Bulletin of the Natural History Museum

148 Pages·1996·13.1 MB·English

by  Natural History Museum (London)

THE
NATURAL
HISTORY
MUSEUM
VOLUME 26 NUMBER 2 28 NOVEMBER 1996
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World List abbreviation: Bull. nat. Hist. Mus. Lond. (Bot.)
The Natural History Museum, 1996
Botany Series
ISSN 0968-0446 Vol. 26, No. 2, pp. 75-217
The Natural History Museum
Cromwell Road
London SW7 5BD Issued 28 November 1996
TypesetbyAnnBuchan(Typesetters),Middlesex
PrintedinGreatBritainbyHenryLingLtd.,attheDorsetPress,Dorchester,Dorset
Bull. not. Hist.Mus. Land. (Bot.)26(2): 75-217 Issued28November 1996
Studies in the genus Hypericum L. (Guttiferae)
6. Sections 20. Myriandra to 28. Elodes THE NATURAL
HISTORY MUSEL
NORMAN ROBSON
K.B.
DepartmentofBotany, TheNaturalHistoryMuseum, CromwellRoad, London SW75BD .PRESENTED
CONTENTS
Introduction 76
SeparationofsectsAdenosepalumandHumifusoideumfromtherestofKeller'ssect.Euhypericum 76
Circumscriptionofseel.Adenosepalum 76
Sect. 20.Myriandra 76
Subdivision 76
Charactersandvariation 78
Leaves 78
Inflorescence 78
Flowersandfruits 79
Cytologyandhybrids 79
Distributionandevolution 79
Sects21. Webbiaand22.Arthrophyllum 82
Charactersandvariation 82
Distributionandevolution 83
Sects23. Triadenioides,24.Heterophyllaand25.Adenotrias 83
Charactersandvariation 83
Distributionandevolution 84
Sect.26.Humifusoideum 85
Charactersandvariation 85
Distributionandevolution 87
Sects27.Adenosepalumand28.Elodes 88
Evaluationofsect.Elodes 88
Charactersandvariation 89
Morphologyandsubdivision 89
Cytologyandhybrids 90
Distributionandevolution 90
Systematictreatment 92
Sect.20.Myriandra(Spach)R.Keller 92
Sect.21. Webbia(Spach)R.Keller 133
Sect.22.ArthrophyllumJaub.&Spach 137
&
Sect.23. TriadenioidesJaub. Spach 141
Sect.24.HeterophyllaN.Robson 146
Sect.25.Adenotrias(Jaub.&Spach)R.Keller 147
Sect.26.HumifusoideumR. Keller 153
Sect.27'.AdenosepalumSpach 170
Sect.28.Elodes(Adans.)W.Koch 208
References 212
Systematicindex 214
SYNOPSIS. Followingcitationofthetypeofanewsubspecies(H.silenoidessubsp.minusN.Robson)omittedfromPart8,those
sectionsofHypericumdirectlyrelatedtosect. 1.CampylosporusthatwerenottreatedinPart3areconsidered,aswellassects
22.Arthrophyllumand28.Elodes,whicharecloselyrelatedrespectivelytosects21.Webbiaand21.Adenosepalum.Adiscussion
ofthemorphology,chromosomenumbers,hybrids,distributionandevolutionofeachsectionisfollowedbyasystematicaccount
ofthe81 speciesintotalthattheycontain.
Sect.20.Myriandraisdividedintofivesubsections:subsect.CentrospermaR.Keller,subsect.PseudobrathydiumR.Keller,
subsect. Suturosperma R. Keller, subsect. Brathydium (Spach) R. Kellerand subsect. Ascyrum (L.)N. Robson stat. nov., all
additionaltoorwithcircumscriptionsdifferentfromthoseinAdams's1962paper;and//,tenuifoliumPurshreplaces//,reductum
W.P.Adams.
Sect. 27.Adenosepalum isdivided intofoursubsections: subsect.AethiopicaN. Robson, subsect. PubescentesN. Robsen,
subsect. Caprifolia N. Robson and subsect. Adenosepalum; and H.joerstadii Lid is treated as a hybrid, H. glandulosum x
reflexum.
TheNaturalHistoryMuseum, 1996
N.K.B. ROBSON
76
Bupleuroidestheleafpairs areconnate andglabrous andthe styles
INTRODUCTION basallyappressed;andinsects9.Hypericumand 14.Oligostemathe
petals become (roughly) erect after flowering, not tightly twisted
Thispart(Part6)oftheHypericummonographincludestreatments round the developing ovary as in sects 27. Adenosepalum and 28.
