Comprehensive Description

provided by Smithsonian Contributions to Botany
Atractantha radiata McClure

Plantarum habitus collectore neglectus. Culmi in specimine suppetenti neque satis representati neque descripti, ita ignoti. Vaginae culmi et vaginae ramorum primariorum in specimine suppetenti deficientes. Vagina foliorum arcta, dorso glabra, opaca, nervis vix aut haud manifestis; auriculis vel nullis vel ad lineam reductis; setis oralibus crebris, superne saltem anfractis, omnino glabris, propter substantiam fragilissimam mox effractis; ligula interiore ca 1.0 mm longa, dorso granulata, apice asymmetrica, margine integra; ligula exteriore arcuata, angusta, margine primo minute ciliolata demum glabrescenti; petiolo usque 5 mm longo, gracili omnino glabro; lamina usque 18 cm longa et 3.5 cm lata, lanceata, apice acuminata, basi inaequaliter vel rotundata vel subdeltoidea, utrinsecus glabra vel faciei abaxiali pro parte subtiliter puberula; nervis pluribus, validis, tertiariis a secundariis haud facile distinguendis, venulis transversis perpaucis inter se late distantibus.

Inflorescentiae capitatae, in ramis ramulisque foliiferis insertae ubi et terminales et laterales, rhachidum ramificationes insertione distichae. Rhachidum segmentum terminale usque 10 mm longum,

apice usque 1.0 mm diametro dilatatum, omnino glabrum laevigatum nitidumque. Bracteae gem-mam subtendentes in nodis basalibus omnis rhachidis vulgo 2, glabrae, substantia delicatissima, infima 2–3 mm, superiore usque 5 mm longa, non laminiferae. Spiculae usque 19 mm longae, omnes maturitate caducae, rhachidi sua turn conspicua relicta apicaeque nuda. Glumae transitionales nullae. Anthecia papyracea, dorso glabra nitidaque, nervis extus haud manifestis. Lemma usque 17 mm longum, lanceatum, attenuate acuminatum. Palea lemmate parum longior, secus latera sulci angusti ciliolis antrorsis crebris ornata. Lodiculae minimae angustae diaphanae acuminatae secus marginem superne ciliolatae. Antherae apice obtusae basi conspicue sagittatae, ubi desiccatae vinaceae. Ovarium superne pilosum. Stylus vel conspicue vel inconspicue hispidulus. Stigmata typice 2 (atypice et rarissime 3). Fructus maturus adhuc non visus.

Plants of unrecorded habit. Culms neither adequately represented nor described in the available specimens. Culm sheaths and sheaths of the primary axis of branch complements lacking in the specimen. Leaf sheaths tight, glabrous, dull, the nerves scarcely or not at all visible externally; auricles either lacking or reduced to a line; oral setae crowded, curved distally, glabrous throughout, very fragile and soon broken off; the inner ligule ca 1.0 mm long, dorsally granulate, apically asymmetrical, the margin entire; the outer ligule arcuate, narrow, the margin minutely ciliolate at first, then glabrescent; petiole up to 5.0 mm long, slender, glabrous throughout; blade up to 18 cm long and 3.5 cm wide, lanceate, acuminate, rounded or subdeltoid at the asymmetrical base, either glabrous on both surfaces, or partly and minutely puberulous on the abaxial surface; many-nerved, the nerves strong, the tertiary ones not easily distinguished from the secondary ones; transverse vein-lets few and far removed from each other.

Inflorescences capitate, terminal and lateral to leafy branches and leafy twigs, the branches (rachises) of distichous insertion. Bracts at the base of each rachis typically 2, approximate, glabrous and of very delicate substance, not laminiferous, soon disintegrating, the lowermost one 2–3 mm, the uppermost up to 5 mm long; each subtending a bud. Spikelets up to 19 mm long, readily falling away at maturity, each leaving conspicuous and naked the apex of the terminal segment of its rachis; the latter glabrous, smooth and lustrous, up to 10 mm long and (at its slightly flared apex) up to 1 mm in diameter. Anthecia papery, glabrous and shining throughout, the nerves not at all visible externally. Lemma up to 17 mm long, lanceate, attenuately acuminate. Palea a little longer than the lemma, the margins of the sulcus close together and densely fringed with antrorse cilia. Lodicules diaphanous, very small, narrow, the margin apically ciliate. Anthers sagittate basally, obtuse apically, dark purple when dry. Ovary apically pilose. Style conspicuously or inconspicuously hispidulous. Stigmas typically 2, atypically and very rarely 3. Mature fruit not yet seen.

ETYMOLOGY.—The trivial name, radiata, alludes to the radiate orientation of the rachises of the capitate inflorescence.

HOLOTYPE.—In the U. S. National Herbarium (nos. 1910764, 1910765, and 2146781) collected at “Estrada de Bom Gosto a Olivença, Estado da Baía, Brasil, March 15, 1943,” by Ricardo de Lemos Fróes (no. 19947). Additional material examined: an isotype from the same collection on loan from the herbarium of the Instituto Agronômico do Norte, Belém, Pará, Brazil (IAN no. 15373).
bibliographic citation
McClure, F. A. 1973. "Genera of Bamboos Native to the New World (Gramineae: Bambusoideae)." Smithsonian Contributions to Botany. 1-148. https://doi.org/10.5479/si.0081024X.9