52 
PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, 28 Sept. 2018, No. 2 
from membranaceous to subsucculent in texture and from subhomomorphic to usually heteromor- 
phic in form. When heteromorphic, the posterior lobe differs from the homomorphic lateral lobes 
either in size, shape, or configuration. The posterior lobe may be smaller or larger than the lateral 
lobes, and is often conduplicate (vs. planar in lateral lobes). In L. parayi, the posterior lobe is 
saccate or bears a two-parted flap of tissue at the basal portion of the abaxial surface that protrudes 
outward or downward from the abaxial surface for up to 2.5 mm (Fig. 4G); this feature is other¬ 
wise unknown in the genus and thus considered to be apomorphic for the species. 
Corollas of Louteridium are primarily nocturnal, relatively large (35 to 72 mm in overall 
length), and mostly drably colored (white, yellow, greenish, dark chestnut to maroon, or brownish, 
and often with maroon discoloration or veins). Corollas that vary conspicuously in color were 
noted for some species (e.g., L. donnell-smithii, L. mexicanum). The tube consists of a relatively 
short (0.5 to 17 mm long) and subcylindric narrow proximal portion (from the base of the corolla 
usually to the point of insertion of the stamens) that abruptly and either symmetrically or asym¬ 
metrically expands distally into a large and obliquely bell-shaped (strongly saccate anteriorly) 
throat. The conspicuous throat extends from the point of insertion of the stamens distally to the 
base of the limb of the corolla. A linear or ± rectangular invagination of the corolla along each side 
of the anterior (= ventral) portion of the throat is evident in most species (Fig. 2D, K). It general¬ 
ly runs from near the junction of the narrow proximal portion of the corolla tube with the throat 
distally along the lateral sides of the throat toward the mouth of the corolla. It varies in size; for 
example, in L. donnell-smithii it is 17 to 25 mm long and 1 to 2 mm wide, whereas in L. char- 
taceum, it is 6 mm long and 4 mm wide. At least in L. mexicanum, the internal architecture of the 
corolla is complex. The lateral invaginations bear flanges (or ridges) along the posterior (upper) 
and anterior (lower) sides of their internal surfaces thereby forming a channel along most or all of 
the throat. Each lateral channel is closed proximally by the curved overlapping of the two flanking 
flanges, but these spread apart toward the distal end of the channel opening it on its inward-facing 
side near the mouth of the corolla. In addition to the lateral invaginations along the throat, there is 
also a ventral invagination with two internal flanges that form a nearly identical channel along the 
most or all of the anterior-most (basal) part of the throat. Collectively, the three invaginations/chan¬ 
nels of the corolla, along with the filament curtain (see below), appear to form an extensive nectar 
chamber along the anterior portion of the saccate throat. Quantities of nectar examined in this 
species corroborate this conclusion (see Reproductive Biology). Lateral invaginations were noted 
to be present, but not as prominent internally in L. donnell-smithii ; and although sometimes these 
were not clearly evident on the external surface in dried corollas of L. parayi, they are clearly 
evident on fresh corollas of that species (Fig. 4H). The subbilabiate limb consists of a bilobed upper 
lip and a trilobed lower lip; the lobes vary from spreading (i.e., ca. 90° from throat) to recurved to 
recoiled, thereby presenting a large (17 to 40 mm in diameter, measured from anterior to posterior 
points) and open mouth at the distal end of the throat. The lobes are shorter than the lips to which 
they pertain, and are either subequal or unequal in size (e.g., lobes of the upper lip are shorter and 
narrower than those of the lower lip in L. parayi ). Internally, corollas are mostly glabrous except 
in the region of the tube at and proximal to the insertion of the staminal filaments. There, eglan- 
dular trichomes are present in most species (or absent, at least in L. chartaceum) and vary from 
sparse to dense. 
The androecium consists of four stamens in section Tetrandrium and two stamens in sections 
Louteridium and Parcostamium. One or two usually short staminodes are commonly evident in the 
corolla tube as well. The epipetalous stamens are generally long-exserted from, and extend up to 
ca. five centimeters beyond, the posterior side of the corolla (Fig. 4). In L. costaricense, they tend 
to be exserted only about 1 to 1.5 cm beyond the upper lip of the corolla (Fig. 4A, B). The fila- 
