From an examination of anatomical characters it appears that the genus Scyphostegia is not related to Monimiaceae and Moraceae but represents a separate family related to Flacourtiaceae

METCALFE, C. R.

REINWARDTIA

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From an examination of anatomical characters it appears that thegenus Scyphostegia is not related to Monimiaceae and Moraceae but represents a separate family related to Flacourtiaceae

C. R. METCALFE

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SCYPHOSTEGIA BORNEENSIS STAPF*Anatomy of Stem and Leaf in Relation to its Taxonomic Position

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VOLUME 4 DECEMBER 1956 PART iREINWARDTIABEING A CONTINUATION OF THEBULLETIN DU JARDIN BOTANIQUE DE BUITENZORG(BULLETIN OF THE BOTANIC GARDENS, BUITENZORG)EDITORSANWARI DILMY(Herbarium Bogoriense)ANDC. G. G. J. VAN STEENIS(Flora Malesiana)Published byHERBARIUM BOGORIENSEKEBUN RAYA INDONESIAReinwardtia Vol.4, Part 1, pp. 1-118, BOGOR, December 1956REINWARDT.IAPublished by Herbarium Bogoriense, Kebun Raya IndonesiaVolume 4, Part 1, pp. 99-104 (1956)SCYPHOSTEGIA BORNEENSIS STAPFAnatomy of Stem and Leaf in Relation to its Taxonomic PositionC. R. METCALFE *. S U M M A R YFrom an examination of anatomical characters it appears that thegenus Scyp'hostegia is not related to Monimiaceae and Moraceae but re-presents a separate family related to Flacourtiaceae.INTRODUCTIONAs the taxonomic position of Scyphostegia has been disputed, an ana-tomical examination of the stem and leaf was undertaken at the suggestionof Dr Van Steenis in the hope that the microscopical structure of theseorgans would afford evidence concerning the affinities of the genus. Aswas only to be expected with a, genus that exhibits so many charactersin the morphology of the inflorescence and flower that are both distinctivein themselves and which cannot readily be matched, in any of the wellestablished families of Dicotyledons, anatomical evidence likewise pointsto the somewhat isolated position of the genus. It is thus reasonable tofollow Hutchinson (2) in recognising that the genus merits the statusof a distinct family. As is shown below,' however, there is little anatomicalevidence to suggest that Scyphostegia is related either to the Monimiaceaeor Moraceae. The facts indicate rather that its nearest existing relationsare to be found amongst the Flacourtiaceae, although there is no parti-cular genus in this family, amongst those of which the anatomy has beeninvestigated, that appears to have a specially close relationship. Thepossibility of a taxonomic relationship of Scyphostegia to the Flacourtia-ceae rests rather on the fact that Scyphostegia exhibits a combination ofcharacters that are also to be found in a number of genera and speciesthat are well established as members of the Flacourtiaceae. In this articlethe anatomy of the leaf and stem of Scyphostegia is described, and theevidence that suggests that the genus has affinities with the Flacourtia-ceae, rather than with the Monimiaceae or Moraceae,. is discussed.LEAF. Hairs; none seen. Adaxial epidermis, in surface view, con-sisting of variously shaped cells with thin, curved/but not sinuous walls.* Jodrell Laboratory, Royal Botanic Gardens, Kew. .— 99 —100 R E I N W A R D T I A [VOL.Abaxial surface also composed of variously shaped cells, with thin wallsbut these are slightly sinuous. Stomata confined to the abaxial surface;abundant; paracytic (rubiaceous), each stoma accompanied on either sideby a subsidiary cell parallel to the pore. Mesophyll dorsiventral, with2—3 rows of short to tall palisade cells, and a broader zone of slightlyspongy parenchyma. In some leaves, e.g. in a leaf from the specimencollected by J. and M. S. Clemens 26062, the layer of cells immediatelybelow the adaxial epidermis is differentiated as a distinct hypodermis,but this hypodermal layer was less clearly apparent in material fromthe Penang Botanic Garden. The height of the palisade cells also variesin different leaves. Some of the mesophyll