The suggested affinities of the New World tropical genus Alzatea have included eight families in five orders since its discovery in the eighteenth century. Until recently, knowledge of the genus has been superficial, primarily limited to macromorphological features. Now evidence assembled from recently published and current research in anatomy, embryology, morphology, palynology, and cladistics of Alzatea and closely related genera allows a more accurate assessment of its relationships. Presence of internal phloem and vestured pitting place the genus in the order Myrtales, while stem and nodal anatomy suggest no close affinities to any one family of the order. Embryologically, Alzatea is unique in Myrtales in having a bisporic Allium-type embryo sac, and shares only with the related genus Rhynchocalyx micropylar development by the inner integument. Pollen features are very generalized, relegating the genus to an ancestral position with respect to the pollen of close associates. Parietal placentation and transeptal vascular supply of the ovary and anatomically simple seed relate Alzatea to Rhynchocalyx (Rhynchocalycaceae) and genera of the Crypteroniaceae sensu stricto, Crypteronia, Axinandra, and Dactylocladus. Alzatea is most similar to Rhynchocalyx, sharing 27 of 43 selected attributes, followed by Crypteronia with which it shares 18 of 43 listed features. Differences between Alzatea and Rhynchocalyx are deemed sufficient to justify establishment of the family Alzateaceae. Plants of Alzatea with large, sessile leaves from Central America are recognized as A. verticillata subsp. amplifolia S. A. Graham, subsp. nov. Alzatea is an enigmatic genus of Central and South America whose suggested affinities, since its discovery in the eighteenth century, have included eight families in five orders. The genus is represented by the single species, Alzatea verticillata Ruiz & Pav6n. It is a small tree of tropical cloud forests, distinguished by broad, oblong, coriaceous leaves and multi-flowered compound inflorescences of small, apetalous, leathery flowers. These produce compressed, conspicuously veined, bilocular capsules with many thin, winged seeds. A history of the systematic placement of Alzatea has been presented by Lourteig (1965), who succinctly reflected that most studies on the genus were as much justification for its exclusion from particular families as arguments for certainty of relationships. The past several years have seen no diminution in shuffling of Alzatea from one family to another (Table 1). Most recently, there has been an increased interest in the genus stimulated by the collaborative reassessment of the Myrtales, the order to which Alzatea most certainly belongs. New observations and data of diverse types for Alzatea and related families now allow an evaluation of the phylogenetic and taxonomic position of the genus in the Dicotyledoneae in a more complete way than was possible previously. The evidence for Alzatea's position as a monotypic family of the order Myrtales is assembled from personal observations and the extensive studies of several specialists, with much of the information generated since the Myrtales symposium of the XIII Botanical Congress in 1981. This paper summarizes the most pertinent contributions of macromorphology, palynology, embryology, anatomy, and cladistics as the basis for recognizing the new family Alzateaceae. CHARACTERIZATION OF ALZATEA Macromorphology. Hemi-epiphytic shrubs or small trees, 2-20 m tall, with stout, gray, roughened trunks or sometimes trunks slender and reaching the forest upper story supported by adjacent trees; branches glabrous, opposite or ' The following individuals are gratefully acknowledged for information shared: Peter Raven, Hiroshi Tobe, Thomas Croat, Alwyn Gentry, Sandra Knapp, James Solomon, Alan Graham, and Barbara Timmerman. John Kress kindly provided photographs of Alzatea in Panama, H. B. Nicholson and Tony Abbott provided photographs of Rhynchocalyx in Natal, and Joan Nowicke provided the scanning electron micrograph of Alzatea pollen. I am also indebted to the curators of CR, MO, and F for loan of herbarium collections of Alzatea and Rhynchocalyx for study. 