oftheremainingsectionsdirectlyrelatedtothemainlyAfricanSect. Elodes. Sect. Adenosepalum is therefore distinguishable among
1. Campvlosporus (sects 20-28), sects 2-3 having been treated in species of 'sect. Homotaenium Boiss.' by the combination offree
Part 3 (Robson, 1985) and sects 29-30 in Parts 7 and 8 (Robson, leaf pairs with inframarginal black glands (or if leaf pairs are
1987, 1990). Parts4 and 5 will include the remaining sections, all connate they are pubescent), petals twisting round the developing
directly relatedtotheAsian sect. 3.Ascyreia (sects7-19). fruit, 3 distinct stamen fascicles (cf. sect. 26. Humifusoideum) and
Before turning to the main concern of this part, however, it is seedswithalinear-reticulatetoscalariformtesta.Thepresenceofan
necessarytoremedyanomenclaturalomissioninPart8.Thetypeof indumentum in many speciesdistinguishesthese from membersof
Hvpericum silenoides subsp. minus, endemic to the Galapagos sects9and 14,whilstthewidespreadoccurrenceofflat-toppedsepal
Islands (Robson, 1990: 90), shouldhavebeencitedas: & marginal glands in sect. Adenosepalum is paralleled only in some
Ecuador,GalapagosIslands,AlbermarleIsland [Isabella], 825 speciesofsect. 17. Hirtella. Sect. 28. Elodes isdifferentiatedfrom
945m,28August 1905(fl),Stewart2064(BM!-holotype;GH!,K!, sect.Adenosepalumprincipallybythefloral modificationstowards
MO!-isotypes). specialized insect pollination, but also by the red marginal sepal
glands, the ribbed-scalariform seed testa and almost always by the
Separation ofsectsAdenosepalum and absenceofinframarginal black leafglands.
Humifusoideum from the rest ofKeller's sect.
Circumscription ofsect.Adenosepalum
Euhypericum
Whentheforegoingcriteriawereconsidered, itbecamecleartome
Sects20-28fallintosixquitedistinctgroups,eachrelateddirectlyto that the Himalayan, south Indian and Chinese species that I origi-
ssetcatm.e1n.sCaampppvalreonstployrunso:t(fi)as2c0i.cMuylartieanadnrda,blwaictkh2gl-a5nsdtsylaebssenatp;pr(eiis)se2d1,. nbaellloyngintchleurdee.dTihnesepcutt.atiAvdeen'olsinekpiangl'umspe(cRioebss,ont,he \H9i1m1abl)aydaon nHo.t
Webbiaanditsderivative22.Arthrophyllum,with3stylesspreading elodeoidesChoisy,isinfactcloselyrelatedtoH.hengshanenseW.T.
from non-contiguous bases, stamens '3'-fasciculate, black glands Wang, from SE China (Jiangsi, Hunan, Guangxi, Guangdong).
absentorpresentandleaves broadwithdenselyreticulatevenation; Indeed,Li(1990:6)broughtthesetwospeciestogetherinhiskeyto
(iii) 23. Triadenioides, with 3 styles spreading from contiguous Chinese Hypericum, placingboth in sect. Adenosepalum.
bases,stamens'3'-fasciculate,blackglandspresentonlyinthemost Three glabrous, western Asiatic species allocated to sect.
derived species and leaves broad (but without clearly reticulate AdenosepaluminPart 1 andpreviouslyinFloraofTurkey(Robson,
venation)to microphyllous;(iv)24.Heterophyllaand25Adenotrias, 1961b)mustalsobeexcludedandtransferredtosect. 12.Origanifolia.
with3stylesspreadingfromcontiguousbases,stamens'3'-fasciculate, TheseareH. huber-morathiiN.Robson,H.minutumPoulterandH.
blackglandsabsentandleavesmicrophyllous;(\)26.Humifusoideum, formosissimum Takht. They were originally excluded from sect.
winidtehfin3i-t5e ssttaylmeesnsfapsrceiacdliesn,gbflarcokmglcaonndtsiguusouuasllybapsreess,en't3'a-n5dlreaatvheesr cOhrairgaacntiefroilstiiacboefcaHu.seortihgeainrifcoalpisuumleWsillladc.keadndthHe.sawvoilcluelnariviefsoilciluesm
broad;and(vi)21.Adenosepalumanditsderivative28.Elodes,with Jaub. & Spach. H. minutum and H.formosissimum, however, have
3blasctykle(sorsprreedadiinngsecftr.om28c)ongtliagnudosusprebasseenst,a'n3d'-lfeasacviecslebdrosatda.meTnhse, ianntderHr.upstaeldsuvigtitnaee,umwhNi.cRhobarseonal&soHfuobu.n-dMoirn.,H.boitmhbcrliecaarltyumrelPaotueldtetro
distributions of these groups are: Group (i) Eastern N. America, H. aviculariifolium;andH. minutumisclearlycloselyrelatedtoH.
eastern Mexico, Belize, Guatemala, Honduras Republic, Greater huber-morathii. When other characters, such as glandularity, leaf
Antilles, Bahamas, Bermuda; (ii) Macaronesia, eastern Mediterra- and flower colour and habitat (all in limestone rock crevices), are
nean;(iii)Socotra,SWTurkey,Levant;(iv)NWAfrica,Mediterranean, taken into consideration, there can be little doubtthattheircorrect
NW Turkey; (v) New Guinea, Luzon, Taiwan, Sumatra, Java, S. position is nearH. aviculariifolium.
