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PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, 28 Sept. 2018, No. 2 
la Via, cerca de Agua de Obispo, 9-VIII-1964 (vegetative) and 23-III-1963 (fruiting), H. Kruse 
1380 (EAP, ENCB, FCME, MEXU, MICH, MO, US); Mpio. Chilpancingo, Rincon de la Via, 
27-1-1970, H. Kruse 2701 [catalog # 4755] (MEXU); same locale, 14-VII-1970, H. Kruse 2701-b 
[catalog #5033] (B, FCME, MEXU). 
11. Louteridium tamaulipense A. Richardson, Sida 3: 448. 1969. Type.— MEXICO. 
Tamaulipas: ca. 5 km NW of Gomez Farias toward Aguacates [ca. 23°03’47.94”N, 
099°10’08.06”W], 370 m, rocky slope in wet forest, 30-VI-1969 (fir), A. Richardson 1388 (holo- 
type: TEX!, mounted on 4 sheets; isotypes: ENCB-image seen, F!, GH, K!, MEXU!, MICH!, NY!, 
OS-image seen, UC!, US!, WIS-images seen). 
Perennial herbs to shrubs to 2.5 m tall, possibly epipetric (Richardson 1972:63). Older 
(woody) stems prostrate (fide Richardson 1972:70), subquadrate or becoming irregularly fissured, 
lacking trichomes; younger (herbaceous) stems quadrate-sulcate to quadrate-alate, glabrous. 
Leaves apparently not all seasonally deciduous, ± evenly dispersed along young stems, petiolate, 
petioles to 85 mm long, blades subsucculent, ovate to elliptic, 80-260 mm long, 22-115 mm wide, 
1.9^1 x longer than wide, acuminate to subfalcate to caudate at apex, subattenuate to attenuate at 
base, surfaces glabrous, margin entire to subsinuate-crenate. Inflorescence a terminal pedunculate 
thyrse to 250 mm long (including peduncle and excluding corollas), peduncles to 84 mm long, 
evenly pubescent with erect to flexuose glandular trichomes 0.1-0.3 mm long, rachises similarly 
pubescent; dichasia sometimes modified by sympodial expansion and appearing as lateral branch¬ 
es (especially from proximal nodes of inflorescence), opposite, pedunculate, mostly 3-many-flow¬ 
ered, up to 115 mm long (excluding corollas), dichasial peduncles 3^15 mm long, pubescent like 
rachis. Bracts caducous, linear-lanceolate, 9-19 mm long, 1-2.3 mm wide, abaxially pubescent like 
rachis. Bracteoles and secondary bracteoles caducous, lanceolate to linear-lanceolate, 9-14 mm 
long, 2-3 mm wide, abaxially pubescent like rachis. Flowers pedicellate, pedicels to 46 mm long, 
pubescent like rachis. Calyx 32—47 mm long, lobes subheteromorphic, membranaceous in texture 
(i.e., neither succulent nor coriaceous), apically acuminate, abaxially pubescent like rachis, poste¬ 
rior lobe planar, lance-ovate to ovate, 33^15 mm long, 10-17 mm wide, slightly to conspicuously 
larger than other lobes, lateral lobes lance-ovate to ovate, 29-39 mm long, 8-14.5 mm wide. Corol¬ 
la whitish to greenish yellow, 55-60 mm long, externally puberulent with scattered glands to 
0.1 mm long, tube ca. 25-30 mm long, narrow proximal portion 3-6 mm long, 3-9 mm in diame¬ 
ter, throat 20-25 mm long, 20-30 mm diameter at mouth, lobes spreading to recurved, triangular 
to ovate, 15-27 mm long, 5.2-9 mm wide, tapered and ± acute at apex. Stamens 2, 50-63 mm long, 
filaments glabrous distally (not seen proximally), thecae 11-15 mm long; staminodes (if present) 
not seen. Style 48-73 mm long, glabrous distally, pubescent with glandular trichomes proximally, 
stigma unequally 2-lobed, lobes often recoiled, ± oblong, 1.5-3.5 mm long, width not determined. 
Capsule 22-28 mm long, diameter not determined, pubescent with glandular trichomes 0.05-0.2 
mm long, stipe 1-4 mm long. Seeds up to 20 per capsule, 3.5-5 mm long, 3^1 mm wide, surfaces 
smooth or with low subconic tubercles. 
Phenology. — Flowering: March-June, September, December; fruiting: March-April, Sep¬ 
tember. Dressier ( s.n .) notes that flowers are nocturnal. Richardson (1972) observed flowers of 
L. tamaulipense over 14 hours (from 18:00 to 08:00) in September of 1969. He noted: 1) that corol¬ 
las began opening at sunset and falling in the early morning; 2) the lack of a floral scent; 3) that no 
nectar was found in the gibbous throat of corollas; 4) the nectary had an intensely sweet taste; and 
5) hummingbirds visited flowers at dusk and in the early morning. 
Distribution and habitat.— Northeastern Mexico (Tamaulipas; Fig. 8); plants occur on 
