Bodgan,A. V.

Biodiversity Heritage Library OAI Repository

DECEMBER 1952. BOGDAN, StolonifeTousGrassesin Kenya. 71
Underside creamy-white;costaof forewing irregularly strigulated
with fuscousbrown. Large subcircularreniformsin all wings. A
brownmaculabelowapexsurroundsa smallareaof groundcolour.
Postmedialindicatedby dark spotson veins. Terminal line very
distinct.
-+- Similar,but greyer;markinglessdistinct.
Genitalia of 10 .Similarin generalbuildto sabinei,Prout;butdiffer-\)
ing in thefollowingpoints:-
Gnathosof evenwidth,not broadenedtowardstheend.Costa
of valvewith onlyonepatchof spines,andthatat themiddle.
Anteriorendof costalmarginproducedto a roundedlobe,not
to a narrow point. The two cornuti are madeup of spine-
clusters,as in sabinei,but of only half their length. The loose
dorsalbeltof spines,connectingthecornutiin sabinei,is absent
in hyrax.
Lengthof forewing,baseto apex: o~ 21 mm.;+- 23mm.
Holotype071 andallotype -+ in my collection:paratype olf in
the British Museum.
Locality: Nakuru,Kenya.Larva on Schinus molle.
I wish to acknowledgegratefullythehelpthat I havereceived
with regardto thesespeciesfrom Mr. D. S. Fletcher,of the British
Museum.The noteson genitaliaaretakenentirelyfrom information
suppliedby him.
Paracotishyrax. Natural size.
Eupitheciapsiadiata.Slightlyenlarged.
OBSERVATIONS ON STOLONIFEROUS GRASSES IN KENYA.
By A. V. Bogdan,F.L·S.
Departmentof Agriculture,Kenya Colony.
In Europeand probablyalso in other temperateregions,stoloni-
ferousgrasses,i.e. grasseswhich produceabove-groundcreepingstems,
rootingfrom nodes,are rare. In TropicalMrica the stoloniferoustype
of grassis, however,fairly common.In Kenya,out of approximatetotal
of 430speciesof grasses,no less than25of themproducestolons. The
stolonsof differentspeciesvary considerC;1blyin structure,shapeand
length,rateof growthetc.,andit is mainlythestructure,i.e.the distri-
butionof leaveson the axis of stolonsand phenomenaconnectedwith
this feature,Whicharedealtwith in thepresentpaper.
The stolonsof all local stoloniferousgrassescan be classifiedinto
two well-definedtypes,examplesof whicharethoseof (a) Digitaria aff.
D.milanjuna Stapf (Bogdan3003)and (b) Cynodon plectostachy,umPilger.
The stolonsof the Digitaria havea structuretypicalof a normalgrass
stem: the nodesare moreor less evenlydistributedon the stem,each
bearinga singleleaf. The leaf bases,or, to be moreexact,thebasesof
the leaf sheaths,ariseat somedistanceonefrom anotherandhavewell
72 BOGDAN, StoloniferousGrassesin Kenya. VOL. XX
detlnedinternodesbetweenthem. The structure of the stolons of
Cynodon is different.The leavesare in groupsof 2 to 6 (butusually4)
andtheleafbasesof eachgroupappearto!arisefroma singlenode.These
nodescanberegarded,however,ascompoundnodesor asgroupsof nodes
with very short, undevelopedinternodesbetweenthem.This supports
the view held by A. Volkart and O. Kirchner in "Lebensgeschichteder
Bliltenpflanzen Mitteleuropas, Gramineae,1,2,p.35(1908-1912)who state:
"bei einigenGrasern(Cynodon, Aeluropus) wechselnan denoberirdis-
chenAuslaufernregelmassiglein gestrecktesInternodiummit 2-4verkiirt-
zenab,sodassdieBlatterstellenweisegebiischelterscheinen".The writer
is unawareof any further referencein the literatureto detailsof the
structureof grassstolons.
