Functional considerations and observations on the flowers of some Labiatae

The general bilabiate flower type or gullet-blossom was already recognized as functioning in diverse families by Delpino (lastly in 1887). The type seems adapted to hymenopters with precision of visits: not only by providing a lower lip as a favoured landing place with optical attraction and by ensuring co-ordination with the upper lip to limit visitor size, but also by providing precision of deposition and reception of pollen, viz. dorsally at the distal end. I add that the bifid stigma requires contact in the median plane, not from a side. This type of stigma may be considered as a consequence of the presence of two median carpels, but it also fits the ecological requirements extremely well. It also occurs in those Verbenaceae that show zygomorphy, but it prevails in Labiatae.