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Full text of "Papers on pollination"

.037 



Charles Robert Darwin 
Papers on Pollination 
1861-69 



Missouri Botaniga*, 



Contents 



1. Om Orchideernes Befrugtning ved Tnsekter. [Tidsskr. 
Naturvidenskj « 

2. Dimorphic Condition in Primula. [Journ. Linn. Soc. 
Bot., 1861]. 

3. Existence of Two Forms in ^ecies of Linum. [Journ. 
Linn. Soc. Bot., 7, I863]. 

k. Fertilization of Lythrum Salicaria. [Journ. Linn. 
Soc. Bot., 8, 1864]. 

5. Notes on Fertilization of Orchids. [Annals and 
Magazine of Natural History, I869]. 



'^"M.A^. %^^---^^^. G,c/ie 



^A 



Oiii Orchideerues Befriigtning ved loseiitcr. 

Af Chailei^ Darwin — i (.'dlog ved M, T. Lange. 



Jllarwins Laere om Arternes Oprindelse *) vil, hvor inleres- 
sant og paa mange Piinkter sandsynlig den end er, dog 
neppe i det hele kiinne vinde Bifald. Men livad enten man 
antager den, eller forkaster den, eller indreminer dens 
Berettigelse i mange Tilfaelde uden at (iliaegge den al- 
mindelig Gyidighed — hvad der maaskee turde komme 
Sandlieden na'rmest — ; eet vil ingen kunne naegte: at den 
Grnndighed, hvcrmed denne udmaerkede Videnskabsmand 
undersoger >'aturen for at begrunde sin Theori, er af 
overordenlig Nytle for iNaturvidenskaben og kaster nyt 
Lys paa mange hidtil lidet asndsede Punkter af Naturens 
llige. Dette er saaledes Tilfsldet med Orchideernes Be- 
frugtning og Insekternes INledvirken derved, der vel ikke 
tidligere var ganske ukjendt, idet allerede Sprengel 1793 
og senere Here andre Naturforskere have paaviist meget 
(lerben liorende, men som dog egenlig forst bar fundet 
en ['remstiller og Forklarer i Darwin, der med dette For- 
bold stutter sin Saetning, at alia INaturens Naesener stun- 
(iom behave en Krydsning af forskjellige Individer, eller 
at ingen stadig Selvbefruglning af tvekjennede Individer 
tinder Sted i Natnren. Darwins V.-erk (On the various- 

*l See dclle Tidsskr. 2. Raektse, 5. Bind. 

Trcilie Rmklie. U. lit 

Mo, Bot, Garden, 
1893 



274 

contrivances by which British and foreign Orchids are 
fertilised by insects, and on the good effects of intercrossing. 
London. 1862) indeholder en Mangde omhyggelige og grun- 
dige (agttagelser, der ere af stor Interesse for Cotanikere; 
men bans Fremstilling af iNaturens vidunderlige Sanimen- 
pasning af disse Forhold, der hvert Oieblik overraske 
baade ved Skjenhed og Snildhed, maa nodvendig kunne 
interessere alle, og det saameget mere som det selv uden 
botaniske Forkundskaber vil viEre temmelig let i Naturen 
at felge og selv at see meget af det, som ban fremstiller. 
Her kan kun gives en Beskrivelse af Forholdet iios en- 
kelte Arter, men dette skal fremslilles saa udforligt, at 
enhver, der ikke vil spare den L'leilighed at saette sig ind 
i den forudskikkede Forklaring af Blomslens Bygning, vil 
kunne forstaae de meddelte Omstaendigheder ved Befrugt- 
ningen og let selv eftersee dem i Naturen. 



Blomsterdaekket hos Orchideerne (Gjogeblomsterne) 
bestaaer af 3 Ba;gerb!ade, der som oftest ere farvede, og 
af 3 ligeledes farvede Kronblade, af hvilke 1 i Regelen 
vender nedad, er starre end de andre og af meget eien- 
domraelig Form. Det er oLaebenu, »Honninglaeben«, som 
afsondrer tlonningsaften, der lokker Insekterne til, og ofte 
bagtil forlaenger sig i en laengere eller kortere Spore (Hon- 
ninggjemmet). 

Indenfor dette Blomsterdaekke findes hos vore Arter 
kun 1 Stovdrager, og denne er sammenvoxet med Griffe- 
len til en "Griffelstotte" , saa at der sjeldent er mere 
at see af den end Stovknappen, hvori det befrugtende 
Saedstov er indesluttet. Stovknappen er deelt i 2 Bum, der 
hos de fleste af vore Arter ere meget kjendelige og saa 



275 

langt fjernede fra hinanden, at de see iid som 2 saer- 
skilte St0vdragere. Medens Ssedstevet hos de tlegte 
andre I'lanter bestaaer af fine, lest liggende Korn, liaenge 
hos Orcliideerne alls de smaa Korn i Inert Rum sarnmen 
og danne Smaakliimper eller Masser, der ofte ba?res af 
en meget eiendommelig Stilk. Disse Smaaklumper lil- 
sammen raed Siilkeii kaldes Stovmassen. 

Der skiilde egenlig vaere 3 Grifler, men de ere heelt 
voxede sammen med Endtagelse af Arrene, og af disse 
flyde selv de to nedersle ofte saa I'lildstaendigl sammen, at 
de see ud som eet; — kun disse to tiave Arrets sa;dvan- 
lige Egenskaber og Bestemmelse, nemlig under Befrugt- 
ningen at gjennemtraenges af Stevkornenes lange, fine 
Flor, der fore Indlioldet ned til zEggene i Frogjemmet; 
— del tredie Ar derimod, der sidder overst, er omdannet 
til et usaedvanligt Redskab, som kaldes Snabelen og hos 
mange Orchideer slet ingen Lighed har med et virkeligt 
Ar. Den indeholder eller bestaaer af et klsebrigl Stof, og 
hos mange Orchideer ere Stovmasserne fasthaeftede til en 
Deel af dens Yderhud, der bliver ha'ngende ved dem, 
naar de bortfores af Insekter. Den Deel, som saaledes 
kan horttages, bestaaer hos de tleste af vore Arter af et 
lille Stykke Hud, som Darwin kalder Klffibeskiven, med et 
Lag eller en Klump kliebrig Materie under; men hos 
mange udenlandske Arter er Klaebeskiven saa stor, at 
dette ^avn kun passer paa en Deel af den, medens den 
anden, paa hvis Top Stovmasserne sidde , kaldes Snabe- 
lens Fod eller Stilk. 

De indenlandske Orchideer inddeler Darwin nu i 3 
firupper, af hvilke den forste indbefatter de (Teste af 
vore almindelige Arter, navnlig Slaegten Orchis (Gjogeurt). 
Stovmasserne hos denne Afdeling have foriieden en med 

19* 



276 

Klffibeskiven samraenvoxet Stilk og Slovknappen er for- 
bunden mefi Snabelen. 



I 




I 



Fig. 1. Orchis mascuia. 

A. En Blomst sect fia Siden, Baget- og Kronblade ere borttagno med Tndtagelse 
af det halve af Lisben og det meste af Sporen. B. Blomsten seet forfra. Alle Blade 
borttagrne undtagen Laben. C. En Stevmasse med de smaa Pakker af Stovkorn, Stilken 
og Kl^beskiren. D. Snabelen seet forfra med nedtrvkt Lsebe- E. Gjennemsnit af 
Sitabelen med den deraf iadesluttede KlEebeskive og Stovmassens Stilk. T. Smaa- 
pakker af Stevkorn , sammenlsenkede ved elastiske Traade, der i Fig. ere trukne ud 
fra hverandre. 

a. Stovknappen. c. Stovmassens Stilk. d, Klaebeskiven. 1. Lseben. n. Hon- 

ningsporen. p. Stevmassen. r. Snabelen. s. Arret. 



277 

« 

Orchis mascula (tyndaxet Gjflgeurt) forekommer 
hyppigt hos os om Foraaret i Krat. I Fig. 1 ere Ba-ger- 
og Kronblade borfsliaarne med Lndtagelse af La_'ben med 
Honninggjemmet. der sees i ,4, n. De to Ar ere na^sten 
sammensraeltede til eet (s), der sees under den pungfor- 
mede Snabel (r). St^vknappen (A, a og I?, a| vise to langt ad- 
skilte Rum, der fortil ere aabnede paalangs og hver inde- 
holde en Stuvmasse. G viser en saadan Stovmasse ud- 
taget at' sit Rum. Den bestaaer af et Antal Smaapakker 
af Stovkoru, der ere indbjrdes forbundne ved fine og 
meget elastiske Traade. I F rremstilles disse trukne ud 
fra hverandre. Disse Traade smelte sammen ved den 
nederste Ende af bver Stevmasse til en lige elastisk Stilk 
(C, c). Enden af Stilken hcenger fast sammen med Klaebe- 
skiven (C, d), der i E sees i Gjennemsnit paalangs, og be- 
staaer af et lille ovalt Stykke Hud og en Klump klaebrig 
Materie ved dets Underside. Enhver Stfivmasse bar sin 
sseregne {ibEbeskive, og de to Klumper kla-brigt Stof ligge 
begge indesluttede i Snabelen (D). 

