THE LEAF PELTATION IN THE HERBACEOUS TAXA OF ANGIOSPERMS IN ITS RELATION TO NATURAL HABITAT AND DISTRIBUTION

This study is an attempt to analyse the leaf peltation principally amo ngst herbaceous plants in its relation to natural habitat and distribu tion, and concurrently to investigate their connection with certain gr owth forms and family groupings. The results confirm that in herbaceou s plants peltation occurs predominantly amongst perennials with advent itious roots, that is to say amongst growth forms possessing rhizomes, creeping shoots, bulbs, tubers and stolons with stem tubers. Peltatio n was only marginally established amongst the phylogenetically young a nnuals which prefer dry growing conditions. Oceanity has a clear influ ence upon the distribution of peltate taxa. The majority of peltate pe rennials are associated with the oz(1-3) degrees of oceanity. In subtr opical, meridional and temperate steppes, deserts, and semi-deserts, p eltation declines dramatically. The influence of zonality upon the dis tribution of peltate taxa is limited. In subtropical, meridional and t emperate areas of N. America (including Central America) and East Asia , the proportion of peltate genera within the total genera stock of on e region is relatively constant. This proportion declines in the borea l zone and peltate ta,va are absent in the arctic zone. Almost all pel tate perennials colonise wet, damp or humid locations, or sites with v ariable wetness and humidity. They favour lakes, ponds, swamps, moors, meadows, damp sand, stream and riverbanks, woods and damp shaded or h alf-shaded rocks. The ascidiate groups of plants resemble peltate spec ies in their preference for wet, damp and humid habitats. Their leaf t ype is also related to the peltate one. The more or less frequent appe arence of peltate taxa within the taxonomic sphere of the ascidiate fa milies (Nepenthaceae. Sarraceniaceae) and genera (Utricularia, Genlise a) may indicate familial relationships. This should be borne in mind i n phylogenetic studies of carnivors. Questions relating to the evoluti on of some succulent peltate plant groups are also discussed.