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The Terminology of Leaf Architecture

R. Melville

Taxon, Vol. 25, No. 5/6. (Nov., 1976), pp. 549-561.

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T A X O N ~ ~ ( 5 1 6 )549-561. NOVEMBER 1976

TH E TERMINOLOGY OF LEAF ARCHITECTURE

SummaryA comparative study of leaf architecture throughout the Angiosperms has been madeand six classes of venation patterns are recognised. The terms employed are defined andarranged in a systematic order fo r convenience of reference . Some new term s have beenintroduced where greater precision was needed and for little known venation patterns.

IntroductionIn the ear ly s ix t ies the Systemat ics Associat ion set up a commit tee for de-scr ip t ive terminology, the objectives of whic h were to consider the m orphologicalt e rms in use in descr ip t ive p lan t t axonomy and to make recommendat ions fo rthei r s tandardisat ion. A s tar t was made wi th the s imple p lane shapes of leavesfo r wh i ch W . B. Turr i l l had a l ready d rawn up a scheme. Th i s was modi f i eds l ight ly and submit ted to botanis ts in many countr ies for cr i t ic ism. An agreedl is t of terms was then dr aw n u p w i th i l lust rat ions an d published in Tax on in1962. I t had been the in tent ion of the comm it tee to pass o n to a considerat ion ofthe terminology of m ore complex shapes an d to characters of leaf m argins,

indumentum, g lands and o ther fea tu res . Unfor tuna te ly they were unab le to f indvolunteers able to devote the t ime necessary to survey the l i terature and produceprel imina ry proposals fo r o the r character systems. The need to review andstandardise botanical terminology has s ince remained a n outs tandin g problem.Recent ly L. J. H i c k e y (1973, 1974) has made a valuable contr ibut ion in th isfield in a paper on the architecture of dicotyledonous leaves. In this he considersthe shapes of leaf bases an d apices, the ma rgina l teeth an d the terminolog y ofthe venat ion pat terns of leaves . Mouton (1970) covered much the same f ield ,g iving terms in French only an d mingl ing marg inal characters w i th purely venat ioncharacters in h is terminology in a manner which is apt to be confus ing. Nei thert reatment i s exhaust ive as Hickey deals only wi th Dicotyledons and Moutonincompletely wi th the whole of the Angiosperms. Both authors approached thesubject f rom the point of v iew of palaeobotany, but go back in the foss i l recordonly to the Cretaceous . Both , a lso , have taken up the terminology of vonEttingshausen (1861) , another palaeobotanis t . Von Et t ingshausen appears to haveset out to devise a new ser ies of terms wi thout g iving ful l considerat ion to termsalready in use. Unfortunately he based his terms on Greek roots which resul tsin an ungainly ser ies of polysyl lables which do not harmonise wi th the Lat interminology used in taxonomic descriptions.Th e purpose of th is paper is to at tem pt a sys temat isat ion of th e terminology ofleaf architecture, introducing a few addit ional terms, where necessary, based onLatin roots. The majority of terms used in the description of leaves have beendef ined and many i l lus t ra ted by S tearn (1966) and i t is not necessary to repeathere those appertaining to leaf shapes, margins, apices and bases or indumentum.With one except ion, a t tent ion wi l l be res t r ic ted to leaf venat ion pat terns , a f ie ldwhich has been much neglected in the past . It is necessary, however, to considerthe evolution of megaphyllous leaves from the t ime of the first invasion of the

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Tab . I . I, Arbuscular fastigiate leaf - Stirlingia tenuifolia. 2, Simple flabellate - Cir-caeaster agrestis. 3, Pedati-flabellate - Leucadendron argenteum. 4 , Pedati-flabellate -Petal of Ploiarium al terni fol ium. 5-7, Rectipalmate leaves of Acer: 5, A . mons pe s su l anum;6, A. campestre; 7, A. palmaturn. 8, Pedate - Platanus occidentalis. 9-12,Convergate(Curvipalmate) leaves of Dioscorea: 9-10,D. spicata; 11, D. a la ta; 12,D. bulbi fera. 13,Palmati-pinnate - Thespesia populnea.of modern Angiosperms is to be attained. The studies on which these proposalsare made have led me to examine cursorily all Angiosperm families and anumber of genera in some detail as well as to scan the fossil record, especiallythat of the Glossopteridae, which play a key role in Angiosperm evolution.Considerable simplification of our terminology can be attained if we payattention to the simple fact that veins may be straight or curved. Then it isnecessary to recognise six primary systems of venation patterns of which pal-mate and pinnate are the most familiar. To this must be added some consider-ation of evolutionary processes and the ontogeny and physiology of developmentof leaves, but the latter aspects will be treated in another paper.Primavy systems of venation patterns

The nomenclature of the primary systems takes into account the order in whichveins are formed du ring leaf developm ent and to some exten t the ma nner in whichthey are formed. Thus, in a pinnate leaf the midrib is the only primary veinand the lateral pinnately arranged costae are secondaries. The intercostal areasare normally divided up by a ternary series of veins and the areolae so formedmay be further divided by a quaternary series and further by a quinary series.