AMfarciacraonetsoiaE,thAiforpiicaa,aWn.dAErqaubaitao,riEaulropGeu,inWe.a,CaMuacdaasguass,caWr.;&(viS). sectW.itAhdtehneotsreoppiaclaulmancdaenasbteAsisaeteincatondhAanvaetoiltisanprsipmeictiivees,exschlruudbebdy,
Tiunrckleuyd,edLeivnasnetc.t.NAodteentohsateptarolpuimcalbealnodngeaisntfAascitattiocssecpte.ciHeyspheirtihecrutmo swpheoclileys gilnabMraocuasr;on(iei)siNaWandAftrhirceaeadnedrivtahteivCeagnraoruypsI:sl(ai)ndAsfrtioca(na,)
sensulato(seebelow). SomalilandandwesternArabiaand(b)thewesternMediterranean,
Althougheachofthesegroups iseasily distinguishablefromthe wholly with indumentum; (iii) Europe to western Caucasus and
others,membersofsects26(Groupv)and27(Groupvi)haveoften adjacentTurkey,theMediterraneanandEthiopia(withadjacentNE
been includedin abroadsect. Euhypericum Boiss.,forexampleby Sudan and Arabia) to northern Tanzania, nearly always with
Keller (1925: 177). Keller placed such species in his subsect. indumentum. H. elodesL. (sect. 28. Elodes) isderivedfrom group
Hcoonmtoatianeendimuoms,tboyftfhaerstpheecilearsgewsitthsunbasrercotwiocnonintitnhueoussecltoinogn,ituwdhiincahl (iinit)oagnrdoHu.pa(fi)rruamthLearmt.ha(nfrionmsTecutn.is9i.aHaynpderaidcjaucme,ntwhAlegreeriIa)orfiigtisnwaelllly
voiutstaaegognlotmheercaatpisounleovfalsvpeesc.ieAsttweemrpetsmtaodreatiboynaSltizeefatnhoifsfhe(t1e9r3o2g-e3n4e)- located it (Robson, 1977a).
and Kimura (1951), both ofwhom divided it into sections, and by
Gorschkova (1949), who retained Keller's subsect. Homotaenium Sect. 20. Myriandra
butdivideditinto 15series.InPart 1 ofthiswork(Robson, 1977a),
IdistributedKeller'sspeciesamongsections8,9, 14, 17, 18,26and Subdivision
27. Sects 17. Hirtella and 18. Taeniocarpium are distinguished
amongthesebyhavingnoregularintramarginalrowofblackglands This well-delimited section comprises 29 species and4 subspecies
onthe leaves and seeds with asmoothtopapillosetesta; in sect. 8. thataremostly shrubsorwiryshrubletsbutincludeafewperennial
STUDIES INHYPERICUM
77
Sect. 20Myhandra
Relationships
7. tenuifolium
18 11. brachyphyll1u8m 19. microsepalum 21 adpressum 22.ellipticum
18 18
9c. nitidum ssp. exile 13.fasciculatum 20. sphaerocarpum
9b. nitidum ssp.
nitidum SUTUROSPERMA
29c. hypericoides
ssp. prostratum
16.apocynifolium 17. nudiflorum
29b. hypericoides
8. lloydii ssp. multicaule
9a. nitidum ssp. cubens
PSEUDO-
BRATHYDIUM
5. densiflorum . tetrapetalum
15. buckleyi 18
4. lobocarpum
18 27. edisonianum
24.dolabriforme
/ 18
CENTROSPERMA
BRATHYDIUM
28.suffruticosum
3. kalmianum 18
18 23. myrtifolium
18
1. frondosum 25.crux-andreae 29a. hypericoides
18,36 18 ssp. hypericoides
18
Fig. 1 Sect.20.Myriandra.Relationshipsandchromosomenumbers(2n)ofthe29species.Limitsofthe5(named)subsectionsindicatedbyboldlines.
herbs.They all lackblackglands and have stamenfasciclesclosely Subsect.Centrosperma-shrubs;leavesandsepalswitharticulationor
merged, so thatthe androecium appears to be polyandrous and (in grooveatbase;sepals5(4),deciduous;petals5(4);stamensdecidu-
contrasttosect.30.Trigynobrathys}remainssoeveninthesmallest ous. 15 species, i.e. Spp. 1-14 in the present treatment + 23. H.
flowers.Thestylesareslenderandcloselymutuallyappressedinthe myrtifolium.
