Three new species of Ageratina subg. Neogreenella are described from Mexico, as follows: Ageratina mayajana, from Mpio. San Miguel Chimalapa, Oaxaca; Ageratina mazatecana, from Mpio. Santa Maria Chilchotla, Oaxaca; and Ageratina pochutlana from Districto Pochutla, Oaxaca. Although all of the taxa belong to the A. subg. Neogreenella, only the latter two relate to the A. mairetiana complex as defined by Turner (1987, 1997). A revised key to that complex is provided.

The genus Hoffmannseggia Cav., now recognized as a monophyletic group distinct from Caesalpinia and Pomaria, consists of 22 species and is amphitropically distributed between North and South America, with 11 species in arid and semi-arid areas of the southwestern USA and adjacent Mexico, and 12 species in southern South America. Recent publications have provided a revision of Hoffmannseggia for North America, a resolved phylogeny, and an analysis of the biogeography of the genus, but there is to date no treatment of all of the taxa. Here we present a key to the genus and its closest relatives, a key to all of the recognized taxa, typification, distributional data for each species, selected specimens examined for the South American taxa, and notes where appropriate.

Three species of Philadelphus are accepted as occurring in Trans-Pecos, Texas: P. mearnsii, P. microphyllus, and P. serpyllifolius. Philadelphus mearnsii is known only from Culberson and El Paso counties; P. microphyllus and P. serpyllifolius are more widespread. Philadelphus microphyllus is treated as having three intergrading varieties: Philadelphus microphyllus var. argenteus, P. m. var. crinitus (C. L. Hitchc.) B. L. Turner, and P. m. var. microphyllus. Philadelphus serpyllifolius is treated as having two intergrading varieties: Philadelphus serpyllifolius var. intermedius B. L. Turner, and P. s. var. serpyllifolius. Maps showing their distributions in the area concerned are provided.

Species-area relationships (SAR) are useful in predicting species richness for a given geographical area. Using SAR and the state of Texas as a case study, we present a model that provides a quantifiable and objective approach for identifying large scale data gaps in species inventories and museum collections by comparing documented species richness (determined by herbarium records) to predicted species richness. For Texas our results indicate that 88% of the counties have documented species richness values that are below predicted values based upon our results from the proposed model. Many biological survey and inventory programs are funded to document species occurrence and richness. Such studies help identify species of concern and enhance species conservation efforts. Future species inventories may benefit from such predictive models in identifying regions of large scale data gaps.

The tribe Mutisieae (excluding Barnadesieae) traditionally comprises 84 genera and approximately 900 species in three subtribes: Gochnatiinae, Mutisiinae, and Nassauviinae. We examined whole and fractured pollen grains of 51 genera from these subtribes by scanning electron microscopy (SEM) and light microscopy (LM). Additionally, we also examined 11 genera (Adenocaulon, Berardia, Brachylaeana, Cratystylis, Dipterocome, Eriachaenium, Gymnarrhena, Hesperomannia, Hoplophyllum, Tarchonanthus, and Warionia) whose tribal positions have been controversial. We present detailed tables of pollen characters for each taxon and 13 plates of SEM photos ofrepresentative taxa. We also provide limited discussion of pollen variation in the subbribes Gochnatiinae, Mutisiinae, and Nassauviinae and the tribal and subfamilial placement of the 11 problematic genera.