Denne (A,r og B,r) er naesten kuglerund, nogel tilspidset 
og hsenger ud over de to Ar. Den believer en fuldstaen- 
dig Beskrivelse, da enhver Enkeltlied i dens Bygning er 
vigtig. E fremstiller et fijennemsnit paalangs g.jennem 
en af Klaebeskiverne og klumperne, og D begge seete for- 
fra i Snabelen, hvis forreste La;be er trykket noget ned. 
Den nederste Deel af Stovknappen er forenet med Ryg- 
gen af Snabelen (B). Paa et tidligere Ldviklingstrin be- 
staaer Snabelen af en Masse mangekantede Celler fyldte 
med briiun Materie, soni snarl oplase sig til to Klumper 
halvtlydende, meget klaebrig og strukturlos Substaus. Disse 
halvflydende Klumper ere noget langagtige, foroven oftest 
flade, forneden hvaelvede. De ligge naesten frit i Snabe- 



278 ^ 

lea, omgivne af Vadske og blot paa Bagsiden sammen- 
liaengende med en lille Skive af Snabelens Ydcrhinde, 
den ovenfor beskrevne Klaebeskive, der baerer Stovmas- 
sens Stilk. 

Den Hud, som danner den liele ydre Overflade af 
Snabelen, er i Begyndelsen sammenbsngende ; men saa- 
snart Blomsten aabner sig, bevirker selv den sagteste Be- 
rerelse, at den brisler i en buet Tvserlinie paa I'orsiden, 
hvorved Snabelens Form ikke forandres, men dens for- 
reste Deel bliver derved en Lsbe , som let kan tnekkes 
ned. II B sees Randen opret, i D nedtrykt). Trykkes 
Laeben lieelt ned, saa komme de to Klumper klaebrjg Ma- 
terie til at ligge frit; men saasnart Trykket ophorer, 
springer I.a;ben op igjen paa Grnnd af den bagerste Deels 
Elasticitet og indeslutter paany de to Klumper. 

Den mindsle Berorelse og endogsaa Cliloroformdampe 
bevirke denne Bristen af tluden i en besteml Linie ; maa- 
skee brister den ogsaa undertiden af sig selv, iallfald for- 
beredes det ved en Svskkelse langsmed den betegnede 
Linie. Samtidig med at Huden brister foran, synes den 
ogsaa at briste bagtil i to ovale Linier, hvorved de to smaa 
Kla'beskiver adskilles fra Snabelens 0vrige Yderflade. Da 
Slovknappens to Rum allerede for Blomstens Edspringning 
have aabnet sig fortii fra Grunden til Spidsen, saa ligge 
begge Stovmasserne nu, naar Snabelens Laebe trykkes 
ned, fuldkommen frit, men endnu paa deres Plads; nem- 
lig Stovmasserne selv og deres Stilke i Slovknappens Bum 
og de smaa, klaebrige Klumper, som ved Klaebeskiverne 
ere forbundne med dem, i Snabelens Pung. 

Vi sknile nn see, hvorledes denne sammensatte Me- 
kanisme virker. Lad os antage, at et Insekt sa;tter sig 
paa Laeben af Blomsten, der frembyder en god Landings- 



279 



plads, og stikker sit Hoved iud i Kammeret, pna hvis 
bagerste Va!g Arret (A, s og B, s) findes, for at naae ned i 
Honningsporen med sin Sugesnabel — eller, iuad der 
gjer samme Virkning, lad os skvde den fine Spids af en 
Blyant meget forsigtigt ind i delte Honninggjemine. Da 
den pungdannede Snabel rager frem i den Vei, som ferer 
til Ilonninggjemmet, er det nteppe muligt at fere nogen 
Gjenstand ind i dette uden at berare Snabelen. Dens 
Yderhud vil derved briste langs med den farnaevnte Linie 
og Lsben eller Pnngen let kunne trykkes ned. Naar dette 
er skeet, maa en af de 
klaebrige Rlumper, eller 
begge, nedveudigviis kom- 
me i Beroring med det 
indfarte Legeme og ved 
sin store Filoebrighed blive 
haengende derved. Wen 
da denne Waterie freni- 
deles bar den Saeregen- 
hed, at den 'i faa iVIinuter 

torrer ind O^ Sti\ner som ^'*^*^* ^^S P^a Blyantea. B. Samme efter at 

den har boiet si^ ned. 

Kit. og da StHvknappens 

Rum i Korveien ere aabne fortil , sua vil en af Stovmas- 
serne, eller begge, klaebes fast til (nsektets Hoved eller 
BIyanten og traekkes ud med, omtrent som det fremstilles 
i Fig. 2 A. 

Det er ganske n0dvendigt, at Stovmasserne klaebe sig 
saa Vast; tlii hvis de fakit ud til Siden eller lilbage, vilde 
de slet ikke kunne befrugte Blomsten. Efter den Stilling, 
hvori begge Stovmasserne sidde i deres Celle, beliolde de 
ogsaa en lidt divergerende Retning paa det fremmede 
Legeme, som de nu ere hfeftede til. Vedbleve de nu at 




Fig. 2. 

A. Stovmasssen strax eftor at den har 



280 

beholde denne oprette, divergerende Stilling iFig. 2 A|, 
vilde de igjen komme tilbage paa deres gamle Plads, h\is 
vi igjen fftrte Blyanten ind i samme eller en anden Blomsts 
Honninggjemme, og ingen Belrugtning finde Sted. Hvor- 
ledes bevirkes da Blomstens Befrugtning? Del skeer ved 
en smuk Indrelning; medens nemlig den kla;brige Over- 
flade holder fast, er den uanseelige lille Hiidskive, hvor- 
paa Stilken sidder, udrustet med en maerkvaerdig Sammen- 
traekningskraft, bvorved Stovmassen nodes til i Lebet af 
omtrent 30 Sekunder at beie sig ned imod Blyanteiis 
eller Sugesnabelens Spids i en Bue af 90" , iudtil den 
faaer den i Fig. 2 B angivne Stilling. Imidlertid flyver 
Insektel til en anden Blomst, hvor da, som Fig. 1 viser, 
den tykke Ende af Stovmassen netop maa traeffe Over- 
fladen af Arret, naar Sugesnabelen eller Blyanten fares 
ind i Elonninggjemmet. 

Her kommer nu en anden interessant Indretning, 
soni R. Brown for lang Tid siden bar beskreven, i Betragt- 
ning. Arret er meget kla^brigt, men ikke nok til at 
sanderrive hele Stavmassen, hvormed det nu kommer i 
Beraring. Det kan kun adskille de elastiske Traade, som 
forbinde de smaa Fakker af Stovkorn med hverandre 
(Fig. 1 F), og fastholde nogle af dem. Derfor kan den 
ene Stevmasse paa Insektets Hoved komme i Berering 
med flere Ar efter binanden og efterhaanden befrugte 
dem alle, saa at Insektet kun beholder Stevmassens Stilk 
tilbage. 

Endnu et Par smaa Omsta?ndigheder ere vaerd at 
laegge Maerke til. De smaa Kliimper klaebrig Malerie om- 
gives i Snabelen af en Vaedske, hvad der er vigtigt, fordi 
denne Materie, som sagt, terrer meget luirtigt ind i Luf- 
ten og i Labet af faa Minuter taber Evnen til at klsebe 



281 

sig fast. DerntESt sidde de smaa Iludskiver, Inis Sam- 
mentraekning bevirker den SiEnkning af St»vmasserne, der 
er saa iiodvendig for Befrugtningen , bag i og nede i 
Snabeleo, taet omgivne og derved holdt fugU'ge af Stov- 
knappens FJasis — livad der ogsaa er iindvendigt, da blot 
30 Sekunders Ldsaettelse, for den frie Luft er nok til at 
bevirke Ssenkningen. Endelig er det meget vigtigt, at 
Laeben , som forlien omtalt, igjen springer tiibage i sin 
forrige Stilling, naar den er bleven trykket ned. ^aar et 
Insekt havde trykket den ned, men ikke medtaget nogen 
eller kun den ene af de kjaibrige Klumper, vilde nemlig 
ellers begge Kiumperne, eller den ene, som blev tiibage, 
udssettes for Luflen og hurtigt torre hen, saa at Stov- 
masserne nu bleve unyttige. >len nu er det vist, at af mange 
Orchidee-Arter bortfore Insekterne kun een Stovmasse ad 
Gangen, og det er sandsynligt, at dette er del alminde- 
ligste TilfcBlde, da de nederste Blomster, som laengst have 
vaeret ndsprungne , saedvanligviis slet ingen Stovmasser 
indeholde , men de yngre , nys udsprungne , oftest 
have den ene tiibage. Saaledes fandl Darwin i Axet af 
en Orchis maculata ti Blomster, og det is»r de ovre, 
hvori der kun var een Stovmasse tiibage, men den hele 
Mekanisme var iovrigt i Orden, saa at de kunde bortfores 
af Insekterne. 

