New evidence from embryology in angiosperm classification

Abstract

New embryological evidence in angiosperm classification is presented from two different lines of research. One deals with a new field in embryological research, the other keeps within the classical framework. The new approach encouraged by the author refers to the exploration of the chemical composition of the pollen tube as a taxonomic tool. The presence of callose in several pollen tubes and the lack of this compound in others has been correlated with other embryological and taxonomical features within the Tubiflorae, showing a great deal of correspondence. In order to exemplify the classical approach, two families have been selected: Loranthaceae and Hydnoraceae. The Loranthaceae have a special structure called the “mamelon”, usually interpreted as a placenta. Recent research based on the position of the ar–chesporial tissue shows that not all “mamelons” should be regarded as homologous structures. Based on this finding, a new scheme of evolutionary lines is proposed. In connection with the holoparasitic family Hydnoraceae, the author discusses its relationships with Mitrastemonaceae and Annonaceae on grounds of embryology and floral morphology.