moreprimitive species; butthey have atendency to part in fruitin Subsect. Pseudobrathydium -shrubs and perennial herbs; leaves and
moreadvanced4-petalledones('Ascyrum").Thestigmasaresmall. sepals withoutarticulationorgrooveatbase; sepals5-4, persistent
MyrKielalnedrra(1i8n9t3o,th1r9ee25m)aidnivsiudbegdrotuhpes,grvoizu.pAtsrceyarteudmhaenrdetawsosseecct-. 2(ind4e-Hc.2i9nduuiodnuitsfhleionrpHru.emsneaunndtditfHrl.eoaartpumomec)ny;tn.pieftoallisu5m^)4.;1s4tsapmeecnisesp,eir.sei.sStpenpt.(1e5x-c2e2p,t
tionsofHypericum,witheachsectionofHypericumcontainingtwo
subsections: Fromtheseattemptsatinfrasectionaldivisionitwouldappearthat
AHsycpyerriucmu-ms-epsaelpsalasndanpdetpaeltsal4s;5p;lapcleancteanttiaotniopnaraixeitlael;tostpyalreiset2a-l3.(4). tshpeerceieasre(Ht.hrebeuckmlaejyoi,r gHr.ounpusdi(falsorKueml,lerH.praoppoocsyendi)f,olbuitumthaantdfoHu.r
Sect.Mvriandra-stamensdeciduous;placentationaxiletoparietal;styles myrtifolium)fallawkwardlyacrosstheproposedgroupdivisions.In
3-5. addition,theAscyrumgroupisheterogeneous,asSpach(18366)had
Subsect. Centrosperma-placentationaxile,pyramidal. already realized. Most species have two unequal pairs of broad
Subsect.Suturosperma-placentationparietal. appressedsepals,butin 19.H.microsepalumtheyareequal,narrow
Sect. Brathydium - stamens persistent; placentation parietal or rarely and recurved. Spach placed the latter in a monotypic genus,
axile;styles3. Isophyllum,as/,drummondii;anditisclearlynotrelatedtotheother
SSuubbsseecctt..EPsueburdaotbhryadtihuymd-iupmla-cepnltaacteinotnatpiaorinetaaxli.le,pyramidal. 4h-apveetableleendsdpeercivieeds.butto 18.H. cistifolium,fromwhichitappearsto
FollowingtheinclusionoftheAmericanspeciesofAscyruminsect. Thesuggestedinterrelationshipsofspeciesinsect.Myriandraare
Myriandra (Adams & Robson, 1961), Adams (1962) recognized showninFig. 1,alongwiththefivesubsectionsintowhichtheyhave
only one section, subdividing it intotwo subsections: beendividedhere. Itwillbeseenthattherearetwobasalspecies(1.
78 N.K.B. ROBSON
H. frondosum and 2. H. prolificum, both variable, especially the Suturosperma (Spp. 16, 17), Brathydium (23. H. myrtifolium) and
latter), from which the remaining species have been derived. H. Ascyrum (Spp. 25, 26) but is wholly absent from subsect.
frondosumisdirectlyrelatedtotheAscyrumgroup(Spp.25-29)and Pseudobrathydium(15. //. buckleyi).Thischaracterchangeisasso-
the Brathydiutn group (Spp. 23-24), whereas the Suturosperma ciated with a tendency for the point ofleaf-fall to move from the
group(Spp. 16-22)and//,buckleyi(Sp. 15)aredirectlyrelatedto//. basalgroovetothepetioleorpseudopetiole. Delayedbasal leaf-fall
prolificum(asare Spp. 3-14). is found in 16. H. apocynifolium, 17. H. nudiflorum, 25. H. crux-
From Fig. 2, which showsthe limitsofcertaincharacters, itwill andreaeand26.H.tetrapetalum,whilesuprabasalleaf-falloccursin
be clear why Keller and Adams had difficulty in defining their 15. H. buckleyi, 18. H. cistifolium, 19. //. microsepalum and the
subdivisions and why nohard andfast linescan bedrawn between remainderofsubsect.Ascyrum (Spp. 27-29).
Myriandrasensustricto(Spp. 1-14)andtheremainingspecies.The In the linear- to acicular-leaved species, there is a contrast be-
groups outlined above, however, can be treated as five reasonably tweenthoseinwhichthemarginisrevolutebuttherestofthelamina
well defined subsections: unaltered(12. H. lissophloeusand the H. galioides and //. nitidum
groups, Spp. 6-11)andtheH.fasciculatumgroup(Spp. 13, 14), in
1. Subsect. Centrosperma (p. 94)-Sepalsandpetals5; sepalsand which the midrib area is raised beneath, forming agroove on each
stamens deciduous; leaves and sepals articulated; sepals very sidebetween itand the revolute margin (cf. Fig. 2).
unequaltosubequal;styles(2)3-5(6);placentationincompletely INFLORESCENCE. The inflorescence of the near-ancestral //.
axile toparietal; shrubs. Spp. 1-14. synstylum is 1-2-flowered, a state that is reflected in the 1-3-
2. Subsect.Pseudobrathydium(p. 112)-Sepalsandpetals5;sepals flowered basic inflorescence of sect. Myriandra (usual in 1. //.
and stamenspersistent; leaves and sepals notarticulated; sepals frondosum). Two evolutionary tendencies lead to (i) the involve-
subequal; styles 3; placentation incompletely axile; low shrub. ment of an increasing number of nodes in flower-bearing
Sp. 15. (basipetal)and(ii)anincreasingdegreeofcymose(i.e.dichasial/
3. Subsect. Suturosperma (p. 113) - Sepals and petals 5(4-3); mnaonntochinassiuabls)ecbtr.ancCheinntgro(ascpreorpemtaa,l).leBaadsiinpgetatlobtrhaenchlionnggisnadormrio-w
sepalsandstamensdeciduousorpersistent;leavesandsepalsnot inflorescences of H. galioides, H. nitidum, H. lissophloeus and
articulated, sepals unequal or usually subequal; styles 3(4); their relatives. Acropetal branching is dominant in subsects
placentation incompletely axile to parietal; shrubs or perennial Suturosperma, Brathydium and Ascyrum, where involvement of
herbs. Spp. 16-22. more than three nodes is rare, occurring only in forms of25. H.
