Trymalium monospermum (Rhamnaceae), a new species from south-western Australia

5 Pages·2000·1.2 MB·

by  B L Rye

Nuytsia 13(2):339-343(2000) 339
Trymaliummonospermum (Rhamnaceae),anewspeciesfrom
south-westernAustralia
B.L.Rye
Western Australian Herbarium, Department of Conservation and Land Management,
Locked Bag 104, Bentley Delivery Centre, Western Australia 6983
Abstract
Rye,B.L. Trymaliummonospermum(Rhamnaceae),anewspeciesfromsouth-westernAustralia.
Nuytsia 13(2): 339-343 (2000). A description and illustration of Trymalium monospermum Rye
(Rhamnaceae)aregiven,togetherwithanupdatedgenericdescriptionandkey. Thenewspecieshas
ahighpriorityforconservationasitiscurrentlyknownfromonlyonesmallpopulation,whichislocated
nearNarroginin the south-westofWestern Australia. Itis uniquein its genus in being completely
glabrous and in its 1-seededtrigonous fruit.
Introduction
A newly discovered species of Trymalium known from a single population in south-western
,
Australia,isdescribedandillustrated. ItdiffersfromallpreviouslynamedspeciesofRhamnaceaefrom
theregioninhavingauniloculateone-seededtrigonousfruit. Thereisoneundescribedsouth-western
speciesofCryptandra Sm. with auniloculateone-seededfruit, butits fruitdiffers inbeing terete.
ThispaperalsogivesafulldescriptionofthegenusTrymalium,encompassingtheuniquefeatures
ofthenewspecies. ThekeytoWesternAustralianmembersofthegenusgivenin(Rye1996)isrevised.
Taxonomy
TrymaliumFenzl(Fenzl 1837: 20). Type: TrymaliumledifoliumFenzl., lectotype/h/eSuessenguth
(1953: 113).
Plantslowshrubstosmalltrees,thebranchletsnotspinescentinmosttaxa;indumentumofsimple
and/orstellatehairs orabsent. Stipulesfree, close andoften overlapping atthebaseon adaxial side
ofpetiolebutwidely separatedon abaxial side. Leafbladeseitherconduplicatein budorrelatively
flatandwithmarginsrecurved,mosttaxawiththemidveinslightlyimpressedandthemarginsrecurved
atmaturity,entireortoothed. Cymesterminalandaxillaryonthebranchlets,usuallyveryloose,with
340 Nuytsia Vol. 13, No. 2 (2000)
fewtomanypedicellateflowers, occasionallysomecymesreducedto asingleflower;pedicelslong
exceptinT. densiflorum. Floraltubeentirelyadnatetotheovaryanddiscoralmostso,notextended
beyondthedisc. Sepals5,prominentandpetalline. Petals5,smallerthanthesepals,spathulate,with
thelaminacuppedaroundanantherinbud. Discprominent,moreorlesshorizontal,thick,formedinto
anundulateringatfirst(with 5 lobesextendingoutwardsbetweenthe stamenbasesalternatingwith
five lobes extending inwards), becoming broader and more uniformly circular in fruit but with 5
indentationsaroundtheoutsidewherethepetalsandstamensinserted,glabrousinmosttaxa. Ovary
(2)3-celled. Style with (2)3 stigmatic branches orlonglobes, orless prominently 3-lobed. Fruita
3-celledschizocarpinmosttaxa,eithera2-celledschizocarpor 1-celledintheremainingtaxa,about
halfto fully inferior, enclosed atthebaseorfor its full length in the floral tube, which either splits
irregularlyfromthebaseupwardstorelease 1-3monocarps(fruitingcarpels)orforms threeregular
longitudinalslitstoreleasethemonocarps;monocarp(s)coriaceoustocrustaceous,entire,indehiscent,
with(2)3surfaces,allsurfacesortheinnerone(s)brownandminutelytoprominentlypatterned. Seeds
withadarkenedbase,theremainderuniformlybrown-colouredorwithapaleborder;arilveryreduced
to athin saucer-like structure, huggingthebaseofthe seedbutreadily detached, entiretodistinctly
3-lobed, translucent.
Notes. Agenusof 15 speciesoccurring in southernmainlandAustralia, with 12 speciesendemic to
thesouth-westofWesternAustralia,onespeciesendemictosouthernSouthAustraliaandtwospecies
endemictoTheGrampiansinVictoria.
