The plantain family as traditionally circumscribed consisted of only three genera: Bougueria, Littorella, and Plantago. However phylogenetic research has indicated that Plantaginaceae sensu stricto were nested within Scrophulariaceae. Although Veronicaceae is the oldest family name for this group, Plantaginaceae is a conserved name under the International Code of Botanical Nomenclature and thus has priority over any earlier family name for a family including Plantago. Furthermore, the ICBN does not consider family names published before 1789 to be nameseligible for conservation, thus ruling out Veronicaceae. The name Antirrhinaceae has been proposed for conservation over Plantaginaceae. In the meantime, the Angiosperm Phylogeny Group has accepted the name Plantaginaceae. However, Olmstead chose to use the name Veronicaceae, a later synonym. A group of genera including Lindernia has now been segregated as the family Linderniaceae, which is recognized by Haston et al. 2007 as "Post-APG II family". Plantaginaceae sensu lato are a diverse, cosmopolitan family, occurring mostly in temperate zones. The group consists of herbs, shrubs and also a few aquatic plants with roots. As the family is so diverse, its circumscription is difficult to establish. The leaves are spiral to opposite and simple to compound. Unusual in Lamiales is the absence of vertical partitions in the heads of the glandular hairs. The structure and form of the flowers is variable. Some genera are 4-merous, such as Aragoa ; others are 5- to 8-merous, such as Sibthorpia. The flowers of most genera are polysymmetric. The corolla is often two-lipped. In some taxa, the androecium is formed before the corolla. The fruit is a capsule that dehisces through the partitions between the cells.
Genera
The enlarged Plantaginaceae consists of 94 genera and about 1,900 species. The largest genus is Veronica, with about 450 species. Veronica also includes the genera Hebe, Parahebe and Synthyris, formerly often treated as distinct. All genera of Plantaginaceae were formerly included in Scrophulariaceae except where otherwise stated. Although GRIN includes Lafuentea Lag. in the tribe Antirrhineae, in the phylogenetic analysis of Fernández-Mazuecos et al. it was a sister to the Antirrhineae, as also noted by Albach. For the time being it should be considered an outgroup.
