DANIEL & TRIPP: LOUTERIDIUM : TAXONOMY, BIOLOGY, AND CONSERVATION 55 
Figure 6. Pollen exine sculpturing of Louteridium spp. A. L. brevicalyx (Daniel & Steinmann 11913). B. L. costaricense 
(van der Werff 7019). C. L. donnell-smithii (Daniel & Veliz 11337). D. L. mexicanum (Breedlove & Thorne 30786). 
E. L. purpusii (Breedlove & Smith 31613). F. L. tamaulipense {Hutchinson s.n.). All scales = 10 pm. 
The gynoecium consists of an oblong to subrectangular ovary that sits on or is partially embed¬ 
ded in a prominent nectar disk; a long-exserted style (less exserted in L. costaricense ), which like 
the stamens is exserted from the posterior side of the mouth of the throat; and an equally to 
unequally bilobed stigma that is positioned near or exserted up to ca. 1.5 cm beyond (i.e., in front 
of) the anthers and either at about the same level or up to 1 cm or more above or below them. The 
ovary is glabrous or pubescent with trichomes like those of the capsule. The nectar disk is annular 
to ± cupulate, fleshy, up to 7 mm in diameter (when fresh), and 1.5 to 3 mm high. 
Pollen. — Pollen of all species of Louteridium except for L. koelzii (unavailable) was studied 
with scanning electron microscopy as described by Daniel (1998). Pollen of the ten species exam¬ 
ined is remarkably uniform (Appendix 1 and Figs. 5, 6), and can be described as follows: spheri¬ 
cal to subspheroidal (because polar and equatorial axes could not be determined in individual 
grains, a P:E ratio could not be determined; however, measuring the longest and shortest diameters 
gave ratios of 0.93 to 1.08), very large (106 to 143 pm in diameter; n = 29, mean = 122, SD = 
10.88), and pantoforate; apertures more than 50, circular, 5 to 18 pm in diameter, and with surfaces 
usually ornamented like those of the interapertural exine; and interapertural exine with sculpturing 
elements of two non-overlapping sizes: the larger elements consist of gemmae (widest above base) 
to baculae (widest at base and not tapering apically) 3.0 to 6.3 pm in diameter and 1.7 to 7.0 pm 
high, the smaller sculptural elements are sparse to dense (sometimes jigsaw-like and nearly form¬ 
ing a reticulum) and vary from gemmae to pilae to baculae to echinae or are irregularly shaped ver- 
rucae to rugulae with the longest axis 0.1 to 2.5 pm. These smaller sculptural elements (and occa¬ 
sionally also a few of the larger elements as well) cover the apertures (Fig. 6), often rendering aper¬ 
tures visible in unacetolyzed grains only when the apertural surface and intine begin to bulge or 
