The tuberous epiphytes of the Rubiaceae 4: A revision of Squamellaria

9 Pages·1991·2 MB·English

by  Jebb, M H P

BLUMEA 36 (1991) 53-61
Thetuberous epiphytes of the Rubiaceae 4:
A revision of Squamellaria
M.H.P. Jebb
Christensen Research Institute,P.O.Box 305,Madang,PapuaNewGuinea
Summary
SquamellariaBecc.isrevisedtoinclude three species, oneofwhichnew, andoneexisting spe-
cies isreduced. Thegenusis endemictoFiji.
Confinedtotheeastern Fijian Islands,Squamellaria, withjust threespecies, is the
smallestgenusoftheHydnophytinae (Huxley & Jebb, 1991).Beccari (1886)origin-
ally separated thisgenusfromHydnophytum Jack, towhichitis mostclosely related,
on accountofthefourfringed plates (squamellae) inside thecorollatube,thecapitate
stigma, andthecurvedpyrenes withshortembryos andbony endosperm.
Study ofthetuberhasrevealedaremarkably complex cavity structure, whichfur-
therstrengthens thetaxonomic 'moat'between this genusandHydnophytum. The
tuberofallSquamellaria species hasthesamebasic structure:itis cylindrical, with
rings ofregularly spaced, rimmedholes,encirclingthe tuber.Between theseringsof
holesthetuber wall,ofS. thekiiinparticular, swellsoutwards, such thatthetuber
appears crenateinoutline.Amaturetubercontainsseveral, essentially similarcavi-
ties. Eachcavityis produced sequentially atthetuberapex,between thelastformed
cavity andthebaseofthestem.Several distinctchambertypesarerecognised (Jebb,
1985).Eachcavity hasasuperficial planar 'Girdle Chamber'(fig. 1).This chamber
all but encircles the tuber, and gives rise apically toaring ofentrance holes. The
GirdleChambersinterconnecttooldercavitiesalong theirbasaledge, andto younger
cavitiesalong theirapical edge. Ventrally they areblind-endedand densely waited,
whiledorsally andbasally they give rise to numerous'Superficial SmoothWalled
Chambers' whichoverlietheGirdleChamberoftheprevious cavity. Fromitsinner
walltheGirdleChambergivesrise to 'Deep-lying SmoothWalledTunnels'(fig. 1).
Squamellaria alsodiffersfromtherest oftheHydnophytinae in thatthestems do
not ariseonly atthetuberapex.InS.imberbisthestemsarisefromthe apical '/2 to
'/3 ofthe tuber,most stemsbeing clusteredcloseto theapex (fig.2). The stemsare
slenderandbranched.InS.majorthestems aremoreremote fromoneanother, one
stemapparently arising betweeneachring ofentrance holes (fig.3); thuseach stem
appearstobeassociatedwiththeformationofanewcavity. Inthis species the stems
are thickenedandunbranched.
54 BLUMEA VOL.36,No. 1, 1991
Fig. 1.Schematic diagramofasinglecavity withinatuber ofSquamellaria imberbis (A. Gray)
Becc.a.Tuberapex; b.entrance hole;c.entrance hole ofprecedingcavity; d.entrancehole oflater
cavity; e. girdle chamber;f. waited extremities ofgirdlechamber; g. superficial smooth walled
chamber;h.deeplyingsmoothwalled tunnel. Scalebar=10cm. Drawn byRosemaryWise.
The stigma and anthers are exserted. The stigma is capitate andfinely fringed
along theloweredge. Noneofthe species shows heterostyly, andthelarge capitate
stigma, lyingimmediately abovetheanthers, suggests apresentermechanism.The
long,oftencurved corollatubesuggests mothpollination. Noobservations ofnoc-
turnalopening or scentproduction havebeenmade.Itis interestingthat solitaryses-
sileinflorescences andrelatively large (110-163 |im) four-colpatepollen, as found
inSquamellaria, alsooccur intheFijian species ofHydnophytum, (pollen 80-130
|xmacross).
