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The North American endemic moss Dicranum howellii Renauld & Cardot, described in 1888 based on material from Oregon, U.S.A., had yet to be validly typified. A lectotype for D. howellii is designated herein based on one of two potential type specimens in the Renauld collection in PC. Dicranum howellii is currently known from western North America in Canada (British Colombia) and the U.S.A (Alaska, California, Idaho, Montana, Oregon and Washington). Traditionally it has been considered as close to, or a synonym of, Dicranum scoparium Hedw. and specimens of it are frequently confused with the latter species. Dicranum howellii can be distinguished from D. scoparium based on its suddenly narrowed inner perichaetial leaves that end in a long, flexuose point; leaves that are concave below and tubulose above; slightly decurrent leaf bases; in transverse section, leaf cell-walls that are of variable thickness; and the presence of a sulcus on the dorsal side of the costa.

Peripheral blood lymphocytes were cultured and treated for early- and late-BrdU incorporation to perform replicating G- and R-banding patterns, respectively. Slides were treated for GBG-, RBA- and RBG-banding techniques. Improved banded karyotypes at early- (350 bands) and pro-metaphase (500 bands) stage were performed and GBG- and RBA-banded prometaphase karyotypes were presented for the first time on this species. All chromosomes, including the small acrocentrics, show clear and distinguishable G- and R-banding patterns. Chromosome identification followed the latest chromosome standard nomenclature (ISCNH 1997). This study is also our contribution to further standard karyotype attempts at the prometaphase stage.

El género Verbena L. no ha sido revisado taxonómicamente en su totalidad, existiendo únicamente aportes regionales, a los cuales se suma la complejidad debida a la estrecha relación de Verbena con los géneros afines Glandularia J. F. Gmel. y Junellia Moldenke, muchas veces considerados como subgéneros, secciones o series del género Verbena por diversos autores. El propósito de este trabajo es por un lado realizar la revisión taxonómica del género Verbena y por el otro establecer la posición filogenética de Verbena, poniendo a prueba su monofilia mediante análisis cladísticos. Para lograr estos objetivos se estudiaron 3070 ejemplares de herbario, depositados en diferentes herbarios de Argentina y del extranjero, y se realizaron viajes de colección para el estudio de material vivo. Como resultado del estudio taxonómico se proporcionan descripciones detalladas, ilustraciones y claves para identificar los taxones reconocidos, se provee una sinonimia actualizada con 107 nuevos sinónimos, cuatro nuevas combinaciones: Verbena gracilescens var. swiftiana (Moldenke) N. O’Leary, Verbena hispida var. obovata (Moldenke) N. O’Leary, V. litoralis var. brevibracteata (Kuntze) N. O’Leary y V. simplex var. orcuttiana (L. M. Perry) N. O’Leary, un nombre nuevo: Verbena subpetiolata N. O’Leary, una subserie nueva Pseudoracemosae N. O’Leary, y se presentan 26 lectotipificaciones y 7 neotipificaciones de taxones. De esta manera, Verbena comprende 44 especies y 10 variedades, en su mayoría de distribución americana. El género se divide en dos series: serie Pachystachyae Schauer y serie Verbena. Verbena serie Pachystachyae incluye 18 especies de distribución sudamericana; a su vez la serie se divide en dos subseries: Pachystachyae y Pseudoracemosae. Verbena serie Verbena comprende 26 especies de distribución principalmente norteamericana, tratadas en tres grupos informales: Verbena, Hastatae y Bracteosae. El género Verbena constituye un grupo monofilético con bajo soporte, sustentado por tres sinapomorfías referidas al hábito herbáceo o sufruticoso rastrero, la presencia de hojas de margen no liso y las clusas con la base no angostada y con repliegue basal y transversal. El grupo hermano de Verbena lo forma el clado de Junellia + Glandularia, sustentado en la sinapomorfía libre de homoplasia definida por el largo del estilo más de tres veces la longitud del ovario y tres sinapomorfías homoplásicas: corola hipocraterimorfa, margen de las clusas alado y clusas entre 0.25-0.3 cm long. Las dos series en que se divide el género, la serie Pachystachyae y Verbena, no surgen como grupos monofiléticos. Unicamente la subserie Pachystachyae y el grupo informal Verbena son grupos naturales, el primero definido por la presencia de parénquima caulinar discontinuo, el segundo basado en las florescencias laxas. La subserie Pseudoracemosae, el grupo informal Hastatae y el grupo informal Bracteosae surgen como grupos polifiléticos en todos los análisis. Las series, subseries y grupos informales dentro de Verbena en muchos casos se ven definidos por combinaciones de caracteres no únicos. Por otro lado, la optimización de los caracteres sobre los árboles filogenéticos evidencia que muchos caracteres tradicionalmente relevantes taxonómicamente muestran altos niveles de homoplasia. The genus Verbena L. has only been regionally taxonomically revised, and never before been completely revised; the close relationship between Verbena and the genera Glandularia J. F. Gmel. and Junellia Moldenke, considered by many authors as subgenus, sections or series of Verbena, makes taxonomy even more complex. The purpose of this work is, on one hand, to perform a complete taxonomical revision of Verbena, and on the other hand, to establish the phylogenetical position of Verbena, testing its monophyly by means of cladistical analyses. To reach this aims, 3070 herbaria specimens deposited in several Argentine and non Argentine herbaria were studied, and collection trips to study living material were done. As a result of taxonomical study, detailed descriptions, illustrations and keys for identification are provided, as well as an actualised synonymy including 107 new synonyms; four new combinations: Verbena gracilescens var. swiftiana (Moldenke) N. O’Leary, Verbena hispida var. obovata (Moldenke) N. O’Leary, V. litoralis var. brevibracteata (Kuntze) N. O’Leary and V. simplex var. orcuttiana (L. M. Perry) N. O’Leary; a new name: Verbena subpetiolata N. O’Leary; a new subseries: Pseudoracemosae N. O’Leary; and 26 lectotypifications and 7 neotypifications are presented. Verbena comprises 44 species and 10 varieties, mostly distributed in America. The genus is divided in two series: series Pachystachyae Schauer and series Verbena. Verbena series Pachystachyae includes 18 Southamerican species; the series is further divided in two subseries: Pachystachyae and Pseudoracemosae. Verbena series Verbena comprises 26 species mainly distributed in North America, treated in three informal groups: Verbena, Hastatae and Bracteosae. The genus Verbena constitutes a monophyletic group, with low support values, defined by three synapomorphies: prostrate herbaceous or suffruticose habit, leaves without entire margins and mericarps with transversal and basal thickening and not narrow base. Junellia + Glandularia is the sister group to Verbena, defined by the style three times the length of the ovary, a not homoplasic synapomorphy, plus three homoplasic synapomorphies: hipocrateriform corolla, winged mericarps 0.25-0.3 cm long. Both series Pachystachyae and Verbena turn out not to be natural groups. Only subseries Pachystachyae and informal group Verbena are monophyletic, the first one defined by the discontinuos caulinar parenchyma, the second one based on the lax florescences. Generally series, subseries and informal groups within Verbena are defined by a certain combination of non excluding characteristics. Besides, character optimization in phylogentical trees shows that many taxonomically relevant characters display high levels of homoplasy. Fil: O'Leary, Nataly. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.