cells, especially those towardsthe adaxial surface, are filled with amorphous, probably tanniniferous,contents that stain readily with haematoxylin. Structure of the largelateral veins obscure in transverse sections of the leaf because of theiroblique course in relation to the long axis of the leaf, but each vascularstand is encircled by a fibrous sheath. Smallest vascular bundles deeplyembedded in the mesophyll, and often accompanied by only a few fibres,mostly on the abaxial side, each small bundle being surrounded by arather irregular sheath of thin-walled cells. Large, solitary, clusteredcrystals occur sporadically throughout the mesophyll tissue.Midrib with a longitudinal ridge that projects prominently from theabaxial, and another that projects slightly from the adaxial surface, theridges consisting mostly of slightly collenchymatous tissue. Vascular sys-tem of the midrib surrounded by a narrow, circular, but abaxially flatte-ned cylinder of fibrous cells with wide lumina, and only moderatelythickened walls. Vascular tissue consisting essentially of adaxial andabaxial parts. The abaxial part appears either as a cylinder of xylemthat is somewhat concave on its adaxial side, or as an arc that is not quiteclosed adaxially. The cylinder or arc of xylem surrounds a central, pith-like tissue, and is itself surrounded externally by thin-walled phloem. Theadaxial part of the vascular tissue consists of a collateral strand of xylemand phloem that lies on the adaxial side of the cylinder or arc that hasjust been described, the phloem of the collateral strand being almost con-tinuous with the phloem on the adaxial side of the abaxial cylinder. Thexylem of the adaxial strand abuts directly, or almost directly, on to thefibrous cylinder by which the whole vascular system is surrounded. Bran-ches from the adaxial strand pass out into the mesophyll at intervals.The vessels, wherever they occur in the xylem, are mostly in radial multi-ples.PETIOLE, in transverse sections immediately at the base of the lamina,exhibiting a vascular structure not unlike that of the midrib, but thereis no fibrous cylinder surrounding the vascular system. The abaxial vas-cular cylinder, or almost completely closed arc, that occurs in the midrib,has the form of a deeply U-shaped strand in the distal part of the petiole.Situated between the arms of the U there is an adaxially flattened cylin-der of xylem and phloem, formed by the amalgamation of the adaxialvascular arc of the midrib with the adaxial part of the abaxial cylinder.1956] C. R. METCALFE: Seyphostegia Borneensis Stapf 101The vascular cylinder between the arms of the U consists externally ofxylem that surrounds the phloem which has the form of a number ofclosely placed strands, the somewhat triangular ground tissue surroundedby the phloem consisting of parenchyma. At a lower level in the petiole,the vascular system has the form of an abaxial cylinder of xylem andphloem, accompanied adaxially by an irregularly shaped and complexmass of xylem and phloem. Towards the base of the petiole the adaxialmass of xylem and phloem has the form of a rather irregular arc whichis, at this level, continuous with the main abaxial vascular strand, sothat the whole vascular system appears in transverse section as a some-what uneven cylinder. Towards the base of the petiole the whole vascularsystem is surrounded by a narrow cylinder of fibrous cells with fairlythick walls and wide lumina, the fibrous ring being similar to that whichsurrounds the vascular system in the midrib. Cluster crystals are abun-dant in the ground tissue, especially at the centre of the petiole, andsmaller, but similar crystals in the phloem. The exact appearance of thevascular system in the petiole, and to some extent in the midrib, variesfrom section to section, and there also appear to be minor variations fromleaf to leaf.STEM, (a) Stem 2 mm in diameter.Stem more or less rectangular in transverse section. Hairs; noneseen. Phloem and xylem in the form of cylinders of about equal width.Large cluster crystals occur in the cortex and near the phloem fibres,and smaller but similar cluster crystals in the phloem. Other particularsas in (b) below.