Beccari'soriginaltwo species are herereducedto one.Smith(1967) describeda
new speciesand reported thatall species hada chamberedtuberinhabitedby ants.
Thepresentauthorcollectedall thespecies in 1985and was abletostudy thetuber
and flowerstructure. All material is cited, marked n.v. ifnot seen. The figure in
brackets afterFlowerinthedescriptions is thenumberofflowersdissected.
SQUAMELLARIA
SquamellariaBecc.,Malesia 2(1886)228;K.Schumannin Engler&Prantl,Nat.Pflanzenfam. IV,
4(1891) 123;A.C.Smith,J. Arn. Arbor. 36 (1955) 289;S. Darwin,Allertonia 2(1979)35;
A.C. Smith,Fl.Vit.Nova 4(1988)245.—Typespecies: S. imberbis (A.Gray) Becc.[Myr-
mecodiaimberbis A.Gray, Proc. Am.Acad. Arts&Sci. 4(1858)42],
Epiphytes. Tubercylindrical, ovoid tooblong. Spines simple, slender, mostly
flexible, scattered,sometimesmorenumerousaroundentrance holes.Surfacesmooth,
blackish, occasionally withnumerous whitetuberclesto2mmindiameter.Entrance
holesindiscreteregularringsaroundthetuber,to4mmindiameter,conical, orwith
prominent, grey or white, spine- fringed rims.Pores andridges absent.Stems few
tonumerous, scatteredor arising fromoneor morebasalstock(s); subherbaceousto
woody, branching or not, to 50 cm long, 1.5 cm thick, rounded, smooth, mostly
M.H.P.Jebb: A revision of Squamellaria 55
lackingspines. Leaves clusteredorremote.Lamina3.5x 1.5- 17 x6.5cm,cordate,
rhomboid-lanceolateorobovate, thin to thick, fleshy. Stipules thin,papery, to3.5
mm, splitting opposite the petiole at first, soon tearing between the petioles. In-
florescence solitary, laterallydisplacedin axil, sessile atfirst, becoming pedunculate
with age. Bracts inconspicuous. Flowers homostylous. Calyx 2-6mm, entireor
with 4 triangular lobes. Corollacommonly distorted, curving sharply at base or
towardsmiddle, quadrangular or inflated, whitethroughout, orwith greenor red
markingsonthecorollalobes,pubescent without;4barbateplates (squamules) to-
wardsbase oftube,occluding lumen.Anthers4-8 mm, exserted. Pollen 3-5-col-
pate, 110-163pm indiameter,colpi almostaslong asthegrain,sometimespartially
occludedby pollen wallextensions; walls9-14pm;reticulationopen,coarse, 6-30
pm; vesicles absent. Stigmacapitate, with4± indistinctlobes, depressed atapex,
recurvedand sometimesfringed atmargin. Fruitfleshy or siccate, markedly tetra-
gonalorovoid, orange-red; calyxremainsprominent. Pyrenes 4,moreor less hooked,
sometimeswitharidge ontheabaxial surface.
Ecology - High or lowinhost tree, inopento dense forestfrom200-2000m.
Allspecies are inhabitedbyIridomyrmex ants.
KEY TO THE SPECIES OF SQUAMELLARIA
la. Petiole0.4-3.5 cm, laminalanceolateto rhomboid,thin, with a flat margin.
Stems slender, not thickenedtowardstheirapex 1. S. imberbis
b. Petioleveryshort, to0.5cm,laminaobovateorovate tocordate,thickandfleshy,
margin irregularlyundulate.Stems markedlythickenedtowardstheirapices 2
2a. Tuberapex blunt. Stemsarisingindividually, to 1.5 cm indiameterneartheir
apices. Leaves obovate, theapexroundedandsometimesminutely acuminate.
