Pennisetum polystachion

Veldkamp, J. F., 2014, A revision of Cenchrus incl. Pennisetum (Gramineae) in Malesia with some general nomenclatural notes, Blumea 59 (1), pp. 59-75 : 63-64

Pennisetum polystachion , a foul-up

The species was first described by Linnaeus (1759) as Panicum polystachion with the phrase name P[anicum] spic[is] teretibus, involucellis unifloris fasciculato setosis, culmis erectis superne ramosis, apparently strictly based on the illustration by Rumphius (1750). The inflorescence shown there is terminal and solitary, so the epithet is not fitting. Rumphius’s editor Burman translated his Vossesteertegras (Foxtail grass) to Gramen vulpinum . For some reason this was misnamed again by Linnaeus (1762: f. 15) as Gramen caricosum alterum but Rumphius’s description and illustration clearly represent Setaria parviflora (Poir.) Kerguélen ( Merrill 1917: 91 as S. flava (Nees) Kunth ) which indeed has a solitary terminal inflorescence. Linnaeus’s citations of the phrase names are not to be found in the cited place. This is again an example of someone trying to match a specimen in hand with existing literature as we even do today. Therefore, the specimen in his herbarium (Herb. Linné 80.6) is here designated as the lectotype and belongs to Setaria glauca (L.) P.Beauv.

The situation was thrown in a lasting confusion by Linnaeus (1771) when he described another Panicum polystach [ium]. According to the diagnosis (“setis ciliatis a basi ad medium pilis longiusculis ”) and the specimen he used (Linn. 80.4) is a species of Pennisetum . Herb. Linné 80.4 (f. 17) has been designated as the lectotype of P. polystachion L. (1771) (Van der Zon 1992: 335).

In fact, it is a later homonym, yet combinations using the Linnaean epithet of 1759 generally, but erroneously, have been applied to it. Because of this widespread confusion I will submit a proposal of conserving the 1771 name with Linn. 80.4 as the conserved type, whereby general usage will be maintained .

The combinations used for the Cenchrus / Pennisetum in fact pertain to Setaria glauca and the correct name in Cenchrus for the moment is C. setosus Sw.

A curious, remarkable and unexplained thing is that neither Panicum polystachion nor Pennisetum polystachion are mentioned by several early to mid-19th century standard compilers of names and grasses, or misused the first for something else. Possibly they thought that when a name could not be placed, or was regarded as a synonym, it was allowed to be used again for something else.

Steudel (1821: 589) only had a Panicum polystachyum based on Oplismenus polystachyus Kunth (1816b) , which is now Echinochloa polystachya (Kunth) Hitchc.

Trinius (1822: 327) equated Gramen vulpinum Rumph. with Pennisetum setosum , which is clearly erroneous, as that species was only recently introduced in Malesia and certainly could not have been seen by Rumphius before he lost his sight in 1670. His illustration not even remotely resembles it. It is Setaria parviflora (Poir.) Kerguélen.

Sprengel (1824: 302–304, 307–309) did not mention them at all. Trinius (1826: 65–66) mentioned Panicum polystachyum L. under Pennisetum parviflorum Trin. (not based on Cenchrus parviflorus Poir. !) noting that it did not belong there as the involucre was not ciliate. On p. 68 under Pennisetum violaceum Trin. he said “an Panicum polystachyon L. sp. pl. ed. 2, et Mant. (tum excl. syn. Rumphii)”.

Trinius (1834) cited Panicum polystachyum L. with doubt under Pennisetum uniflorum Kunth (1816a , b), now regarded as a synonym of Pennisetum polystachion (or P. setosum ?).

Steudel (1854: 81, 461) had only Panicum polystachyum J.Presl , but this is also a later homonym and now a synonym of Hymenachne donacifolia (Raddi) Chase.