Platycarpum orinocense var. orinocense

  • Authority

    Rogers, George K. 1984. Gleasonia, Henriquezia, and Platycarpum (Rubiaceae). Fl. Neotrop. Monogr. 39: 1-135. (Published by NYBG Press)

  • Family

    Rubiaceae

  • Scientific Name

    Platycarpum orinocense var. orinocense

  • Type

    LT: Humboldt & Bonpland s.n.; no date; Pl. Aequin., pl. 104 LT designated by Rogers 1984, Pl. Aequin., pl. 104

  • Synonyms

    Sickingia orinocensis (Bonpl.) Spreng., Henriquezia aturensis Standl.

  • Description

    Variety Description - Young stem with pubescence in 2 layers, the shorter layer cinereous- to ferrugineous-hispidulous, the hairs of longer layer light tan to fulvous (occasionally ferrugineous), to 2(-3) mm long. Lamina adaxially strigose, the hairs to 0.6(-2.3) mm long, abaxially usually bearing white to tawny, variably bent hairs to 1.5 (-2.5) mm long; petiole usually with U-shaped gland abaxially near base, this (2-)3-6(-9) mm in longest dimension. Inflorescence axes with pubescence usually in 2 layers, the shorter layer densely white- to ferrugineous-tomentose to hispidulous, the longer layer cinereous- to ferrugineous-hirsute to pilose, the hairs to 1.8(-3) mm long. Calyx lobes (5-)6-8(-12) x l .5-2.5(-5) mm, acuminate to acute at apex; corolla (1.2-)1.5-2.0(-2.2) cm long; corolla lobes (4-)5-9(-ll) x 4-8 mm, rounded to acute at apex; filaments 4-8 mm long, inserted 2-6 mm from base of tube. Capsule 2.5-3.5(-4) x 2.8-3.5(-4) cm. Embryo 0.8-1.5 x 1.8-3.0 cm. n = 20(-21).

  • Discussion

    Illustrations. Bremekamp (1952), testa; Bremekamp (1957), floral diagram, fruit, ovary, pollen, testa; Humboldt and Bonpland (1811), floral dissection, flowering branch, fruits (corollas inaccurate); Steyermark (1952, 1974), floral dissection, flowering branch, fruits.

    Ecologically, Platycarpum orinocense var. orinocense shows unusual amplitude in altitude and substrate. Whereas it usually occurs at approximately 100 m elevation along the Río Orinoco and tributaries, it also grows on nearby mountains, up to 900 m on Cerro Yapacana (Rogers 62, 67).

    This variety is well known for growth on more or less bare granite outcrops (lajas), and is the predominant (or nearly so) tree of the local savannas. According to Huber (undated), P. orinocense [var. orinocense] is encountered in at least two types of savannas: (1) “sabana graminosa densa,” characterized as rapidly drained sandy soil with a paucity of trees; and (2) “sabanas de ripio,” with a soil comprised mostly of small stones. A third habitat is stunted, thick forest on rocky soil (Rogers 62).

    Despite the wide ecological amplitude, the northern boundary of the range is mysteriously abrupt. Otto Huber (pers. comm.) has pointed out that, although seemingly suitable habitat continues far to the north of Puerto Ayacucho, the variety extends no more than 35 km north of that city, an observation that I have verified for the area along the eastern shore of the Rlo Orinoco.

    Several features of the flower are commonly associated with bee-pollination: a bearded lip, sweet aroma, lines within the corolla tube, and abundant nectar. Nevertheless, the flowers are visited by several other animals. I have been among flowering individuals at all hours between dawn and dusk and observed visitation by hummingbirds, moths, and (mostly) a variety of bees. Pollination within the context of the entire tribe is discussed in the section on ecology. Individuals tend to be homogeneous with regard to reproductive stages, but within a population, the entire range of stages can be sometimes simultaneously found on different individuals.

    I have heard the last-mentioned name frequently around Puerto Ayacucho; it is also applied to Platycarpum decipiens.

    Platycarpum orinocense var. orinocense is among the most common and conspicuous trees in and near Puerto Ayacucho, Venezuela. The shape of the tree and its flowers are beautiful, so when allowed to grow along streets and associated with homes, it is ornamental. Steyermark (1952) reported the use of the wood for fuel and supports.

  • Common Names

    Chaparro de Sabana, platanote, picaton

  • Distribution

    Common in savannas and on rocks along the Río Orinoco in Colombia and Venezuela between 4° and 6° N latitude and eastward to 66° W longitude. Flowers November through February; other flowering collections date from April, July (buds), and September. Collections bearing fruits have been made from January through June and in September.

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