From a morphological point of view, two main groups are distinguished within the Guayana-Highland centered genera and relatives: (1) the zygomorphic-flowered genera with epaleate, homogamous capitula of all bilabiate corollas (rarely ligulate by abortion of the inner two corolla lips) and smooth style branches (Table 8), and (2) the actinomorphic-flowered genera with epaleate to paleate, homogamous capitula of all tubular corollas and rugulose to papillose styles beyond the branches bifurcation point.
Capitula homogamous or heterogamous; discoid, radiate, ligulate, or disciform; receptacle epaleate, less frequently paleate, glabrous to pubescent, alveolate, ciliate, setose to fimbriate; involucre uniseriate to multiseriate.
Capitula homogamous, discoid or radiate by extension of the outer lip in marginal corollas, rarely disciform; involucre uniseriate to multiseriate; receptacle epaleate to paleate
, glabrous to pubescent.
Capitulescences monocephalous, or corymbose to paniculate; capitula pedunculate, homogamous, discoid or radiate; involucre one- to five-seriate; receptacle epaleate to paleate, paleae embracing the marginal florets, with the open part facing either the center of the capitulum or the outer part of the capitulum.
Capitulescences a capituliform pseudocephalium; capitula subsessile, homogamous, discoid; outer capitula of the pseudocephalia with two florets, the involucre of two phyllaries, the outer phyllary keeled, embracing the two florets, the inner phyllary not embracing and placed between the two florets and interpreted as a palea; central capitulum one- to five-flowered, involucre uniseriate; receptacle paleate or epaleate.
Capitulescences monocephalous, terminal; capitula pedunculate, homogamous, radiate or discoid; receptacle paleate
; involucre multiseriate.