Hvad der hidtil er sagt om Indretningen hos Orchis 
mascula, passer i alt vaesenligt ogsaa paa Orchis Morio, 
fusca, maculata og latifolia; derimod linder der en vaesen- 
lig Forskjel Sted hos Orchis (Anacamptisi pyramidalis 
(Horndrager — hos os meget sjelden i Skove paa Kalk- 
grund) *). Denne Art, der er afbildet i Fig. 3, har to 



*) Med denne Art stemmer Orchis uatulata i det vaesenlige overeens. 



■282 

ninde, heelt adskilte Ar (A, ss), et paa hver Side af den 
piingformede Snabel (ri. Denne sidder ikke over Hon- 




Fii:. 3. Orchis pyraniidalis. 

A. Blomsten seet forfra. Alle Blade borttag-ne undtagen Lsben, B Samme fra 
Siden. Ben halve Lsebe og et Stykke af det everste af Lteben bortskaame. C. 
Begge Stovmasser paa dp.n sadelformede Klsebeskive- B, Samme efter Sammeii- 
trsekningen, naar den ikke er fasthseftet til nog-et. E. Stevroasserne, som have heef- 
tet sig til en Naal, der er fert ind 1 Honninggjemmet. F. Samme efter at de have 
boiet sig ned. 

a Stovknappen. s. s Arret, r Snabelen. I Laeben. 1' Laebens Ribber. n Hon- 

ningsporeo. 



283 

ningsporen, men saa dybt, at den da;kker og tildeels 
lukker dens IMunding (smlg. IJ). [^ollnillggjemmets For- 
kammer, der dannes af Laeben og Griffelstetten og er 
rummeligt hos Orcliis mascula og dens besla-gtede Arter, 
er her kun Idle. Snabelen er forneden i IMidten udhulet 
og fyldt med eii Vscdske. Der er kun een Klaebeskive af 
Form som en Sadei (C), der paa sin na'sten flade Ryg 
baerer de to Stevmassers Stilke. Saalaenge Snabelens Hud 
ikke er bristet, er det naeppe muligt at see, at den sadel- 
formede Skive udgjor en Deel af Snabelens samnienliaen- 
gende Overflade , da den tildeels skjules og holdes fngtig 
af de to Stavknaprums Grundbinder, der foldes vidt ud 
over den. Skivens ovre Hud bestaaer af flere Lag smaa 
Celler og er derfor tyk; forneden er den overtrukket af 
et Lag nieget fast klaebende Materie , som dannes i 
Snabelen. 

Naar Snabelens Lsbe er trykket ned ved en eller 
anden svag lierering, bloltes den nederste Deel afKlaebe- 
skiven , som ikke forandrer sin I'lads, og den kan nu 
klaebe sig fast til en Gjenstand, som bererer den; et Haar 
er endogsaa stivt nok til trykke Laeben ned, og Sadelens 
klaebrige (Jverflade haefter sig da til det. Endelig er 
Laeben forsynet med to opheiede Ribber (A, 1' og 15, 1'l , der 
udenfra indad lobe skaevt sammen imod .Midten som en 
Fiskeruse og derved ere fortraeffelig skikkede til at lede 
et beieligt Kedskab, som en liorste eller et Haar, ind i 
den lille, rundagtige og derlios tildels af Snabelen spaer- 
rede Munding af Honninggjemmet. 

Naar nu en Sommerfugl — disse Dyr besoge meget 
hyppigt Orcbideerne — stikker sin Sugesnabel ind mellem 
Laebens ledende Ribber, eller naar man efterligner denne 
Bevaegelse med en fiin lierste, saa vil den ledes sikkert 



284 

ind i Honninggjemniets fine Munding og vil neppe kunne 
undgaae at Irykke Snabelens Lfebe ned. Derved kommer 
Bersten i Berering med den sadellormede Skive , som nil 
er blottel og kliEbei- sig fast og felger med tilligemed de 
to Stovmasser, naar Bersten trifikkes tilbage; Saasuart 
Sadeien kommer iid i den frie Liift, pleier der eieblikke- 
ligt at foregaae en rask BevcEgelse med den, idet begge 
Endelapperne krnmme sig indad og oinfatte Borsten. 
Drages Stovmasserne derimod ud med en Tang, uden at 
•Sadeien faaer noget at omfatte , saa rulle Enderne sig i 
Lebet af faa Sekunder ttet sammen (D>. Mange Sommer- 
fugies Snabei er saa tynd, at Sadeien netop omfatter den, 
saa at Enderne naae sammen imder den, luorf'or en 
Natiirforsker, der saae en Sommert'ngl med Stovmasserne 
paa Snabelen, blev forledt til at tree, at den havde 
boret Snabelen midt igjennem St»vbolderen. 

Denne raske SanimenbHining tjener til at befa'ste 
Sadeien med dens Stovmasser oprelle paa Sugesnabelen. 
Dog vilde dette knnne opnaaes alene derved, at Kla'be- 
stoffet st0rkner meget hurtigt, saa at den egenlige Hen- 
sigt smirere er, at Stovmasserne derved bole sig ud fra 
hinanden. Tbi da de sidde paa Sadeiens flade Ryg , saa 
rage de i Hegyndelsen lige op i parallel Betning, men alt 
som Sadeien krummer sig oni Snabelen, maa de nodven- 
digviis buies ud fra hinanden. Men neppe er denne Be- 
vaigelse endt, hvad der medtager en halv Suees Sekun- 
der, for der begynder en anden Bevaegelse, dev ligesom 
den forste alene bevirkes af den lille Hudskives Sammen- 
trfekning, og nu er ganske den sarame, som for blev be- 
skreven ved Orchis mascula, idet Stovmasserne fra den 
lodrette Stilling beie sig i en ret Vinkel ned mod Sna- 
belens Spidse, saa at de ligge parallelt med den (E. F). 



285 

Hensigten med denne dobbelte Hevaegelse hlivcr klar, 
naar man forer liorsten med St0vmasserne tiibage, efterat 
Bevsgelsen er endl (smlg. A og F). Tlii nil lia\e begge 
Stevrnassernes Ender netop f'aaet en saadan Stilling, al 
den ene stroifer Arret paa den ene Side, den anden 
paa den anden Side, saa at de khebrige Ar nu kiuine 
l0sne de elastiskc Traade og fastliolde nogle af Slov- 
kornene. 

Da der ikke lios andre Planter, neppe lios noget Dyr, 
findes fuidkomnere Tilpasning af Organenie, end lios disse 
Orchideer, saa fortjener det ovenfor beskrevne vel endnu en- 
gang at sammenfattes i Fiorthed. Bloinsternes glimrende 
Farver tiltra-kke Dagsommerfngiene, deres eiendommelige 
Lugt Natsonimerfuglene. Det «vre Itaegerblad og de to 0vre 
F^ronblade danne eu lla'tte til lieskyttelse for Sttnknap- 
pene og Arrene. Lseben er udviklet til et langt llonning- 
gjemme, hvis Indhold drager Sommerfnglene til og er 
saaiedes opbevaret, — ganske anderledes end i andre 
F'amilier — at det kun langsomt kan opsuges for at give 
det klaebrige Stof under Sadelen Tid til at sterkne. De 
sammenlebende IVibber paa Laeben lede Sngesnabelen i 
den rigtige Retning, for at Stovmasserne ikke skulle komme 
til at sidde skjavt og gaae forl)i Arrene. Snabelen er 
opstillet paa Veien til Honningsaften som en Snare paa 
Vildtets Vei; den er saaiedes bjgget, og de Linier, hvor- 
efter den brister, saaiedes dragne, at Sadelen dannes for- 
oven, Fungens Laebe forneden. Denne Laebe er saa let 
at trykke ned , at lilaebeskiven ikke godt kan undgaae at 
blottes og haefte fast ved Insektets Sugesnabel, og skulde 
det ikke skee , saa springer den elastiske Lsebe igjen op, 
bedaekker paany den klaebrige Flade og holder den fugtig 
til naeste Gang. Vi see frenideles, at det klaebrige Stof i 



286 

Snabelen er befaestet alene til Klaebeskiven og omgivet af 
Vcedske, saa at det ikke kan sturkne, fer Skiven drages 
ud , ligesom Sadelens Overtlade holdes fiigtig indtil Ud- 
dragningen , da den eieiidommelige B0ining af Stovmas- 
serne begynder, I'erst til Siden og saa fremad, en Boining, 
der er neingtigt beregnet paa at bringe begge StBvmasser- 
nes Ender i lieroring nied Arfladerne. Disse Flader ere 
klaebrige nok til at fastholde nogle StHvpakker, medens 
de overlade Resten til andre IJlomsler. — Endvidere inaa 
maerkes , at selv om Insektet bruger lang Tid til at op- 
suge Honningsaften, saa begynder Stevmassernes Uoining 
ikke, far de ere trukne fuldstaindigt ud af deres Rum, og 
at deres Bevaegelse ferst et halvt Minut efter er saa vidt 
fuldendt, at de kunne trjeffe Arrene, naar de paany fores 
ind i en Blomst, saa at Insektet faaer Tid nok til at 
tlyve til en ny Piante og saaledes befrugte den nied en 
andens Stev. 

