In foliage. and mode of growth this group does not differ essentially from the Nymphaeas, but in the structure of the flowers there is an easily-recognised distinction. In Nuphar, the parts of the flower - sepals, petals, stamens - are closely crowded on a raised fleshy disc surrounding the base of the seed-vessel, while in Nymphaea they are more loosely arranged, and spring direct from the base and sides of the seed-vessel itself. There is, moreover, so far as I know, no hardy yellow-flowered Nymphaea, whereas all the hardy cultivated Nuphars are yellow-flowered.

Nuphar Advena, Stranger Yellow Water-Lily

The leaves are deeply heart-shaped, with widely-spreading lobes; the calyx is usually composed of six sepals. Flowers in July and August. Native of Nuphar America.

Nuphar Kalmiana, Canadian Yellow Water-Lily

The leaves are deeply heart-shaped, with spreading lobes, and the calyx has usually only five sepals. Flowers in July and August. Native of Canada.

Nuphar Lutea, British Yellow Water-Lily

Leaves larger than in either of the foregoing, deeply heart-shaped, with overlapping lobes. The calyx composed usually of five sepals. This is the best known of the Yellow Water-Lilies, being a native of our own country, but found also in Europe generally, and in Northern and Central Asia sparingly.

Nuphar Minima, Syn. Nuphar Pumila, Smaller Yellow Water-Lily

This is regarded as a diminutive variety of the last species. It is found in some of the mountain-lochs in the Nuphar of Scotland, and differs from the species only in respect of size, and would be found more suitable for shallow waters, and the margins of deeper lakes.