DANIEL & TRIPP: LOUTERIDIUM : TAXONOMY, BIOLOGY, AND CONSERVATION 67 
Conservation 
Walter and Gillett (1998) listed L. chartaceum and L. mexicanum as rare, and L. rze- 
dowskianum (as “L. rzedowskii”) as endangered. Data pertinent to conservation and preliminary 
conservation assessments, based on more recent IUCN (2017) guidelines, are here provided for all 
11 species of Louteridium. For each species, the presence of protected areas within their respective 
extent of occurrence (EOO; calculated using Google Earth Pro, 2018) is summarized, and the 
known occurrences of species in protected areas are also indicated. Protected areas noted in the dis¬ 
cussions include international, national, natural, and pertinent state/municipal parks; biosphere 
reserves; forest/nature reserves; field/research stations; formally protected biotopes and archeolog¬ 
ical sites; conservation centers; and wildlife sanctuaries. The inclusion of species in these areas is 
based on information from specimen labels and/or georeferenced collection data that show pres¬ 
ence of occurrences within the boundaries of such areas. 
Based on EOO calculations, six species ( L . brevicalyx, L. chartaceum, L. dendropilosum, 
L. koelzii, L. rzedowskianum, and L. tamaulipense ) are known from limited geographic ranges of 
less than 200 km 2 . One of these, L. rzedowskianum, is known only from the type locality, from 
which it was collected twice over a period of eight years. Two species ( L . parayi and L. purpusii) 
have EOO’s between 900 and 2,500 km 2 ; and three species (L. costaricense, L. donnell-smithii, and 
L. mexicanum) have relatively large distributions with EOO’s between 32,500 and 62,000 km 2 . 
Threats to species and/or reductions in populations, where known or perceived, are discussed in the 
taxonomic treatment below. 
The preliminary conservation assessments proposed here can be summarized as: Data Defi¬ 
cient ( L . rzedowskianum). Least Concern (L. costaricense, L. donnell-smithii, L. mexicanum). Near 
Threatened (L. tamaulipense). Endangered (L. chartaceum, L. dendropilosum, L. koelzii, L. parayi, 
L. purpusii), and Critically Endangered ( L . brevicalyx). Thus, six of the 11 species appear to per¬ 
tain to a threatened category. 
Taxonomy 
Louteridium S. Watson, Proc. Am. Acad. 23:283. 1888. Type. — Louteridium donnell-smithii 
S. Watson, [from Greek, luterion, a washing basin on a pedestal, and diminutive suffix, -ium, in 
reference to the form of the corolla] 
Neolindenia Baill., Bull. Mens. Soc. Linn. Paris 2:851. 1890. Type. — Neolindenia mexicana 
Baill. (= Louteridium mexicanum (Baill.) Standi.). 
Terrestrial, epiphytic, or epipetric (perennial herbs) shrubs or usually trees to 12 m tall and 25 
cm dbh (sometimes multi-trunked and/or with prop roots) bearing cystoliths. Leaves seasonally 
deciduous (i.e., leafless for part of the year) or persistent (some leaves always present), clustered 
at shoot apex or distributed ± evenly along new growth, opposite (often appearing quatemate when 
clustered), petiolate (to subsessile), petioles often tinged with pink or red, blades membranaceous 
to subsucculent, midvein (and secondary veins) often red or pinkish, margin entire to crenate-den- 
tate. Inflorescence a terminal open or contracted raceme to thyrse (or modifications thereof, see 
discussion in Morphology above); dichasia opposite or alternate, sessile to pedunculate, subtended 
by a bract, 1-many-flowered, often expanded and appearing like a lateral branch. Bracts (i.e., along 
primary rachis) opposite, green, often caducous, margin entire (to subcrenate). Bracteoles (i.e., sub¬ 
tending floral pedicels and lateral branches, when present, of dichasia) often caducous, those of a 
pair homomorphic. Flowers homostylous, long-pedicellate. Calyx deeply 3-lobed (or 5-lobed with 
3 prominent lobes and 2 reduced lobes in some presumably teratological calyces of L. brevicalyx ; 
see discussion under that species), somet im es ± accrescent in fruit, lobes subhomomorphic to het- 
