We reconstructed phylogenies of populations of three closely related species of Spigelia (Loganiaceae sensu lato) to test hypotheses about relationships and taxonomic boundaries. The species studied occur in the southeastern U.S. with a disjunction in their distribution along the Gulf Coastal plain between Florida and Texas. Two sets of data, restriction sites of cpDNA and ITS sequences, were analyzed. We found three well-supported clades of cpDNA types that correspond to previous species delimitations, and the cpDNA clades representing the two Texas species were most closely related. This pattern of relationships was unexpected based on strong morphological similarities between the coastal plain Texas taxon, S. texana, and the Florida taxon, S. loganioides. Phylogenetic hypotheses based on ITS sequences were not strongly supported because there were few informative changes among the sequences, and therefore a combined analysis recovered similar topologies as with the cpDNA data alone. The distributional pattern in this group of Spigelia was compared to that of other groups of organisms in the Gulf Coast region in an effort to find similarities that may indicate a shared geological history.

Hoffmannseggia, a genus of the Caesalpinieae, Caesalpinioideae, has been treated as a synonym of Caesalpinia or as a distinct genus with as many as 25 species. Recent molecular and morphological work has provided strong support for a monophyletic Hoffmannseggia distinct from either Caesalpinia or Pomaria. This revision provides the first complete nomenclature and discussion of the 11 species (12 taxa) of Hoffmannseggia occurring in North America. Included are a key to the species, maps showing distributions, and photographs of flowers or fruits of six species.

Umber (1979) provided a brief overview of Glandularia for North America. In this treatment he recognized 21 taxa as occurring in Mexico (excluding the widely cultivated G. pulchella), 19 species, with two of these (G. bipinnatifida and G. elegans) possessing varietal categories. From among these I can recognize only 15 species G. amoena, G. bajacalifornica (including G. shrevei), G. bipinnatifida (including 3 varieties), G. brachyrhynchos, G. delticola, G. elegans (without designated varieties), G. gooddingii, G. lilacina, G. polyantha, G. pumila, G. quadrangulata (including G. racemosa and G. verecunda, these believed to be forms having nutlets without apical appendages), G. teucriifolia (including G. rinconensis), G. tumidula, and G. turneri Nesom, the latter described after Umber's treatment. Additionally, one new species from southern Nuevo Leon and closely adjacent Zacatecas, G. alejandrana B. L. Turner, is proposed and illustrated. A key to all of the species is provided, along with maps showing their distributions.

A systematic treatment of Dyschoriste (Acanthaceae) of northern Mexico, Arizona, and Texas is provided. The taxa show few unique characteristics; taxonomy is largely based on differences in vestiture and growth habit; intergradation is widespread. Five species are recognized: (1) D. schiedeana with four intergrading varieties, var. schiedeana, var. cinerascens, var. decumbens, and var. prostrata, of central-northern Mexico north to trans-Pecos Texas and Arizona; (2) D. linearis var. linearis and var. sanpatriciensis of Texas; (3) D. crenulata, of the Big Bend area and southmost Texas and adjacent Mexico; (4) D. poliodes var. poliodes, var. obispoensis, and var. glabra; and (5) D. greenmanii of Nuevo León and Tamaulipas. Keys and descriptions are provided.

A taxonomic treatment of Sida L. sect. Ellipticifoliae Fryxell is presented in which eight species and two varieties are recognized. Brief descriptions, a key to species, distribution maps, illustrations, and notes on ecology, etymology, typification, and species relationships are included. Sida inflexa Fernald is reduced to synonymy under S. elliottii Torr. & A. Gray, S. rubromarginata Nash is resurrected in light of new characters, and S. elliottii var. parviflora Chapm. is broadly redefined.

The new species Sterculia xolocotzii represents the second native New World Sterculia species with palmately compound leaves to be described, the first being S. mexicana R. Br. Sterculia xolocotzii is known only from Mexico, where it has been collected in lowland rain forests of the Uxpanapa-Chimalapa region of Veracruz and Oaxaca and once in the Los Tuxtlas area of Veracruz. It can be distinguished from S. mexicana, with which it often grows, by habit, phenology, and numerous morphological characters. The morphology and ecology of S. xolocotzii are detailed, and the distribution and typification of S. mexicana are also discussed.

A new species from Honduras, Tintinnabularia murallensis, is described and illustrated. The new species broadens the current circumscription of the genus. An illustration of the new species is provided, as is a distribution map for all recognized species of the genus.

Heterocentron chimalapanum, an unusual species from the dense cloud scrub forest of the Chimalapa region of the Isthmus of Tehuantepec in Oaxaca, Mexico, is described and illustrated. Most closely related to H. elegans, H. chimalapanum differs from that species in its bright pink petals, smaller leaves, and strigose hypanthia.