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In palmate leaves the number of primary veins varies from 3-y-7-9-11. .Probably these primaries are always init iated in r a p ~ d uccession, but any attemptto discriminate between them on this account would lead to confusion. Betweenthese primaries the intercostal areas may be divided up successively by secondaryand higher orders of veins in much the same manner as for the intercostal areasbetween the secondaries of pinnate leaves. Somewhat different considerationsarise in connection with the remaining primary venation systems and these arediscussed separately. They are taken in the following order:I Arbuscular (arbuscularis) 4 Pinn ate (pinnatus)2 Flabellate (flabellatus) 5 Collimate (collimatus)3 Palmate (palmatus) 6 Conglutinate (conglutinatus)I Arbusctllav (Arbuscularis)

This term is proposed for leaves that branch repeatedly by regular dichotomyto give rise to a three dimensional bush-like structure consisting of linearsegments. Two classes can be recognised:1.1 Arbuscular simple: Segments containing a single vascular strand. Found in Rhyniaspp., Actinoxylon banksii Matton and common in the Psilophytes. Not found inAngiosperms.These structures are strictlv branch svstems which functioned as leaves. Thev arethe proto-phyllomes from which megaphyllous leaves evolved.1.2 Arbuscular, fastigiate. Segments containing a fascicle of d ichotom ous vascularstrands; e.g. Stirlingia tenuijolia (R. Br.) Endl. (Fig. I), Isopogon villosus Meissn.(Proteaceae)z Flabellate (Flabellatus)

Primary veins straight or only slightly curved, idverging frrom the base in afan-like manner.2.1 Simple jlabellate: Vein anastomoses absent or rare. e.g. Ginkgo biloba L., Adiantumcapillus-veneris L. (leaflets), Circaeaster agrestis Maxim. (Fig. 2), Kingdonia uni-flora Balf. f. & W. W. Sm.2.2 Reticuli-jlabellate: Vein anastomoses frequent, usually forming a dichotomo-reticulate mesh.2.21 Cuneati-flabellate: Primary veins diverging from I to 3 veins at the base. e.g.Leucadendron platyspermum R.Br., Myrothamnus jlabellijolius (Sond.) Welw.,Euryops latijolius B. Nord., Stylidium striatum Lindl.2.22 Pedati-jlabellate: Primary veins forming a broad band at the base, often unitinginto pedate basal branches attached to a single trace at a unilacunar node, as inAeonium. e.g. Aeonium arboreum Webb & Berth., Gangamopteris spp., Leucaden-dron argenteum (L.) R.Br. (Fig. 3). Also in petals, e.g. Ploiariurn alternijolium(Vah l) Melchior (Fig. 4), Calophyl lum inophyl lum L.The exact mode of attachment in Gangamopteris is not known, but it is possiblethat some species had pedate bases uniting into a single trace as in Aeonium.3 Palmate (Palmatus)

There is no sharp break between flabellate and palmate venation systems andcomparative studies indicate that palmate leaves have evolved from flabellateancestors. When the primary veins are straight and z 0 veins are absent thesep ara tion is sim le, bu t if z0 veins are present the dichotomo-reticulate venationis the distinguisting character of the flabellate system. Leaves with curvedprimary veins that might justifiably be called curvi-flabellate, are not readilydistinguishable by means of superficial characters if the venation pattern is

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T a b . 2 . 14, Rectipinnate - Carpinus betulus. ~ j ,Compound rectipinnate - Corylusavellana. 1 6 , Curvipinnate - Cornus sanguinea. 17, Co-arcuate - Prunus svium. I 8,Paxil la te - Calophyl lum inophyl lum. 19, Curvi-paxil la te - Calathea zebrina. z o , Lirate -Adenanthe bicarpellata Z I , Collimate - Hordeum vulgare. 22, Sub-collimate - Olyralatifolia.nised. In the rectilinear series the I ' veins are s t ra ight or nearly so and theyradiate from a node which may be basal or supra-basal . The I ' veins of thecurvilinear series diverge from a basal node and arch towards a second nodea t the leaf ap ex. In either series, startin g wit h three I " veins additional veins canbe added a nd the leaf expan ded la teral ly, the base passing f rom acute to t runcateto co rdate and finishing with overlapping basal lobes or by becoming pei ta te . Theshapes resulting from this process form natural intergrading series, which canreadi ly be reduced to a mathematical formula (D'Arcy Thompson 1942) . T h esl ight changes in growth rhythm underlying the process are often expressed indifferent species of a genus and are illustrated here by a rectilinear series inA c e v (Figs. 7 , 6 , 7) and a curvilinear series in Dioscovea (Figs. 9-12) .3.1 Rectipalmate (Recti-palmatus).e.g. Acer monspessularium L. (Fig. I) , A campestre L. (Fig. 6 ) , A paimatumThunb. (Fig. 7 ) .Synonym : Actinodromous.3.2. Pedate (Pedatus)Leaf shape palmatifid or palmatisect, with the upper lobes supplied by I " veinsbut lower lobes on either side supplied not by I " veins, but by 2 " recti-pinnatelaterals of the lower primaries. e.g. Platanus occidentalis L. (Fig. S ) , Cucurbitapep0 L. Synonyms: Palmactinodromous (Von Ettingshausen), pedalCe (Mouton).3.3 Convergate (Convergatus) or Curvi-palmate (Curvi-palmatus).Although the curvilinear primaries of this series can be correctly described ascurvipalmate, it is convenient to have a simple alternative and Convergate, meaning"bowed together", which implies both the cur vature of the veins and th e presence

of basal and apical nodes is here proposed. e.g. the series in Dioscorea (Figs. 9-11).D. spicata Roth with elliptic-acute convergate leaves with 3 or 5 I " veins.D. alata L. with ovate truncate convergate leaves with 7 I " veins.D . bulbijera L. with cordate convergate leaves with 9 I " veins.