4. Subsect. Brathydium (p. 122) - Sepals and petals 5; sepals crux-andreae and 29. H. hypericoides. Pseudo-dichotomous
persistent, stamens deciduous or persistent; leaves articulated branchingisconfinedtosubsect.Ascyrum,whereitoccurswholly
incompletely or not at all, sepals not articulated; sepals very or partly in all species.
utboneepqadriuisaetltiantlog;ussiuhsbrheueqbdusafolrr;ossmutbytlshehesru3pb(rs4e).c;Seppdlpia.ncge2n3ot-na2tei4ob(nyTihnitchseosmuupbnlseeetqceutlaiylonaxacinalnde eFvLoOlWutEiRoSnaAryNDreFdRUuIcTtSi.on Rinefenruemnbceesrhoafveflboeraeln mmaedmebearbsoveintosetchte.
persistent sepals, more numerous stamens and widely branched Myriandra.Thepolyphyleticreductionfrompentamerytotetramery
5. Siunbfsleocrte.sceAnscce,yrsueemk(epy. p1.2943)).- Sepals and petals 4: sepals and atinridtmhieemreporeuorsiuasenxtcgheyipnstoaesicsnioucSmip.apt.eTd2hi-en5,sguwbyshneeocrete.ciAtushmceryerisuamoptpwheieatrrhwiatsoreehdaruvecgetuilobanereltnyo
stamens persistent; leaves articulated or not, sepals not articu- secondaryincreasesto4-5-mery,andoccasionally inthegalioides,
lated; sepals very unequal; styles 2-3(4); placentation parietal; nitidum andfasciculatum groups (Spp. 6-14).
shrubsorwiry shrublets. Spp. 25-29. The sepals areprimitively unequal (e.g. in 1. //.frondosum) and
remainmarkedly so intetramerousformsofthatspecies and inthe
Characters and variation (Fig. 2) directly related subsect.Ascyrum, where the outerpairis largeand
T(Hbc1o.lhna.ethcHryk.sappfcegertlrcioaiionnecndsodsiooi,dsnfeuasstmnehc)dsetu.tbtaoMshnypemd.rirpinpoeaurletnolcedsuitcrupriarmdaotvsgtuatolmrra)yaan.tpfdepArsmaosraametrmnbe-etufnasotplhriowymolainyysneahsgndrdupwarbuibsnyrocyutvipsiehfetaotrocrhbc3emsoy.m(ml2Tpt9ahaaccle-.kl artsaelempslatptylrrolaebfmsoeestrrcehoedeouvmss(eeecncsoptenaircbloiesenasaenslen,tixthnc,(sgeiopn1tt9hst.eshouaHdmtb.eseveimcefntilo.cortrpmBhioesrnsaogetofpthfahy2relu8diru.itmu)H,sm.ap,entscthduiehfeetfsshrieeunptweiaiiqnlctunsoaheslrauiramtpe)ya.uiagsrIlrunmavaodeltusrlh-tyye
nied by trends towards a reduction in number of members ofthe equal. In subsect. Brathydium (Spp. 23, 24), however, both species
floral whorls. have unequal sepals, although the inequality is less in 24. H.
dolabriforme than in 23. H. myrtifolium. The curved-dolabriform
LEAVES. The most closely related species to sect. Myriandra in (hammer-shaped)petalsintheformerarethemostextremeinform
sect. 1. Campylosporus is the north-east African H. synstylum, in the section. Otherwise the petals do not provide specifically
whichhaspinnateleafvenation.Thusthevenationinsect.Myriandra distinctcharacters.The trendfromdeciduoustopersistentstamens
isalsobasicallypinnate.Intheprimitive,broad-leavedspecies(e.g. hasalreadybeen mentionedabove, andthestamensotherwisevary
1.H.frondosum)thetertiaryreticulationisverydenseandclear,but only in numberand length, decreasingfromc. 650ofupto 12 mm
mm
itislessclearorobscure in species with thickerleaves (e.g. 18. //. long(1.//.frondosum)toc.30of2.5-4 (28.H. suffruticosum).
cistifolium). The more advanced species in subsect. Centrosperma The relatively large number of stamens is one of the reasons for
have linear, often needle-like leaves with only a midrib visible associating//,dolabriformewithH.myrtifoliumratherthanwith20.
beneath. H. sphaerocarpum.
