Lasiacis (Griseb.) Hitchc.

Baldini, Riccardo M., 2010, Panicum maculatum Aubl.: its type and the correct use of Lasiacis maculata (Aubl.) Urb. (Poaceae, Paniceae), Adansonia (3) 32 (1), pp. 109-119 : 110-114

Lasiacis (Griseb.) Hitchc. , under the combination L. maculata (Aubl.) Urb. , considering in its synonymy L. sorghoidea (Desv. in Ham.) Hitchc. & Chase and/or L. ligulata Hitchc. & Chase.

However, what is reported by Emmet Judziewicz about L. maculata (Aubl.) Urb. ( Judziewicz 1990: 303) is noteworthy: “Aublet’s description is too brief to permit identification and no type was cited, only the illustration in Plumier’s unpublished manuscript 4, t. 82 (not seen), which must serve as the type. [...]. Until the plate can be examined, L. maculata must be regarded as a name of uncertain application”. Meanwhile, Davidse (2003: 280) is of the same opinion, without any specific reference to the Plumier’s plate, that L. maculata (Aubl.) Urb. can be applied to “either Lasiacis sorghoidea (Desv. ex Ham.) Hitchc. & Chase or L. ligulata Hitchc. & Chase , but until the type can be examined, its application remains uncertain”.

Owing to the conflictual opinions, the scope of this contribution is to definitevely elucidate the identification and consequent application of P. maculatum Aubl. and the correct use of Lasiacis maculata (Aubl.) Urb.

THE TYPE OF PANICUM MACULATUM AUBL. : THE ULTIMATE ACT OF A NEVER ENDED DEBATE?

As pointed out by Lourteig (1983) the Aublet’s descriptions cannot be well interpreted because the names are based on pre-linnean publications and without careful investigation of them we are not able to define either their nomenclature or taxonomy leading to mistakes and misconceptions in their current identification.

Aublet (1775: 51) provides a brief description and a polynomial in the protologue of P. maculatum from C. Plumier’s unpublished manuscript as follows:

“5. PANICUM ( maculatum ) scandens, caule arundinaceo.

Milium arundinaceum , scandens & maculatum. Plum. Mss. 4. tab. 82 ”

Jean Baptiste Christophe Fusée Aublet (1720- 1778), during his stay of two years (1762-1764) in French Guyana, made many drawings and preserved the specimens which constituted the basis of his four volumes Histoire des plantes de la Guiane Françoise. The Aublet’s main herbarium is kept in part at BM and P ( Stafleu & Cowan 1976), and after many attempts in the past (see Davidse 1978) and recently by us, it was not possible to trace any specimen to be considered as the type of P. maculatum Aubl. Anyway , a possible endeavor in order to find the type of P. maculatum Aubl. can be done taking into consideration the Plumier’s description and table both cited in the Aublet’s protologue.

According to Pennell (1945), Howard (1975), Stafleu & Cowan (1983), Rankin Rodríguez & Greuter (1999) and McClellan & Regourd (2000), Charles Plumier (1646-1704) did not collect plants during his stay in the Caribbean area between 1689 and 1695 but instead made drawings and descriptions of the plants he saw in the field, even if some specimens of Pteridophytes recently have been discovered in the Vaillant, Danty d’Isnard and Jussieu herbaria at P ( Cremers & Aupic 2007). A Plumier’s collaborator, Joseph Donat Surian, collected some specimens that from his return to Paris in 1691 have been kept at P ( Pennell 1945; Rankin Rodríguez & Greuter 1999) but they cannot be considered as type material which Plumier’s names are based, except in several cases as suggested by Stafleu & Cowan (1983: 301). In the Surian’s herbarium at P no specimen has been found under P. maculatum Aubl. Furthermore Stafleu & Cowan (1983: 301) suggest that “The types of Plumier’s American plants are his original drawings”, so that the original Plumier’s plate cited by Aublet (1775) may be considered the type for P. maculatum Aubl.

At the Bibliothèque centrale du Muséum national d’Histoire naturelle in Paris where the original unpublished Plumier’s manuscripts and the related drawings of Caribbean plants are preserved in a set of 8 volumes under the common title “ Botanicon americanum ” (cf. also Rankin Rodríguez & Greuter 1999), we have found the manuscript cited in the Aublet’s protologue including the related beautiful colour plate n. 82 ( Figs 1 ; 2 ).

The description ( Fig. 1 ) is in accordance with the related plate and is as follows:

“ Radicem habet hac planta ex innumeris fibris compactam crassiusculis, longissinis nigricantibus et tenuissimis villis et ruttescentibus capillaris.

Eius summum caput plurimas producet arundines seu arundinaceos culmos digitum minimum crassos, fistulosos, longisque intervallis nodosos rados variegatos, ac tandem membranaceis inuductis usque ad medium internodium contectos.

Longissimi fiunt sive culmi seu arundines, potissimum arborum vicinarum filamenta nactae. Cum et enim altissime sese execrentes et supra arborum ramos scandentes, longissimos ramos suos fistulosos etiam sed tenues cum late diffundunt ut fere totam arboris quam occupant superficiem complectantur.

His ultimis ramis ad nodos singulos arundinacea inhaerent folia alterno fila ordinata, pediculo seco dimidiam internodii partem amplectentia tres aut quator pollices longa, unum circuler lata, acuminata , caule paulisper rudia, neruulisque quinque aut sex in longum sulcata.