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4 Pinnate (pinnatus)With a single primary vein, the midrib, along which straight or arching 2'veins are arranged at f egular intervals.

4.1Rectipinnate 4.4 Lirate4 .2 Curvipinnate 4 . s Palmati-pinnate4.3 Paxillate 4.6 Meta-pinnate4.1 Rect ipinnate (rectipinnatus)Secondary veins straight or nearly so.4." Simple rect ipinnate - z o veins terminating a t m arginal teeth.e.g. Ulmus glabra Huds., Alnus glutinosa (L.) Gaertn., Carpinus betulus L. (Fig.14), Quercus castaneifolia C. A. Mey. Synonyms: Craspedodromous Craspedo-drome aristCe. (Mouton).4.12 Compound rect ipinnate - 2" veins branching near the margin to supply severalteeth. e.g. Corylus avel lana L. (Fig. IS), V iburnum lan tana L. Synonym: Cras-pedodrome composCe (Mouton).4.2 Curvipinnate (curvipinnatus)Secondary veins curving gradually towards the margin and not supplying amarginal tooth directly.4.21 Simple curvipinnate - z o veins curving grad ually towards the margin a nd oftenforming marginal or submarginal veins (see below). e.g. Cornus sanguinea L.(Fig. 16), Bridelia ferruginea Benth. (Fig. 37). Synonym: Camptodromous.4.22 Co-arcuate (co-arcuatus). - 2' veins connected by arching loops some distancefrom the margin forming a strong infra-marginal vein; e.g. Prunus avium L.(Fig. 17), Ficus populifolius Vahl, Ligustrum ovalzfolium Hassk., Aucuba japonlcaThunb. Synonym: Brochidodromous.4.23 Multi-arcuate (multi-arcuatus) - z o veins forming a coarcuate infra-marginal veinand breaking up into a series of small arching loops forming a zone between the

infra-marginal vein and the margin. e.g. Napoleonea leonensis Hutch . & Dalz.Synonym : Brochidodrome arch (Mouton ).4.3 Paxillate (paxillatus)Secondary veins numerous, closely ~ a r a l l e l o one an other, generally making anglesof 60-90 degrees to the mid rib. Deriv ed f rom pax illus, "a little stake or pale",hence paxillate, made of little stakes or pales and forming a small fence or palings.4.31 Recti-paxillate - 2" veins unbranched or with a few basal dichotomies, withfree ends at the margin or looped together at the m argin to f orm a simple marginalvein. N o specialised areolae along the midrib.4.311 Vein endings free e.g. Taeniopteris spp., Glossopteris clarkei Feistm.4.312 V eins te rm ina ting in a ma rgin al vein, e.g. Oleandridium brackebuschianum Kur tz

(Kurtz 1921) , Calophyllurn inophyllum L. (Fig. 1 8). These constitute thetaeniopteroid leaves of earlier papers (Melville 1969, 1971).Synonym : Parallelodrome transverse (Mou ton).4.32 Dichotomo-paxi l la te - 2" veins dichotomous and anastornosing to form a simplereticulum (dichotomo-reticulate see below) and with specialised types of areolaeassociated with the midrib. (Fig. 76-83) e.g. Glossopteris communis Feistm.(Fig. 23), Gyr inops wal la Gaertn. , Roucheria calophyllum Planch. (Fig. 24).Angiosperm leaves of this class have hitherto been called glossopteroid in earlierpapers (Melville 1969, 1971).4.33 Sub-paxillate - Derivatives from simple paxillate types, lacking specialised areolaealong the midrib, but with some 2" veins stronger than others and the intercostalareas dichotomo-reticulate or occupied by pendent or dendroid 3" veins. Inter-

mediate between simple paxillate and more advanced reticulate venation. e.g.Tyleria tremulea Mag. & Wurd., Schuurmansiella angustijolia (Hook . f . )Hallier f. , Qualea gestasiana St. Hil ., Lorostemon bombycif lorus Ducke .4.34 Reticuli-paxillate - Covers stages in the conversion of a simple paxillate venation

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known from Rubiaceae. e.g. Timonius avenis Val., T . a f f in i s A. G ra y (Fig. 29). Curvi-paxi l late - W ith numerous closely parallel 2" veins, arching t o ne arly straight, except near the m argin where they curve m ore or less ab rup tly into a marginal vein. e.g. Strelitzia reginae Banks, Musa spp., Heliconia spp., Calathea zebrina Lindl. (Figs. 19, 36). Syno nym : Parallelodrome transverse. Lirate (liratus) W ith nume rous parallel for w ard ly directed (oblique) 2" veins making angles of 10-30" with the midrib. Derived from lira, a r idge between tw o furrows, as on a ploug hed field. Palaeo-lirate wi th the mi drib consisting of a single stra nd as in some fossils. e.g.

