Hemiepiphyte to scandent herb. Internodes 2-8 x 1-22 cm. Prophyll deciduous, 10-12 x 1.2-1.5 cm. Petioles flattened adaxially, 30-63 x 0.8-1.2 cm. Leaf blade pinnatiparrite, ovate in outline, 30-60 x 28-50 cm, chartaceous, adaxial surface dark green, paler adaxially, anterior division pinnatipartite, 18-36 x 28-50 cm, midrib triangular in transverse section, apex acute to acuminate, secondary nerves 4-6 per side, arising at an angle of 60-70°, lobes elongate-elliptic to oblanceolate, falcate, 6.5-23 x 1.5-4 cm, posterior divisions 8-15 x 18-25 cm, denuded portion of the basal rib 0.5-3 cm, acroscopic lobes 1-2, basiscopic 1-2. Inflorescences 1-3 per leaf axil, peduncle 8-20 x 0.8-1.3 cm; spathe white inside, green outside, 12-17 cm long; spadix 8-13 x 0.7-2 cm, fertile male portion tapering to the apex, 5-8 x 0.7- 1.5 cm, sterile male portion 0.5 x 1-2 cm, female portion adnate up to 1/2 of its length, 2- 5 x 1.3-2 cm. Male flowers 4-androus, stamens prismatic ca. 1 x 0.5 mm, staminodes clavate, ca. 2 x 0.5 mm, gynoecium 1.5-2 x 0.8-1 mm, 6-8-locular, locules 2-3-ovuled, funicles ca. 1/5 of the ovule length. Berry unknown.
Terrestrial, creeping, scandent or hemiepiphytic herb. Stem with younger internodes green, older ones ochre, internodes 1 - 22 x 2 - 8 cm, terete in cross- section; adventitious roots brown, 0.3 - 0.6 diam. Prophyll straight, deciduous, linear- lanceolate, translucent, 10 - 12 x 1.2 - 1.5 cm. LEAVES: Petiole green, with red verrucosities, slightly flattened adaxially, 30 - 62 x 0.8 - 1.2 cm; Lamina pinnatifid, ovate in outline, 30 - 60 x 28 - 50 cm, chartaceous, upper surface dark green, lower surface paler, with minor veins pink-tinged; anterior division pinnatifid, 18 - 36 x 28 - 50 cm, midrib V-shaped in transverse section, apex acute to acuminate; primary lateral lobes 4 - 6 per side, long-elliptic to oblanceolate, often falcate, 6.5 - 23 x 1.4 - 4 cm, apex rounded to acuminate, sinuses ending 0.5 - 1.3 cm from the midrib; primary lateral veins 4 - 6 per side, arising at an angle of 60 - 70º; posterior divisions 8 - 15 x 18 - 25 cm, basal rib denuded for 0.5 - 3 cm, sinus obtuse, basioscopic lobes 1 - 2, poorly-developed, acroscopic lobes 1 - 2. INFLORESCENCE: erect at anthesis, 1 - 3 per leaf axil; peduncle green, 8 - 20 x 0.8 - 1.3 cm; spathe 10 - 17 cm long, green outside, white inside, apiculate, tube usually as long as the lamina, or nearly so; spadix white, sessile, 8 - 13 x 0.7 - 2 cm, fertile male zone cylindrical , tapering to the apex, 5 - 8 x 0.7 - 1.5 cm, sterile male zone c. 0.5 cm long, equal in diameter to the fertile zone, female zone adnate to spathe for half its length, 2 - 5 x 1.3 - 2 cm. Male flowers 4-androus, stamens prismatic, c. 1 x 0.5 mm; staminodes subprismatic, slightly tapering to the base, c. 2 x 0.5 mm; gynoecium 1.5 - 2 x 0.8 - 1 mm, stigmatic crown well-developed; locules 6 - 8, ovules 2 - 3 per locule, elongated, funicle approximately 1/5 of the length of the ovule, with funicular trichomes. INFRUCTESCENCE: Fruit unknown.
The closest species seems to be P. radiatum Schott, from Mexico and Guatemala, but P. mayoi differs in having fewer ovules per locule (2 - 3, not 4 - 5), the inner surface of the spathe tube white (instead of red), the peduncle as long as the spathe and an unthickened sterile male zone in the spadix. It also seems to share some features with P. fendleri K. Krause from Trinidad and Venezuela (Croat & Lambert 1986), but differs in the basal rib always being denuded, the more deeply incised leaf blade and the completely white inner surface of the spathe.
This species is common in ravines along streams or on limestone outcrops but flowering individuals are rather rare. Young individuals can grow as creeping plants but only hemiepiphytic plants were observed in flower.
Brazil: Distrito Federal.