bundle sheath extensions, and midvein structure, among others in a suite of leaf traits, are incongruent with those in an earlier study. Based on the lack of bundle sheath extensions, it is suggested that Chrysoma, Euthamia, Gundlachia, and Petradoria should be distinct taxa and outside of Solidago. However, Brachychaeta, Brintonia, Oligoneuron, Oreochrysum, and Aster should be considered as components of Solidago. To summarize, the relation of Brachychaeta and Oligoneuron to Solidago is inconsistent based on these results. Both support the separation of Chrysoma, Euthamia, and Petradoria from Solidago. A study reviews the taxonomic position of Oligoneuron relative to Solidago, as based on taxonomic evidence, treats it as separate from Solidago, similarly to Kapoor & Beaudry (1966). The first molecular phylogeny based on chloroplast DNA treats Brachychaeta, Brintonia, Oligoneuron, and Oreochrysum as constituents of Solidago. Using consensus trees from ITS data, another study found support for Oligoneuron as part of Solidago, and the findings of Zhang (1996). More recently, an analysis of combined ITS and ETS data provided additional support for the inclusion of Oligoneuron as part of Solidago. Until the 1980s, the genus Euthamia was largely considered to be a part of Solidago due to morphological similarities between species in both genera, and a history of synonymy of Solidago lanceolata and Euthamia graminifolia. As mentioned, the lack of bundle sheath extensions in Euthamia compared to Solidago, and deviations in floral morphology present evidence for separation of these taxa. A taxonomy of Euthamia as a genus was presented, providing a detailed description of distinguishing external morphological characters, such as fibrous-roots, sessile leaves, and mostly corymbiform inflorescences. Evolutionary relationships within Solidago Chromosome counts and advances in molecular systematics have enabled greater understanding of evolutionary relationships within Solidago. At the time a taxonomy of Solidago was published, related taxa causing contention, such as Chrysoma, Euthamia, Oligoneuron, and Petradoria, were excluded from this genus. The number of Solidago species has remained relatively stable, around 120, with approximately 80 in North America. Due to monophyletic support for the New World taxa and taxonomic difficulties with Old World taxa, the taxonomy provided in the 1990s only includes North American taxa and thus treats Solidago as non-monophyletic. Existing molecular-based phylogenies provide monophyletic support for Solidago given its inclusion of Oligoneuron. Chromosome counts have proven to be a valuable character in Solidago taxonomy and in elucidating the cytogeographic history of the genus. Similar chromosome counts may indicate close