. Ilirate (or neo-lirate) with the midrib consisting of a few to many closely aggre-gated strands, e.g. Hanguana malayana (Jack) Merrill, Dracaena spp., Cor dy l i nespp., In Adenanthe bicarpel lata Maguire & Wurdack (Fig. 20) the veinsoccasionally dichotomise.Palmati -pinnate.Intermediate between palmate an d pinnat e, with the distal part of the leaf pinna te and a basal or suprabasal pair of pinn ated major veins extending for ' I3- ' 1 3 of the length of the lamina. e.g. Corchorus olitorius L., Tilia cordata Mill., Apeiba t ibourbou Aubl., Gr e wi a spp., Thespesia populnea (L.) Soland. (Fig. 13) . Syn onym : Actinodrom e composCe (Mouton, in par t). Meta-pinnate (meta-pinnatus) Com posite veins formed by the app roxim ate alignment of cross connections between the longitu dinally paralle l veins of collim ate or lira te leaves giving rise to regular, i rregular o r broken veins arranged transversely t o the p rincipal vein system in a p inna te m anner. Normal meta-p innate , when they may be ascending in the upper pa rt of the leaf, spreading in the middle and declining in the basal part. e.g. Hanguana malayana (Jack) Merr. (Figs. 43,44,45). Broken meta-pinnate (fracti-meta-pinnatus). With the veins interrupted and f irregular e.g. Helmhol tz ia acori fol ia F. Muell. (Fig. 42). Gradate (gra datus ). Broken meta-pinnate veins in w hich the cross veins are separated and arranged like the steps of a stairway e.g. Pandanus adinobotrys Merr. & Perry (Figs. 40, 41).

5 Collimate ( C o l l i m a t u s )L e a v e s w i t h n u m e r o u s l o n g i t u d i n a l l y p a r a ll e l p r i m a r y v e i n s a ri s i ng f r o m at r a n s v e r s e m e r i s te m .

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T a b . 4. 28, Irregular polygonal ret iculum - Roupala montana. 29, Reticuli-paxillatevenat ion - Timonius affinis. 30, Sinuous dichotomo-reticulate - Senecio scorzoneroides.The term is der ived from coll imatus, directed straight forward. Compare theparallel usage in physics for collimator, an instrument for collecting light andprojecting it as a parallel beam. Synonyms: parallelodromous, paralleledromelongitudinale (Mouton) .

f . 1 Transverse meristem at the base of the lamina. e.g. Endymion, Haemanthus .5.2 Transverse meristems at the bases of the lamina and of the leaf sheath. e.g.Gramineae, Horde um vulgare L. (Fig. 21).f . 3 Transverse meristem at the base of the lamina, where the longitudinal veinsare at tach ed t o pedate t ransverse basal veins in the adul t leaf . e .g. Richea spp.5.4 Transverse meristem at the leaf apex, growth cont inuing unt i l arrested by drought .Found in a few Proteaceae e.g. Hakea multilineata Meissn.1.5 Sub-collimate may be appl ied to leaves in which the longi tudinal veins becomebowed by different ial growth and the leaf shape changed to lanceolate or el l ipt ic .Then dist inguished from convergate by the larger number of longi tudinal veins andthe presence of a secondary series of longitudinal parallel veins between the pairsof the primary series. e.g. Olyra lat i fo l ia L. (Fig. 22), Zeugites mexicana Trin .6 Conglut inate (Conglutinatus)

Simple leaves or leaflets evolved by the coalescence of leaflets of compoundpinnate, bipinnate or tripinnate leaves with fusion of the formerly separatevenation systems producing zones of interaction along the lines of the originalleaflet margins.All stages in the condensation of a complex frond into a simple leaf occurredin Gigantopteridaceae (See Asam a, I 9 5 9) .6 . 1 Simple conglutinate. One stage of fusion between leaflets.a. leaf lets: e.g. Gigantonoclea lagrelii (Hal le) Koidzumi , Thelypteris megaphylla (Mett . ) Iwatsuki (Fig. 35) and other Thelypteroid ferns, Tou roulia guianensis Aubl. This is the un icoheren t leaf segment stage of Asam a. 6.2 Bi-conglutinate. T w o stages of fusion, simple conglutinate leaflets fused to fo rma complex leaf or leaflet. e.g. Bicoemplecopteris hallei Asama. Quiina guianensisAubl. Sy no nym : Bicoherent leaf segment stage of As ama. Plumose-reticulate ofFoster. (Foster 1950).

