Digitaria Effusa (Gramineae), a new species from Vietnam

2 Pages·1999·0.31 MB·English

by  Veldkamp, J F

BLUMEA 44 (1999) 447-448
Digitaria Effusa (Gramineae),
a newspecies from Vietnam
J.F. Veldkamp
Rijksherbarium/HortusBotanicus,P.O. Box9514,2300RA Leiden,The Netherlands
Duringanagrostological surveyintheLamDongProvince, Vietnam,Mr. J.B.Hacker
(St.Lucia, Queensland, Australia)collectedaremarkableundescribedspeciesofDigi-
taria.Among theAsiantaxa itispeculiar becauseofitsmontaneprovenancecoupled
witha combinationofaninflorescence withwell-developed commonaxis withalter-
nate racemes, thepresenceofasmalllowerglume,andtheabsenceofany indument
on the spikelet. Somewhatsimilaris D. wallichiana(Steud.) Stapf, also a montane
species occurring with onesubspecies in SriLankaandMadras, andanotherin Java
andBali.Itdiffersbythewhorledlowermostbranchesoftheinflorescence,theabsent
lowerglume, andalonger upperglume (1.6-2 mmlong, 0.8-0.95times as long as
thespikelet), anda usually presenceofanindumentonthespikelet.
Thespikelets aresurprisingly similartothoseoftherare Vietnamesespecies Pani-
cum amoenum Balansaand P. smithiiM.M.Rahman, butthese have a much larger
habit with larger inflorescences, long-pedicelled spikelets, large and nerved lower
glumes, andaninduratedfertilelemmainfruit.Hacker’s specimens donothavemature
fruits, butthepaired spikelets withshortandsomewhatlonger pedicels aretypicalfor
binateDigitaria species andnot foraPanicum.
Digitaria effusaVeldk., spec. nov.
Perennes culmis geniculatis, ligulis c. 1 mm longis, foliorum laminis 6-8 mm latis
pilosis, paniculaeffusa,axecommuni 1-3cm longo,racemis paucispatentibus alter-
nis (infimis inclusis) 3.5-5.5 cm longis,pedicelliapice discoideo,spiculis 1.8-2mm
longis,glumainferiore 0.25-0.3 mmlonga,glumasuperiore 1.4-1.5mmlongaspicula
0.74-0.79-plolongiore glabra, lemmate sterili glabro, lemmate fertili spicula paulo
breviore verosimiliter flavido in fructu, antheris c. 0.9 mm longis.—Typus: Hacker
1613 (holoL).
Perennials,rhizomeabsent, cataphyllspresent,pilose. Culms0.25-0.35mlong,geni-
culately ascending, rooting inthedecumbentnodes.Nodes glabrous. Sheathspilose,
margins pilose. Ligule amembranousglabrous collar, c. 1 mm high,erose. Blades
flat,linear,4-8cmby6-8mm,pilose,base rounded,margin atbase pilosetoslightly
pectinate, apexacuminate,underneathwithc. 7 majornerves. Panicle lax, 4.5-5 by
6-10 cm. Mainaxis 1-3 cm long, smooth, glabrous. Panicle branches patent, all
alternate, 4-8, rhachis triquetrous, scaberulous, glabrous, spikeled to base, the
lowermost3.5-5.5 cm long.Pedicels straight, appressed, shorter thanthespikelets,
scaberulous, abscission discoid, margin ciliolate. Spikelets paired, homomorphous,
not yawning atmaturity, 1.8-2mmlong, acute.Lowerglume ovate,0.25-0.3mm
448 BLUMEA—Vol. 44, No. 2, 1999
long,0.14-0.15timesaslongas thespikelet, acutetorounded,0-nerved. Upperglume
1.4-1.5mmlong, 0.74-0.79timesas long as thespikelet, acute, glabrous, 3-nerved,
nerves withouttransverse veinlets.Firstlemmaacute,glabrous, nerves 7,equidistant,
smooth,withouttransverse veinlets. Secondlemmaslightly shorterthan thespikelet,
smooth, shiny, possibly turning yellowish infruit, glabrous, apexapiculate, straight.
Anthersc. 0.9mmlong.
Distribution—Vietnam,LamDong Prov., 2km SofDaLat, N 11°54.9', E 108°
25.7'.
Habitat—Roadsideinpine treewoodland,soilclayey, pH6.0,altitudec. 1200m.