De hidtil omtalte Orchis-Arter believe nodvendigviis 
Insekters Medvirkning til deres Befrugtning. Dette freni- 
gaaer af, at Stovmasserne ligge saa fast i deres Bum og 
Klaebeskiverne i Snabelen, at de ikke kunne rystes ud ; 
men Darwin bar yderligere godtgjort det ved Forsog, idet 
ban bedaekkede adskillige Planter med Glasklokker, saa at 
Adgangen spaerredes for Insekterne, hvorved det viste sig, 
at ingen Bestovning fandt Sted og ingen Fro ansattes, 
skjondt Planterne iovrigt intet led. 

Det synes efter Darwins lagttagelser isar at vaere 
Sommerfugle, der bestove Orchis-Arterne; ban na-vner 23 
Arter, paa hvis Snabel ban bar fundet Stevmasser af 
Orchis pyramidalis. Dog deeltage ogsaa mindre Insekter, 
f. Ex. Empis-Arter, i Bestovningen og bortfore Stovmasserne 
paa Hovedet eller Brystet. FIvorvidt derimod Darwins 



1 



287 

Mening, — at nogle sjeldne Arter, f. Ex. Orchis fusca, skiilde 
vedblive at vaere saa sjeldne, fordi de ikke tiltraekke In- 
sekter nok, eller fordi de kiin besoges af enkelte Arter, 
— er rigtig, tiirde vsere tvivisomt, da tirnnden ligesaa 
vel kan S0ges i andre Forliold, og Jordbonden aabenbart 
bar raegen Indflydelse herpaa. 

Men endnii staaer der tilbage at onitale en mierkeiig 
OmstiEiidigbed ved de omtalte Orcbis-Arter, nemlig at deres 
»Honninggjemme«, som skulde lokke insekterne til, ingen 
Honningsaft indeholder! Sprengel bar undersegt de 
fleste Arter, tlere andre efter ham, og Darwin liar anstillet 
mangfoldige Undersegelser til de forskjelbgste Tider, selv 
oin iSatten, i Solskin og i Regnveir, men selv ved Hjaelp 
af Mikroskopet har ban aldrig fandet mindste Spor af 
Saft i Elonningsporen. Ilvorledes skal man forklare sig 
dette? — Sprengel kaldte disse Filomster »Scheinsal't- 
bliimen-; han antog, at her fandt et systematisk Bedrageri 
Sted, at Insekterne, uagtet de bestandig skuflfedes, dog 
bestandig kom igjen for at sege Honningsaft; men vi maa 
give Darwin Ret i, at det er umuligt at tree paa et saa 
kaempemaissigt Bedrageri, naar man erindrer, hvor uhyre 
ofte det maatte gjentages. Og naar man busker, at Be- 
stavningen forudsalter, at Insektet gjentager sit Besog hos 
disse Blomster Here Gange umiddelbart efter hinanden, 
saa maatte man, for at give Sprengel Ret, saetle Insek- 
ternes Forstand eller Instinkt meget lavt og kunde dog 
ikke forklare Grunden til, at disse Blomster vare saa 
overordenligt snildt indrettede, men at et af de vigtigste 
Led i Kjaeden manglede. Imod Rigtigbeden af Sprengels 
iNIening taler ogsaa i hei Grad bvad Darwin har iagttaget, 
at monstrose Blomster, som manglede Honninggjemmet, 
men hvis Befnigtningsapparat var i fuldstaendig Orden, 



288 

ikke vare blevne berBvede deres Stevniasser, medens dette 
var Tilfffildet med alle de fuldstandige Hlomster i samme 
Ax. Kt Fors0g, som Darwin anstillede ved at skjaere 
Euden af Honninggjemmerne paa endeel Blomsterknopper 
lios Orchis pyramidalis, f0rte til et lignende Hesultat, saa 
at insekterne ikke synes at lade sig saa let narre. 

Wen livor er da Noglen til denne Gaade? Darwin 
synes at have fundet den. idet lian bem«rkede, at den 
indre og ydre Nsg i Sporen hos disse Orchideer skilles 
ved et temmelig vidt Mellemrum , al dette er opfyidt af 
Vifidske, og al den indre Veeg eller llinde ev meget fiin 
og saerdeies let gjennemtraenges af Vaedsken; medens der 
ikke Andes noget saadant Mellemrum hos Gymnadenia 
conopsea og Platanthera solstitialis 'j, hvis Sporer altid 
ere fyldte med fri Honningsaft. Han slultede deraf, at 
insekterne med deres Sugesnnbe! kunne gjennembore den 
fine Indrehud i hine Arters Honningsporer og opsiige 
ViEdsken fra Mellemrummet. Naar man seer, hvor mange 
sindrige Foranstaltninger der ere Irulne for Orchideernes 
Befrugtning, og af hvor stor Vigiighed det er, at Stov- 
masserne komme til at sidde fast paa Insektet og ikke 
falde til Siden eller tilbage, og naar man erindrer, at 
Klaebeskiven behover nogen Tid for at saette sig fast ved 
Saftens Storkning, saa at det vilde viere til stor Nylte om 
Insektet blev lidt opholdt i at indsuge Saften, saa synes 
det ikke urimeligt at antage, at den usaedvanlige Indret- 
ning, at Honningsaften afsondres indenfor Overhuden, er 
truffen her for at node Insekterne til et laengere Ophold, 



*) Darwin nsevner ikke, oni det samme er Tilfaelilet med de andie 
Arter, hvis Sporer indeholde fri Honningsaft. 



289 

niedens de paa Here Steder gjennembore denne Hinde og 
udsuge Saften af Mellemriimmene. 

Rigtigheden heraf bestyrkes ved en L'ndersegelse af 
Klabeskiven hos de Arter, hvis Sporer indeholde fri Hon- 
ningsaft, nemlig Gymnadenia conopsea og albida, Platan- 
(hera solstitialis og cliloraniha og Coeioglossiim viride. 
Ilos de fire ferste er Fvlfebeskiven ikke indesluttet i en Pung, 
men nogen, hvoraf man strax seer, at den kicebrige Ma- 
terie maa have en anden kemisk IJeskaffenhed end Orchis- 
arternes og ikke saa hurtigt sterkne, hvilket Darwin og- 
saa liar overbeviist sig om ved Forsog, der viste, at 
Skiven beholdt sin Evne til at ilaebe sig fast i flere I2 — 24) 
Timer. Hos den sidste Art er Klaebeskiven vel bedaekket 
af en pungformet Hinde, men denne er saa lille, at 
Botanikerne have overseet den, og Skiven bevarer ogsaa, 
ligesom de andre Arters, sin Ktebriglied i liEngere lid 
efter Ldtagelsen. Da den kla-brige iMaterie hos disse fem 
Arter altsaa forrnaaer at haefte Stovinasserne tilstraekkelig 
fast paa Insekterne uden strax at storkne heelt'i, saa 
\ilde del ikke nytte, at Insekterne opholdtes hengere med 
at suge Saften op, og derfor finde vi hos dem og hos dem 
alene Saften frit i Honninggjemmet. Hvis dette Sammen- 
stod — paa den ene Side af et langsomt storknende 
Kl8ebes.tof og en Opbevaring af Honningsaften. der op- 
liolder Insekterne i iaengere Tid, paa den anden Side af et 
Klaebestof, der fra forst af er meget seigt, og en Opbe- 
varing af Saften, der tillader en hiirtig Indsngning — er 
tilfaeldigt, saa er det et meget heldigt Tilfaelde for disse 



*i Del egciilig bevisende: at Klsljestoffet hos disse Arter strax er 
tilstraekkelig seigt til at lade StBvniasserne sidde saa fast som 
tornodent, liar Darwin dog ikke paaviist. Den lange Tid der nied- 
gaaer til fiild Storkning synes derfor at tale for det modsalle. 

Tredie Rskke. 11. 20 



290 

Planter. Men er det ikke tilfaeldigt, saa er det et hoist 
raterkeligt Exempel paa Tilpasning. 

De Bvrige indenlandske Arter at denne Gruppe 
(Slaegterne : Gytnnadenia, Platanthera, Coeloglossum, Her- 
minium og Ophrys) skille sig fra de hidtil omtalte ved 
to adskilte Snabler. Neppe to Arter stemme ievrigt over- 
eens i Blomstens Indretning til Befrugtningen, men da 
Afvigelserne t'ra det i det foregaaende beskrevne ikke ere 
meget store, skal jeg indskraenke mig til at omtale et Par 
maerkeligere Tilla;lde. 

Hos Slffigterne Ophrys og tierminiura mangier Ilon- 
ningsporen , men erslaltes af en Fordybning i Laibens 
nedre Deel, der dog, ligesom Orchisarternes Spore, ingen 
fri Honningsaft indeholder. At Klaebeskiven hos nogle 
Arter er nogen og den kltebrige Materie derfor af en an- 
den Beskaffenhed, er allerede omtait. At Pungen, som 
indeslutter Klsbeskiven hos de fleste andre Arter, ikke er 
elastisk som hos Orchisarterne, hvor den igjen springer til- 
bage i sin Stilling, naar en Stovmasse er udlagen, — en 
Elasticitet, som her vilde. vaere unyttig, da hver Snabol 
kun indeshuter I Klaebeskive, — er et Vidnesbyrd cm 
iVIidlernes Tilpasning til det Maal, der skal naaes. 

