Mapania pycnostachya (Benth.) T.Koyama

Authority

Maguire, Bassett. 1967. The botany of the Guayana Highland--Part VII. Mem. New York Bot. Gard. 17: 1-439.

Family

Cyperaceae

Scientific Name

Mapania pycnostachya (Benth.) T.Koyama

Description

Species Description - Perennial sedge in small clumps; rhizome short; roots fuscous, stout. Leaves radical, broadly linear, 60-80 cm long, 15-20 mm wide, unicostate, deep green above, pale beneath, gradually narrowed above to a long acuminate apex, gradually attenuate below to a more or less petiole-like base, the margins serrulate-scabrous except at the midway portion where margins are smooth for 5 to 15 cm; sheaths dilated, margins widely membranous, purple-fuscous. Culm solitary, central, scapose, shorter than leaves, 32- 45 cm tall, 3 mm thick below, 3-sided, the angles scabrous only below the inflorescence. Inflorescence a globose head, with 15 to 20 spikes, 2.5-3 cm in diam, 2-2.5 cm high, brownish at maturity; involucral bracts 3(-4) leaf-like, patent in anthesis and reflexed later, very unequal, the longest up to 60 cm long, 2 cm wide, gradually long acuminate at apex, the base attenuate, not sheathing. Spikes sessile, oblong ellipsoid, terete, 10-14 mm long, 5-8 mm across, obtusish at apex, with many spikelets. Glumes elliptic to slightly obovate-elliptic, 6-6.5 mm long, 2.25-2.5 mm wide, shallowly navicular, obtuse on back, the median portion coriaceous, several nerved, brown, the margins very widely hyaline pale, quickly disappearing after anthesis. Squamellae 4. the lower 2 lateral, the remainder dorsiventral, all linear to linear-lanceolate, acute at apex, 6.5-7 mm long, scarcely 0.5 mm wide, hyaline, pale. Anther ca 2 mm long. Fructifications ovoid-ellipsoid, thickly biconvex, ca 4 mm long, 1.5 mm wide, the spongy portion 23 as long as the total length of fructification, yellow-cream, the portion containing an achene 1.5 mm long, brown-tinged; style 3.5-4 mm long; stigmas 2, 1.5 mm long.

Distribution and Ecology - Endemic to southern Venezuela and adjacent Brazil; rare.

Discussion

Diplosin pycnostachya Bentham, Jour. Linn. Soe. 15: 512. 1877.

Hypolytrum condensatum C. B. Clarke, Kew Bull. Add. Ser. 8: 50. 190S. New Name for Diplasia pycnostachya Bentham

Type. Prope Barra, Prov. Rio Negro (Brazil), R. Spruce 3833 (holotype K, photo NY).

Mapania pycnostachya was originally described by Bentham under the genus Diplasia and then transferred to the genus Hypolytrum by C. B. Clarke. The structure of spikelets as I see it (cf. the description) does not support either view, but places this species in the genus Mapania as was fully discussed under M. imeriensis. Two previously published names, Hypolytrum pycnocephala Bentham and Mapania pycnocephala Bentham, have been causing nomenclatural confusion when Diplasia pycnostachya is considered to be a species of Hypolytrum or Mapania. These two names, which actually indicate a single taxon differing from D.pycnostachya, were published in a discussion as follows:“Aublet’s genus Mapania (Plate 7, fig. S) , of which my original Hypolytrum pycnosta-chyum, from Panama, is a second American species [Mapania pycnostachya] ” (Bentham, Jour. Linn. Soc. 15: 512. 1877) where the epithet, pycnocephala, was mistakenly spelled as pycnostachya

When C. B. Clarke transferred Diplasia pycnostachya Bentham to Hypolyti urn in 1908, he gave it a new name, H. condensatum C. B. Clarke because of the presence of H. pycnostachyum Bentham. In my opinion, however, Bentham’s names do not constitute the earlier homonyms as defined by the Article 64 of the International Code of Botanical Nomenclature. First of all, these names were never validly published. Secondly, the name H. pycnostachyum Bentham as meant by Bentham is an apparent mistake for his H. pycnocephala. Bentham did not describe H. pycnostachya from Panama, but he described H. pycnocephala from the Bay of Choco of Colombia near Panama. The two Benthamian names in question should, therefore, be read as H. pycnocephala and M. pycnocephala respectively. The specific epithet, pycnostachya, of Diplasia is thus legitimately transferable to either Hypolytrum or Mapania. For this reason, I here propose a combination, Mapania pycnostachya (Bentham) T. Koyama.