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T a b . j. 31 , Dendroid veins - Lorostemon bombyci f lorus. 3 2 , Incomplete dichotomo-reticulate - Heliophila linearis. 33, Pinnati-ret iculate - Trochocarpa laurina. 34, Corrivateveins - Astroloma tectum. 3 5 , Compound corr iva te - Thelypteris megaphyl la.7 Th e Ternary and higher order reticulum

The finer reticulum of Angiosperm leaves can be analysed into three classes.The first of these is a direct descendant of the dichotomous branch systems ofearly land plants which by planat ion and webbing gave r ise to the f lat mega-phyllous leaf with flabellate venation (Fig. 2 ) . The next s tep was the developmentof anastomoses between the dichotomous veins which gave rise to a simplereticulum, here called dichotomo-reticulate. The other two classes are the productof diffusion reactions which ta ke place ear ly in the ontogeny of the leaf (M el-vil le 1971). These diffusion reactions are responsible for the spatial distributionof the morphogens which determine the posi tions of pro cam bial s t rands a ndsubsequently of the vascular t issue of the veins. With a uniform distribution ofmorphogens over the meristematic t issue of the developing leaf a hexagonalpat tern is produced. In the cl imax condi t ion of th is system a pat tern of regularhexagons should be produced, but in terfer ing factors rarely al low the cl imaxto be achieved and the common result is a system of polygons in which pentagonsand hexagons predominate. For this reason, the second class is here calledpolygonal. When the diffusion reaction is constrained between previously formedveins , as for example between the approximately paral lel secondary veins of apinn ate leaf , a s ine-wave-like dis t r ibut ion of morphogens m ay be producedwhich gives rise to regu larly spaced transverse veins between th e secondaries.The arrangement of veins is l ike the rungs of a ladder and hence this class iscalled scalariform. Interfer ing factors of ten cause i rregular i t ies in the pat ternand the con t inuat ion o f mer i s temat ic ac t iv i ty may separa te the p rocambia ls t rands to the point where an addi t ional vein may be intercalated into the system,as in the example of Hosta ventricosa (Salisb.) Stearn ( H . coerulea auct.), studiedb v P r a v I ~ s q t i ., \ ,,,,Transit ions between the three principal classes of reticulum are frequent.Th er e is a tendency for the dichotomo-ret iculate system to break d ow n par t ial lyand become incomplete before one of the other systems takes over in an evolution-ar y sequence. The areolae m ay be invade d by free s imple or dendro id veins beforea l ink up to f orm a closed reticulum is achieved. Scalar i form 3' veins may bearching or i r regular in t ransi t ions between scalar i form and polygonal systems orthere may be a gradual change from scalar i form 3' veins to polygonal j0 veinsin one leaf .7.1 Dichotomo-reticulate (Dichotomo-re t icu la tus ) . Reticulum formed by vein dicho-tomy and anastomosis usually giving rise to elongated areolae in which the veinjunctions are similar to those of Glossopteridae. See vein junctions of the glos-

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cheria calophyl lum Planch. (Fig. 24), Lil ium martagon L. (Fig. r ~ ) , yr inops wal laGaer tn .Incomplete dichotomo-reticulate. Some of the areolae incomplete with some veinends free and failing to link up with neighbouring veins. This occurs frequentlyin the transit ional evolutionary stages between glossopteroid venation patternsand more advanced Angiosperm types. It often occurs in petals as a result ofreduction in size and complexity. e.g. Leaves: Heliophila l inearis DC. (Fig. 32),Mairea coriacea Bolus, Lepidium draba L. Petals: Ranunculus spp., Roucheriacalophyl lum Planch.Sinuous dichotomo-ret iculate . Veins of the areolae sinuous. e.g. In leaf tip ofSenecio scorzoneroides Hook. f. (Fig. 30).Polygonal (Polygono-reticulatus). Areolae formed by 3" or higher order veinsangular, commonly with 5-6 sides, but varying from 3-7.Regular. Areolae of k uniform size and shape tending towards regular hexagons(climax condition), but commonly pentagonal or hexagonal. e.g. Dryandra n iveaR.Br. (Fig. j8), Laurus nobilis L., Cinnarnonum zey lanicum Bl., Glossopterisret i fera Feistm.. Hemioni t is ari fol ia (Burm.) Moore.\Irregular. Sides of the areolae of unequal length and areolae of unequal size.Very common in many families. e.g. Roupala montana Aubl. (Fig. 28).Polygono-scalariform. Intermediate between polygonal and scalariform types ofreticulum with polygonal passing into irregular scalariform often within a singleintercostal area. Frequent in many families. e.g. Eriob otrya japonica (Thunb.) Lindl.Scalari form (Scalari formis) . Intercostal areas bridged at regular intervals bytransverse veins either at right angles or with a regular orientation and havingthe appearance of rungs on a ladder. Common in many families. The processrepeated into 4" and j o order veins produces a fine meshed rectangular orquadrangular reticulum e.g. Apeiba t ibourbou Aubl. (Fig. 39).Regular scalariform. Bridging veins straight or nearly so and regularly spaced. e.g.m any Melastomaceae, in curvipinnate leaves of Bridelia ferruginea Benth. (Fig. 38),in curvipaxillate leaves of Calathea zebrina Lindl., in Marantaceae a nd Musaceaeand in collimate leaves of Gramineae.Irregular scalari form. Bridging veins arched, sinuous or angled passing intopolygono-scalariform (7.23), e.g. Hevea brasiliensis Muell. Arg., Corylus avel lanaL. (Fig. 11).Tesselate (tesselatus) Bridging veins in collimate leaves well spaced producingbrick-shaped areoleae, those between adjace nt pairs of longitud inal veins alternatin gand giving the appearance of brick wall or tesselate pavement, e.g. Zeugitesmexicana Trin. (Fig. 46), Arundinaria fastuosa (Mitf . ) Makino.

