The 29 genera of this subtribe, which contains about 4,000 species, are discussed and illustrated. The introduction contains a detailed discussion of pleurothallid morphology and a key to the genera.

Each of the 100 species of Trichosalpinx found in the New World tropics are described and illustrated in this volume. Addenda contain species new and old of previously treated genera.

The latest volume in this series treats three distinct subgenera of the immense genus Pleurothallis, which includes about 30 subgenera and over 3,000 species. Subgenus Crocodeilanthe contains 70 comparatively large species, whereas subgenus Rhynchopera has eight species and subgenus Talpinaria only four species.

This volume treats six infrageneric subdivisions of the genus Pleurothallis: section Abortivae, section Truncatae, two subsections (Acroniae and Pleurothallis) of section Pleurothallis, and two subgenera: Dracontia and Unciferia. Twenty-one new species are described in the Addenda. 111 species are illustrated in black and white.

Icones 18 contains section Pleurothallis subsections Antenniferae, Longiracemosae, and Macrophyllae, and subgenera Pseudostelis and Acuminatia on 182 pages with 172 line drawings, and with the addenda occupying about one-fourth the volume of the book. The species treated are characterized by a usually many-flowered, racemose inflorescence, which is reduced to a single flower in a few species. Many of the species are frequently cultivated.

A guide to Pleurothallis with keys to subgenera, sections, and subsections, and lists of representative species for each infrageneric taxon.

The 33 taxa included in these pleurothallid genera are not closely related, but each has a similar pollination mechanism.

Eight species of Dresslerella and 44 species of Scaphosepalum.

Species in these subgenera are described, keyed, and illustrated.

MSB 79 Icones Pleurothallidinarum XX: Systematics of Jostia, Andinia, Barbrodria, Pleurothallis and Subgenera Antilla, Effusia and Restrepiodia with addenda to Lepanthes, Masdevallia and Pleurothallis.

Myoxanthus is described, and a key to the subgenera and species is given. Each species is described and illustrated with a black-and-white line drawing, and distribution maps are given. Types and representative specimens are listed, followed by a brief discussion.

Masdevallia Part Three continues with subsections Masdevallia and Minutae, together containing about another 100 species, each with at least one black-and-white illustration in addition to the text, citation of collections, and distribution maps.  A looseleaf version is also available.

Ecuadorian Stelis is described, with a key to 100 species. Each species is described and illustrated with a black-and-white drawing. Types and representative specimens are listed in the distribution, with a brief discussion of each species.

Part 5, with the remaining 100 species of Masdevallia, completes the genus and its treatment as Parts 1-4, in Icones 19, 21, 22, 23, respectively. Considered herein are Masdevallia subgenera Masdevallia, Amanda, Cucullatia, Fissia, Meleagris, Nidificia, Scabripes, Teagueia, and Volvula. Taxa are represented by text, formal descriptions, distribution maps, and line art. A loose-leaf edition is available upon request, so that future rearrangements can be made.

Icones Pleurothallidinarum XXXI

Part three of four presents 100 new species of Stelis.  The new species are presented alphabetically in three artificial sections, groups of more or less allied species with some similarities to aid in orientation and identification.

Icones Pleurothallidinarum XXVI: Pleurothallis subgenus Acianthera and three allied subgenera; A Second Century of New Species of Stelis of Ecuador; Epibator, Ophidion, Zootrophion. Also includes addenda to Brachionidium, Dracula, Lepanthes, Platystele, Pleurothallis, Porroglossum, and Masdevallia. Additionally, new genera and combinations are presented.

Icones Pleurothallidinarum XXVII, Dryadella and Acronia section Macrophyllae-Fasciculatae, the 103rd volume of the Monographs in Systematic Botany from the Missouri Botanical Garden, continues Carlyle Luer�s treatment within the Orchidaceae. Treated here are Dryadella and Acronia section Macrophyllae-Fasciculatae, in addition to nomenclatural addenda for Acianthera, Andinia, Dracula, Dresslerella, Lepanthes, Masdevallia, and Restrepia. Miscellaneous new taxa and combinations are also validated. More than 250 line drawings and a color frontispiece of Dryadella barrowii Luer illustrate this volume.

In addition to the taxonomic treatment of Specklinia and similar pleurothallid genera, segregate taxa are recognized within the large genus Masdevallia. New orchid taxa are validly described for the first time, and other nomenclatural changes are validated within these Neotropical Orchidaceae.

From among the subgenera of Masdevallia are established the new genera Acinopetala, Alaticaulia, Buccella, Byrcella, Fissia, Luzana, Megema, Petalodon, Pteroon, Regalia, Reichantha, Spectaculum, Spilotantha, Streptoura, Triotosiphon, and Zahleria.

The polyphyletic genus Specklinia is dismembered, with the ten new segregate genera Dondodia, Gerardoa, Incaea, Lomax, Muscarella, Panmorphia, Ronaldella, Sarcinula, Sylphia, and Tridelta. Five new species are described as Muscarella rojohnii, M. werneri, M. xyloura, Specklinia ordinata, and S. pectinifera.

Miscellaneous new taxa appear in the pleurothallid genera Acianthera, Acronia, Arthrosia, Colombiana, Crocodeilanthe, Dracula, Dryadella, Loddigesia, Masdevallia, Myoxanthus, Ogygia, Platystele, Porroglossum, Restrepia and Trichosalpinx. New genera include Arthrosia, Loddigesia, and Ogygia. New species include Acianthera rinkei, Acronia lynniana, A. pyelophera, A. tobarii, Arthrosia freyi, Crocodeilanthe suinii, Dracula saulii, Dryadella marilyniana, Myoxanthus werneri, Platystele tobarii, Porroglossum marniae, P. parsonsii, P. sijmii, Restrepia persiciana, and Trichosalpinx jostii.

Seven new species, three among the new generic segregates for Masdevallia, include Alaticaulia royi, Luzama gemmula, Masdevallia gastrodes, M. ivanii, M. magaliana, M. nijhuisiae, and Spilotantha ferrusii.

A color frontispiece is included, with 681 plates of black and white line art by Carl Luer.