This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
In this genus the sepals, which exceed 4 in number, are coloured, and conceal the smaller scale-like petals. Flowers always yellow, globose, and smaller than in Nymphoea. There are four or five species, all natives of the temperate zone of the northern hemisphere. The name is from the Arabic Naufar.
1. N. lutea (fig. 27). Yellow Water-Lily, Brandy-Bottles.- Leaves orbicular, deeply lobed at the base; lobes contiguous or overlapping. There is also a smaller form of this species.
2. N. pumila. - Leaves oblong, lobes at length spreading.
Very much like the last, but differing in the smaller more orbicular petals, shorter anthers, and the stigma lobed at the margin. Also British, but limited to the lakes of Scotland and Shropshire in England.
Fig. 27. Nuphar lutea. (1/6 nat. size.)
N. advena is similar to No. 1, but rather larger, and the flowers of a brighter colour. It is a native of North America.