Trematolobelia: Seed Dispersal; Anatomy of Fruit and Seeds

Abstract

The endemic Hawaiian genus Trematolobelia (Lobeliaceae, or Campanulaceae, subfamily Lobelioideae) was erected on the basis of its distinctive fruit. This fruit has a seed-dispersal mechanism unique in the family. Assertions have been made by some workers that holes in the fruit wall are the work of insects, and are not related to the dispersal mechanism. This contention has been adequately disproved by other investigators, but, in fact, the precise nature of the dispersal mechanism and the anatomical structure responsible for its action have never been adequately described. In addition, the present study reveals the potential taxonomic use of capsular anatomy, a feature of importance because various authors recognize one, two, or three species in the genus. These species are based largely on floral features or foliar characteristics, and not on those of the fruit. Unusually good material of Trematolobelia collected by the writer during the summer of 1958 provides a sufficient basis for presenting the features mentioned above in some detail.