Theoccurrenceofagroovewheretheleafjoinsthestem('leaves Theovaryplacentationisnevertrulyaxile,i.e.theplacentaenever
articulated') is a plesiomorphic character in Hypericum in general meet in the middle ofthe ovary. The primitive state, incompletely
andinsect.Myriandrainparticular(Fig.2).Itisconstantinsubsect. axileorpseudo-axile,isfoundinSpp. 1-5ofsubsect.Centrosperma
Centrosperma and present in primitive members of subsects andinsubsect. Pseudobrathydium(Sp. 15)and23. H. myrtifolium.
79
Sect. 20Myriandra Characters
Inflorescencebranchingmainlybasipetal \ Inflorescencebranchingmainlyacropetal Stamensdeciduous
Fig.2 Sect.20.Myriandra.Limitsofcertaincharacters.Notetheisolatedapomorphicoccurrencesof5(6)-styledandpersistentstamensrespectively.
Elsewhere there are parallel developments to truly parietal species of sect. Campylosporus in which (i) the styles are com-
placentation in all subsections. The variation in testapattern ofthe pletelyunitedeveninfruitand(ii)therearetendenciesforthepetals
seedsisnotsogreatasitisinsomeothersections:fromreticulateto to fall tardily (H. quartinianuni) and for the black glands to be
finely scalariform via scalariform-reticulate and linear-foveolate. completelyabsent(H.synstylum).Inthesespecies,too,thedevelop-
ment ofpinnate venation is almost complete, only the lowermost
Cytology andhybrids (Fig. 1) pairoflateralveinsoroneofthemremainingfree.H. quartinianum
occursfromsouth-westernArabia(Yemen)tonorthernMalawiand
Tnh=e9c,h2rnom=o1s8o,meexcneupmtbfeorrainreseccotr.dMoyfri2ann=dr1a6ifsoarl2m2o.stH.coenlsliisptteinctulmy, nisorctohnefrinneMdoztoamtbwioqaudej,acwehnitlsatretahseirneleaatsitveerlynaEptohmioopripahi(cH/a/r.ars)yansntdyolnuem
Ha=.t1ed1ter-na1sp4ilof(ilAdodrrauemmcsof,rrdo1f9mo5rM9)a1..cHDo.ensfprCioot.ne,dtoNhsoisrutmrhe(lpCa.tair9vo6el)uiannniadftoharamptiohtpayudloaf2tnciho=nro2o7mf,o5-n. AinfrTnihocreatrheaenridsnasSoowumitahdl-eieaad.sitsterrinbuUt.iSo.nAa.l,gawph,erteher1e.fHor.ef,robnedtwoeseunm,notrhteh-meoasstt
some number, natural hybrids appear to be very rare except in primitive species in sect. Myriandra, occurs sporadically from
cultivation, which suggeststhatthe speciesare isolatedbyecologi- Kentucky to Georgia and eastern Texas. There is a considerable
cal and/orbiologicalfactorsratherthanby geographical separation morphological gap, too, as H.frondosum has deciduous petals and
alone.Thecultivatedhybrids,whicharosespontaneouslyanddoubt- stamens,thestamenfasciclesarecompletelyunitedwithaconsider-
lesscontinuetoappearwhensuitablespeciesaregrowntogether,all ablyincreasednumberofstamens,andtheovaryis3-merous.Inthe
involve Spp. 1-6only. leaves, the acute to obtuse apex ofthe African plants has become
Distribution andevolution (Fig. 3) apipnincautlea,tew-oibtthusweidtoelryousnpdreeda,dianngd(tnhoetveansacteinodninigs)whloaltelryalcs,lodseendsaenldy
The north-eastAmerican andCaribbean sect. Myriandra is, aswas reticulatetertiary venation and punctate(notelongate) glands.
noted in Part 3 (Robson, 1985: 169), mostclosely related to those FromH.frondosumthreecladesdiverge(i,vii,viii),thesecorre-
80 N.K.B. ROBSON
Sect. 20. Myriandra
Distribution
14 nw Fla
NC-c Fla s Ala II Ga->La
13 se NC-*.Fla Miss
9c |9 s Ga, nw Fla
NC--n Fla- e Tex w Cuba 9b
nw Fla
s SC, Ga,
n Fla, e Ala 21 22
NC -*e La 18 Mass -*-Ga- Minn-Nfld
Tenn, Mo,
WVa, Tenn
111, Ind
9a
NJ-+Ga, Ala-Pa w Cuba, Belize 16 Va, Tenn-nw Fla 20
Ga Fla lowa^Ohio^
La' Ark Miss, [La], e Tex? n A^-a-*ne Tex, e Okla
17
e Tex,
e Okla -( Ga?, SC c Fla
Mass-vSC-y
26 n Tex-*s Ohio
Que, Ont, Wis-*NY 23 sFlGaa,, ws CAulbaa, 29 b
SC?, Ga-Miss
s NC-e La, c Fla
28
c Hisp (Dom R)
29a 29c
se NY-Fla-e Tex,
e Okla Va-*Fla--e Tex,
Okla-Ky; e Mex-rHond;
Gr Ant, Jam; Bah, Berm; [Azores]
Fig.3 Sect.20.Myriandra.Distributionofthe29species,showingmajor(==)andminor( )disjunctionsandtrends(-).Lowercaselettersindicate
compasspoints;squarebracketsindicateextinctions(Sp. 17)orintroduction(Sp.29c);romanfiguresindicatemajorclades(seetext).Geographical
abbreviationsusedinFig.3:Ala-Alabama,Ark-Arkansas,Bah-Bahamas, Berm-Bermuda,DomR-DominicanRepublic,Fla-Florida,Ga-
Georgia,GrAnt-GreaterAntilles,Hond-HondurasRepublic,111-Illinois,Ind-Indiana,Jam-Jamaica,Ky-Kentucky,La-Louisiana,Mass-
Massachusetts,Mex-Mexico,Minn-Minnesota,Miss-Mississippi,Mo-Missouri,NC-NorthCarolina,Nfld-Newfoundland,NJ-NewJersey,
NY-NewYork,Okla-Oklahoma,Ont-Ontario,Pa-Philadelphia,Que-Quebec,SC-SouthCarolina,Tenn-Tennessee,Tex-Texas,Va-Virginia,
Wis-Wisconsin,WVa-WestVirginia.
