A NEW SPECIES OF XANTHOSOMA FROM ECUADOR MICHAEL MADISON The Marie Selby Botanical Gardens, 800 S. Palm Ave., Sarasota, Fla. 33577 The genus Xanthosoma Schott 12 mm longa; pars sterilis candida, 3 mm includes about 45 species of terres­ crassa, 1 cm longa ; pars staminata candida, trial herbs native to the wet tropical 4-6 mm crassa, 3 cm longa. regions of the new world. The huge sagittate leaves of many species TYPE: Ecuador, Provo Pastaza, VICI­ have earned them the common nity of Puyo, collected 1977 by name of 'elephant ears,' which is Ron Weeks, cultivated at his nur­ also applied to the related old-world sery in Miami, Florida, flowered in genera Colocasia and Alocasia. cultivation March 1978, Madison Several species of Xanthosoma 4216 (SEL, isotype to be distribut­ are widely cultivated as food plants ed MO). in tropical regions, either for their ETYMOLOGY: The name honors Ron starchy edible tubers or for the Weeks, aroid grower of Miami, Flor­ young leaves, which are used as ida and founding member of the In­ greens. Several other species, such ternational Aroid Society, who col­ as X. lindenii (Andre) Engler, are lected the species. horticulturally desirable ornamen­ tals but are not widely grown. The selective forces leading to During a recent visit to the evolutionary diversification in Xan­ Miami nursery of aroid grower Ron thosoma are not well understood. Weeks, I was given a plant of Xan­ The species apparently share an un­ thosoma he had collected in Ecua­ specialized pollination syndrome dor, and which proves to be an un­ involving ruteline scarab beetles as described species. pollinators. Fruits, though hardly known, are evidently also similar from one species to the next, con­ Xanthosoma weeksii Madison, sp. sisting of a mass of pulpy orange nov. berries containing minute seeds which are dispersed by a variety of Species foliis glabris ovatis haud cordatis birds, mammals, and insects. One a congeneribus diversa. apparent area of ecological speciali­ Herba terrestris ad 60 cm alta. Caudex zation is in the habitat preferences hypogaeus, carnosus, 3-4 cm crassus, of the species; some are weedy spe­ erectus. Petiolus folii 30-40 cm longus, 6- 20 mm crassus, vagina 15-25 cm longa in­ cies of open pastures or disturbed structus. Lamina ovata, apice acuta, basi areas, others are understory herbs truncata, nec cordata nec sagittata, glabra, of climax forest, and still others supra viridis impolita, subtus pallida, ner­ are riparian or montane species. vis lateralibus primariis utrinque 6, in ner­ vum collectivum a margine 4-8 mm remo­ Obviously an understanding of tum conjunctis. Inflorescentia monocha­ the relationships of the species of sialis spadicibus (2-4) composita. Pedun­ Xanthosoma can only result from a culus viridis, 4-8 mm crassus, 3-6 cm lon­ thorough study of the plants in their gus. Spatha 8-10 cm longa, extus ebernea, tubo intus atropurpureo. Spadix suaveo­ native habitats. Such a study is now lens, pars carpellata eburnea, 8 mm crassa, under way and the results of Sue 24 1978 MADISON: X A NTHOSOMA 25 XANTHOSOMA WEEKSII 2em I .. : , " :::".'::i . : . : ' : I ; lIT}\ : ~ : ',·IJ.1 2mm 5 em Thompson's researches on Xantho­ tures Xanthosoma weeksii is clearly soma are eagerly anticipated. In the a distinct species. The glabrous ovate meantime names are still needed for leaves which are rounded to truncate the species, especially those in culti­ at the base and not at all cordate, vation, even if their relationships and the short peduncles, readily are not well understood. distinguish it from the other species In the past species of Xantho­ of the genus. Xanthosoma weeksii soma have been distinguished on suckers freely from the base, so the basis of leaf shape, pubescence, that an old and well-grown plant and the relative sizes of the parts of makes a full and handsome horti­ the spadix. In terms of these fea- cultural specimen. .