Hos Ophrys myodes og Coeloglossum viride 
(to Arter, der ere meget sjeldne her i Landet) Andes der 
vel ogsaa en Pung, men den nederste Lteel af Stovinas- 
sernes Stilk og Klaebeskivens evre Deel ere ikke indeslut- 
tede deri, og da de saaledes ere udsatte for Luftens Paa- 
virkning, mangle de den eiendommelige Evne til at baie 
Stovmassen ned i Reining af Arret. Hos Ophrys myodes 
erstattes denne Mangel derved, at Stilken i sit naturlige 
Leie har en dobbelt Bftining naesten under en retVinkel; 
dog synes denne Indretning ikke tilstraekkelig til sit P'or- 



291 

maal, der kiin kan opnaaes ved en gjentagen Flaeven og 
Saenken af Insektets [loved. Det staaer da after al Sand- 
synlighed i Forbindelse liermed , at Stevmasserne hos 
denne Art efter Darwins lagttagelser meget sjeldiiere 
bortfures end hos de andre Orchideer, og at den kun 
meget sjeldent og sparsomt udvikler sine Fr0kapsler. 
Indretningen hos Coeloglossum viride er meget afvigende 
og f'ortjener en na:'rniere F?eskrivelse. Arret er her lille 
og stillet i Midten af Dlomsten, medens Stevmasserne 
ligge hoit over det, og de 2 I'unge, der indeslutte Klaebe- 
skivernes nedre Deel, ere fjernede langt fra hinanden ud 
til Siden af Rlomsten, saa at et Insekt, der opsugede 
Flonningsaften af Sporen, hvis Aabning Andes lidt foran 
og under Arret, ikke vilde komnie i Beroring med Klaebe- 
skiverne, selv om det loftede Hovedet i Veiret. Men der 
er serget for, at dette alligevel skeer, paa den maerkelige 
Maade, at der paa h\er Side af Laebens Grund, lige under 
Klaebeskiverne, findes en lille Fordybning omgivet af 
LiEbens opheiede Rande, hvori der afsondres Honning- 
draaber. Tilmed er der en lang opheiet I\ibbe lige under 
det rigtige Honninggjemrae , der leder Insekterne til at 
sa;tte sig paa Siden af La'ben taet ved det mindre Hon- 
ninggjemme. Opsuge de nu ffirst Saften af dette, ville 
de nwppe kunne undgaae at bortfore Stovmassen, og naar 
de derefter vende sig til det egenlige Honninggjemme, 
vil den netop korame til at berare Arret. Skjondt det 
saaledes i Regelen vil voere med Blomstens eget Stov, at 
Arret befrugtes , er en Krydsning mellem forskjellige 
Blomster dog ikke udelukket; i det Tilfa;lde nemlig at 
Insektet forst opsugede Hovedbeholdningen og derefter 
Randdraaberne , vilde det flyve til den naeste Blorast med 

20* 



292 

St0vma?serne paa Hovedel og kunde saaledes bestave 
dennes Ar. 

Fmp vi forlade denne Griippe, maa vi endnu opholde 
OS nogle 0ieblikke ved Ophrys apifera, en i England 
og Sydeuropa, men ikke i Danmark, forekommende Art, 
fordi den, saavidt vides, er del eneste Exempel paa nor- 
mal SplvbeS'rugtning af en Orchidee 'i. Dens to pung- 
formede Snabler, Klaebeskiverne og Arrenes Stilling ere 
omtrent som bos de andre Ophrysarter, men Stevmas- 
sernes Stiike ere meget lange, tynde og b0ielige , saa at 
de mangle den fornwdne Stivhed til at holde sig oprette, 
som de ellers have hos alle Arter i Gruppen. Da Stev- 
knappens to Rum ere beiede steerkt fremad, have Stilkene 
foroven den samme Reining, og de paereformede St0\- 
masser sidde derfor iige over Arrene. Strax efter liloni- 
stens Aabning aabne ogsaa Stovknappens Rum sig, — og 
det usaidvanlig vidt — og Stovmasserne falde ud. Da 
Stilkene ere saa svage, hegynde de meget snart efter at 
synke nedad, saa at Stovmasserne haenge frit i Luften 
Iige foran og i Hflide raed Arrene, medens lilaebeskiverne 
vedblive at holde deres nedre Ende fast i Pungen. En 
svag Luftstromning er nu tilstrsekkelig til at lade dem be- 
rore Arret, ved hvilket de klicbe fast, hvad Darwin har 
overbeviist sig om ved Fors0g, idet han omgav'Blom- 
sterne med et Net, der holdt Insekter, men ikke Luft- 
stramme borte. Cdelukkedes derimod Luftslromningen, 
vedbleve Stovmasserne ogsaa at svaeve i Luften foran 
Arret. Bestuvningen gaaer paa denne Maade saa regel- 
massigt for sig i Naturen, at Stovmasserne na'sten altid 



') En meget mangelfuld Selvbefmgtning forekommcr lios Ceplialan- 
theia grandiflora, som siden slial omlales. 



29.3 

Andes paa deres Ar og Frflkapslenie nsESten aldrig slaae 
feil — medens det omvendte er Tilfaddet hos Ophrys 
myodes. — Det er unaBgtelig' hoist maerkeligt, at denne 
Indretning til Seivbefrugtning ikiie findes lios de andrc 
Optirysarler, ikke engang lios Ophrys arachnites, der dog af 
flere Botanikere ansees for at va^re kiin en Varietet af 
Ophrys apifera; og man fatter let, at Darwin af dennc 
OmstaBndighed i Forbindelse med, at Ophrys apifera des- 
uagtet liar alls de ntidvendige Indretninger til at befrugtes 
som de andre Arter, iedes til den Formodning, at der 
hos denne Art liar skullet bevirkes en rigeligere Idvik- 
ling af Fro — hvad der kun kunde skee med Opgivelse 
af de Fordele, som Krydsningen kunde medfore; men at 
en saadan Krydsning med andre Individer dog i enkelte 
Tilfaelde finder Sted, om end sjeldent. f)og,'disse Gis- 
ninger kiinne \i her lade staae hen. 

\i koHune nu til en anden Hovedafdeling af Orchi- 
deerne , som have en fri , bag \rret stillet Stovknap. 
St0vkornene ere sammentenkede ved fine, elastiske Traade, 
der tildeels haenge sammen og rage frem ved den overste 
Ende af Stovmasserne og ere befa'stede til Ryggen af 
Snabelen, hvorfor de mangle Stilken, der spiiler en saa 
vigtig Holle hos de forhen omtalte. Af de lierlien linrende 
Sluegter: Epipactis, Cephalanthera, Goodyera og Spiranthes 
skiille et Par Arter her narmere omtales. 

Hos Epipactis pal us tris (Sump-Huullaebe), der fore- 
kommer hist og her i vaade Enge, rager den forreste 
Deel af Arrene noget frem foran Griffelstntten (Fig. 4, 
B, s og C, s). Paa dens Top sidder en enkelt lille, naesten 
kugleformel Snabel (B, r og C, ri, h\is Forside rager noget 
frem foran Overfladen af Arrene , hvad der er af megen 
Vigtighed. I ung Tilstand bestaaer Snabelen af en skjor 



294 

Cellemasse med ru Yderflade; disse Yderceller forvandles 
under Ldviklingen til en blod, glat og megel elastisk Hud, 
der er saa overordenlig flin, at el Haar kan tra-nge igjen- 





Fig. 4, Epipactis 1)alnstris. 

A. Blomsten seet fra Siden ; kun de nederste B^gerblade borttagne. B. Samme 
med alle Blade borttajpie undtagen Halvdelen af Lfeben. C. Griffelatotten seet for- 
fra. Snabelen er i Afbildnin^en noget nedtrykt ; den rager i Virkeligheden noget 
heiere op og skjuler mere af StoTknappens Rum., 

a. Stovknappen, hvis to aabne Rum i C sees forfra a'. Rudimontser Stovknap. 