spendingto(i)H.prolificutnandtherestofsubsect. Centrosperma esis that H. kalmianum had a recent, post-glacial origin (from H.
alongwithsubsectsPseudobrathydiumandSuturospertna,(vii) sub- prolificum).Theothersingle-speciesderivative(15.//. buckleyi)(v)
sect.Brathydiumand(viii)subsect.Ascyrum.Thetransitionfrom 1. hasanareaintheCarolinasandGeorgia(theBlueRidgeMountains)
H.frondosumto2.H.prolificumisgradual,consistingessentiallyof thatiswhollywithinthatof//,prolificum.Thespeciatingfactorsfor
reductionsinsizeofpartsandincreaseofvariation north-westward this dwarf straggling shrub with reductions in size and inflores-
NW
from Georgiatothe uplandsbordering thecentral Mississippi cence-branching would seemtobe altitude andexposure.
basin; but there is a morphological 'gap' between these species, at The remainderofsubsect. Centrosperma (clades iii and iv) show
least in the wild. The wide distributional range of2. H. prolificum several parallelisms, so that extreme members of each (7. H.
includes acomparably wide range ofvariation, so that as many as tenuifoliumand8.H.lloydiiontheonehandand 11.//.brachyphyllum
five clades (ii-vi) appear to have arisen directly from it. 3. H. on the other) have come to resemble one another, with resultant
kalmianum (ii) is anorthern derivative in which reductions in size taxonomicconfusion.Adams(1959, 1962)resolvedthisconfusionas
(overallandofmostparts)andinflorescence-branchingareaccom- regardstheU.S.species,andIhaveattemptedtoincorporatethetaxa
paniedby a(secondary) increaseto5-mery intheovary.TheGreat from Cuba and Belize. Clade (iii) is relatively straight-forward. A
Lakestypeofdistributionmaybeassociatedwiththeglacialnunatak southwardtrendfrom//.prolificumresulted intwotaxa, one north-
in this region, i.e. the species may have reached its present area in eastern (5. H. densiflorum), the other south-western (4. //.
&
pre-glacialtimes. Utech Iltis(1970),however,favourthehypoth- lobocarpum). The reasons for treating these taxa as species rather
STUDIES INHYPER/CUM 81
than subspecies are explained on p. 100. In both species there is a subsect. Centrosperma (iv) forms the H. nitidum-H. fasciculatum
reductioninsizeofflowerandleafandanincreaseinflowernumber. group, which comprises two subgroups: the H.fasciculatum group
In H. lobocarpum, these changes are accompanied by a marked (Spp. 12-14), confined tothe American lowland mainland from N.
tendency towards a 5-merous ovary and lobed fruit, whereas in H. Carolina to Mississippi, and the H. nitidum group (Spp. 9-11),
densiflorumtheyarenot. H. lobocarpumis mainly intheuplandsto having a similardistribution but extending into Louisiana, western
the west ofthe lower Mississippi; H. densiflorum has a two-armed CubaandBelize.Theprimitiveformsof9.H. nitidumwouldappear
distribution:coastalplainfromNewYorktoS.Carolinaandalongthe to be in Cuba and Belize, but those of 13. H.fasciculatum are in
westernsideoftheAppalachianMts.Butan'arm'of//,lobocarpum^ Florida.Theoverlappingareasandincompletemorphologicaldiffer-
areaextendseastward inthe southto south-eastern S.Carolina; and entiation of the taxa in the H. nitidum group suggest that
wherethe southernendoftheH. densiflorum areameetsthis 'arm', land-connectionsbetweenBelizeandFloridaviaCubaexistedfora
incentralAlabama, someintermediates(hybrids?)occur.Anarrow- longtime.
leavedformof//,densiflorumfoundinTennessee(H.interiorSmall) The remaining clade from 2. H.prolificum (Clade vi)comprises
providesamorphologicallinktothenarrower-leaved6.H.galioides, subsect. Suturosperma, of which the lowest branch (Spp. 16, 17)
which has acoastal-plain distribution (N. CarolinatoeasternTexas includes species that are morphologically somewhat intermediate.