The structureof the two typesof stolonsconsideredhere,which
will bereferredto in futureas" A" (Digitaria) typeand" B" (Cynodon~
type,is showndiagrammaticallyin Figs.1 and2.
The differencein distributionof leaveson the two typesof stolons
is closelyconnectedwith characterof the branching.Beforebranching
startsthe axillary budswhich produceside branchesare hiddenunder
the basalpartsof the leaf sheaths. As soonas a youngbranchstarts
growingfrom thebud it usuallydepressestheleaf sheathfrom thestem.
In the" A" typeof stolons(Dfgitaria), with only oneleaf per isolated
node,the depressionof the leaf sheathleavesthe correspondinginter-
node unprotected,the basal part of the internodebecomeshard and
ceasesto grow. Towardsthe apexof a stolonthereare alwaysseveral
internodesgrowingsimultaneously;the branching,therefore,beginsat
somedistance- which may at timesbe considerable- from the apex
of the stolonwherethe appropriateinternodeshaveceasedto grow.It
alsonaturallyfollows that, sinceonly one leaf arisesfrom an isolated
node,this typeof stolonproducesonly onebranch(or noneat all)' from
a node,exceptat an advancedstageof branchingwhen a sidebranch
mayproducebranchesin its turn.
On the whole the characteristicfeaturesof the "A" (Digitaria)
typestolonscanbe summarisedas follows:-
a) The stolonshavestructuretypicalof a normalgrassstem,with
isolatedsinglenodeseachproducingoneleaf.
b) The stolonsproduceonly onebranchpernode(or noneat all).
c) An internodeceasesto grow as soonas the branchingfrom the
correspondingnodebegins.
d) The branchingbeginsat somedistancefromtheapexof a stolon.
A differentprocessof branchinghas beenobservedin the "B"
( Cynodon)' type of stolons. It has already been mentionedthat
the stolons of this type have compoundnodes each bearing 2-6
leaves. The branching begins from the axil of the "lowest leaf.
The young'branchdepressestheleaf sheathfrom thestem,butthelatter
is still protectedby thesheathsof theupperl~avesof thesamecompoun~
node. The secondbranchstartsfrom the aXIl of the nextleaf,etc.untIl
onlytwo ( or sometimesone)uppersheathsremainadpressedto thestem.
If, for example,four leavesarisefrom the samecompoundno~e,two of
themproducebranchesfrom axilsandtwo uppersheathsremamadpres--
sed, protectingthe correspondinginternode.The basal part of the
DECEMBER 1952. BOGDAN, StoloniferousGrassesin Kenya. 73
internoderemainssoftandproceeds.to growfor up to severaldaysafter
thebeginningof thebranching.Thusthebranchingin "B" typestolons
doesnot dependon the longitudinalgrowthof internodes,andone can
expectbranchingto beginat any time after the appropriatenodehas
beenfully formed. In actualfact,in Cynodon plecto:3Lachyum,aswell as
in manyother specieswith "B" type stolons,branchingbeginsat an
earlystageof developmentof theupperinternodes,andtherefore,in the
growingpart of thestolon,very nearto the apex.
The characteristicfeaturesof the "B" (Cynodon) type stolons
maynow be briefly summarisedas follows:-
a) The stolonshave a structurea-typicalof a normalgrassstem,
in that theyhavecompoundnodeseachproducing2-6 leaves.
b) The stolonsproducein generalmore than one branchfrom a
compoundnode.
c) An internodeproceedsto grow after branchingfrom the corres-
pondinginternodehas takenplace.
d) Branchingusuallybeginscloseto the apexof thestolon.
The actualgrowthof the stolonsof Digitaria aff. milanjana and
Cynodon plectostachyumas observedin the grassnurseryat the Scott
AgriculturalLaboratories,Nairobi,is shownin Figs.3-8.