1. Ljeben. r. Snabelen. s. Arret. 

nem den. Ved den svageste Gnidning, stundom maaskee 
ogsaa uden en saadan, bliver denne Overflade kliebrig, 
saa at Slavkornene biive haengende ved den. Denne blade 
Yderhud danner en Rappe om Snabelen og er forinden 
overtrukken af et mere kisebrigt Lag, soin i Luften stork- 



295 

ner i Lebet af 5 — 10 Minuter, nenne hele Kappe med 
dens indvendige Beklaedning bortfares sserdeles let, naar 
et Legerae skydes let imod den, i Retningen opad og til- 
bage, og der bliver da kiin en lille Stump tilover.s ved 
Grunden. 1 Knoppen rager StHvknappen ganske frit op 
bag Snabel og Ar; den aabner sig paaiangs f0r lilomsten 
springer ud, saa at de to ovale Stovmasser ligge frit og 
Inst i deres Rum, De bestaae af runde Smaakorn, der 
liffinge sammen 4 og 4, og disse ere forbundne ved frie, 
elastiske Traade, der i Knipper stra'kke sig langs Midter- 
linien af hver Stovmasses Forside, hvor de komme i Be- 
roring med den ovre Deel af Snabelens Ryg, der for 
Hlomstens Aabuing er laenet mod Stuvknappen , og fsste 
sig til dens Kappe, Derefter krtimmer Snabelen sig 
fremad og traekker derved Stevmassserne tildeels frem af 
deres Rum, Stuvknappens overste Ende bestaaer af en 
stump, solid Spids udeu Stov, der rager noget frem over 
og foran Snabelen (B, a og C, ai, Blomsterne staae na'sten 
lodret ud fra Staengelen (A), l.aebin bestaaer af to Dele: 
den nederste danner en Skaal, der indeholder Honning- 
saft; den overste, der kun hunger sammen med den 
nederste ved et smalt, boieligt og meget elastisk Led, er 
krummet opad, saa at den tildeels lukker for Blomsten. 
En Flues \»gt er tilstraekkelig til at boie den ned i den 
i B fremstillede Reining, men naar Vaegten borttages, 
springer den igjen op i sin forrige Stilling, 

Lad OS nu see, bvortil alt dette tjener. At trykke 
Snabelen ned, sora hos de forhen beskrevne Arter, losner 
ikke St0vmasserne, Et Insekt, der satte sig paa La'bens 
0vre Deel for at suge Saften op, vilde slet ikke komme 
til at berore Snabelen; naar det derimod \ar krobet ind i 
Blomsten , og Loeben altsaa havde lukket i for det ved at 



296 

rette »ig op, vilde det viere nodt til at kravie op ad Arret 
over Snabelen og den fremragende Ende af Stavknappen 
for igjen at komme ud. Eftergjer man nu denne He- 
vaegelse med en Pensel, saa losnes Snabelens Kappe med 
stor Lethed, klaeber sig fast til I'enslen og medforer 
Stavmasserne. Og hvor noie alt er tilpasset til sin Be- 
stemmelse, viser sig tydeligt her, idet StHvmasserne kun les- 
nes ftildstaendigt, naar Penselen fores i Retning af den 
fremragende Ende af Stovknappen — den Vei, sonT In- 
seklet maa tage for at slippe ud; fores den mere indad, saa 
folger der kun enkelte Stovklumper med. — Naar nu alt- 
saa et Insekt paa sin Vandring ud af Blomsten har faaet 
Snabelens Kappe med de vedhaengende Stevmasser be- 
fiBStet til sit [loved, og tlyver til en anden Blomst, saa 
vil Arret vsre det f«rste Sted, imod livilket StMvmassen 
vil st0de, og der vil den haeftes fast paa Grund af Arrets 
klsbrighed. Og det er ikke uden Betydning, at den ydre 
Deel af Lasben saa let bfiies ned ved Insektets Vaegt, da 
der saaledes aabnes saa stor en Indgang til Blomsten , at 
Stovmasserne ikke let komme i Berering med Blomster- 
daekket, hvorved en Deel af Stevet vilde gaae til Spilde, 
da Stavmasserne meget let sonderrives. 

Epipactis latifolia (bredbladet Huullaebe), som er al- 
mindelig i vore Skove, stemmer i det va-senlige overeens 
med den forrige Art; kun er Adgangen til Blomsten friere, 
idet La'bens ydre Led mangier Elasticitet og St0vknap- 
pens Ende ikke rager frem foran Snabelen, hvorfor Stov- 
masserne kunne borlferes uden at denne berares. Der- 
imod afviger C ephalanthera grandiflora (hvidguul 
Skovlilie) — som Andes i Skove paa Kalkbund og tilherer 
en Slaegt, der ellers staaer meget nar ved Epipactis — 
vaesenligt fra denne og alle andre, idet Snabelen ganske 



297 



mangier. Stevkornene eve skilte — ikke forenede i Smaa- 
klumper — og kun forbundne ved I'aa og svage elastiske 
Traade. StHvknappeiie aabne sig fur lilomstens IJdspriiig- 
ning og skyde Stevmasserne noget frem , saa at de staae 
naesten frit scim to oprette Soiler, dcr fortil l;ene sig irnod 
Arrets ovre Hand, der naaer op til ornlreiU ^ af deres 
Hoide (Fig. 5). De Stovkorn, som saaledes berore Arrets 
skarpe Rand -- men hverken de hoiere eller lavere 
staaende — sende allerede for Blomsten 
er fiildkommen udsprungen en Ma^ngde 
Stovrer dybt ind i Arrets Vav. Der- 
el'ter krummer Arret sig fremad , saa 
at Stavsoilerne biive heelt frie fra Stov- 
knappen og kun holdes oprette af Arret, 
hvorlil de laene sig og hvormed de ere 
forbundne ved Stovrorenes Indtra'ngen i 
Arret. Uden denne Understotteisc vilde 
de snarl falde oni, uagtet Blomstens Stil- 
ling er oprel og uagtet de ere beskjt- f'i?. 5, Ceplialan- 
tede mod vmden af Kronbladene og 

GriffelstottGn seet fra 

Lsebens nedre Oeel, der slutle sig tat siden, efter at ajie bk- 

. ger- og Kronblade ere 

sammen om Grittelstotteu. borttagne. stovsaiieme 

Ladien bestaaer, som bos Epipaclis, ^^ ""'"'="' ''"""T"^ 

af to Dele, og naar Blomsten er fuidt ». stovkappen. p. stev- 

masseme. s. Arret. 

udviklet, vender den ovre , trekantede 
Deel nedad i en ret Vinkel til den nedre Deei , saa at 
den danner en god Landingsplads for et Insekt foran en 
trekantet Aabning til den na;sten rorformede Blomst. 
Rort efler at Blomsten er befrugtet, relter denne 0vre 
Deel af Laben sig igjen op, tilslutler Aabningen og inde- 
slutter fuldstaendigt Befrugtningsorganerne. Darwin bar 




298 

ikke fundel Uonningsaft i Laebens nedre skaalformede 
Deel, men antager dog, at der afsondres en saadau. 

Cephalanthera grandiflora *) synes altsaa at yde os 
det andet Exempel paa stadig Selvbefrugtning lios Orchi- 
deerne, el'tersom endeel Stevkorn allid befrngte Arret, og 
Insekters Medlijaelp kiinde synes overfledig, da roan kunde 
tsenke sig, at Stovsftilerne ved at falde sammen, vilde 
sprede de andre Stovkorn over Arrets Flade. Darwin bar 
imidlertid godtgjorl ved Porsag, at Stevsailerne knn und- 
tagelsesviis falde sammen, at Stovet altsaa ikke kommer 
til Arret, og at de fleste Fro blive golde, naar liloinsterne 
ndebikkes fra Insekternes IJesog, medens IJIomsternes Ar 
i fri Tilstand ere bedaekkede med Stovkorn og Soilerne 
ganske nedbrudte. Det vilde ogsaa va;re foninderligt, cm 
det skulde vaere uden Hensigt, at Lipben en kort Tid 
aabner Indgang til lilomsten og sidcn lukkes, at iilom- 
stens Form netop er saaledes, at et Insekt maatte krybe 
hen over Arret, og at Stevsnilerne ere stillede saaledes, 
at knn nogle faa StHvkorn komme til at virke, medens 
store Masser over og under disse bleve nbrugte. 

Her synes altsaa at va>re et sammensat Tilfaelde. Her 
finder en stadig, men meget ufiildstaindig Selvbefrugtning 
Sted, der deels tjener til at erstatte Insekternes njttl[>, 
hvis den skulde udeblive, deels til at lette insekternes Ar- 
beide ved at bolde St0vsnilerne oprette. Men denne 
ufuidstaendige Befrugtning suppleres ved Besog af insek- 
ter, der sprede Stovet over Arret af saimme Blomst, men 
tillige maa fare en Oeel med sig til andre Hlomster, saa 
at her kun tildeels finder en Lndtagelse Sted fra den al- 



■) De lo andre Arter af denne Slaegt, soni forekomme her i Lan- 
det. omtaler Darwin ikke 



299 



mindelige Regel, at den ene Blonist befmgles af de 
andre Blomsters Slav. 

Derimod afgiver SpiranHies autumnalis (Host- 
Skrueax) — en her i Landet meget sjelden Arl — Exenn- 
pel paa en Orchidee, der ikke alene ntidveudig beliaver 
Insekters Medhjaelp ved fiestevningen, men livor desuden 
den ene Blomst kun kan besteves med den andens Sa-d- 
st0v, hvad en kort Beskrivelse af Blomslens Bygning vil 
godtgjere. Blomster- * 

dffikket danner et Uor 
omkring GrifFelstetten, 
og paa den Tid . da 
Blomsten aabnes, er 
Laebens ydre Deel vel 
saaledes nedadbeiet, at 
Insekter kunne satte sig 
derpaa , men dens 




Fig. 6. Spiianlhes autuninalis. 



