Editing Solidago (section)

===''Solidago'' and related taxa===
Related Asteraceae genera, such as ''[[Chrysoma]]'', ''[[Euthamia]]'', and ''[[Oreochrysum]]'', have been included within ''Solidago'' at one point or another,<ref name="Anderson-1975">{{Cite journal|last1=Anderson|first1=Loran C.|last2=Creech|first2=Jessica B.|date=1975|title=Comparative Leaf Anatomy of ''Solidago'' and Related Asteraceae|jstor=2441956|journal=American Journal of Botany|volume=62|issue=5|pages=486–493|doi=10.2307/2441956}}</ref> but morphological evidence<ref name="Phytologia-1994">{{Cite journal|date=1994|title=Subtribal Classification of the Astereae (Asteraceae)|last1=Nesom|first1=Guy L.|url=http://biostor.org/reference/131828|journal=Phytologia|language=en|volume=76|issn=0031-9430}}</ref><ref name="Anderson-1975" /><ref name="Rhodora-1981">{{Cite journal|date=1981|title=The Taxonomy of the Genus ''Euthamia'' |url=http://biostor.org/reference/138608|journal=Rhodora|language=en|volume=83|issue=836|issn=0035-4902}}</ref> has suggested otherwise. In a study comparing morphological characters of ''Solidago'' and related subgroups, the authors consider the subjectivity of classifying a genus and how to define it within broader tendencies concerning the taxonomy of North American Asteraceae. Little to no differences were observed between ''Solidago'' and the subgroups in terms of karyotype. However, external morphological characters such as habit, or the general appearance of the plant and how a suite of traits contribute to its phenotype; pappus size; and the point of freeing of stamen filaments from the corolla tube, are useful classification schemes for ''Solidago'', since they are applied to differentiating between Asteraceae taxa. One school of Asteraceae taxonomy thought unites all taxa sharing similar floral head structure and subsequently ignores deviation from this morphology, while another places greater weight on these morphological deviations. The authors argue that the latter opinion should be applied. Since there is no theoretical foundation for relative taxonomic importance of traits, they assert that habit should be a central trait when defining taxa, and subsequently that all the subgroups considered in their study (''[[Brachychaeta]]'', ''Chrysoma'', ''Euthamia'', ''Oligoneuron'', and ''[[Petradoria]]'') should be segregated from ''Solidago''.<ref name="Kapoor-1966">{{Cite journal|last1=Kapoor|first1=B. M.|last2=Beaudry|first2=J. R.|date=1966-09-01|title=Studies on ''Solidago''. Vii. the Taxonomic Status of the Taxa ''Brachychaeta'', ''Brintonia'', ''Chrysoma'', ''Euthamia'', ''Oligoneuron'' and ''Petradoria'' in Relation to ''Solidago''|journal=Canadian Journal of Genetics and Cytology|volume=8|issue=3|pages=422–443|doi=10.1139/g66-053|issn=0008-4093}}</ref>

Results from a leaf anatomy study comparing differences in mesophyll, [[Vascular bundle#Bundle-sheath cells|bundle sheath]] extensions, and midvein structure, among others in a suite of leaf traits,<ref name="Anderson-1975" /> are incongruent with those in an earlier study.<ref name="Kapoor-1966" /> Based on the lack of bundle sheath extensions, it is suggested that ''Chrysoma'', ''Euthamia'', ''[[Gundlachia (plant)|Gundlachia]]'', and ''Petradoria'' should be distinct taxa and outside of ''Solidago''.<ref name="Anderson-1975" /> However, ''Brachychaeta'', ''[[Brintonia]]'', ''Oligoneuron'', ''Oreochrysum'', and ''Aster ptarmicoides'' should be considered as components of ''Solidago''. To summarize, the relation of ''Brachychaeta'' and ''Oligoneuron'' to ''Solidago'' is inconsistent based on these results.<ref name="Kapoor-1966" /><ref name="Anderson-1975" /> 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'',<ref name="Phytologia-1994" /> similarly to Kapoor & Beaudry (1966). The first molecular phylogeny based on chloroplast DNA treats ''Brachychaeta'', ''Brintonia'', ''Oligoneuron'', and ''Oreochrysum'' as constituents of ''Solidago''.<ref name="Zhang-1996" /> Using consensus trees from ITS data, another study found support for ''Oligoneuron'' as part of ''Solidago'',<ref name="Beck-2004">{{Cite journal|last1=Beck|first1=James B.|last2=Nesom|first2=Guy L.|last3=Calie|first3=Patrick J.|last4=Baird|first4=Gary I.|last5=Small|first5=Randall L.|last6=Schilling|first6=Edward E.|date=2004|title=Is Subtribe Solidagininae (Asteraceae) Monophyletic?|jstor=4135444|journal=Taxon|volume=53|issue=3|pages=691–698|doi=10.2307/4135444}}</ref> 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''.<ref name="Schilling-2008" />

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''.<ref name="Rhodora-1981" /> As mentioned, the lack of bundle sheath extensions in ''Euthamia'' compared to ''Solidago'',<ref name="Anderson-1975" /> and deviations in floral morphology<ref name="Kapoor-1966" /> 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.<ref name="Rhodora-1981" />