RevisionofkeytoWesternAustralianTrymaliumspecies
ThenewspeciesfallsintothesecondmaindivisionofthekeytoWesternAustralianspeciesgiven
inRye(1996). Thisportionofthekeycoversthetaxawithaglabrousovaryandisrevisedbelowto
includeT.monospermumandtocorrectalaterreferencetothefruitofT.ledifoliumFenzl. Intheprevious
keyTrymaliumledifoliumwasdistinguishedfromT.elachophyllumRyepartlyonthebasisofitsfully
inferiorfruit,butitwasrecentlyobservedthathalfofthefewfruitingspecimensofT. ledifoliumvar.
ledifolium do not have fully inferior fruits like the other varieties of this species. One specimen
(E.A. Griffin 6673)hasthefruitsvaryingfromaboutthree-quarterstoalmosthalfinferior.
1. Ovary (only summitvisible) glabrous. Fruitglabrous, partially
orfullyenclosedin thefloral tube, which is usually alsoglabrous.
9. Leaves narrowly obcordate tobroadlyobtriangular, with margins
flatorincurvedat maturity. Floral tube constrictedbelow apex infruit
and extended slightly above the fully inferiorfruit.
10. Leavesentire,hairy. Fruitterete, 3-seeded T.urceolare
10. Leaves distally toothed, glabrous. Fruittrigonous,!-seeded T.monospermum
9. Leaves linearto oblong-elliptic, withmargins somewhatrecurvedto
revolute atmaturity. Floral tube notconstricted in fruitand exceeded
orequalled inlengthby the half-inferiortofully inferiorfruit.
mm
11. Leaves2-5 long. Fruitc. two-thirdsinferior,erectorspreading,
regularly dehiscentinto three equal parts. Monocarps coriaceous to
brittle atmaturity; inner surface finely reticulate, notridged T.elachophyllum
mm
11. Leaves 8-40 long. Fruitusuallyfully inferior(exceptin
T. ledifolium var. ledifolium), pendulous, irregularly dehiscent.
Monocarps very hardatmaturity; innersurfaceprominently
ridged, with large deep lacunae T.ledifolium
Rye, B.L., Trymalium monospermum, a new species from south-western Australia 341
TrymaliummonospermumRye,sp. nov.
Plantae omnino glabrae; folia conduplicata, dentata; ovarium uniloculare; fructus trigonus,
uniseminalis.
Typus: Narrogin area [precise locality withheld], WesternAustralia, 15 July 1999, L.W. Sagel540,
J.P. Pigott&E.B. Pigott{holo:PERTH05301661;iso:CANB,K,MEL,NY).
Shrubs0.1—0.3 mhigh andupto0.5 mwide, multi-stemmedatbase, notspinescent, completely
glabrous. Youngstemswithminutetubercles,becomingdarkgrey. Stipulesovateorbroadlyovate,
0.7-1 mmlong,acuteorshortlyacuminate,entireorsomewhattoothed. Petiolec. 0.5mmlong. Leaf
bladesconduplicateorwithmarginsincurvedatfirst,becomingflatornearlyflat,narrowlyobcordate
tobroadlyobtriangular,5-8x2—4.5mm,entireinthebasalpartanddentatedistally ratherprominently
,
2-lobedatapexwithatriangularmucronulatesub-lobeorapointatthejunctionofthetwomainlobes,
eachofthemainlobesusually2—5-denticulatebutsometimesjustwithasinglemucronulatetip;upper
surfaceminutelyreticulate-pitted;lowersurfaceminutelyrugosewithfurrowsandpits. Flowerscream
oroff-white. Cymesterminalandaxillaryonthebranchlets,mostly5-12-flowered,veryloose,upto
14mmlonginfruit,notincludingthepeduncle,whichisuptoc. 6mmlong. Pedicels 1-1.5mmlong
inflowerandupto4mmlonginfruit. Floraltubec. 0.5 mmlonginflower,enlargingtoc. 2.6mm
longinfruitandbecomingconstrictedjustbelowthesummitwhichformsaspreadingterminalportion
c.0.15mmlong. Sepalsc.0.8mmlong. Petalsc.0.4mmlong. Discc.0.25mmwide. Ovary3-celled.
mm
Stylec. 0.2 long; apexwith aflattened3-lobed stigma. Fruitfullyinferior, 1-celled, trigonous,
mm
truncate-obovateinoutlineand6-7x3.5^1 includingthefloraltubeandotherattachedparts,the
floral tube splitting irregularly from the base upwards to release the single monocarp; monocarp
equilaterally triangularin cross-section with each ofthe three surfaces obovate to elliptic, c. 2,4 x
I.4mm,brown,coriaceous,veryminutelyreticulate-pitted. Seedc. 1.7x1mm,mediumorange-brown
withadarkenedbase; aril 3-lobed,clear-translucent. (Figure 1)
Otherspecimens examined. WESTERN AUSTRALIA [precise locality withheld]: Narrogin area,
29Aug. 1997,G.J.Keighery<£N. Gibson2088;Narroginarea, 15July 1999,L.W.Sage1541 & 1542,
J.P. Pigott&E.B. Pigott.