The differencein structureand branchingof the two types of
stolonsdescribedresults in somewhatdifferentpatternfor the whole
systemof stolonswhich arisesfrom a singleplant. It hasalreadybeen
notedthat in the "A" type of stolonseachnode producesonly one
branch(if any). This,asa rule,becomesa verticalsterileor fertileshoot,
and.only seldomdoesit becomea side stolon. Thus the wholesystem
of stolonsof Digitaria or of othergeneraproducing" A" typestolonsis
rathersimple,and consistsusuallyof scarcelybranchedstolons(Fig.9),
eachproducinga row of verticalshoots. In the "B" typeeachnodeof
a stolonusuallyproduces2-4branchesof which oneor two mayoften
becomesidestolons. Thus the wholesystemof stolonsof Cynodon and
othergrasseswith "B" typestolonsis as a rule morecomplicated,and
it consistsof a netof moreor lessmuchbranchedstolons(Fig.10).
The stolontypeof a grassspeciesis connectedwith its taxonomical
positionin the Gramineae and specieswhich belongto the sametribe
usuallyproducethe sametype of stolons. The followinglist showsthe
occurrenceof the two fypesof stolonsin the differenttribesof Kenya
grasses.
1.SPECIES WITH" A" (DIGIT ARIA) TYPE STOLONS.
PANICEAE.
1. Digitaria aff. milanjana Stapf.(Bogdan3003)x
2. Digitaria? macroblepharaStapf (Bogdan873and2257)
3. Digitaria mombasanaHubbard
4. Digitaria scalarumJChiov. (normallya rhizomatousgrasswhichonly
occasionallyproducesstolons)
5. Pennisetum clandestinum Hochst. ( produces both stolons and
rhizomes)
6. Brachiaria humidicola Schweickerdt
74
BOGDAN, Stoloniferous Grassesin Kenua. VOL. XX
ANDROPOGONEAE.
7. Bothriochloa insculpta A. Camus
SPOROBOLEAE.
8. Sporobolus he!volus Dur. & Schinz
II. SPECIES WITH "B" (CYNODON) TYPE STOLONS.
ERAGROSTEAE.
9. Dj,plachnecaudataK. Schum.
10. Diplachne jaegeri Pilger.
11. DactylocteniumgeminatumHack.
12. Dactylocteniumscindicum Boiss.
13. Dactylocteniumsp. (Bogdan866and3155)
CHWRIDEAE.
14. Eustachys paspaloidesLanza& Mattei
15. Chloris amethysteaHochst.
16. Chloris aff. amethysteaHochst.(Bogdan1590)x.
17. Chloris gayana Kunth
18. Chrysochlora orientalis Swallen
19. Cynodon dactylon Pers.
20. Cynodon plectostachyumPilger.
SPOROBOLEAE.
21.Sporobolus marginatusHochst.
22. Sporobolus spicatus Kunth
23. Sporobolusvirginicus Kunth
LEPTUREAE.
l4. Leptwrus radicans A. Camus
25. Lepturus repens R.Br.
AVENEAE.
26. Lintonia nutans Stapf.
The abovelist showsthat all Kenya stoloniferousspeciesof the
Paniceae have"A" type stolons.x)On the otherhand all stoloniferous
speciesof the Chlorideae, Sporoboleae,Leptureae, and Eragrosteaepro-
duce"B" typestolons. In the last groupof tribeswith the "B" type
stolonsthe Chlorideae occupysomewhatcentralpositionandhavenum-
erousstoloniferousforms. The othertribes and generaof this group
are moreor less closelyrelatedto the Chlorideae"with the exception,
*) I haverecentlyCQrneacrossfreshstolonsof Steno,taphrumdimidiatum
( Paniceae) whichprovedto be essentiallyof thej"B" type!
x Refersto the specimensdepositedin the Herbariumof theRoyal
BotanicGardens,KewI England.
