B. Potamogeton perfoliatus l. - claspingleaf pondweed. Date: 1885.