En moden Blomst efter at Laiben (hvis Om- 
rids er punkteret) har fjernet sig fra Snabelen. 
indre Deel skitter Saa A"e "lade "e bor,skaar„e, me„ de evre B«ger- 

blades Stilling ligeledes antydet ved Funkter. 
imt on til Snabelen ^" Stevknappen. n. Honninggjemmet. p. Stev- 

koriiene, r. Snabelen. s. Arret. 

— her en lang, tynd og 

flad Freraragning — og det deriinder skraat Ireniragende 
Ar (Fig. 6 r, s), at kun en (iin Ilende, loroven dannet af 
Snabelens lidt udhuiede Forside, forneden af en [hiulhed i 
Loeben, forer ind forbi Arret lil Liebens P^ude, bvcr FJoii- 
ningsaften opbevares (n). Da Snabelen rager langt frem 
over Arret og under Stovknappeu — Blomslens Stilling 
er nemllg vandret — og altsaa danner en Skillevieg mellem 
Arret og Stavet, kan dette ikke befriigte hiint uden saa- 
ledes, at Stovmasserne forst bortfores fra deres Plads og 
derpaa feres ind lil Arret; men paa den Tid er Indgangs- 
aabningen til Arret altfor snever til at Stevmasserne kunne 
bringes derind. Insekterne, som besoge Blomsterne strax 



MM 

efter deres Aabning, kunne derfor vel opsuge Honning- 
saften, og idet de traekke deres Sugesnabel tilbage, ville 
Stfivmasserne felge med ud af lilomsteii, men de formaae 
ikke at bringe dem i ISeroring med Arret. Det er ferst et 
Par Dage senere, at Lieben fjerner sig saameget fra 
Snabelen, at Aabningen bliver stor nok til at lilstede 
St0vmasserne, som sidde paa Insektets Sugesnabel, Ad- 
gang til Arret. Hvorledes skeer da Bestovningen? Det 
skal strax bliAe paaviist, men ferst maa det i Korthed 
forklares, hvorledes Stuvmasserne , der sidde i Stov- 
knappeu over Snabelen, kunne bortferes med Insektets 
Sugesnabel, der slikkes ind under Snabelen. Denne 
bestaaer nemlig af en Slags togrenet Gaffel, og Mellemrum- 
met mellem Grenene udfyldes paa Bagsiden (den overste 
Side) af en langstrakt Skive, der er fvldt med klaebrig 
Vaedske, som i Liiften slorkner i Lobet af 1 Minut, men 
allerede efter 4—5 Sekunders Forlub klaber en Gjen- 
stand fast. Paa Forsiden er der en Ihuiining mellem 
Grenene og i deiine er Huden saa skrebelig, at den 
brister ved den svageste Berering og det ikke blot i Huul- 
ningen , men langs Fdaebeskivens Bande, saa at denne 
selv bliver fri og udsveder saamegen V'aedske, at den 
fastgjares ved det Legeme , der har foraarsaget Biften og 
bortfores med det. Men med denne Klsebeskive falger 
da med det samme St»vmasserne, Inis Traade iiave be- 
fiBStet sig dertil allerede fer Blomstens Aabiiing, da St0v- 
knappens Hum nemlig aabne sig for Blomsten og Stov- 
masserne ligge tat op til Snabelens Ryg. Det er altsaa 
indlysende, at en Humlebi — det skal isjer vaere disse, 
der bes0ge Spiranthes, — ikke kan fore sin Snabel ind i 
den fine Bende , h\is Overside netop er Snabelens Huui- 
ning, uden at Stovmasserne ville haefte sig fast og bort- 



801 

f0res. Men nu er disse Dyrs Fremgangsniaade den, at 
de ffirst satte sig paa den nederste Bloinst i Axet, der 
er snoet i Spiral, og derpaa krybe opad fra liloin.^t til 
Blomst, idet de folge Spirallinien. Dp komme altsaa fsrst 
til de aeldste, laengst udsprungiie lilomster, sid?t til de sidst 
udsprungne. Gik de den modsatte Vei, vilde Stuvet 
spildes. Nu finde de Stovet allerede horlffirt i de aldre 
Blomster; naar de komme til de nys udsprungne, endnu 
ikke besegte ISlomster, uddrage da Stuvniasserne ug lly\e 
saa til en ny Plante, hvor de begynde paa samme Viis, 
og hvor nu (Jestevningen kan gaae tor sig i de sldre 
Blomster, idet, som ovenfor viist, Laeben nu bar fjernet 
sig tilstraekkeligt fra Arret. I de avre lilomster hentes 
nyt Stev og saaledes fremdeles. Darwin liar langet 
Humlebier mad indtil 5 llaefteskiver paa Snabelen. Idet 
de saaledes bente Honning til sig selv, serge de tillige 
for at Spirantbes forplanter sig og kan berede Honning 
til nye dnerationer af Humlebier. 

I den tredie og sidste Afdeling af de indenlandske 
Orchideer, af bvilken Darwin omtaler SliBgterne; Malaxis, 
Listera og Neottia, er ingen Deel af Snabelens Overbud 
vedvarende befa'stet lil Stevmasserne. Hos Malaxis palu- 
dosa (Sump-Hjertelaebe) — den raindsto af de danske Orchi- 
deer — foregaaer Befrugtningen meget let og simpelt, 
idet Stovmasserne ved IJIomstens Aabning ligge frit — 
StBvknappen skrumper nemlig meget tidligt sammen — 
og kun med deres evre spidse Ende stette sig til Snabe- 
lens Top, hvor de fastboldes af en lille Draabe klisbrig 
Vaedske; denne Draabe vil et Insekt, der stikker Hoved 
eller Snabel ind i Blomsten, nedvendig maatte berore og 
vil saaledes medfare Stevmasserne til andre Blomster, 



302 



hvor de viUe trKffe Arret ifolge deres Stilling paa Insaek- 

tets Hoved eller Snabel. 

Derimod foregaaer Befruglningen hos de to andre 

SlcEgter paa en meget maerkelig Maade. Uet vil vare til- 

straekkeligt at omtale 
Listera ovata (aag- 
bladet Fligla'be) — 
der er temraelig al- 
miudelig i fuglige 
Skove — da de an- 
dre sjeldnere Arter i 
alt vffisenligl slemme 
overeens med denne. 
Snabelen (Fig. 7, 
rl) som hvffilver sig 
ud over Arfladen (s,i, 
er bladagtig, stor og 
tynd, foran hvieivet, 
bagtil fordybet og 
paa begge Sider af 
den spidseTop noget 
udhulet. St0vknap- 
pen aabner sig aile- 
rede i Knoppen, saa 




Fig. 7. Listera o\'ata. 

Blomaten seet fra Siden ; alle Blade borttagne 
uadlagea Lseben. 

a. Stevknappen. col. Griifelstettens Top. 1. Laben. 
n. Lsebens. Honniogfure p. Stovmassen. r. .Snabe- 
lea. s. Arret. 



fuldkommen frie i de 
udsprungne Blom- 
iter, laenede til Sna- 
belens Kyg. Denne 
beier sig nu lidt frem- og nedad itnod Arfladen, hvorved 
den fjernes noget fra Stevknappens Spids (a). Naar man 
nu bererer Snabelens Spids — om ogsaa blot med et lint 



303 

Haar — saa springer der aieblikkelig en Draahe klaebrig 
Vaedske frem af den, der fraeffer den spidse Ende afStev- 
masserne (p), sora hvile paa Snabelens Ryg. I Lobet af 
2 — 3 Sekunder sterkner denne Draabe og bliver meget 
haard. Havde Snabelen ikke i Forveien boiet sig lidt 
frem, vilde den trisffe Spidsen af Stovknappen og saaledes 
lukke til for Stevet; nu traeffer den knn StHvinassernes Spids 
og Elovedet af det Insekt, der bar bevirket Explosionen, og 
fasthaefter saaledes St0vet til dette. 

Ijlorasterne beseges af en stor Maengde Insekter, der 
opsuge Honningsaften, som afsondres i en lang, smal Fure 
midt i Laeben (n), og denne Fure fortsaettes opad den 
lange Laebe indtil dens Grund under Arret. i\aar Insek- 
tet er kommet hertil og lofter Hovedet op for at flyve 
bort, vii det trseffe Snabelens Spids og frembringe den 
ovenfor beskrevne Virkning. Darwin bar fanget flere Indixi- 
der af Slasgterne Hemiteles og Cryptus, der kum ud af 
Blomsten med Stovmasserne befaestede til den indre0ierand. 
Ganske smaa Insekter, som ikke have Kraft til at bortfore 
St0vmasserne, blive underliden baengende og omkomme. 