Singuli ultimi rami in iubam seu paniculam definunt ampliam speciosam et late diffusam ex multis glumis constantem membranaceis concavis acuminatis, axique affixis tenuissimo nigricante et dentato in mediis glumis flores nascuntur apetali duobus aut tribus staminibus constantes. Pistillum autem quod vix dimidium acicula minoris adaquat quodque ex calyce bifolco ex duabus sulicet glumis compacto surgit a bis in semen rotundum orobo paulo maius glumisque aliis nigricantibus et squamatis involutum.

Rivulos aut sylvas humidas amat hac planta quam circa regiones arci Regiae vicinas apud insulam Martinicanam (un?)dies adinveni.”

The plate ( Fig. 2 ) consists of a watercolour illustration of lignified, maculate stem base, median and a terminal culm; the latter with an open, large and prominent panicle with ascending and spreading branches, and the spikelets in oblique position; sheath with acuminate apex and not evident ligule which is supposed to be inconspicous. The polynomial clearly related to P. maculatum Aubl. at the bottom of the plate is in Plumier’s handwriting. An additional sketch of a panicle possibly attributable to Olyra sp. is at the bottom on the right side of the plate and a single floret belonging to the main subject is sketched below on the right side of the plate.

Urban (1919: 149) in his comment on P. maculatum Aubl. , maintains that the Plumier’s plate resembles two similar species like P. sorghoideum Desv. in Ham. ( Hamilton 1825) and P. sloanei Griseb. ( Grisebach 1864) , opting for P.sorghoideum (= L. sorghoidea (Desv. in Ham.) Hitchc. & Chase) a common species present in Martinique where the plant sketched by Plumier was found instead of L. sloanei that seems not to be present in Martinique, as confirmed later also by Davidse (1978) and Fournet (1978) and after a consistent check in BM and P herbaria by us. Th e presence of L. sloanei in Martinique reported by Gould (1979) seems not to be supported by any herbarium specimen.

In contrast, Davidse (1978) hypothesizes that P. maculatum Aubl. could be referred to Lasiacis ligulata Hitchc. & Chase because: “He [ Urban 1919] further stated that Plumier probably (my emphasis) described a plant from Martinique, and since L. sloanei did not occur there, the name must apply to L. sorghoidea . However, Aublet’s description almost certainly was based on a plant from the Guianas. Since L. ligulata is the most common species in this region, the name may actually refer to L. ligulata .” ( Davidse 1978: 1233, 1234). Both unusual and provisional postulated interpretations are difficult to accept.

Considering Plumier’s description and colour plate, we can confirm that the species in question must be referred to Panicum sorghoideum Desv. in Ham., actually recognised under Lasiacis sorghoidea (Desv. in Ham.) Hitchc. & Chase as firstly suggested by Urban (1919, 1921) and later reported in Adams (1972), Fournet (1978) and Tovar (1993).

Lourteig (1983) confirmed the nomenclatural validity of P. maculatum Aubl. , and the correct application of Lasiacis maculata (Aubl.) Urb. , but she gave an incorrect taxonomical interpretation considering erroneously as synonyms both L. sorghoidea (Desv. in Ham.) Hitchc. & Chase and L. ligulata Hitchc. & Chase , which are definitively recognized as two different species (cf. Hitchcock 1920, 1922, 1927; Lemée 1955; Davidse 1978, 2003; Smith et al. 1982; Renvoize 1984, 1998; Judziewicz 1990; Killeen 1990; Tovar 1993; Garcia Santos & Takeo Sano 2001; Funk et al. 2007).

Lasiacis sorghoidea is a robust plant, frequently with maculate stem base, an inconspicuous ligule (0.3- 1.5 mm long; up to 3 mm long only in Southern American populations (!) and an open, occasionally curved, dense inflorescence.

In contrast, L. sloanei Griseb. presents a ligule up to 1 mm long, and slender culms with open, scarcely dense inflorescences.

On the other hand, L. ligulata Hitchc. & Chase is characterized by a very long ligule up to 3-4(-5) mm long, with a scarcely dense inflorescence, where the spikes are normally curved. As a matter of fact, in Plumier’s description no reference is made to the presence of a conspicuous ligule, and this led us to exclude any relationship with L. ligulata Hitchc. & Chase , as suggested by Davidse (1978).

In conclusion we assume Plumier’s unpublished colour plate 82 ( Fig. 2 ) as the holotype of Panicum maculatum Aubl. In order to endorse the interpretation of the unpublished Plumier’s plate, we designate an epitype specimen according to Art. 9.7 of the International Code of Botanical Nomenclature ( McNeill et al. 2006) as follows:

Figures

FIG. 1. — C. Plumier’s unpublished manuscript of “Milium arundinaceum scandens et maculatum”: manuscript 4 in C. Plumier’s handwriting. Photo Bibliothèque centrale du Muséum national d’Histoire naturelle, Paris.

FIG. 2. — C. Plumier’s watercolour plate 82 related to manuscript 4, holotype of Panicum maculatum Aubl.(= Lasiacis maculata (Aubl.) Urb.). Photo Bibliothèque centrale du Muséum national d’Histoire naturelle, Paris.