62 
PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, 28 Sept. 2018, No. 2 
Figure 11 . Map of southern Mexico (showing states) and northern Central America with distribution of Louteridium 
mexicanum. Circles may pertain to multiple collections. 
Flowering Phenology. — Flowering of Louteridium occurs throughout the year. Table 3 
shows the known months of flowering for each species (i.e., their flowering seasons). It is clear 
from these data that two phenological patterns are evident among species, corresponding to the 
sections of the genus. Fruiting periods are noted for each species in the taxonomic accounts below. 
Species of section Tetrandrium, all of which occur in dry forests, only flower between Decem¬ 
ber and March. These months are in the middle of the dry season (i.e., November to April) along 
the western and southern coasts of Mexico (Rzedowski 1978) and near the end of the rainy 
season/first half of the dry season in Belize (Balick et al. 2000). Among species in this section, both 
L. brevicalyx and L. rzedowskianum are known from relatively few collections, and it is likely that 
their respective flowering periods may be somewhat longer than currently known. Flowering 
during dry seasons is a pattern typical of other Acanthaceae that occur in dry forests of the north¬ 
ern Neotropics (e.g., Daniel 1986, 1990; Tripp 2010; Tripp and Lujan 2018). 
Species in sections Louteridium and Parcostamium, all of which occur in moist to wet forests, 
tend to have longer flowering periods that last either throughout (i.e., L. costaricense ) or for a 
greater portion of the year than those of species in section Tetrandrium. All of species of sections 
Louteridium and Parcostamium flower, or continue flowering, during some or all of the months 
between June and September, which corresponds to the wettest season in Mexico (Rzedowski 
1978) and Central America (Anonymous 2018). 
