STUDIES ON THE TRICHOMES OF SOME ASTEREAE (COMPOSITAE)

Some species of Baccharis and other genera of Astereae were investigated with regard to their trichomes. After anatomical and morphological analysis of the occurring trichomes and their ontogeny several trichome forms are described. In the investigated taxa these are of taxonomic value at the level of species and subspecies. The trichome forms arc classified in two major groups according to the direction (anticlinal or periclinal) of the first division of the hair mother cell during trichome formation. Other classification systems for trichomes, especially that of RAMAYYA, are discussed. Two major types of indument can be distinguished among the taxa under investigation, one consisting of syncladeous hairs and the other of hairs with pedestal. The distribution of these indument types in the investigated taxa is discussed. Baccharis s. str., Heterothalamus, Baccharidastrum and some species that have been excluded from Baccharis are characterised by the presence of syncladeous hairs, whereas hairs with pedestal occur in most of the genera of Astereae and the whole family.