Zur Lebensgeschichte der Gattung Helleborus L. (Ranunculaceae)

Abstract

Summary The growth form and growth rhythm of seven Helleborus species of different sections are investigated on the basis of cultivated plants and herbarium specimens. Special attention is drawn to germination, plant development, radication, stem morphology, leaf sequence, inflorescences, and innovation. H. foetidus is an allo-homorhizous, evergreen, chamaephytic, short-living perennial with dicyclic to pleiocyclic, slightly rhythmically growing stems, many-flowered inflorescences and bracteose hypsophylls. In the mountains of Mallorca, dwarfed, long-living pleiocormous perennials grow which approach shrubs. H. argutifolius is an evergreen rhizomatous perennial with dicyclic, strongly rhythmically growing stems, inflorescence buds, many-flowered inflorescences and bracteose hypsophylls. H. lividus is an evergreen rhizomatous perennial with dicyclic, continuously growing stems without inflorescence buds, and with several-flowered inflorescences and frondose-bracteose hypsophylls. H. niger is an evergreen rhizomatous perennial with basal leaves, very few-flowered, geophilous inflorescences and bracteose hypsophylls. H. orientalis is an evergreen rhizomatous perennial with basal leaves, few-flowered inflorescences and frondose hypsophylls. H. viridis is a summergreen rhizomatous perennial with basal leaves, few-flowered inflorescences and frondose hypsophylls. H. vesicarius is a rhizomatous perennial with monocyclic stems, few basal and cauline leaves, green in winter to spring, several-flowered inflorescences and frondose hypsophylls. In view of morphological character progressions, the results are discussed under consideration of all species and further features, and of the relations to environment and distribution. In conclusion, a hypothetical phylogenetic tree of the genus is presented (fig. 29). The pinnate-palmate leaves of H. vesicarius are considered to be primitive. The pedate leaf, typical to the genus, is derived from it. An additional pedate division of the leaf segments occurs in H. multifidus and related species. The ternate leaf of H. lividus and H. argutifolius is interpreted as neoteny. The generally accepted groups, Caulescentes and Scapigeri, are understood as grade groups. The species belonging to the Caulescentes, with elongated, leafy, usually dicyclic stems grow in the mild winter climate of the Mediterranean-Atlantic range. Derived from this group, the Scapigeri with their basal leaves are, for the most part, submediterranean to south-temperate plants of deciduous forests. The development of a scape is explained by the strict growth rhythm of these species: The inflorescence buds are transferred underground and develop very fast in early spring. The whole part above the leaves belongs to the reproductive region. The scales at the base of the scape are referred to as hypsophylls, which adopt the function of bud scales and have a vaginal structure. In accordance with their environment and distribution, the evergreen H. lividus and H. foetidus are characterized by a vegetation period beginning in autumn and a continual inflorescence development with a long flowering period. They develop no, or only loose, inflorescence buds. On the other hand, H. argutifolius develops compact inflorescence buds that unfold quickly, but not before January. The relatively short flowering period of the Scapigeri is delayed even further towards spring. Among them, the summergreen species have a clearly defined winter rest period. The wintergreen H. vesicarius, though, demonstrates a clearly Mediterranean growth cycle with a rest period in summer. The Sicilian plants of H. multifidus subsp. bocconei diverge considerably in growth rhythm and leaf sequence from the species, and need further morphological and taxonomical investigation. In order to achieve a more natural classification, the genus is differentiated according to the structure of the hypsophylls into two new subgenera, s ubgen . Helleborus with undivided, bracteose hypsophylls, and subgen. Helleborastrum (Spach) W erner & E bel with divided, frondose hypsophylls.