T a b . 6. 36, Curvi-paxillate veins - Calathea zebrina. 37, Dendroid veins - As ar umcanadense. 38, Regular scalariform veins - Bridelia ferruginea. 39, Scalariform veins, 3 ,4 ' & 5. - Apeiba t ibourbou. 40-41, Gradate veins - Pandanus adinobotrys . 42, Broken

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Gradate Bridging veins between adjacent pairs of longitudinal veins arrangedlike the steps in a stairway. (see 4.63).Accessory t ypes o j minor venat ion . A variety of accessory types of vein archi-tecture occur in the intercostal areas of leaves in intermediate stages of evolution.Some of the more frequent and significant types are enumerated here.Dendroid (Dendroideus). Regularly or irregularly dichotomous veins occupyingan areolus and at tached to the areolar veins at one point . e.g . Asarum canadenseL. (Fig. 37), Lorostemon bombyci j lorus Ducke (Fig. 31), Melaleuca globijera R.Br.Dendro-reticulate (Dendro-reticulatus). Dendroid intra-areolar veins in whichadditional branches unite with the areolar veins or with one another. A stagein the evolution of a polygonal reticulum in some families. e.g. Mareya spicataBaill.Free pinnate (Libero-pinnatus). Pinnately branched veins standing free in anintercostal area and connected to the costae only at their base, occur in Proteaceae( leaves and bracts) and in Epacridaceae. e.g. Petrophtle carduacea Meissn. (Fig. 59).Pinnati-reticulate (Pinnati-reticulatus). Pinnatelv branched veins some of thelateral branchlets of which anastomose with adjacent veins to produce an incom-plete and irregular reticulum. e.g. Trochocarpa laurina R.Br. (Fig. 33).Corrivate (Co rriva tus). Veins fro m opposite sides of an intercostal a rea which runtogether and anastomose to form a gamma-shaped vein. Derived from corrivo -"runnin g togeth er like tw o streams of a river". e.g. Astvo loma tec tum R.Br.(Fig. 34).Compound corr iva te . A series of corrivate veins united by their apices. InThelypteroid ferns compound corrivate veins mark the line of union of adjacentleaflets in con glutina te leaf segments (6.1). e.g. Thelypteris megaphyl la (Mett.)Iwatsuki (Fig. 35).Zig-zag (Fractiflexus). Medianly placed intercostal veins running approximatelyparallel with the costae are frequent in pinnate leaves. They commonly take azig-zag course and may be formed by the approximate alignment of certainveins in a polygonal reticulum or in intergrades between polygonal and scalariformpatterns. e.g. Degeneria vitiensis Bailey & Smith. (Fig. 27). Synonym: compositeintersecondary (Hickey).Pendulous. Branching veins lying free in an intercostal area or an areolus, attachedat their distal ends and appearing to be pendulous from a submarginal vein orcostal vein. e.g. Qualea gestasiana St. Hil. (Fig. 26).Digammoid (Digammoideus). When a sinus extends into a dichotomous vein systemit is held up at a dichotomy, which is commonly attached by a short vein to asecond dichotomy. This combination has the appearance of two Y's (or gammas)one inside the other. It is a feature of the initial disruption of an entire margin incertain primitive leaf types. e.g. Petrophile carduacea Meissn. (Fig. fg), Sty l id iumbarleei F. Muell., Isopogon villosus Meissn.Flabellate leaj apex. In some species of Glossopteris transitional between Ganga-mopteris and Glossopteris the midrib of the dichotomo-paxillate leaf breaks up atthe apex and spreads out into a f labellate pattern l ike that of Gangamopteris . Asimilar phenomenon occurs in some relatively primitive paxillate angiosperm leaves.e.g. Glossopteris antarctica Plumstead, Lepinia solomonensis Hemsl. (Fig. 60).

8 Marginal Ve insVeins associated wit h the leaf edge prod uce a n um ber of characteristic patterns .In pr imit ive leaves the excurrent veins remain simple and straight and run u pdirectly to the leaf edge. With the diversification of the leaf reticulum, veinsparallel with the leaf edge have developed at different levels so that marginal,sub-marginal and infra-marginal types can be distinguished.Recently Hic ke y (1973) has proposed th e use of the term "fimbriate" forsimple linear marginal veins, but this conflicts with its normal usage in botanical