DECEMBER 1952. BOGDAN, StoloniferousGrassesin Kenya 75
of the Aveneae, which in Kenya have only one stoloniferousspecies,
namelyLintonia nutans. This speciesin its habit,distributionandecology
approaches,however,morethe Chlorideae than the rest of theAveneae,
and its taxonomicpositionrequiresa revision. In the groupof tribes
characterisedby the "B" type stolons,Sporobolus helvolus with its
" A ". type stolonsis an exception.The stolonsof Sporobolus helvolus
are not, however,comparablemorphologicallywith thoseof Sporobolus
marginatus or Spor'ob,olusspicatus. In these two latter speciesthe
stolonsarise as specialisedstructures,and grow horizontallyfrom the
momentof their formation,while in Sporobolus helvolus the young
stolonsappearas ordinary stems. Initially they grow vertically,and
only later on do they benddownwards,acquiringa creepinghabit and
rootingfrom nodes. The writer is inclinedto believethat the stolons
of Sporobolus helvolus can be regardedas a structuremorphologically
independentfromthetrue\stolonsof otherspeciesof Sporobolus,a struc-
ture which wasprobablyformedat a later datein the evolutionof the
genus. SporoboL-usvirginicus, althoughit producesrhizomesandnot the
above-groundstolons,is also included. Its rhizomeshave a struc-
ture typical pf the "B" type stolonsin (producingseveral,(usually
3); leavesfrom a node. Naturallytheseleavesarein the formof scales,
as it is typicalof the rhizomes.The rhizomesof Sporobolus virginicus
produce,however,only onebranchfrom a nodewhich arisesfrom the
axil of the lowermostscale as an extravaginalshoot. The branches
form vertical"leaf-bearingshoots,while the rhizomeitself does not
branch.The rhizomesof Sporobolusvirginicus canberegardedasmodi-
fied "B" type stolonswith its typical structure,which apparentlylost
its adaptativecharacter.
Although in the Paniceae the forms with true stolonsare not
numerous,manyspecieswhichproducecreepingstemsrootingfromnodes
are encounteredin the tribe. Thesecreepingstemsterminate,however,
in floweringheads,and they cannotbe regardedas stolons. They are
more comparablewith ascendingor creepingstem baseswhich also
frequentlyroot from the nodes. In fact, numeroustransitionalforms
betweenlong creepingstemsand thosewith only slightly ascending
basesarefound. The creepingor trailinggrassesof thePaniceaearepar-
ticularly numerousin forestsand in bushthickets,and to someextent
alsoon swampyground. Severalspeciesof Panioum, Pseudechinolaena
polystachya Stapf, Sacciolepis curvata Chase,Chloachne oplismenoides
Stapf..•speciesof Oplismenusandmanyothersbelongto theforestcreep-
ing grasses.On swampygroundthe grasseswith creepingstemsare
representedby Paspalidium geminatumStapf,Panicum repensL., Acro-
ceras macrum Stapf,Pennisetum dowsonii Stapf& Hubbard,Pennisetum
salifex Stapf & Hubbard,and by severalothers. Even on dry open
groundthereareseveralspeciesof thePaniceaewith longcreepingbasal
partsof the stems. Theseincludemainly speciesof Urochloa, Melinis..
and a few others. In the Andropogoneaetrailing forms are muchless
numerousalthoughsomespeciesof Andropogon and Hyparrhenia and
Eulalia geniculata Stapfproducefairly long creepingstembases.
In the Chlorideae groupof tribesthe numberof speciesproducing
specialisedstolonsis comparativelylarge.muchlarger than that in the
PaniceaeandAnd1'Opoqoneae.On theotherhand,thenumberof species
whichproducepartlyor entirelycreepingshootsof the structurenormal
in a typicalgrass-shoot,is surprisingly3mall. Apart from alreadymen-
tionedSporobolus helvolus, only a few speciesof this kind are known
76 BALLY, A Little-known Waterlily of Tanganyika VOL. xx
to theauthor,namelytwoor threespeciesof Eragmstis andDrake-Brock-
maniasomalensisStapf,anannualwith prostratestems.Evenformswith
ascendingand rootingstembasesare rare in this groupof tribes. In
generalthe Chlorideae groupof tribesis characterisedby highlyspecial-
isedstolonswhich differconsiderablyfrom the normalfertile shootsof
grasses.Even someannualspecieswith creepingstembases(Chloris
pycnothrix Trin!.,Dactyl;Octeniumaegyptium Beauv.) repeat,in their
basal,spreadingpartsof the stem,the structuretypicalof the "B" type
( Cynodon) stolons,by producingseveralleavesfrom each compound
node.•
The length and rate of growth of stolonsvary considerablyin
differentspecies.In theCht01"'ideaeandin thealliedtdbes,two typesof
stoloniferousgrasses,characterisedby therate of growthof the stolons,
havebeenobserved.To one type belongspecieswith rapidly growing
stolonswhichformextensive,thoughrather!thin,netsandin a compara-
tivelyshorttimeproducelarge,opencolonies.Beingopen,thesecolonies
allow the growthof otherplantsin the areasoccupiedby the colonies.
