The European species Wahlenbergia hederacea (L.) Rchb. (Campanulaceae) is molecularly distant from the remainder of the wahlenbergioids, and its inclusion with them renders the tribe Wahlenbergieae Endl. (1838) non-monophyletic. Additional support for this conclusion may be derived from its gross morphological characteristics, which are essentially campanuloid. However, although not strictly identical to that of Wahlenbergia Schrad. ex Roth, the capsule dehiscence mechanism of W. hederacea is still fundamentally wahlenbergioid and differs from the majority of campanuloids. Several genera such as Feeria and Jasione, which are intermediate between typical wahlenbergioids and typical campanuloids, have similar capsule characteristics, and it is postulated that Wahlenbergia hederacea, together with these ‘transitional’ genera, are all relatively ancient components of a campanulaceous palaeoflora of the early Tertiary of Eurasia. The wahlenbergioid type of dehiscence is considered to be a plesiomorphic character whereas the diverse campanuloid types of dehiscence mechanisms are derived under conditions of intense selection. It is suggested that Wahlenbergia hederacea is probably most closely related to, and ancestral to, the rapunculoid lineages of Campanula s.l. that subsequently evolved over much of Eurasia and North America. Consequently, Wahlenbergia hederacea should be classified in the Campanuloideae and the new generic name Hesperocodon Eddie & Cupido gen. nov. is proposed.

The seed coat morphology of 50 species of Campanulaceae sensu stricto, representing all 10 South African genera, was studied by scanning electron microscopy to gauge its usefulness in the diagnosis of genera or to support clades. Possible correlations with life form (annual, herbaceous and woody perennial) and ecological requirements such as fire response, rainfall requirements, bedrock and soil preferences, as well as habitat (e.g. fynbos, strandveld, renosterveld, grassland and karoo), were also investigated. Patterns of variation are described and interpreted as conforming to two seed coat types: reticulate (Type 1) and striate/wavy (Type 2). Type 1 seeds are further divided into eight subtypes. Some general trends emerged; for example, Type 1 seeds occur in all major clades of wahlenbergioids, Type 1A with a smooth coarsely reticulate surface being predominant in fynbos taxa, all of which are woody perennials. Several of the Type 1 seeds, together with Type 2 seeds, also occur in species with wider ecological amplitude, for example in karoo, strandveld or montane grasslands. In Siphocodon there is remarkable disparity in seed type between species. These variations in seed type generally appear to accord with current knowledge of climatic changes and soil evolution during the Tertiary of South Africa, and may be useful indicators of generic emergence and mosaic speciation in the major lineages of wahlenbergioids. However, it was concluded that seed coat types do not correlate closely enough with specific ecological requirements or life forms to be of unequivocal predictive value. Also, apart from Merciera and Treichelia, they are of limited use as a diagnostic character for genera, but are useful for distinguishing species.