Astranthium and Related Genera

Abstract

Monographic studies of Aphanostephus and Achaetogeron have made it necessary to investigate some of the related genera, particularly as to the value of certain morphological characters which are used in generic differentiation. The genera are quite similar in habit but the pappus, which furnishes important diagnostic characters, varies greatly within the group and is on the whole inconspicuous. For this reason it is necessary to make microscopic studies of the minute achenial and pappus characters upon which the differentiation of genera is primarily dependent. In this connection it was desirable to study Astranthium and Keerlia in detail; and it seems advisable to put on record the results which have been obtained relative to these genera. Astranthium, a genus of the Compositae belonging to the tribe Astereae, was described by Nuttall in 1841.1 It contained but one species, A. integrifolium, based on Bellis integrifolia Michaux.2 The 'Flora of North America,' published by Torrey and Gray in 1842, relegated Astranthium to synonymy. Since that time American and Mexican species have been merged with the genus Bellis3 which is indigenous to the Old World and especially to Europe. Three South American species have been described by Vellozo4 as occurring in Brazil. Two of these, Bellis campestris Vell. and B. pedunculata Vell., may well be members of the genus Spilanthes. The relationship of the third, Bellis scandens Vell., is unknown to me. Bellis perennis L. is an attractive plant, and for this reason it has been cultivated in the north Atlantic states where it has become naturalized. The American species which have been referred hitherto to the genus Bellis are so strikingly different that it seems strange the two generic elements should have been regarded