The actualcompetitionbetweenthespeciesstartsonly later,when,after
havingcovereda considerableareawith a thin netof stolons,thestoloni-
ferousgrassbeginsto form a densesward. As examplesof this typeof
stoloniferousgrass,Cynodondactylon,Cynodonplectostachyum,Diplachne
jaegeri, andChloris gayanacanbe named.The secondtypeis character-
isedby the comparativelyslowgrowthof stolons. Specieswhichbelong
to this type produceslowly spreading,but dense,nets of stolons,and
form densecoloniesfrom the very beginningof their growth. Grasses
of this groupoccupyan areaslowly,stepby step,butoncein occupation
theyretainit firmly. Amongstthe grassesof this typeare Chloris ame-
thystea,Eustachys paspaloides,andSporobolus marginatus.
ACKNOWLEDGEMENT.
The authoris muchindebtedto Mr. C. E. Hubbard,PrincipalRe-
searchOfficer,Royal BotanicGardens,Kew, for very valuableadvice
on taxonomyof the grassesdealtwith in the pr0sentpaper.
Nairobi,
November,1951.
A LITTLE.-KNOWN WATERLILY FROM TANGANYIKA.
By P. R. O. Bally.
Botanist,CoryndonMuseum.
In UnyamwesiandUssukuma,in WesternTanganyika,grows
oneof the loveliestand leastknow of all waterlilies:Nymphaeastuhl-
manni ( Schwfth.) Gilg.
At theendof August,1942,the writer hadthe goodfortuneto see
it for the first time, from a railway carriage,travellingfrom Tabora
towardsDar-es-Salaam.Immediatelybesidetherailwaytrackwasa little
pond,coveredwith large,bright yellow waterlilies. The temptationto
pull thesafetycordwasstrong;but a senseof proprietyprevailed,anda
uniqueopportunitywas missed.
Ten yearslater, almostto the day,on Augustthe 24th,1952,the
occasionaroseto visit the areaagain. My enquiriesrevealedthat the
very pondthat I hadpassedin the train wassituateda few milesfrom
eM
32
W : 28
272.1.lS~3.10198
'/1- 11
If>I
JII ____~~y~. V ,~ II
2
Figs. 1-2, Structureof Digitaria (1) and Cynodon (2) stolons.
Diagrammatical.
Figs. 3-5. A stolon of Digitaria aff. milanjana. 3-14.11.1950
4-16.11.1950;5-13.11.1950.(Grass nursery, Scott
Laboratories,Nairobi).
3/
3'0
29
ZB
,7
2.1•
.25
24
23
22-
21
20
19
18
17
16
IS
1+
/5
12.
7
9
5
4
o
Figs. 6-8. A stolon of Cynodon plectostachyum.6-14.11.1950;
7-16.1.1950;8-18.11.1950.(Grass nursery, Scott
Agric. Laboratorfes,Nairobi).
Figs. 9-10. Nets of stolonsof Digitaria aff.mitanjana (9).and
Cynodon dactylon (10).(Grassnursery,ScottAgric.
Laboratories,Nairobi,1949).


Observations on Stoloniferous grasses in Kenya

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Observations on Stoloniferous grasses in Kenya

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