DANIEL: NEW AND RECONSIDERED MEXICAN ACANTHACEAE XII 
145 
diameter near midpoint, throat 11-20 mm long, 20-25 mm in diameter at mouth, upper lip 11-15 
mm long, lobes ovate to subtriangular, 10-11 mm long, 9-11 mm wide, lower lip 12-15 mm long, 
lobes ovate to subtriangular, 12-13 mm long, 11-12 mm wide. Stamens 4, exserted 35 mm beyond 
lips of corolla, 55-75 mm long, filaments not seen, thecae 7.5-8 mm long. Style 80-82 mm long, 
glabrous, stigma ± funnelform, 1.5 mm long. Capsule 38-47 mm long, pubescent throughout with 
erect glandular trichomes to 0.1 mm long, stipe 4 mm long. Seeds up to 24 per capsule, 4-4.5 mm 
long, 3-4 mm wide, surfaces minutely granulate to ± scurfy, marginal region swollen, periphery 
pubescent with appressed hygroscopic trichomes. 
Phenology. — Flowering: January; fruiting: January-March. Label information on the type 
notes that flowers are “pronto caedizas,” possibly referring to their being soon deciduous during 
the day, and thus likely largely nocturnal as in other species of the genus. 
Distribution and habitat.— Western Mexico (central Guerrero; Fig. 6); plants occur on 
l im estone slopes in tropical subdeciduous forests (selva mediana subcaducifolia) at elevations near 
750 m. 
Illustration. — Rzedowski (1973: fig. 4). 
Conservation. — This species remains known only from the type locality, where an unknown 
number of individuals occurs, and from which specimens were collected over a period of seven 
years (1963-1970). No information is known as to the current status of this population or any pos¬ 
sible threats to it. Therefore, according to IUCN (2017) guidelines, Louteridium rzedowskianum 
has to be assessed as Data Deficient (DD). 
Paratypes. — MEXICO. Guerrero: Mpio. Chilpancingo, Rincon de la Via, cerca de Agua de 
Obispo [ca. 17°17’45.05”N, 099°28’17.54”W], 9-VIII-1964 (vegetative) and 23-III-1963 (fruit¬ 
ing), H. Kruse 1380 (EAP, ENCB, FCME, MEXU, MICH, MO, US); Mpio. Chilpancingo, Rincon 
de la Via [17°17’15”N, 99°28 , 55”W], 27-1-1970, H. Kruse 2701 [catalog # 4755] (MEXU); same 
locale, 14-VII-1970, H. Kruse 2701-b [catalog #5033] (FCME, MEXU). 
Discussion. — Although validly published at the time, but illegitimate, Louteridium brevica- 
lyx Rzed. is no longer accepted as valid because more than one gathering was included within the 
type—a retroactive change in Article 8 of the nomenclatural rules enacted in the “Saint Louis 
Code” (Greuter et al. 2000). This species subsequently became known as “L. rzedowskii” when 
Daniel (1984) proposed a new name for Rzedowski’s later homonym. Daniel’s name also became 
invalid with the change in Article 8. To rectify this situation, and to honor Jerzy Rzedowski and his 
recognition of the species, Louteridium rzedowskianum is herewith newly described. 
The sole collector of this species, Hubert Kruse, obtained specimens of these plants on multi¬ 
ple occasions in order to have leaves, flowers, and fruits. These were admixed to create “complete” 
herbarium specimens, with an indication of the date of collection of foliage (i.e., 9 Aug 1964), 
flowers (i.e., 19 January 1964), and fruits (i.e., 23 March 1963) on each one. Because the speci¬ 
mens all contain materials of these organs collected on different dates, the citation of any one of 
the specimens as the type is no longer acceptable for valid publication of the name. The flowering 
portion (only) of the Kruse specimen designated by Rzedowski as the holotype of L. brevicalyx at 
ENCB is designated above as the holotype of L. rzedowskianum. Fruiting and vegetative portions 
of this specimen, those same portions on the isotypes noted above, and the subsequent (1970) 
Kruse collections noted above are all paratypes. 
Agua de Obispo is about 3 km (linear distance) NE of Rincon de la Via, on the old Chilpancin- 
go-Acapulco highway (Mexico 95). It is at an elevation of about 960 meters, whereas Rincon de 
la Via is at about 750 meters. Therefore Kruse’s locality information is somewhat contradictory. 
I have mapped the species between these two locales. Kruse made additional collections from the 
type locality in 1970. Plants bearing leaves only were collected from the type locality in July and 