(b) Stem 3 mm in diameter.Cork originating in the epidermis; consisting of thin-walled markedlyrectangular cells. Amorphous, (tanniniferous?) deposits present in someof the cork cells. Primary cortex about 7 cells wide, consisting mostlyof thin-walled parenehymatous cells, but outer cells locally smaller thanthose elsewhere, and somewhat collenchymatous. Outer boundary of thephloem marked by a continuous sclerenchymatous ring, consisting of thick-walled fibres with narrow lumina and irregularly shaped sclereids withwider lumina. Phloem and xylem in the form of closed cylinders traversedby narrow rays. Phloem devoid of sclerenchyma apart from the ring atthe outer periphery. Vessels solitary and in short radial multiples of2—4 or occasionally more; even those vessels that are solitary are locatedon definite radii from the stem centre. Individual vessels 31—58µ. ininternal radial diameter. Inner part of the primary xylem consisting ofspecially small elements that are stained more readily by haematoxylinthan by safranin, and are therefore apparently less lignified than thoseof the rest of the xylem. The occurrence of these unlignified portions ofxylem abutting on the pith suggests that there is considerable centrifugaldevelopment of xylem before the primary xylem is wholly lignified, andthere may be some centripetal lignification of the xylem. Pith somewhatstellate in outline, with 4 arms; parenehymatous; thick-walled and ligni-fied at the periphery, and thin-walled and less lignified at the centre. The102 R E I N W A R D T I A [VOL. 4thickening and lignification of the cells continue centripetally as thestem grows older, and the pith ultimately becomes homogeneous in ap-pearance. Crystals similar to those described under (a) above, but lessnumerous.(c) Secondary xylem, 1 cm in diameter.Vessels sometimes solitary, but mostly in radial multiples of 2—4,or occasionally more; a few irregular multiples also present. Individualvessels in each multiple flattened where in contact with one another;those not pressing against one another are circular or oval in outline.Vessels 40—100 JA in internal radial diameter. Vessel members with simple,but very oblique, perforations; lateral pitting alternate, pits crowded torather sparse, mostly rounded in outline and with circular to horizontallyoval apertures. Fibres constituting practically the whole of the groundtissue of the wood; with fairly thick walls and oval to circular lumina;with numerous, fine, transverse septa, and rather large bordered pitswith slit- shaped apertures in the radial, but not in the tangential walls.Parenchyma absent, apart from occasional paratracheal cells. Rays verydensely crowded, not conspicuous in transverse sections; mostly uniseriate,but a few partly bi- or triseriate; uniseriate rays composed mostly of tall,narrow cells, but some rays, especially those that are more than uniseriate,are markedly heterogeneous; at least 9—28 cells high, and sometimesappearing higher owing to fusions between rays.TAXONOMIC AFFINITIESIt seems, from the anatomical evidence, that Scyphostegia has novery close affinities with well established families. This is also empha-sized by the distinstive morphology of the inflorescence and flower. Hith-erto the most commonly expressed opinion has been that the genus hasaffinities with the Monimiaceae, although it has always been felt thatthe affinities cannot be very close. Hutchinson (2), on the other hand,has taken the view that the genus should be in a distinct family relatedto the Moraceae. This discrepancy of view largely depends on varyinginterpretations of the morphology of the flowers and inflorescence, which,in turn have been partly due to lack of adequate material. Hutchinson, nowthat more material has been at his disposal, has changed his views aboutthe relationship of Scyphostegia to the Moraceae. The varying interpreta-tions of the morphology of the flower and inflorescence have