144 
PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 64, No. 7 
15°58’39.7”N, 096°05’54.9”W, J. Pascual 1396 (MEXU, SERO, TEX); Distr. Pochutla, Mpio. 
San Miguel del Puerto, 300 m de la terraceria sobre la vereda rumbo Rio la Laja, 15°58’49.9 ,, N, 
096°06’6.9”W, A. Saynes V. et al. 3831 (MEXU, SERO); Distr. Juchitan, Mpio. El Barrio, parte 
alta del Cerro Palmasola, junto a la antena de microondas [ca. 16°44’32.52”N, 095°5’36.04”W], 
S. Zamudio R. 6352 (CAS, IEB). 
Discussion. — Pollen of Louteridium dendropilosum (Fig. 4F, I) resembles that of its con¬ 
geners. The posterior calyx lobe of this species is conspicuously venose with the major veins pur¬ 
ple, whereas the lateral lobes are green (Fig. 7). A major morphological distinction among species 
of Louteridium S. Wats, is the number of stamens (two vs. four). This distinction does not appear 
to correlate with either geography or molecular phylogenetic relationships (based on the limited 
sampling to date; Tripp et al. 2013). Louteridium dendropilosum is unique among congeners by its 
dendritic trichomes, which are present on both vegetative and reproductive organs. Trichomes of 
other species may consist of one or more cells and be either glandular or eglandular, but they are 
not branched. 
Louteridium rzedowskianum T.F. Daniel, sp. nov. 
Louteridium rzedowskianum differs from its congeners by the following combination of char¬ 
acters: stamens four, calyx 5-9 mm long with lobes broadly ovate to triangular and 3.5-6.5 mm 
long, and capsule pubescent with glandular trichomes only. 
Louteridium brevicalyx Rzed., Ciencia (Mexico) 28: 53. 1973, non Louteridium brevicalyx 
A. Richardson (1972), nom. inval. Louteridium rzedowskii T.F. Daniel, Madrono 31: 91. 1984, 
nom. inval. 
Type. — MEXICO. Guerrero: Mpio. Chilpancingo, Rincon de la Via, cerca de Agua de Obis¬ 
po [ca. 17°17’45.05”N, 099°28’17.54”W], 750 m, 19-1-1964 (fir), H. Kruse 1380 (holotype: 
ENCB-002790-shoots bearing flowers only; photo seen; isotypes (shoots bearing flowers only): 
EAP!, ENCB-002789!, FCME!, MEXU!, MICH!, MO!, US!), see discussion below. 
Shrubs to trees to 4 m tall, trunk to 15 cm in diameter at base. Older (woody) stems irregular¬ 
ly fissured-striate, lenticellate, glabrous; younger stems not seen. Leaves deciduous, clustered at 
branch apices, petiolate, petioles 20-90 mm long, blades apparently subsucculent, lanceolate to 
ovate to elliptic, 82-260 mm long, 35-110 mm wide, 2-2.6 x longer than wide, (rounded to) acumi¬ 
nate at apex, cuneate to subattenuate at base, abaxial surface minutely glandular punctate (some¬ 
times not evident) and sparsely pubescent (especially near base) with flexuose eglandular 
trichomes 0.2-0.7 mm long or trichomes absent on mature leaves, adaxial surface very sparsely 
pubescent (if at all) with similar trichomes, margin entire to subsinuate, sparsely ciliate with tri¬ 
chomes like those of abaxial surface. Inflorescence a terminal, pedunculate thyrse to 30.3 cm long 
(including peduncle and excluding corollas), peduncle glandular puberulent with glandular 
trichomes to 0.1 mm long, rachis pubescent with erect glandular trichomes 0.05-0.2 mm long; 
dichasia opposite, pedunculate, mostly 1-3-flowered, to 50 (-70 in fruit) mm long (excluding corol¬ 
las), dichasial peduncles 6-14 (-29 in fruit) mm long, pubescent like rachis. Bracts caducous (not 
seen). Bracteoles caduceus (not seen). Flowers pedicellate, pedicels 23-30 (-48 in fruit) mm long, 
pubescent like rachis. Calyx 5-9 mm long, lobes subheteromorphic, apparently subsucculent, abax- 
ially pubescent with erect to flexuose glandular trichomes 0.05-0.2 mm long, posterior lobe sub- 
conduplicate, broadly ovate to subtriangular, 3.5-4.5 mm long, 3-4.3 mm wide, somet im es smaller 
than lateral lobes, subacute to acute at apex, lateral lobes planar, ovate to subtriangular, 4-4.8 mm 
long, 3-4 mm wide, acute at apex. Corolla dark purple with green in places or green with purple in 
places (fide Rzedowski 73), 35-39 mm long, externally puberulent with erect glandular trichomes 
to 0.1 mm long, tube 17-30 mm long, narrow proximal portion of tube 4.5-9 mm long, 6-11 mm in 
