98 
PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, 28 Sept. 2018, No. 2 
Illustration.— Figure 4F. 
Local name.— “palo de agua,” {Quarles van Ufford 137). 
Conservation.— Louteridium purpusii has an EOO of 944 km 2 . Two prominent threats are 
evident throughout most or all of its known distribution, coffee agriculture and volcanic eruptions. 
Numerous active volcanos lie within and adjacent to the entire EOO of this species. Most of the 
occurrences of the species are within the prime growing elevations (i.e., 900 to 1800 m) for Cof- 
fea arabica L., and within two important coffee-growing regions (the Soconusco region of Chia¬ 
pas, Mexico and the departments of San Marcos and Quetzaltenango in Guatemala). Mexico and 
Guatemala are two of the top 10 coffee-producing countries in the world (Anonymous 2003, 2018). 
Increasing demand for coffee worldwide (e.g., Lorenzetti 2016) has or could result in increased 
conversion of natural vegetation in the EOO of this species to agriculture. Thus, coffee production 
would appear to be the more immediate threat to L. purpusii. However, based on either threat, there 
would appear to be a single location for the species. A preliminary conservation assessment of 
Endangered (EN; Bl, a, b; IUCN 2017) is proposed for this species. 
Discussion.— This species resembles some plants of L. mexicanum (see discussion under that 
species), but differs by its more obovate leaves and pubescence. Additional morphological tenden¬ 
cies that distinguish these species include the more racemose (vs. thyrsoid) inflorescences of 
L. purpusii (with dichasial peduncle lengths of 0 to 2 (vs. 1 to 22) mm; the caducous bracteoles (vs. 
usually persistent in L. mexicanum)', and the generally longer styles (85 to 92 vs. 72 to 85 mm 
long), capsules (22 to 30 vs. 16 to 24 mm long), and capsular stipes (3 to 3.5 vs. 1 to 2 mm long). 
The distributional ranges of these two species are not known to overlap and are restricted to dif¬ 
ferent versants of Mexico and Guatemala. 
Additional specimens examined.— MEXICO. Chiapas: Mpio. Union Juarez, 17 km E of 
Cacahoatan [ca. 15°1’56.19”N, 092°5’27.65”W], D. Breedlove & A. Smith 31613 (DS, MEXU, 
MO); FincaNubes [ca. 15°03’43.30”N, 092°0V39.20”W], F. Miranda 1723 (LL,US); from [Finca 
San Antonio] Chicharras, E. Nelson 3749 (US); Finca San Antonio [Chicharras; ca. 15°7’26.12”N, 
092°14’45.30”W], L. Quarles van Ufford 137 (U). GUATEMALA. Quezaltenango: Sta. Maria 
Ikibal [not located, possibly Santa Maria de Jesus], C. Bernoulli & O. Cario 2254 (K); lower 
S slope of Volcan Santa Maria, 0.3 mi W of jet. Finca Pirineos road with hwy. 95 at KM 97 [ca. 
14°41’5.41”N, 091°32’50.04”W], C. Broome 728 (CAS, DUKE, F, MICH, US); de la represa de 
Santa Maria al Volcan Pecul [ca. 14°43’26.73”N, 091 o 30’42.09”W], Equipo CECON1063 (MO); 
San Jose Buena Vista, Costa Cuca, [ca. 14°41’53.74”N, 091°46’35.82”W], L. Rodriguez 444 (P); 
Palmar, [ca. 14°39’12.22”N, 091°35’25.38”W], A. Skutch 1451 (F, US); Finca Pireneos, below 
Maria de Jesus, [ca. 14°41’38.02”N, 091°32’30.77”W], P. Standley 68259 (F, US); along old road 
between Finca Pirineos and Patzulin, P Standley 86714 (F); 86726 (F), 86749 (F), 86750 (F, US), 
86763 (F); along Quebrada San Geronimo, Finca Pirineos, lower S-facing slopes of Volcan Santa 
Maria, between Santa Maria de Jesus and Calahuache, J. Steyermark 33435 (F); off Hwy. 95 at KM 
197, old road to Finca Pirineos, ca. 0.5 mi from main hwy., D. Stone 3086 (DUKE); Colomba, 
Finca San Francisco Pie de la Cuesta, 14°43’41.05”N, 091°43’04.45”W, L. Velasquez & W. Lopez 
1792 (CAS). San Marcos: Finca El Porvenir along Rio Chopal, S-facing slopes of Volcan Taju¬ 
mulco [ca. 14°57’36.58”N, 091°56’40.73”W], J. Steyermark37501 (F); El Tumbador, fincaNueva 
Granada, 14°51’19.9”N, 091°53’05.9”W, L. Velasquez et al. 658 (BIGU, CAS). 
10. Louteridium rzedowskianum T.F. Daniel, Proc. Calif. Acad. Sci. 64:144. 2017. Louterid¬ 
ium brevicalyx Rzed., Ciencia (Mexico) 28:53. 1973, nom. inval., non Louteridium brevicalyx 
A. Richardson (1972). Louteridium rzedowskii T.F. Daniel, Madrono 31:91. 1984, nom. inval. 
Type.— MEXICO. Guerrero: Mpio. Chilpancingo, Rincon de la Via, cerca de Agua de Obispo 