excludingpeninsularFlorida).Thisspeciesofrelativelywethabitats H.apocynifoliumandH.nudiflorum,whichhaveinflorescencesthat
isecologicallydistinctfrom its largelyco-extensivereducedderiva- aremoreacropetallybranchedthanthoseof//,prolificumaswellas
tive, 8. H. tenuifolium, a plant ofdry sandy habitats. Between the smallerflowersandbroaderleaves,formanothereast-westpairwith
'arms' of H. densiflorum'^ range there occurs 7. H. lloydii, a low, overlapping distributions: H. apocynifolium from Oklahoma and
spreading, narrow-leavedderivativeofthatspeciesfromtheeastern TexastoLouisianawithoutliersontheFlorida-Georgiaborder, //.
South Appalachian foothills. The remaining derivative clade of nudiflorum from eastern Texas to Virginia excluding Louisiana,
Sects 21. Webbia and 22. Arthrophvllum
Relationships Distribution and Characters
a) b)
nanum var. prostratum vacciniifolium
4b 5 s Turkey
4d
pamphylicura / ?
O nanum var. nanum
rupestre
canariense
pal margin
contiguous \ sprt
ne trop. Africa style bases
revolutum ssp. revolutum
Fig.4 Sects21. Webbiaand22.Arthrophvllum.a)Relationshipsandchromosomenumber(2n).b)Distributionandlimitsofcertaincharacters.Forkeyto
annotationsseeFig. 3(p. 80).
82 N.K.B. ROBSON
Sects 23. Triadenioides, 24. Heterophylla. 25. Adenotrias
Relationships
aegypticum ssp. aegypticum
aciferum IC
aegypticuw
ssp. webbii 1L
aegypticum ssp. maroccanum
20
N
dogonbadanicum
I
ssp. smithii
socotranum
Fig.5 Sects23. Triadenioides,24.Heterophyllaand25.Adenotrias.Relationshipswithinsectionsandwithspeciesofsect. 1 Campylosporus,showing
chromosomenumbers(2n).
where it is apparently extinct. The rest of the clade consists of a easternTexas),butitalsooccursdisjunctlyalongtheEasternCordillera
southern branch (18. H. cistifolium in the Coastal Plain from N. inMexico,Guatemalaandthe HondurasRepublic. Inaddition, itis
Carolina to Louisiana including Florida, 19. H. microsepalum in foundinthemainislandsoftheGreaterAntillesandintheBahamas
Florida)andanorthernone(20.H.sphaerocarpuminthecentraland andBermuda.ArecordfromtheAzoressuggestthatitisarelatively
upper Mississippi valley 'giving rise to' the herbaceous 21. H. recentarrivalthere;butwhetheritcamebynaturalextensionofrange
adpressum (north-eastern) and 22. H. ellipticum (northern). or with human assistance is not clear. Overlapping the northern
To return to the clades directly related to 1. H. frondosum, in marginoftherangeoftheerect29a.subsp.hypericoidesisthatofthe
subsect. Bmthydium 23. H. myrtifolium (Clade vii) has smallerbut morespreading29b.subsp.multicaule(OklahomatoMassachusetts);
broadleavesandamoreacropetallydeveloped,morewidelybranch- andinHispaniola(DominicanRepublic)thereisaprostrate,almost
inginflorescencethanH.frondosum,anditsdistribution(Georgiato herbaceousform(29c. subsp.prostration).
Mississippi) is to the south-east and distinct. The derivative 24. H.
dolabriforme, with narrowerleaves and more unequal sepals, hasa Sects 21. Webbia and 22.Arthrophyllum
smallrelictareatothenorth-westcentredinKentuckyandTennessee.
Foicncaulpliy,esinaCwliaddeevairieia(ssuobustehcwt.a/rUdcyorfMa/nl)itnehefvraormiasboleutHh.-ecarsutxe-rannOdkrleaa-e Characters and variation (Fig. 4a, b)
homatoNewYork(LongIsland).Threeofthederivativespeciesoccur Sects Webbia and Arthrophyllum form a monophyletic group di-
wholly(27.H. edisonianum,28.H.suffruticosum)orlargely(26.H. rectlyrelatedtosect.Campylosporus.Aswillbeexplainedonp.135,
tetrapetalum) within thatarea, H. tetrapetalum being found also in I now regardthenearestrelativeofH. canariense(sect. Webbia)to
westernCuba.Theveryvariable29.H.hypericoides,however,hasa benot//, roeperianum(asinRobson, 1985: 166-168,ff. 1-3)but//.
much wider distribution and is divided into three subspecies. The revolutum subsp. revolutum, more specifically the relatively broad-
subspeciesmorphologicallynearesttoH. crux-andreae,29a. subsp. leaved form of that species that occurs sporadically in Ethiopia.
hypericoides,occupiesalmostthe sameregionintheU.S.A. asthat From it, H. canariense differs inter alia in having '3' stamen
species (Delaware and Maryland west to eastern Oklahoma and fascicles, a3-merous ovary with divergent styles, noblackglands,