Corolla lobes parallel-sided in middle, with red and green markings
2.S. major
b. Tuberapextapered. Stemsarising in clusters, to0.8 cm in diameterneartheir
apices. Leaves ovatetocordate, apexacute. Corolla lobesobovate, pale green
3.S. thekii
1. Squamellaria imberbis (A. Gray) Becc. — Fig. 2.
Squamellaria imberbis (A. Gray) Becc., Malesia 2(1886)228, t.46, figs. 1-12;A.C. Smith,J.
Am. Arbor. 36 (1955)289; J.W.Parham, PI.Fiji Isl. (1964)209, ed. 2(1972) 293; A.C.
Smith,Fl.Vit. Nov. 4(1988)247. — Myrmecodia imberbis A.Gray, Proc. Am.Acad. Arts
& Sci. 4(1858)42; B.C. Seemann,Fl. Vit.(1866) 138.— Myrmecodia inermisA. Grayex
Hook. f. in Benth. & Hook, f.,Gen. PI. 2 sphalm.(1873) 132. — Hydnophytum imberbe
Benth. & Hook.f. ex Drake, 111. Fl.Ins. Mar. Pac. (1890) 200. —Type: Fiji, U.S. Expl.
Exped. U.S. 62266 (holotypeUS; isotypeK).
Squamellariawilsonii (Homeex Baker)Becc.,Malesia2(1886)229, t.46,figs. 13-21;A.C.
Smith,J.Am. Arbor. 36 (1955) 289; J.W.Parham,PI.Fiji Isl.(1964)209, ed. 2(1972)293,
sphalm. wilsoni; S. Darwin, Allertonia 2(1979) 35,fig. 3D; A.C. Smith,Fl. Vit. Nov. 4
(1988)247, figs. 9A-D& 13a.— Hydnophytum wilsonii Home,AYear inFiji (1881)263,
nom. nud.; Home exBaker,J.Linn. Soc. Bot. 20 (1883)365; Drake, 111.Fl. Ins. Mar.Pac.
(1890)200.—Type:Fiji,Home 1139(holotypeK).
56 BLUMEA VOL.36,No. 1, 1991
Wise.
Rosemary
by
Drawn
467).
Jebb
(all
pyrene
d.
fruit;
c.
flower,
b.
plant;
Whole
a.
Becc.
Gray)
(A.
imberbis
Squamellaria
2.
Fig.
M.H.P. Jebb: A revision of Squamellaria 57
Tubergrowing horizontally from host,regularly oblongto subovoidnearly hori-
zontalbelow,swollen above,moreor less bluntly hemispherical fromtheside, el-
lipticinlongitudinal section, to30cm long, 18 cm high, and 12cm wide; surface
glossy tomattblack. Spines to2 cmmountedon smallprotrusions. Entranceholes
conical,0.6 cm indiameter,morenumerous onupper surface;rims to 0.4 cm high,
greentogrey. Stemsseveral, branching, to50x0.6cm,pendent toupcurving; most-
ly arisingontheapical partofthetuber,lessremote towardstheapex.Internodesup
to4cmlong when sterile. Spinesonlypresent very closeto tuber,rare elsewhereon
stem.Leaves. Lamina4.5x 1.5- 8 5 x 3.5cm,lanceolatetorhomboid,apexacute,
base tapering topetiole, mid green.Midribprominentbelow,pale greento pinkish;
veins c. 5-7. Petiole0.4 to 3.5 cm, pale greento pink. Stipules to 3.5 mm long,
apiculate,with asmallcentralprocessto0.15cm, caducous.Inflorescence sessile to
pedunculate, to0.6cm long and0.3cmthick.Bractsto0.1 cm.Flowers [11], Calyx
2-3 mm,entireor finely mucronate,pubescent. Corolla white,quadrangular, to 32
mm,pubescent without, especially on corollalobes,bud densely so,rarely glabrous.
