Pinanga tenella (H.Wendl.) Scheff., Natuurk. Tijdschr. Ned.-Indiƫ 32: 179 (1871)

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Distribution

Map uses TDWG level 3 distributions (http://www.nhm.ac.uk/hosted_sites/tdwg/geogrphy.html)
Borneopresent (World Checklist of Arecaceae)A

Discussion

  • Mention has already been made of the confusion between P. salicifolia and P. tenella caused by Scheffer and Miquel; now that P. salicifolia is better understood, the plants can be seen to be totally different. Pinanga tenella is one of the extraordinary rheophyte species, confined to rocks on banks of rivers throughout Borneo. These rheophytic species all have very slender stems and leaves with very narrow but tough-textured leaflets; they grow above the average water level but in a zone liable to be flooded. It is assumed that the fine foliage is an adaptation offering relatively little resistance to water flow. Lobb's specimen, the holotype of P. tenella, is annotated 'Shrub 2 feet, by the river at Bungal, NE Borneo'. Another collection from Bungal of the same taxon made by Burbidge, is annotated 'Grassy leaved caespitose palm, Tawaran River near Bungol in N Borneo. ?subaquatic'. Beccari himself collected fine-leafleted species of Pinanga from river banks in Borneo on three occasions. One, from the banks of the Tubau in Ulu Bintulu he named P. rivularis (PB 3773), a second from the banks of the Rejang he named P. calamifrons (PB 3841), and the third from the banks of the Sekrang (Batang Lupar) P. calamifrons var. tenuissima (PB 3848). Beccari distinguished P. rivularis from P. tenella on its shorter, fatter, unbranched inflorescence and by the calyx lobes of the pistillate flower being obtuse; he described the leaflets of P. rivularis as being less acuminate than those of P. tenella. The two taxa both have unicostate leaflets. P. calamifrons was separated by Beccari on the basis of its leaflets being bicostate rather than unicostate. The rheophytic Pinanga spp. do look remarkably similar, yet on close examination some specimens are separable on characters of the flowers. In some specimens the calyx of the pistillate flower consists of a low tube with 3 obtuse lobes, whereas in others the calyx comprises 3 free imbricate sepals. This striking difference is the difference used by Burret to distinguish the genus Pseudopinanga from Pinanga. I have followed Moore (1973) in disregarding Burret's genus, but the difference is still striking. The holotype of P. rivularis has the tubular type of calyx; though the calyx may become split as the fruit ripens, its essentially tubular state can be seen in flowers which have not been fertilized. The types of P. tenella and P. calamifrons have imbricate sepals. There are other features which make P. rivularis very distinct. Its stems frequently bear branches, one at each inter- node and sometimes one borne adaxially to the inflorescence at the node; this situation has never been observed in the other rheophytic Pinanga species. The corolla of its staminate flower consists of 3 subequal petals rather than 2 subequal and one smaller petal; the triads are frequently not strictly distichous, the rachilla is thick and densely hairy, and there is a tendency for the pistillate flowers to be borne in two rows, adaxial and abaxial, rather than lateral in relation to the stem. P. rivularis is thus easily distinguished from the other rheophytes; all collections are from the 4th Division of Sarawak. The remaining collections of rheophyte Pinanga can be grouped into two- those with single fold leaflets and those with two-fold leaflets. The former are all from Sabah, and the latter from throughout the rest of Borneo, excluding Sabah. The inflorescences even within populations may have 1-4 branches tion of number of ribs in the leaflet is normally unreliable for distinguishing species in Pinanga, populations of other Pinanga species frequently being very variable among themselves. Yet from the available specimens the two leaflet states in the rheophytes (excluding P. rivularis) appear to be very consistent and geographically separated. I feel P. calamifrons is not specifically distinct from P. tenella but that the consistent leaflet difference should receive some taxonomic recognition. I therefore have reduced P. calamifrons to varietal rank within P. tenella. (J. Dransfield, Systematic Notes on Pinanga (Palmae) in Borneo. 1980)B

Bibliography

A. World Checklist of Arecaceae
B. J. Dransfield, Systematic Notes on Pinanga (Palmae) in Borneo. 1980