66 
PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, 28 Sept. 2018, No. 2 
The greenhouse studies reveal that, like most Acanthaceae studied to date (e.g., Daniel 1993 
and additional unpublished data), L. mexicanum is self-compatible; of the 22 self-pollinated flow¬ 
ers, 17 set fruit (77%). None of the emasculated flowers set fruit, which strongly suggests that 
autonomous agamospermy does not occur in this species. Two of the 13 control flowers (15%) set 
fruit. Although neither bats nor birds had access to the plant studied, other potential pollinators 
were not specifically excluded in the greenhouse. Thus, whether the control flowers that set fruit 
resulted from pollination by a floral visitor or via autogamy remains unknown. The presence of 
pollinators in the greenhouse, if any, would not appear to have been pervasive because none of the 
10 emasculated flowers set fruit. 
It is worth noting that although asexual reproduction via autonomous agamospermy was not 
shown to occur in Louteridium mexicanum, vegetative propagation via fragmentation was noted to 
occur in this and two other species. One of the plants of L. dendropilosum cultivated from seed rot¬ 
ted at the base. Prior to the death of this plant, the apical two to four centimeters of six branch stems 
were excised and partially buried in potting soil. All six cuttings grew into healthy plants. Addi¬ 
tionally, cuttings made in the field of both L. chartaceum and L. mexicanum were subsequently 
planted and successfully cultivated in San Francisco, California. The degree to which sexual repro¬ 
duction vs. reproduction via fragmentation is important to natural populations remains unknown. 
Floral Abscission, Pollen Viability, and Stigma Receptivity.— Observations of 
Louteridium mexicanum grown in a greenhouse (Breedlove & Daniel 70879gh) revealed that 
unpollinated flowers abscise from the plant (thus terminating anthesis of those flowers) on the 
morning of the second day the flowers are open. Abscission of the entire flower and pedicel occurs 
at or near the base of the pedicel (vs. corolla with epipetalous stamens falling first from the flower 
in most other Acanthaceae). It was also observed that manually self-pollinated flowers generally 
do not abscise (although the corolla eventually either falls or withers), but continue developing 
toward fruit-set. Thus, floral abscission was used to test whether pollination is more effective 
during the evening of day 1 (at the com- Table 5. Efficacy of pollination at different times in the 
mencement of anthesis) or during the floral life-cycle of Louteridium mexicanum based on floral 
morning of day 2 (ca. 15 hours later, but abscission. See text for discussion, 
prior to floral abscission). Isolated 
flowers were marked and treated as 
shown in Table 5. 
From this experiment, it would 
appear that, in most instances the pollen 
is viable and the stigma is receptive for 
most or all of the time that flowers typically remain on the plant. Thus, both diurnal and nocturnal 
pollinators could be effective ones. Fruit-set, which only occurs when embryos develop in Acan¬ 
thaceae, was not determined for the self-pollinated and retained flowers in this experiment. It 
remains to be determined whether abscission at or near the base of the pedicel of non-pollinated 
flowers is widespread, and thus possibly synapomorphic, for species of Louteridium. Somewhat 
similar abscission was observed (by TFD) in cultivated plants of two species of Ruellia ( R . conzat- 
tii and R. laslobasensis ), both of which have mostly nocturnal flowers with corollas that are some¬ 
what similar to those of Louteridium in size, shape, and coloration. However, in these two species, 
floral abscission occurs at the base of the calyx, between two and four days after earlier abscission 
of the corolla. 
Treatment 
No. Tagged 
No. Abscised 
Control (no manual self-pollination) 
10 
10 
Selfed on evening of day 1 
10 
2 
Selfed on morning of day 2 
8 
2 