Corolla tube moreor lessrecurved atbase,tapering tobase. Lobes triangular,6.5
mmlong, acute,tetragonal inbud. Anthers4-5 mmlong, blue-black; filamentsto
2mmwide.Pollen(3-)4(-5)-colpate, 110-152(134.5) pm indiameter;colpi with
aslightly thickenedborder, about aslong as theheightofthegrain; walls9-10pm
thick, theinnerwall to3pm, theouterlayer regularly reticulate, theselumina6-16
pm across, thefootlayerwithinthe luminawithminuteperforations. Stigma imme-
diatelyaboveanthers, with 4indistinctlobesandafringeofshorthairsbelow.Fruit
turbinate, strongly quadrangular,not fleshy,to7 mmincluding calyx. Pyrenes 5 mm
long,tighdy appressed in fruit,strongly curved.
Ecology - Altitude300-700m.Not solitary, several specimens usuallypresent
ina given tree.
Notes- Theregular, oblong, andslightly compressed tuber, with fine-rimmed
unarmedentrance holesis diagnostic. Thethin,lanceolateleafandflowersalso iso-
latethisspecies fromtheremainderofthe genus.
Squamellaria wilsonii was formerly distinguished by its shorter corolla, lobes
longer relativetothe tube, stamens longer thanfilaments, fruitmore globose, py-
renes less hooked, andleaves more acute and gradually attenuate (Beccari, 1886),
andlonger calyx limb(Smith, 1988).In thelightof furthercollectionsandstudyof
freshmaterial,thesedifferenceshaveproved insignificant, or dueto developmental
stages,or thevagaries ofdrying.
Collections - FIJIISLANDS. Vanua Levu. SE 16°30' 179° 19',Thakaundrove,Yanawai River
region,Mt Kasi, Smith 1787 (BO, GH,K, UC). 18°04 178°25' Korotini Range, nearnew road
from Savusavu toLambasa,Jebb467(BISH,K), 468 (LAE,SUVA),469 (BULOLO,K,SUVA),
470 (A,BRI,CANB,SUVA),471 (BISH,FHO,K,SUVA),472 (SUVA).CrestofKorotini Range,
between Navitho Pass and MtNdelaikoro,Smith 564 (n.v.).—Taveuni. 16°48 179°58 Western
slopes between Somosomo andWairiki, Smith 750(BO, H,UC). AboveQacavuloEstate,A.C.S,
J.W.P,P.B.T.D.K. 16935(BRI).SlopesofMtManuka,eastofWairiki,Smith 8191 (GH,L,UC),
8326 (K,L,UC). 16°50' 180°00',on road to Devoeux Peak,Jebb 479(BISH,K, SUVA),480
(BISH,SUVA),481 (BISH,K,SUVA),482 (LAE,SUVA,UPNG).Above NggathavulaEstate,DA
16935 (n.v.). Nggarawalu,Freehold DA 11901 (n.v.). ForestCreek,Horne 1139 (K)(typeofS.
wilsonii). — Locality uncertain. Seemann s.n. (K, P).Mathuata Prov.,U.S. Expl. Exped. US
62266 (type).
58 BLUMEA VOL. 36,No. 1, 1991
Wise.
Rosemary
by
Drawn
483). Jebb
b—d:
475;
Jebb
(a:
fruit
d.
bud;
c.
flower,
b.
plant;
Whole
a.
Smith,
A.C.
major
Squamellaria
3.
Fig.
M.H.P.Jebb: A revision of Squamellaria 59
2. Squamellaria major A.C. Smith — Fig. 3.
Squamellaria majorA.C.Smith,Cont. U.S.Natl. Herb. 37 (1967)90; J.W.Parham,PI.FijiIsl.
ed. 2(1972)293; A.C. Smith,Fl. Vit.Nov. 4(1988)247. — Type:Fiji, Smith 8323 = US
2191043 (holotypeUS; isotypeBISH,K,L,US).
