Wuchsformenuntersuchungen an zentraleuropäischen Hypericum-Arten

Abstract

An analysis of growth forms and growth rhythms of 9 central European Hypericum species shows various lines of differentiation related to ecology. Hypericum pulchrum is dwarf shrub-like, with procumbent lignified stems and evergreen leaves. H. elodes is also widely procumbent but remains herbaceous. Both species are typical of the temperate atlantic zone, they overwinter in areas with mild winters. H. humifusum , growing on open sandy soils, annually produces creeping stems from a perennial rootstock, but as a segetal weed it is eapable of hapaxanth growth. The four representatives of the section Hypericum are pleiocormous perennials. In H. perforatum seasonal change between plagiotropous and orthotropous stem formation deserves particular attention. H. tetrapterum is similar but depending on the conditions of the swamp habitat shows more plasticity. H. elegans and even more H. maculatum tend to develop runners below the soil surface. This is correlated with the distribution on the borderline of the genus in the southsiberian steppe ( H. elegans ) and in subboreal Europe ( H. maculatum ). H. montanum and H. hirsutum overwinter with short autumnal innovation shoots. The results are discussed with referenee to life form and taxonomic position of the species within the genus. Hypericum is characterized by monotelic inflorescences. The species studied here are forming thyrsi or cymoid inflorescences which range from many flowered much branched to few flowered. They differ also in the relation of reproductive to vegetative parts within the total growth form.