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Classification and Phylogeny of Nymphaeaceae and Allied Families

1955; University of Notre Dame; Volume: 54; Issue: 1 Linguagem: Inglês

10.2307/2422174

1938-4238

Hui-Lin Li,

Diatoms and Algae Research

The Nymphaeaceae, sensu lato, are a heterogeneous assemblage of plants grouped together mainly because of their aquatic habitat. The family as generally accepted is of less uniform nature than most families of flowering plants and the component genera exhibit widely varied characters in all essential features. The only characters common to nearly all genera are the presence of lactiferous vessels, air spaces and scattered vascular bundles devoid of cambium and vessels. In some genera there are idioblasts or supporting cells which frequently occur in the angles of the large intercellular spaces, especially of the petioles (DeBruyne, 1922). These characters are apparently all results of the specialized aquatic habitat anid do not reflect genetic aflinities. Some of these charact,ers occur in other aquatic plants of very remote phylogenetic relationships. The Nymphaeaceae are one of the few families of wholly aquatic plants in the angiosperms. Aquatic plants in the angiosperms are generally admitted as derivatives, which have actually originated independently from many widely separated terrestrial stocks,. As a rule these aquatics represent a final and specialized evolutionary stage and consequently the families are usually very small containing but few genera and species, or when large, highly specialized and homogeneous, the Nymphaeaceae, sensu lato, being the only exceptions. There are eight entirely aquatic families of angiosperms. Closely associated with Nymphaeaceae are Ceratophyllaceae, with one genus and thr,ee species of nearly cosmopolitan distribution. The Podostemonaceae are the largest family with about 30 genera and 130 species. These plants form a homogeneous group of highly modified thalloid plants adapted to the rapid running water and all species are of very local occurrences. Hydrostach-yaceae with one genus and about 15 species, and Tristichaceae with three genera and six species are also highly modified commonly thalloid plants related to, the Podostemonaceae. Trapaceae (Hydrocaryaceae) with one genus and several species are widely distributed in the Old World. The remaining two families are the cosmopolitan monotypic Callitrichaceae and Hippuridaceae. None of these aquatic families is comparable with Nymphaeaceae, sensu lato, in diversity of fundamental structures among the component members.