Tubersubpendent, cylindrical, obovate,apexbluntto 24(-40) x 17cm. Surface
withsmallwhitetubercles,black. Spines stiffto flexible, to 1.5cmlong. Entrance
holes 1 cmin diameterwith a thickened,spine-topped, whiterimto0.3 cm across.
Stems several, apparently arising from immediately withineach ring ofentrance
holes, unbranched, scattered, to 20 x 1.5 cm, fleshy, surface smooth, grey; inter-
nodes 0.5-1.5 cm,shortestandthickest towards apex. Leaves clusteredat apices.
Laminaobovate to broadly oblong-elliptic, 8 x 4.5- 17x6.5cm; apexrounded,
apiculate or not, base abruptly narrowed,blunt or cordate, drying thin, yellowish
greenaboveandbelow. Midribnarrowing abruptly ateach venationbranch,often
bifurcatenearapex. Lateral veinsprominent above andbelow. Margin irregularly
undulate, white.Petiole0.3to0.5 cm.Inflorescence sessile.Flowers [3] to35mm.
Calyx cup-like,narrowedatmargin, with4gentleundulations, to5 mmlong. Corol-
larecurved,white,lobes greenwithapaleredorpink patch atthecentre,to 31 mm
long; lobes to7 mm, pubescent, roundedin bud,sides paralled whenmature. Tube
inflatedtowardsmiddle, to7 mmin diameter, narrowing towards apex, and then
widening slightly atmouth; barbate scales 2mm abovethedisc. Anthers5-6 mm;
filamentsto 2.5 mm. Pollen4-or5-colpate, 125-163(140) pm indiameter; colpi
edges barely thickened, colpi to 14 pm across, about as long as the height of
the grain,the colpi being moreor lessoccludedby anumberoffineoutgrowths of
the pollen grainwall,whicharise fromboth edges ofthecolpus andinterdigitate;
walls to 12 pmthick, the innerwall to6 pm, theouter wall irregularly reticulate,
theselumina9-30pm,thefootlayer within theluminawithnumerous small out-
growths. Stigma squarein sectionwith4mounds, exsertedaboveanthers.Fruitto
1cm,fleshy, quadrangular below,withprominentcalyx to3mm. Pyrenes hooked,
to5.5x 3mm.
Ecology - Growingontrunksorlargelimbsoftreesinclosedforestat300-400m.
Oftensolitary or fewinnumber.
Note- Theleavesofthisspecies always appearchlorotic and diseased.Exami-
nationoffreshtubermaterialrevealsthatthesmallwhitetuberclesthatcover theout-
sideofthetuberhavefungal hyphaeinthem.
Collections - FIJIISLANDS.Taveuni. SE 16°50' 179°59'SlopesofMtManuka,eastofWari-
ki, Smith 8323 (type). 16°50' 180°00',onroadto Devoeux Peak,Jebb 475 (FHO, SUVA), 476
(BISH,SUVA),483(SUVA).
3. Squamellaria thekii Jebb, spec. nov. —Fig. 4.
Tuber fusiforme,tumidum inter annulosforaminum,qua foramina margineincrassato. Caules
paulloincrassati apicemversus, ad 8mm diametro,ramosi,ab tubere unofasciculo vel pluribus
orientes. Folia fasciculata,obovata usque ovata,apice acutousque rotundo,basi obtuso,carnosa,
marginecorrugata.Calyx4-dentatus. Corolla alba,lobi tumidiin alabastro,obovati in maturitate.
Fructusovoideus, calycemanifeste coronatus. —Typus:Fiji,Jebb477 (holotypusSUVA; isotypi
BISH,K;cotypus Jebb478,SUVA).
60 BLUMEA VOL. 36,No. 1, 1991
Wise.
Rosemary
by
Drawn
477).
Jebb
(all
pyrene
f.
apex;
fruit
at
disc
and
calyx
e.
fruit;
d.
bud;
c.
flower;
b.
plant;
Whole
a.
thekiiJebb.
