Trichocereus (Cactaceae: Cactoideae: Trichocereeae) is a South American genus primarily inhabiting arid and semiarid areas in the Andean region of Ecuador, Peru, Bolivia, Chile and Argentina. The phylogenetic relationships of Trichocereus were examined on the basis of 39 exomorphological characters and chloroplast DNA sequences trnL-F and rpl16 for 17 species of Trichocereus, including three other genera of the tribe Trichocereeae (Echinopsis, Lobivia, Setiechinopsis), two of Notocacteae (Eulychnia, Wigginsia) and one of the Hylocereeae (Harrisia). The simultaneous phylogenetic analysis of both morphological data and noncoding DNA sequence data recovered Trichocereus as monophyletic if two species of Harrisia are part of it. Moreover, the Trichocereus clade is supported by three synapomorphies: basitonic growth with prostrate branches, imbricate scales along the floral tube, and subglobose fruits.

This paper clarifies the identity of Cereus macrogonus Salm-Dyck, the type species of the genus Trichocereus (Berger) Riccob., and specifies its synonyms and affinities. It is also intended to contribute toward stabilizing the generic nomenclature. An examination of Salm-Dyck's original description of C. macrogonus leads to an interpretation of the species, very plausibly of Peruvian origin, as a cactus which was later also named Trichocereus peruvianus Britton & Rose. A Neotype is designated that is consistent with the protologue. That interpretation coincides with the use of this name (C. macrogonus) in the botanical literature and in horticulture, which has been adhered to up to now. Trichocereus pachanoi Britton & Rose is here presented as a variety of T. macrogonus (Salm-Dyck) Riccob.: T. macrogonus var. pachanoi (Britton & Rose) S.Albesiano & R.Kiesling, nov. comb., and a lectotype for it is designated.

The arborescent Coleocephalocerus goebelianus occasionally has axillary branches arising from lateral cephalia, which is unexpected due to stem asymmetries in cephalia and the resulting mechanical stress. Axillary branching from cephalia is much more common in C. decumbens, C. fluminensis, and C. buxbaumianus, but these branches are largely (but not exclusively) on decumbent stems, therefore the cephalia act as less of a mechanical constraint. The clade containing Coleocephalocereus, Siccobaccatus, Melocactus, and Discocactus is sister to the clade containing Arrojadoa and Stephanocereus, the latter two genera usually branch from cephalia, indicating that axillary branching may be plesiomorphic in Coleocephalocereus.

Plant mines are structures with the form of a cavity caused by consumption of host plant tissue by the insect's miner larvae. Plant mines are more common in leaves, but in Cipocereus minensis, a species in which the leaves are modified spines, the miner activity is restricted to the stem. The aim of this paper was to document the morphological and anatomical differences in the infected and uninfected stems of C. minensis due to the feeding habit of the mining agent. Fresh tissue samples of non-mined and mined young stem of C. minensis were collected and examined in transverse sections. We hypothesize that the infection begins following mating when the females scratch the surface of the stem or while they feed on fruits and lay eggs, which subsequently develop into larvae, invading the cactus stem. The insect's miner larvae had mostly consumed the parenchyma tissue towards the center of the stem, and periderm formed along the entire path of the insect. This meristematic tissue or “wound periderm” is a common response for compartmentalization to isolate the damaged tissue, in this case the incubating chamber, in which the eggs will be placed. There were no signs of consumption of vascular tissue in the infested samples, further suggesting a compartmentalized infestation. The nest chamber was found in the stem pith region, with periderm surrounding an insect's miner pupa inside identified as a member of the Cerambycidae. The mining insect depends on a host plant to complete the life cycle; however, the nature of this partnership and the long-term effects of the insect on the plant tissue are unknown. The complex mechanisms by which herbivorous insects control the morphogenesis of the plant host are discussed. We propose that C. minensis has a recognition system to identify insect attack and evaluate the effectiveness of early response triggering compartmentalized defense mechanisms by protecting the injured area with a new layer of periderm.

The current work describes an in vitro conservation technique employing slow growth conditions in 16 threatened species and subspecies of the genus Turbinicarpus (Cactaceae), all native to the Chihuahuan Desert in Mexico. It was demonstrated that the addition of osmotic agents like mannitol (30 g L^-1) and sorbitol (30 g L^-1) to the culture medium, as well as low-temperature incubation (4 ± 0.5 °C), are able to reduce the in vitro growth rate without affecting the viability of shoots subjected to these treatments. The material that was kept under the aforementioned treatment conditions for 12 months was able to regenerate shoots through areole activation when transferred to media containing cytokinins. These shoots are able to root, and the generated plants can adapt and survive in soil, with similar efficiencies to those that were not subjected to slow-growth treatment. With this methodology it is possible to maintain a bank of viable tissues of these species in vitro, with minimal maintenance and the possibility of obtaining complete plants whenever required.