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t r a n s l a t e d f imbr ia tu s a s " f ri n g e d o r ja gg ed ". I t i s i n t h e l a t t e r s e n se t h a t t h e t e r mh a s a l w a y s b e en u s e d i n B o t a n y , a s i n D i a n t h u s f i m b r i a t u s Lam. , C a r e x f i m b r i a t aS c h k u h z , G a i l l a r d i a f i m b r i a t a M i c h x , C y p e r u s f i m b r i a t u s N e e s a n d H a b e n a r i af imbr ia ta R . B r. T o a l t e r t h e w e l l es ta bl is he d a p p l i ca t i o n n o w c o u l d o n l y l e a dt o c o n fu s io n .Marginal vein absent.Excurrent veins simple, running direct to the leaf edge and remaining free fromone another. e.g. Glossopteris spp. (Fig. 47), Gangamopteris spp., sepal of Tyleriafloribunda Gleason (Fig. 48).Excurrent veins branched or dendroid at the leaf edge. e.g. Beauprea spathulifoliaBrongn. & Gris (Fig. 49).Marginal vein simple, si tuated close to the leaf edge and without any other veinsextending beyond i t .Linear: wi th a single con tinuo us vein "linking" the ends of all of the excurren tveins at the margin. e.g. Calophy l lum inophy l lum L. (Fig. IS), Enkleia siamensis(Ku rz) Nevling (Fig. 54), Qualea gestasiana St. Hil. , Asarum canadense L. (Fig. 57).Incomple te : marginal vein broken, linking some of the excurrent veins but leavingothers free. e.g. Glossopteris angustifolia (Fig. ~ o ) ,Stylidium striatum Lindl..(Fig. 51).Arcuate: marginal vein formed of arching veins linking the ends of the excurrentveins. e.g. Ranunculus parnassiifolius L. (Fig. yz), Qualea mult i f lora Mart. (Fig. 56).Irregular: marginal vein irregular, formed by the random union of veins adjacentto the leaf edge. e.g. Grindelia buphthalmoides DC. (Fig. 53).Submarginal veins. Any vein running parallel with the leaf edge, but separatedfrom it by other veins must be classified as a submarginal vein. One, two oroccasionally more submarginal veins may exist together in a leaf. The submarginalzone between two adjacent submarginal veins may have distinctive features.Fimbriate submarginal. Submarginal vein simple, linear, with a fringe of simple

Tab. 7 . 47-48, Simple excurrent veins: 47 - Glossopteris damudica Feistm.; 48 - sepal ofTyleria floribunda. 49, Branched excurrent veins - Beauprea spathulifolia. 50-51,Incomplete marginal veins: 50 - Glossopteris angustifolia; 5 1 - Stylidium striatum. $ 2 ,Arcuate marginal vein - Ranunculus parnassiifolius. 5 3 , Irregular marginal vein -Grindelia buphtalmoides. 54, Linear marginal vein - Enkleia siamensis. $5, Fimbriatesubmarginal vein - Tyleria floribunda. 56, Paxillate submarginal zone - Qualea mul-

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Tab. 8. 61-6 9, Vein junction types: 61 - gamma, 62 - lambda, 63 - eta, 64 - kappa,65 - Psi, 66 - Psi-lambda, 67 - chi, 68 - Zeta, 69 - zeta series. 70-75, Free vein islands(areolae): 70 - biconvex lenticular; 71 - planoconvex lenticular; 72-73 - hexagonal;74-75 - hydroid. 76-83, Attached vein islands: 76 - deltoid; 77 - arching; 78 - angled ;79 - t r iangular; 80 - t runcate tr iangular; 81-82 - curvi-tr iangular; 83 - prismatic.veins projecting towards the margin. This occurs in some paxillate leaves. e.g.Tyleria floribunda Gleason (Fig. 55).

8.4 Subm arginal zone. A submarginal zone may be formed between a margina l and asubmarginal vein, or between adjacent submarginal veins. The following conditionshave been noted.8.41 Marginal and submarginal veins simple, linear, intervenal zone irregularly reti-culate. e.g. Jacquinia pungen s A. Gra y. Fig. 57).8.42 Marginal veins arcuate, submarginal vein linear, intervenal zone paxillate. e.g.Qualea mult if lora Mart . (Fig. 56).8.5 Inf ra ma rgi na l veins. Arching veins connecting the 2" veins at some distance fromthe mar gin (10-zoolo of the leaf w idt h) are common in curvipinnate leavesproducing the coarcuate condition (4.22). The infra-marginal vein so formed may

be regular or irregular.8.51 Regular. Loops of the infra-marginal vein uniformly arching. e.g. Prunus aviumL. (Fig. 17).8.12 Irregular. Infra-marginal vein angled or irregular. e.g. Persoonia elliptica R.Br.9 V ei n junctions and v ein islands

For mechanical reasons only a limited number of different types of veinjunction is possible in a dichotomo-reticulate system of venation. In the absenceof a midrib the number of vein island types (areolae) was also limited, but withthe development of a midrib a new diversification was possible and led to anumber of new types in the Glossopteridae and primitive Angiosperms. Someof these are shared with other groups, such as the ferns, which also produce typesof vein island not observed in Angiosperms and not discussed here.Vein junctions. I n the dichotom o-reticu late system, vein junctions resemble ce rtain letters of the G reek a lpha bet which can conve niently be used to describe them. Gamma junction. The result of a simple dichotomy of a vein. y (Fig. 61). Lam bda junction. Th e result of the simple anastomosis of t w o appr oxim ately paralle l veins. (Fig. 62). Et a junction. Formed by a transverse vein between tw o appro xim ately parallel veins. H (Fig. 63). K ap pa junction. The result of a dichotomy an d a n anastomosis resembling K or its (Fig. 64) mirror image. Psi junction. Formed by 3 veins diverging from one point. Y (Fig. 65). Psi-lam bda junction A psi-junction combined w ith an an astomosis. (Fig. 66) or its mir ror image. Chi junction. Formed by the union of veins at an oblique crossing X (Fig. 67). Zeta junction. Formed by a n oblique transverse vein between tw o a pproxima tely