2 Department of Biological Sciences, Kent State University, Kent, Ohio 44242. ANN. MISSOURI BOT. GARD. 71: 757-779. 1984. This content downloaded from 157.55.39.58 on Wed, 16 Nov 2016 04:19:48 UTC All use subject to http://about.jstor.org/terms 758 ANNALS OF THE MISSOURI BOTANICAL GARDEN [VOL. 71 TABLE 1. Systematic placement of Alzatea by selected authors. Year Author Classification 1794 Ruiz & Pav6n Santalaceae (Between genera of) 1825 Candolle, A. P. de Celastraceae 1826 Blume Celastraceae, near 1845 Planchon Lythraceae 1862 Bentham & Hooker Celastraceae 1868 Candolle, A. L. P. P. de Crypteroniaceae 1872 Miers Rhamnaceae 1892 Loesener Celastraceae, doubtfully 1911 Hallier Lythraceae sensu lato 1918 Hallier Melastomataceae sensu lato 1942 Loesener Flacourtiaceae 1955 Willis Celastraceae 1956 MacBride Rhamnaceae (or Clusiaceae or Icacinaceae) 1965 Lourteig Lythraceae 1966 Airy Shaw Lythraceae 1967 Hutchinson Flacourtiaceae 1975 van Beusekom-Osinga & van Beusekom Crypteroniaceae 1981 Cronquist Lythraceae, questionably verticillate, distinctively purple-red, peeling, becoming red-brown with age; stems of the inflorescence distinctly 4-angled to narrowly winged, the young branches scarcely 4-angled, the mature branches round in cross section; nodes enlarged, especially knobby when branches are verticillate; leaf scars half-round to nearly circular, the base slightly raised, the bundles forming a crescent, U-shaped, or nearly closed-circular scar. Leaves mostly clustered at the ends of the branches, opposite, less often verticillate, simple, entire, stipulate, the stipules axillary, 2 to a few in the axils at the base of the petiole, the stem wings of the inflorescence also extended at the nodes into stipule-like projections; petioles none or short, thick, deep purple-red, to 13 mm long; blades oblongobovate, elliptical, or oblong-oval, thick, leathery, lustrous above, 50-145 mm long, 25-100 mm wide, with blades of terminal leaves smallest and mostly about 70 mm long, 40 mm wide, the bases variable, attenuate to acute or rounding, commonly acute, the apices rounding, occasionally retuse, the veination brochidodromous, the secondary vein pairs 16-22, parallel, oriented at 450 to the prominent midvein. Inflorescences anthotelic, basically paniculate (sensu Briggs & Johnson, 1979, traditionally termed cymose) with each axis terminating in a flower, axillary at the ends of branches, 10-30 flowered, the pedicels 1.5-2 mm long, lacking bracteoles (prophylls), articulated at the base, the lateral flowers of a cyme subtended at the base by small fugaceous fertile bracts, i.e., the bracts themselves subtending buds. Flowers actinomorphic, 5(-6)merous, apetalous, bisexual, hemi-epigynous; floral tube leathery, green to yellow, conical in bud, open-campanulate at anthesis, 4-6 mm long, 4-7 mm wide, the thick, persistent, valvate lobes 3 mm long, extending nearly to the base of the floral tube, the interior surface of the lobes irregularly thickened and fleshy; nectary-disc 1 mm wide, lobed, extending from the ovary to the sinuses of the calyx lobes. Stamens 5, situated in the floral tube at the sinuses of the lobes, outside the nectary, alternating with the lobes; filaments green, stout, short, as long as the anthers; anthers dorsifixed, introrse, the connective broadly expanded, heart-shaped, pink with white edges, fleshy, at anthesis held at right angles to the filament with the distal apiculate apex extending out of the calyx between the lobes, thus simulating petals, the bisporangia positioned horizontally along the broad terminal end of the anther on each half of the connective, dehiscing longitudinally. Gynoecium slightly bilaterally flattened, with a capitate stigma and stout, short style 1 mm long; ovary bicarpellate, bilocular, placentation parietal, the placentae terminating shortly below the style on the inner ovary wall and septum; septum divided into 2 half-septa, the lower fourth provided with a circular opening; ovules horizontally imbricate in staggered This content downloaded from 157.55.39.58 on Wed, 16 Nov 2016 04:19:48 UTC All use subject to http://about.jstor.org/terms 1984] GRAHAM-ALZATEACEAE 759