Distribution. OccursintheNarroginareaintheSouthWestBotanicalProvinceofWesternAustralia.
Habitat. Recorded in red-brown gravelly sandy soil on a lateritic ridge, in a low heath vegetation
includingMelaleucapungens,anumberofmembersoftheProteaceaesuchasDryandraarmata,and
twoAllocasuarina species.
Phenology. FlowersandyoungfruitsrecordedinJuly, andmaturefruitsinlateAugust.
CALM
Conservationstatus. ConservationCodesforWesternAustralianFlora;PriorityTwo. Known
from asinglesmallpopulation, locatedonanaturereserve. When surveyedinDecember 1999, the
populationcomprised28plants (Kim Kershawpers. comm.). Searches innearby areas ofbushland
failedto locate anyfurtherpopulations ofthespecies (Leigh Sagepers. comm.).
Etymology. FromtheGreekmono-one,andsperma-seed,referringtothe 1-seededfruit.
342 Nuytsia Vol. 13, No. 2 (2000)
Figure 1. Trymalium monospermum. A -fruiting branch (xl), B -stipules and undersurface of leaf(x6); C - upper
surface ofleaf (x6) with enlargement ofreticulate pitting; D - top and side view of fruit (monocarp enclosed in floral
tube) and pedicel (x8); E - floral tube splitting at base to reveal monocarp (x8), F - monocarp (xlO), G - seed with
basal aril (xlO). Drawn from G.J. Keighery & N. Gibson 2088.
Notes.ItsclosestrelativeappearstobeTrymaliumurceolare(F.Muell.)Diels,whichissimilarinhaving
conduplicate leaves, completely glabrous flowers, the floral tubeconstricted near the summit and a
completely inferiorfruit.
Trymaliummonospermumisaverydistinctivespecies,apparentlythesmallestmemberofitsgenus
andtheonlyonetobecompletelyglabrous, andisreadilyidentifiedbyitsmoreorlessobcordateto
obtriangularleaves with two large tooth-like orprominently denticulate lobes. Also uniqueto this
species are the flattened stigma and 1-celled trigonous fruit with a solitary seed. Although
T. monospermum has a 3-celled ovary with an apparently fertile ovule in each cell, only one cell
develops into amonocarp, the twoabortedcells noteven being visible in the mature fruit.
All other species of Trymalium have a terete fruit with more than one monocarp. Apart from
T.floribundum Steud. subsp.floribundum, they all have a stigma with three long lobes, and three
unequally3-facedmonocarps. Eachmonocarphas aroundedoutersurface, whichislargerthanthe
twoflatterinnersurfaces,andtheinnersurfacesaremoreprominentlypatternedthantheoutersurface.
InT.floribundumsubsp.floribundumtheovaryis2-celled,thestigma2-lobedandeachmonocarphas
aroundedoutersurfaceandflatter,moreprominentlypatternedinnersurface. Alogicalexpectation
fora 1-celledfruitinTrymaliumwouldbeforittohaveasingleroundedsurface,i.e.tobeterete,since
thesolitarymonocarphasnointernalsurfacesadjacenttoothermonocarps. Insteadthemonocarpof
Trymaliummonospermum istrigonous,withthreesurfacesofuniformshape, sizeandpatterning.
Rye, B.L., Trymalium monospermum, a new species from south-western Australia 343
Acknowledgements
IwouldliketothankLeighSageforbringingthenewspeciestomyattentionandforhisfieldwork,
includingthecollectionoffloweringmaterial,alsoKevinThieleandJudyWestfortheirconstructive
comments,PaulWilsonfortranslatingthediagnosisintoLatin,andMargaretPieronifortheillustration
ofthenewspecies.
References
Fenzl,E. (1837). Rhamneae. In: Endlicher, S.L.,Bentham,G., Fenzl,E. &Schott,H.“EnumeratioPlantarum....Hiigel.”
pp. 20-27. (Beck.)
Rye,B.L. (1996). Asynopsisofthe generaPomaderris, Siegfriedia, Spyridium and Trymalium (Rhamnaceae) in Western
Australia. Nuytsia 11: 109-131.
Suessenguth, K. (1953). Rhamnaceae. In: Engler, H.G.A. & Prantl, K.A.E. “DieNaturlichen Pflanzenfamilien.” Vol.
20d, pp. 7-173. (Duncker & Humblot: Berlin.)