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Series 4, Volume 65, 28 Sept. 2018, No. 2 
trichomes 0.05-0.2 (-1) mm long, rachis pubescent with erect to flexuose eglandular trichomes 
0.1-0.4 (-1) mm long; dichasia opposite, pedunculate, 1-3 (or more)-flowered, to 63 mm long 
(excluding corollas), dichasial peduncles 3-20 mm long, pubescent like rachis. Bracts caducous, 
lance-elliptic to elliptic, 12-17 mm long, 3.5-5 mm wide, abaxially pubescent with erect to flexu¬ 
ose eglandular trichomes 0.05-0.2 mm long. Bracteoles and secondary bracteoles usually present 
on young inflorescences but becoming deciduous as inflorescence matures, lance-elliptic to ellip¬ 
tic, 7-14 mm long, 2-3.5 mm wide, abaxially pubescent like bracts. Flowers pedicellate, pedicels 
10-50 mm long, pubescent like rachis. Calyx 17-28 mm long, lobes subheteromorphic, mem¬ 
branaceous, abaxially pubescent with erect (to ± antrorse) eglandular trichomes 1-2 (-2.3) mm 
long, posterior lobe planar to ± conduplicate, ovate-elliptic, 17-25 mm long, 11-15 mm wide, usu¬ 
ally slightly larger than lateral lobes, acuminate at apex, lateral lobes ovate-elliptic to elliptic to 
obovate, 15.5-22 mm long, 9-15 mm wide, rounded to acute at apex, veins of lobes prominent 
(ca. 9 major veins). Corolla “pale green” to greenish yellow, 50-55 mm long, externally glabrous, 
tube 29-33 mm long, narrow proximal portion 9-13 mm long, 9-16 mm in diameter near midpoint, 
throat 15-20 mm long, 30-35 mm in diameter at mouth, lobes spreading to recurved, “narrowly 
ovate to subcircular” (fide Miranda and McVaugh 1962), 18-24 mm long, 17-27 mm wide, round¬ 
ed to acute at apex. Stamens 4, 72-90 mm long, filaments glabrous distally, pubescent proximally 
with eglandular trichomes, thecae 10-12 mm long; staminode (if present) not seen. Style 50-55 
mm long, glabrous, stigma lobes 1.5 mm long, shape and width not determined. Capsule 25-30 mm 
long, 7-10 mm in diameter, pubescent throughout with erect to flexuose to antrorse eglandular 
trichomes 0.05-0.2 mm long, stipe 1.5-2 mm long. Seeds up to 16 per capsule, 7-8 mm long, 5-6 
mm wide, surfaces minutely papillose. 
Phenology. — Flowering: December-February; fruiting: February. 
Distribution and habitat.— West-central Mexico (Jalisco, Michoacan; Fig. 8); plants occur 
on limestone slopes in “high forest dominated by Brosimum ” in regions of tropical subdeciduous 
and deciduous forests at elevations from 500 to 1400 meters. 
Illustrations. — Figure 14; Miranda and McVaugh (1962:183, fig. 2). 
Conservation. — Louteridium koelzii is currently known from a very limited region of west¬ 
ern Mexico (EOO = 5.3 km 2 ; AOO =12 km 2 ). The species is not known to occur in a protected 
area, and it has not been recollected since 1975 (i.e., McVaugh 26180; although see discussion 
below about an undetermined plant from a nearby region of Jalisco). Based on current knowledge, 
there appear to be two subpopulations about 80 km apart, one in Jalisco and one in Michoacan. 
Comparing historic landsat images (2006 to 2017) via Google Earth Pro (2018) in the region of the 
known collections from Jalisco, it is evident that deforestation for agriculture has reduced the 
natural vegetation there substantially (ca. > 30%), thus creating a threat to this species, at least in 
that region. No specific threat has been identified for the subpopulation in Michoacan. Thus, there 
are two locations for the species, and a threat is evident for one of them. Based on these observa¬ 
tions, a preliminary conservation assessment of Endangered (EN; Bl, a, b) is proposed for 
L. koelzii. 
Discussion.— An undetermined specimen of Louteridium from western Mexico (Jalisco: 
Mpio. Jilotlan de los Dolores, Cerro de San Antonio, 15 km N de Tazumbos, matorral subtropical 
en suelos con pedregocidad de toba volcanica, 900 m, 6 Feb 1982, F. Santana Michel 1081, IBUG) 
does not seem to pertain to either species known from nearby regions (i.e., L. brevicalyx or 
L. koelzii ) or other species of the genus. The plant, which lacks mature flowers, is geographically 
closest and morphologically most similar to L. koelzii. Like that species, it occurs in an apparent¬ 
ly dry habitat and has seasonally deciduous foliage. Both of these characteristics suggest that the 
