STUDIES ON SOLIDAGO. VII. THE TAXONOMIC STATUS OF THE TAXA BRACHYCHAETA, BRINTONIA, CHRYSOMA, EUTHAMIA, OLIGONEURON AND PETRADORIA IN RELATION TO SOLIDAGO

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Abstract
The North American taxa Brachychaeta T. et G., Brintonia Greene, Chrysoma Nutt., Euthamia Nutt. ex Cass., Oligoneuron Small, and Petradoria Greene, of the tribe Astereae, have been recognized as distinct genera or attributed to the genus Solidago L. by different students of the Compositae. Morphological and chromosomal data gathered by the authors from representatives of these peripheric taxa have been compared to similar data obtained from a sample of taxa considered as typical representatives of the genus Solidago. These data can best be interpreted as evidence that the entities of the peripheric group are in the process of diverging from, or of converging towards those of the Solidago group, and that they are, for the purpose of generic delimitation, borderline cases. The authors consider that the union of these taxa to the genus Solidago. or their segregation from this genus, are both acceptable practices but prefer and opt for the 2nd. The taxonomic designations corresponding to this option are given for all taxa of the peripheric group and involve 1 new comb. Oligoneuron corymbosum (Ell.) Small var. humilis (Basionym: Solidago rigida humilis Porter).