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PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, 28 Sept. 2018, No. 2 
in section Louteridium generally have membranaceous leaves. Geographically, species in section 
Parcostamium span the range of the genus, whereas species in section Louteridium occur only from 
southern Mexico to western Honduras. Although ancestral state reconstructions were not explicit¬ 
ly conducted on any character in this study owing to a relative paucity of terminals, it is plausible 
that plants that occurred in moist forests and plants having flowers with two stamens 
represent ancestral states in Louteridium, with later transitions to dry habitats and flowers with four 
stamens. Regarding stamen number, numerous other species in Trichantherinae {sensu Tripp et al. 
2013) similarly have flowers with only two stamens. Regarding habitat, this hypothesis is congru¬ 
ent with data from other lineages of Acanthaceae, such as Ruellia, in which arid habitat lineages 
Figure 3. Trichomes (SEM) of Louteridium spp. A, B. L. dendropilosum {Daniel etal. 11784), with dendritic trichomes 
bearing scattered micropapillae. C, D. L. donnell-smithii {Breedlove & Daniel 71197), with unbranched trichomes bearing 
micropapillae mostly arranged in lines. 