Opuntia fragilis, O. humifusa s.l., and O. macrorhiza s.l. are widely distributed prickly pear taxa that have been studied cytologically mostly in western North America, but upper Midwestern United States populations, which form most of the northeastern-most extent of their distributions, have not been analyzed previously. The wide-ranging and most northern of all cacti, O. fragilis, is relatively abundant, at least historically, in the upper Midwestern United States but does not occur further southeast than Jo Daviess County, Illinois, while O. humifusa s.l. is found throughout most of the eastern United States. This difference in distribution may indicate that environmental variables impede the establishment of O. fragilis in most of the eastern United States. We present the first chromosome counts of O. fragilis, O. humifusa s.l., and O. macrorhiza s.l. for 40 populations over part of their Midwestern range and employ habitat niche modeling using 19 environmental variables to extrapolate potential reasons why O. fragilis may not be found in the eastern United States.All twelve populations of O. fragilis analyzed were hexaploid, a finding consistent with previous reports, and adding further evidence for its vegetative dispersal from the southwestern United States, where the species likely originated. Populations of O. humifusa s.l. and O. macrorhiza s.l. were all tetraploid, indicating that the northeastern-most range of those taxa is occupied by polyploid derivatives of their southern diploid relatives. Results from niche modeling suggest suitable habitat for O. fragilis in the upper Midwest is strongly predicted for areas with seasonal fluctuations in temperature but annual precipitation homogeneity, variables that may present significant environmental barriers to the existence of the species in the eastern United States.

The names Opuntia bulbispina, O. clavata, O. emoryi and O. grahamii, originally proposed by George Engelmann between 1848 and 1856, are reviewed and typified after new findings of previously unknown voucher specimens. Original materials collected by some of the collaborators employed by Engelmann during the Mexican Boundary Survey were discovered in a loan from the Torrey Herbarium at the New York Botanical Garden (NY). Many of the materials include fragments of stems and fruits, and others include only sectioned flowers and some seeds. Particularly good descriptions of the species here concerned were published in Engelmann's “Synopsis of the Cactaceae” in 1857, and exceptional illustrations were produced by Paulus Roetter and printed in “Cactaceae of the Boundary” in 1859. The problems surrounding some previous typifications of these names range from typification of joint lectotypes to illegitimate typifications of illustrations when original material was known to exist. The materials selected for typification were collected by the Mexican Boundary Survey and are lodged at the herbaria of the Missouri Botanical Garden (MO) and the New York Botanical Garden (NY); some are illustrations published by Engelmann.

Opuntia ficus-indica (L.) Miller is a globally important cactus species with a long history of human use. In addition to the importance of O. ficus-indica as a food for humans and livestock, it also has long served a role in the production of cochineal, a once important textile dye. This cactus also is intimately interwoven into the story of Cactoblastis cactorum (Berg) (South American cactus moth), one of the best-known examples of biological weed control. In this regard, O. ficus-indica has been a target weed as well as an unintended host in C. cactorum invasion. Although the distribution and human-assisted movement of this cactus throughout much of the world is well documented, surprisingly little has been written about its history and movement within the Americas. Literature associated with Opuntia and their phytophagous pests in North and South America was examined in an attempt to determine the history of O. ficus-indica in the Americas. Available information suggests with some certainty that O. ficus-indica originated in present-day Mexico, but the timing of its introduction to South America is much less clear. Taxonomic difficulties associated with distinguishing among Opuntia species and the long pre-Columbian history of exchange between South American and Mesoamerican cultures are two primary complicating factors associated with dating the dispersal of this species to South America. Additionally, previous evidence in support of a pre-Columbian introduction to South America relied on questionable identification of insect-based textile dyes. These uncertainties are significant because clearer knowledge of the history of O. ficus-indica introduction to South America could provide a more complete biological and ecological context to efforts at managing this species in its native and introduced ranges, particularly with respect to the threat posed by C. cactorum in North American and Argentinean plantations.

Sedum mesoamericanum is described as a new species, and illustrated based on collections from the Mexican states of Oaxaca and Chiapas, as well as Guatemala. It is distinguished by the possession of subclasping leaves with denticulate margins. Previous phylogenetic analyses placed this species in a clade of Villadia species from the Sierra Madre del Sur, with which it is compared. Additionally, the morphological similarities of Sedum mesoamericanum to S. goldmanii and S. porphyranthes are discussed.

Although several species of Agave L. (Agavaceae/Asparagaceae) are known to have become established in southern Africa, particularly South Africa, this is the first time that evidence supported by herbarium specimens is documented for the occurrence of the agavoid Yucca aloifolia L. in the region. Notes are provided on the reproductive biology and uses of Y. aloifolia, with emphasis on South Africa.

In the framework of a monophyletic circumscription of Agave L., twelve new combinations are proposed in Agave L. (Agavaceae/Asparagaceae) for taxa published in Manfreda Salisb., Polianthes L. or Bravoa Lex.

In this paper we describe a new species of Rhytidocaulon known from two localities in the Hadramawt Governorate of Yemen in the Arabian Peninsula. This species was seen at the same locality in 2008, on which occasion a new site was also discovered, suggesting that the species is more widespread in this area. We also record R. macrolobum subsp. minimum for the first time from this area. On the basis of our current knowledge, we suggest that the wider surroundings of the Ras Huweira settlement in the Hadramawt Governorate is a centre of Rhytidocaulon diversity in the southern part of the Arabian peninsula. R. elegantissimum differs from R. ciliatum mainly by the longer pedicel, the larger, pale green flowers with more slender corolla lobes and more obviously pentagonal corona.