been summa-rized by Swamy (6), who, however, does not make any constructive sug-gestions concerning the affinities of the genus. A study of the anatomyof the stem and leaf fails to provide any convincing evidence that thegenus has any close affinities with either the Moraceae or Monimiaceaee.On the contrary the anatomical evidence suggests rather remote affinitieswith the Flacourtiaceae or with the Euphorbiaceae. The suggestion ofa relationship with the Euphorbiaceae is, however, of doubtful signifi-1956] C. R. METCALFE: Scyphostegia Borneensis Stapf 103cance, as the Euphorbiaceae themselves constitute a large heterogeneousgroup, in which the range of anatomical structure is correspondinglygreat. Furthermore some genera of Euphorbiaceae are themselves notunlike some of the Flacourtiaceae, at least so far as their wood structureis concerned.It must be emphasized that there is no particular genus in the Fla-courtiaceae to which Scyphostegia is especially similar. The point is ratherthat Scyphostegia exhibits a number of characters that occur in certaingenera of Flacourtiaceae, and this combination of characters suggeststhat Scyphostegia may have affinities, although these may be somewhatremote, with the Flacourtiaceae. The characters that suggest this relation-ship include the following: — In the leaf, the paracytic (rubiaceous)stomata and the occurrence of adaxial hypoderm. The midrib structureof Scyphostegia. is not unlike that of certain Flacourtiaceae such asDipentodon. On the other hand, petiolar vascular structure of the type thatoccurs in Scyphostegia, has not yet been recorded in the Flacourtiaceae. Thesuperficial origin of the cork in the stem of Scyphostegia, and the thin-walled cells of which it is composed, have their counterparts in the Fla-courtiaceae. This applies also to the radial multiples of small vessels in thewood; the sparse wood parenchyma; the uniseriate rays composed of hign,upright cells; the ociurrence of vestically fused rays the septate woodare common to both Scyphostegia and the Flacourtiaceae.fibses, with pits limited to the radial walls. Specially large cluster crystalsThe first anatomical objection to the inclusion of Scyphostegia in theMonimiaceae came from Perkins and Gilg (5) who pointed out that theleaves of Scyphostegia, unlike those of the Monimiaceae, do not containsecretory cells. Baehni (1), and, more recently, Money, Bailey and Swamy(4) and Swamy (6) have reminded us of this fact. In addition, the last3 authors have pointed out that Scyphostegia differs from the Monimia-ceae in having trilacunar nodes, and tricolpate pollen grains. A perusalof Metcalfe and Chalk's "Anatomy of the Dicotyledons" (3) reveals furtheranatomical reasons for believing that there are no close affinities betweenScyphostegia and the Monimiaceae. For example the stomata in Monimia-ceae are usually anomocytic (ranunculaceous) in contradistinction to theparacytic rubiaceous) stomata of Scyphostegia. The Monimiaceae alsodiffer from Scyphostegia in having crystals that are usually needle-shaped; vessels that are seldom in radial multiples; a less complex vas-cular structure in the petiole. The rays in the wood of the Monimiaceaeare variable in form, but uniseriates of the type that occur in Scyphostegiaare unknown.104 R E I N W A R D T I A [VOL. 4Turning now to the Moraceae it may be noted that the family as awhole generally differs from Scyphostegia in not usually having paracytic(rubiaceous) stomata, whilst laticiferous canals, unknown in Scyphostegia,are characteristic of many members of the Moraceae. The wood of theMoraceae differs from that of Scyphostegia in having vessels that aremostly solitary; parenchyma that is typically paratracheal, and usuallyaliform or confluent. Uniseriate rays are uncommon in the family, and,where they do occur, they are not of the same type as those in Scypho-stegia. On the other hand the wood of Scyphostegia resembles that ofboth the Moraceae and Monimiaceae in having septate fibres, but thischaracter, although of diagnostic value because of its restricted occur-rence, is to be found sporadically throughout the Dicotyledons, and itoccurs in families between which there are no close affinities.Taking all of these facts into consideration, the anatomical evidenceseems to suggest that Scyphostegia can best be treated as a distinct familythe Scyphostagiaceae, having some taxonomic affinities with the Flacour-tiaceae.REFERENCES(1) BAEHNI, C. (1938): in Ber. schweiz. bot. Ges. 48: 22—28.