Geniostoma biseriale Rech.
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Authority
Smith, Albert C. & Stone, Benjamin C. M. 1962. Studies of Pacific Island Plants, XVII: The Genus Geniostoma (Loganiaceae) in the New Hebrides, Fiji, Samoa, and Tonga. Contr. U. S. Natl. Herb. 37, Part I: 1-41; plates 1-3.
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Family
Loganiaceae
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Scientific Name
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Type
Upolu, Samoa, in forest near Tiavi, at 700 m. alt.; the type is Rechinger 446, presumably deposited in the Berlin Herbarium and subsequently destroyed. The cited illustration is excellent and permits adequate understanding of the concept.
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Description
Description - Shrub or small tree 2-A m. high, glabrous throughout except for some floral parts, with slender pale gray-brown subterete or obscurely quadrangular branchlets, these distally about 2 mm. thick; stipules intrapetiolar, forming a short subtruncate sheath 1-1.2 mm. long; leaves subsessile, the petioles at most 2 mm. long, the blades oblongelliptic or narrower and lanceolate-elliptic (rarely slightly lanceolateovate), subauriculate, cordate, or subcordate at base, acuminate at apex, 6-15 cm. long, 2-6 cm. broad, the costa sulcate above, raised beneath, the lateral nerves 7-12 per side, slightly raised on both surfaces, the veinlets obscure; inflorescences axillary among the leaves, dichasial, 5-10-flowered, the peduncle 1-2 mm. long, the axes and pedicels glabrous, 1-3 mm. long, bracteate, the flowers glabrous externally; calyx cupuliform, the lobes 0.8-1 mm. long, deltoid-ovate; corolla short-tubular, 3.5-4.2 mm. long, lobed nearly to middle, the tube glabrous basally within, at throat sparsely pilose with trichomes 0.3-0.4 mm. long, the lobes deltoid-ovate, glabrous distally, the venation complex, that of each lobe derived from a single central main nerve producing 1 or 2 pairs of lateral branches in the tube, these in turn producing 1 or 2 lateral branches, all ascending into the lobe; stamens inserted at throat, the filaments about 0.2 mm. long, the anthers narrowly deltoid-oblong, 0.6-0.8 mm. long; ovary glabrous, depressed-globose, about 0.7 mm. high and 0.9 mm. broad, the style slender, glabrous, 1.5-2 mm. long, the stigma (in our specimens poorly preserved) apparently obovoid, about 0.7 mm. long; capsule ellipsoid, 7-8 mm. long, 2-4 mm. broad, apiculate.
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Discussion
Geniostoma biseriale is readily distinguished from other species of our region by its essentially sessile leaves, of which the petioles do not exceed 2 mm. in length, the blades being proportionately unusually narrow, prevailingly cordate or even subauriculate at base. The indument of the corolla-throat is short, suggesting that the closest relatives of G. biseriale may be G. gracile and G. macgregorii, but the relationship is not close.