Nuphar Sm.

Abstract

Accounts of the genus Nuphar and its British representatives for the Biological Flora of the British Isles, including details of their morphology, distribution, ecology, phenology, reproduction, predators and history. Statistics of floral and vegetative features from British colonies of the 3 taxa are given and compared with the variability of continental European material. N. X intermedia is shown to be intermediate in nearly all features between its presumed parents N. lutea and N. pumila; in Britain it appears to be the F1 hybrid, perpetuating itself at the present time only vegetatively in a few colonies, sometimes isolated from its original parents. Its chromosome number (2n = 34) is the same as that of N. lutea and N. pumila and its fertility corresponds with that of the F1 progeny of these 2 spp. made reciprocally by Caspary. In continental Europe various other grades between the 2 spp. exist, but in Britain only 1 colony, which appears to consist of N. pumila introgressed with N. lutea, is known; its pollen fertility (c. 85%) compares with about 95% for N. pumila and seed set is correspondingly lower.