Urticales, Their Differentiation and Systematic Position

Abstract

The Urticales constitute a group of plants with surprising diversity and confusing complexity, especially in the Moraceae round which family the present paper is centred. Main trends in the differentiation of the growth habit, flower, fruit, and inflorescence are sketched and as far as possible connected to distribution, pollination, and dispersal. The reduced state of the urticalean flower is a main factor in the differentiation of the reproductive structures. Two main complexes may be distinguished in the variation patterns: one centred round adaptations to wind pollination, the other round adaptations to insect pollination, the latter resulting in several types of pseudanthous or pseudocarpous inflorescences. In both complexes there occur well adapted large genera (Ficus, Cecropia) and apparently less well adapted, as well large genera (Dorstenia, Elatostema). The Urticales appear to belong to a central complex in the Angiosperms. The affinity of the order with the Malvales is reasonably clear, while its connections with the Hamamelidales and their allies are much more vague.