(2) HUTCHINSON, J. (1926): Families of Flowering Plants 1: Dicotyledons, London.(3) METCALFE, C. R. & CHALK, L. (1950) : Anatomy of the Dicotyledons, 2 vols. Oxford.(4) MONEY, L. L., BAILEY, I. W. & SWAMY, B. G. L. (1950); in Journ. Arnold Arbor.31: 372—404.(5) PERKINS, I. & GILG, E. (1901) ; in Engler, Pflanzenreich Heft 4 (Monim.) : 117.(6) SWAMY, B. G. L. (1953) : in Proc. Nat. Instit. Sci. India 19: 127—142.MATERIAL EXAMINEDSample 927 from the Botanic Gardens, Penang.Herbarium specimens collected by J. and M. S. Clemens, referenceno. 26062.ACKNOWLEDGEMENTSThe author is indebted to Mr J. W. Purseglove, Director of the BotanicGarden at Singapore, and to Mr H. Ritchings, Horticultural Officer atthe Botanic Gardens at Penang, through whose courtesy it was possibleto obtain material of Scyphostegia preserved in formalin acetic alcohol.Thanks are also due to Dr J. Hutchinson for his kindly interest and advice.The microscope slides examined during the investigation were preparedat the Jodrell Laboratory by Mr F. Richardson.REINWARDTIAPublished by Herbarium Bogoriense, Kebun Raya IndonesiaVolume 4, Part 1, pp. 105-112 (1956)NOTES ON INDONESIAN FRESHWATER ALGAE II.Ichthyodontum, a new desmid genus from Sumatra.ARTHUR M. SCOTT * and GERALD W. PRESCOTT **SUMMARYDescribed and figured are Ichthyodontum, a new genus belongingto the desmidiaceous algae, with /. sachlanii, a new species with its newvariety parorthium, showing a peculiar bipolarity. From southern Sumatra.I c h t h y o d o n t u m Scott & Prescott, gen. nov.Cells elongate-cylindric and rectangular in front view, the polestruncate and bearing at each angle a blunt spine or tooth which maybe either vertically or laterally directed, the apical margin with a shallowmedian notch or depression; semicells slightly swollen at the base, witha circumferential supraisthmian row of blunt teeth, the two series ofteeth intermeshing and completely enclosing the shallow median incision;side view of cell elongate subfusiform; basal view broadly elliptic.Cellulae a fronte visae elongato-cylindricae reetangularesque, polistruncatis et in utroque angulo spinam obtusam vel dentem verticaliterlateraliterve directum ferentibus, margine apicali incisuram mediam nonprofundam vel depressionem praebente; semicellulae ad basim subinflataedentibus obtusis in ordine circumferentiali supraisthmiali praeditae, den-tibus amborum ordinum implexis et incisionem median non profundamomnino includentibus; cellula a latere visa elongato-subfusiformis; a basivisa late elliptica.Ichthyodontum sachlanii Scott & Prescott, spec. nov.—Fig. 1Cells of medium size, length 6 to 7 times the width, in front viewelongate-cylindric and decidedly curved, apices truncate with a shallowmedian subcircular notch with a prominent tubercle at each side on themargin, each apical angle bearing a stout upwardly directed tooth that isprolonged into a sharp fine spine; semicells slightly swollen at the basewith one lateral margin more inflated than the other, and bearing asupraisthmian row of 10 longitudinal folds (5 showing) which bear eacha prominent basally directed tooth, the teeth of one semicell intermeshing(not interlocking) with those of the other, thus completely enclosing theshallow median incision of the cell; cell wall sparsely punctate and having*2824 Dante St., New Orleans 18, La., U.S.A.** Dept. of Botany, Michigan State University, East Lansing-, Mich., U.S.A.— 105-

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SCYPHOSTEGIA BORNEENSIS STAPF*Anatomy of Stem and Leaf in Relation to its Taxonomic Position

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