Squamellaria
4.
Fig.
M.H.P.Jebb: A revision ofSquamellaria 61
Tubersubpendent, regular, cylindrical-fusiform, tapering to baseandapex,ab-
ruptly swollen betweentherings ofentrance holes, to27 cm long,9-15cm wide;
surfacerough, with numerous small protuberances, some giving rise to hair-like
spines to 1.5cm long, darkbrown toblack. Entranceholes numerous, in rings 1 to
5 cmapart; prominent, withathickenedrimto0.2cm,the inneredge abrupt, to0.8
cm across. Stemsseveral, arising fromone tofew scatteredclusters, unbranched,
to 36x0.8 cm. Internodes0.3-3 cm.Leaves clusteredatapex. Laminacordate to
ovate rhomboid,apexacute,baseblunttocordate, margin crinkled.Petioleupto0.2
cm. Stipules rounded, to less than 0.1 cm long, caducous. Inflorescence sessile.
Bracts papery,to0.2 cm.Flowers[2] to36mm.Calyx to5 mm, fleshy, quadrangu-
lar, 4-dentate,abruptly flattenedatmargin. Corolla white, minutely pubescent on
lobes, to31mm. Corollatube swelling towardsmiddle,to6mmindiameter,gently
recurved.Lobesobovate, blunt,to 8 mm,with adeep grooveontheoutersurface,
moreor lessorbicularinbud,scales 2mmabovethedisc.Anthersto 3.5mm,fila-
ments to3 mm.Pollen4colpate, 150-163pm;colpi to 19pm across, edges thick-
ened;wallsto 14pm,theinnerwallto 4.5 pm,the outer wall irregularlyreticulate,
theselumina9-22pm,roundthe footlayer withintheluminasmooth. Stigma above
anthers, to2 mmindiameter,rounded,marginreflexedandfimbriate.Fruitto 10mm,
ovoid, fleshy. Pyrenes to 6.5 x 3 mm, slightly recurved, witha prominent abaxial
keel.
Ecology - A low levelepiphyte, growing on trunks oftrees in forest at 300-
400m.
Notes - Alittleknown species, only collectedonce, andapparently not ascom-
monas thetwo species with whichitis sympatric. Its stemandleafcharacters sug-
gestanintermediateposition betweentheotherspecies, butflowercharactersindicate
its specific status. The distributionofstems onthe tuber surfaceis peculiar tothis
species; inS. majorandS.imberbis thestems are scattered,whileherethey arisein
clustersattheapexofthetuberandelsewhere.
ThespecificepithetderivesfromtheFijian name'theketheke nkau'forant-plants,
meaning 'testiclesofthetrees'.
Collections. FIJIISLANDS.Taveuni. SE 16°50' 180°00',Taveuni road toDevoeux Peak,Jebb
477(type),478 (cotype).
ACKNOWLEDGEMENTS
I thankF.White and C.R. Huxley fortheir support, A.C. Smith for nomenclatural clarifica-
tion,andRosemaryWiseforher meticulous drawings.
REFERENCES
BECCARI,O. 1886.Piante Ospitatrici. Malesia 2 : 228-230.
HUXLEY,C.R.,&M.H.P.JEBB.1991.Thetuberous epiphytesoftheRubiaceae 1:Anewsubtribe-
the Hydnophytinae.Blumea 36: 1-20 (thisissue).
JEBB,M.H.P. 1985. Taxonomy and tuber morphology of the rubiaceous ant-plants. D.Phil.
Thesis,Oxford University.
SMITH,A.C. 1967. Studies ofPacific Islandplants XVIII.New andnoteworthyfloweringplants
fromFiji. Contr. U.S. Natl. Herb. 37: 69-106.
SMITH,A.C. 1988.Flora VitiensisNova4.PacificTropicalBotanic Garden,Hawaii.