Two New Brazilian Species of Oryctina (Loranthaceae) with a Revised Key to the Genus

Abstract

Two new species from central Brazil of the South American genus Oryctina (Loranthaceae) are described and illustrated, 0. eubrachioides Kuijt and 0. quadrangularis Kuijt. The absence of a calyculus in the male flower of several Oryctina species represents a nearly unique feature within the family, and the lack of staminodia in the female flower has elsewhere been noted only in two species of Cladocolea. The affinities of Brazilian species with Venezuelan ones are briefly discussed. Distinctions between the two groups of species, based largely on the structure of bracteoles and staminodia, suggest that the generic name Maracanthus may have to be revived for the Venezuelan species. A new key to the genus is presented, including the new species. In recent years, the South American genus Oryctina (Loranthaceae) has significantly swelled from its original monotypic status (Kuijt, 1991). The genus currently consists of six species, but recent collections have brought to light two more, distinctive Brazilian species. Both are herein described and illustrated, and followed by some general comments on the genus, including a new key to all species now comprising Oryctina. Oryctina is one of 16 hemiparasitic genera of Loranthaceae, all of which are strictly limited to the New World. This group of genera may consist of two distinct lineages as indicated by flower size and other features, Oryctina being part of the smallflowered group also containing the better known and larger genera Phthirusa and Struthanthus. Nearly all New World Loranthaceae possess an inconspicuous calyculus directly below the 4 to 6(7) petals. The frequently minute flowers and, upon occasion, the much contracted inflorescences, have in the past posed considerable challenges to the taxonomic interpretation of some of these genera. Oryctina eubrachioides Kuijt, sp. nov. TYPE: Brazil. Minas Gerais: Januaria, Vale do Peruaqu, inicio do Cerrado de Judas, 15*7'10S, 44*13'21W on Aspidosperma, Salino & Gotschalg 4037 (holotype, BHCB not seen; isotype, LEA). Figures 1, 2. Frutex dioicius, squamatus, gracilis; internodiis ad 1.5 cm longis, teretibus. Folia ad 1.5 mm longa, cucullata peltata. Spicae paene sessiles, ca. 4 mm longae. Squamate plants, sparsely branched, the branches very slender, stiff, internodes to 1.5 cm long, terete, covered with innumerable raised stomata forming conspicuous, minute tubercles. Leaf-scales about 1.5 mm long, strongly cucullate and peltate, fringed with dark brown hairs, the adaxial surface also with brown hairs, hairs becoming white with age, leaf-scales paired but in threes on vigorous shoots. Dioecious, the inflorescences nearly sessile, about 4 mm long at anthesis, in the male plant often some 20 pairs in series on an unbranched shoot, mostly singly in the axil of scale-leaves, sometimes with a second, smaller, superposed inflorescence; peduncle somewhat less than 1 mm, followed by up to 10 pairs of brown-fringed, minute scale-leaves, each subtending a bright lemon-colored bud or flower, the mature bud ca. 1 mm diam., globular, flanked by 2 laterally placed, very inconspicuous, blunt, hair-fringed prophyllar bracteoles. Petals 6, strongly dimorphic in both sexes, the longer ones 1 mm long, shorter ones ca. 0.5 mm. Male flower lacking a calyculus, anthers ca. 0.25 mm, globular but slightly bilobed, bilocular, sessile on the middle of the petals; style 0.5 mm long, cylindrical, stigma not differentiated. Female flower 1.5 mm long when mature, half of which is ovary, calyculus distinct, petals without staminodial remnants, style to 0.5 mm long, cylindrical, stigma slightly differentiated as a terminal swelling, very slightly papillate. Fruit at least 3 x 1.5 mm, ellipsoid but with a somewhat expanded calycular region, blunt-tipped. The specific name indicates a striking general similarity to the genus Eubrachion (Eremolepidaceae), a similarity that is carried through to the more or less peltate scale-leaves (see the illustration in Kuijt, 1988, fig. 2d & e). In the present species, however, the scale-leaves are profusely fimbriate, which is not true for Eubrachion. The partial base of the plant included in the LEA specimen cited below suggests that no epicortical roots are present in 0. eubrachioides. The occurrence of such roots and/or their placement on the plant in NovoN 10: 391-397. 2000. This content downloaded from 157.55.39.40 on Thu, 28 Apr 2016 06:21:17 UTC All use subject to http://about.jstor.org/terms