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Free vein islands (A reolae). The following types of vein islands occur free in the reticulum, i.e. not associated with a midrib or major vein, in leaves of Glossop-teridae and in primitive Angiosperm leaves with dichotomo-reticulate venation. Lenticular - shap ed like the cross-section of a lens, either bico nvex or p lan o convex. (Figs. 70, 71). He xago nal. Either regular h exagonal or elonga te hexagonal. (Figs. 72, 73). Hy droid . Vein islands tapering to the proximal end and enlarged towards the distal end to which 4-7 other veins are attache d giving a H ydra -like appearance . e.g. in Gangam opteris a nd Glossopteris leaves; leaves of Laccopetalum giganteum (Wedd.) Ulbrich, Pringlea antiscorbutica R.Br. (Figs. 74, 75). Petals of Rosa spp., Geranium spp. Atta che d vein islands. Vein islands attach ed to the m idrib or to a major vein. e.g. Glossopteris spp. Gyrinops walla Gaertn., Roucheria calophyllum Planch., Timonius affin is A. Gra y, Lepinia solomonensis Hem sl. Deltoid. E rect , or sl ightly oblique, tr iangular areolae at tached to a major vein by a smaller side (Fig. 76). Arching. E longate cu rvi-tria ngula r areolae (Fig. 77). Angled. O bliqu e triangul ar areolae w ith a vein inserted along one side which is ang led . (Fig. 7.8). T r i angu la r . T r~ angu la rareolae a ttach ed by a broa d base. (Fig. 79). Truncate tr iangular. Triangular areolae with the apex truncated. (Fig. 80). Cur vi-trian gular . Triang ular areolae with the free sides arched (Figs. 81, 82). Prismatic. Usually o blique areolae with parallel sides capped by a lam bda junction. (Fig. 83).

AcknowledgmentsThis paper has been read by senior members of the staff of the Royal Botanic Gardens,Kew, and by Dr . N . K. B. Robson of the British Museum (Natural History), to all ofwhom I am indebted for constructive suggestions. I am especially grateful to Mr.H . K. A. Sha w for discussing the correct lat in form of the new terms.

ReferencesA S A M A ,K. 1959 - Systematic study of so-called Gigantopteris. Sci. Rep. Tohoko Univ.,Ser. 2 (Geol.) 31: 1-72.CANDOLLE, . P . DE, & S P R E N G E L ,. 1821 - Elements of the philosophy of plants.Edinburgh.ETTINGSHAUSEN,. VON 1861 - Die Blattskelete der Dikotyledonen. Vienna.FOSTER,A. S. 1950 - Morphology and venation of the leaf in Quiina acutangula Ducke.

Amer . J. Bot. 37: 159-171.H I C K E Y ,L. J. 1973 - Classification of the architecture of Dicotyledonous leaves. Amer.J. Bot. 60: 17-33.H I C K E Y ,L. J. 1974 - Clasificacion de la arquitectura de 10s hojas de Dicotyledoneas.Bol. Soc. Argent. Bot. 16: 1-76.K U R T Z ,F. 1921 - Atlas de plantas fosiles de la Republica Argentina. Act. Acad. Nac.Cienc. Cordo ba 7 : 129-153, pl. 1-27.LINDLEY,. 1832 - An introduction to botany. London.MELVILLE,. 1969 - Leaf venation patterns and the origin of the Angiosperms. Nature224: 121-125.MELVILLE,. 1971 - Some general principles of leaf evolution. S. Afr. J. Sci. 67: 310-316.M O U T O N ,J. A. 1970 - Architecture de la nervation foliaire. Compt. Rend. 92 Congr.Nat. Sci. Sav., Strasbourg & Colmar 3: 165-176.P R A Y ,T. R. 1955 - Foliar venation of Angiosperms and histogenesis of the venationof Hosta. Amer. J. Bot. 42: 698-706.S T E A R N ,W. T. 1966 - Botanical Latin. London.

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You have printed the following article:

The Terminology of Leaf Architecture

R. Melville

Taxon, Vol. 25, No. 5/6. (Nov., 1976), pp. 549-561.

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Morphology and Venation of the Leaf in Quiina acutangula Ducke

Adriance S. Foster

American Journal of Botany, Vol. 37, No. 2. (Feb., 1950), pp. 159-171.

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Classification of the Architecture of Dicotyledonous Leaves

Leo J. Hickey

American Journal of Botany, Vol. 60, No. 1. (Jan., 1973), pp. 17-33.

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Foliar Venation of Angiosperms. IV. Histogenesis of the Venation of Hosta

Thomas R. Pray

American Journal of Botany, Vol. 42, No. 8. (Oct., 1955), pp. 698-706.

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Systematics Association Committee for Descriptive Biological Terminology. II. Terminology ofSimple Symmetrical Plane Shapes (Chart 1)

Taxon, Vol. 11, No. 5. (Jun., 1962), pp. 145-156.

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