1 det Oieblik, da Snabelen saaledes bar udsendt sin 
Draabe, krummer den sig endnu mere frem og nedad, saa 
at den danner en ret Vinkel med Arret; derved beskytler 
den dette, men forhindrer tillige Befrugtningen, saa at 
det her ligesom bos Spiranthes er de yngre Blomsters 
Stev, der befriigte de aeldre Blomsters Ar; thi i Lobet af 
nogle Timer eller en Dag, i hvilken Tid Arret udvikler 
meget mere Klcebrighed, beier Snabelen sig alter tilbage, 
indtil den faaer en ganske opret Stilling, og Adgangen til 
Arret bliver fri, saa at Stovmasserne kunne berfire det, 
dels Klffibrighed fastholde Stevkornene, sonderrive Traa- 



304 

dene, hvormed fie ere forbundne, og Befnigtningeu saa- 
ledes gaae for ?ig. 

Darwiiis l.nders0gelser omfatte endiui ioruden disse 
Slagter en stor Ma;ngde tropiske Orchideer, der frem- 
b\de man,-'foldige Aivexiinger i de Tilpasninger, livorved 
Inseklenie kiiiine udfere IJesttnningen. Da bans Materiale 
til liidersMgeisen af disse imidlertid bar Vipret mindre 
rigt end til de indenlandske , og derfor de fleste endnn 
tra;iiKe til iia'rmei'e Lndersogelse, og da naesten alle dette 
Tidsskrifts Lwsere ville savne Materiale til at eftersee de 
beskrevne Forbold i Naturen, hvad Afbildninj^er kuu ufuld- 
staendigt kunne erstatte, niaa jeg benvise dem, der kunde 
0nske en fuldstandigere Uundskab, til Darwins eget \a'rk. 
Jeg skal kiin iindtagelsesviis omtale en enkelt Sbegt, bvor 
Befrugtningen foregaaer ved en endnii ma^rkeligere Explo- 
sion, end den sidst beskrevne, Slffigten Calasetum, der 
desnden frembyder den Sieregenbed, at Kjonnene ere 
adskilte, saa at del kun er undtageisesviis, at der paa 
samme Plante forekommer baade Han- og Hun-niomstei ; 
og disses Bygning er saa forskjellig, at de have vaeret 
henforle til ganske forskjellige Slwgter *). 

Hos Catasetum (hvoraf Darwin bar undersogt ',i Arten 
mangier Arret Klaebrigbed til at fastholde Stovkornene, 
Mggene ere uudviklede og sknlle heller ikke i deres 
Hjemslavn nogensinde iidvikle sig lil Fro; Frokapslen er 
ogsaa meget kort og tynd. Derimod er det lios Monachan- 
thus Stovmasserne, der ere aldeles rudiment*re, deres 



*)Catas(>(»m tridentatum (Hanblomsl. Fie. 8i, Monacan- 
thus viridis (Hunblomst, Kig 9 A; <»s; Myantlius barliatiis 
(Tvekjensblomst, Fig. 9 B) fandtes af R. Schomburgl; og seneie af 
Flere paa en og samme Plante. Til andre Catasetum - Arter 
kjender man endnii ililie Hiinplanterne. 



305 

Rum aabne sig ikke. og de mangle Snabelens vigtigste 
Organer, medens Ar og iEg ere fuldkomment udvikiede. 
Hos Myanthus endelig Andes Best0vningsredskaberne, Ar 
og Mg omtrent ligeligt udvikiede. Kun hos denne sidste 
kunde altsaa en Bel'rugtning ved eget Stev foregaae. For 
at overfore Stevet fra Cataselum (tridentatum) til .Mona- 
cantbus behoves nodvendigt Insekters MedhjiBlp, og dertii er 
der triiffet en b0ist m;erkelig Raekke af Foraustaltninger. 





Fig. 8. Caliisetum triilenlatum. 

A. Blomsten fra Siden ; 2 Bsgerblade Itortskaariie. B. GrifteUtotten opret og 
scet forira. 

a. Stovknappen. an. Snabelens Folehorn. 1. Lseben. pd. Kliebeskivens Fod. 
(Klaebeskiven selv er skjult i det merke Rum — Ar^ruben — under denne). 

StBvmasserne ere ved en temmelig solid og meget 
elastisk Fod f'orbundne med en stor Klaebeskive. Men 
denne er utilgaengelig for Insekter, da den ligger gjemt i 
en Grube (der hvor Arret skulde v;ere) med sin klaebrige 
Deel trykket op mod Fjoftet, saa at insekter, selv om de 
tr*ngte derind, hvortil der ingen Aniedning er, ikke vilde 
komme i Berering dermed. Men Ivlsbeskivens elastiske 
Fod (Fig. 8 pd) er bHiet over Snabelen og holdes i denne 
Stilling som en spipudt l!ue ved en fiin Hinde, der er 
sammenvoxet med to lange. bnle Folehorn (an), der ud- 

Trcdie Riekke. II. 21 



306 

gjore en Deel af Snabelen og beie sig ned foran Argru- 
ben og ere gjemte i Laebens Huiilhed. Disse Folehorn ere 
i den Grad folsomme, at Beroring med en Btirste i deres 
Spidse eller et andet Sted paa dem oieblikkeligt foraar- 




Fig. 9. 

A. Monacanthas viridis seet fra Siden, B. Myanthus barbatas ligeledes. 
a. Stovknappen. an. Foleborncne. I Lieben. s. Arret, sep. R?eg:erblade. 

sager en liristen af den omtalte Hinde ved deres Grund luden 
at der iovrigl foregaaer nogen kjendelig Indvirkning pan 
■•"olehornene selvi. Derved biiver Kleebeskivens Fod fri, og i 
samnie Nu retter den boiede Fod sig ud med en saadan 
[vraft, at den slynger Klaebeskiven frem og flyver 2 — 3 
Fod ud i Luften medforende Stovmasserne. Klaebeski 
ven slynges altid foran og vil after al Sandsynlighed 
trffffe det Insekt i Hovedet, som ved at gnave paa Laeben 
og saaledes at berore Folehornene bar bevirket Explosio- 
nen. Her hajfter den sig fast, og Stovmassen fores saa- 
ledes med, indtil den paa Monachanthus, — hvor hele 



307 

dette Apparat mangier, men hvor der i Stedet er et klaib- 
rigt Ar — finder en Plads beredt for Stevet. Kolehornene 
ere det eneste Sted i Blomsten, hvis Heroring befrier 
St0vmasserne, men de udfere det ogsaa med Sikkerhed. 
I Sandhed, en mserkelig Foranstaltning! Stevmasserne ud- 
sendes som Pile, der maa tra;ffe Insekferne for saaiedes 
at bortferes til det Sted, hvor de skiilie virke. En sind- 
rigere Tilpasning Andes vel neppe nogensteds i Naturen. 
Det er vist intet forgjaives Elaab, Darwin udtaler, at 
iMeddelelsen af disse Kjendsgjerninger fra Orchideernes 
eiendomraeligt og mangfoldigt uddannede Familie vil for- 
anledige , at mange iagttage de indonlandske Arters Liv 
noiere. En Undersogelse af deres sindrige Indretninger 
kan ikke andet end give mange et hoiere Begreb om 
hele Planteriget og vil vaere tiltaJende saavel for den, der 
anseer alt i det for afhaengigt af Naturlove, som for den, 
der i alt seer Skaberens umiddelbare Indgriben. 



21 



He mpuuoskelignende Abcr: Orang'ens, €hiiu|)anseii$ 
og Gibboiioriies Leveniaade ug iXatiirhijttoric. 

Eitcr Huxlejs » Evidence as to man':- place in natiue«. Lonilon. 1864. 



Opflrgsmaalet om Menneskets Forhold til Dyreriget og 
navnlig til Aberne, i systematisk Henseende, har ol'tere 
vaeret paa Bane og er navnlig bleven meget dreftet i de 
senere Aar, da Sporgsmaalet om Arterues Oprindelse 
og det hele organiske Livs L'dviklingsliistorie paa Jorden 
har sat ikke alene den videnskabelige Verden, men og- 
saa den uvidenskabelige (men just ikke ulidenskabelige) 
Almeenhed i eo \is IJevaegelse. Anskiielserne have staaet 
saa langt fra hverandre, som vel var muHgt; medens 
nogle oprettede el eget Rige for Mennesket*), ansaae 
andre Slaegtskabet meliem Mennesket og Aberne for at 
vaere saa inderligt, at de ikke toge i Bet^nkning at er- 
klaere, at Mennesket maatte nedstamme (gjennem den 
hypothetiske Darwinske Artsraetamorphose) fra en eller 
anden Abeform. Diskussionen herom bar bavt den gode 
Folge, at der derved er kastel en beel Deel Lys over 
Forholdet meliem Mennesket og Aberne i zoologisk Hen- 
seende; om de Kjendsgjerninger, som i denne Henseende 
korame i Betragtning, kan der i al Fald neppe disputeres 



*) See delte Tidsskrift •_' Raeklve. 3 Bri 



be /t> 



ME. DiRWIN ON THE DIMOBPHIC CO>'Dn'IO>; IN PRIMULA. /7 

Ccelanthium, limited to two Cape species, differs from Pliarna- 
ceum as Thylacospermum from Arenaria, by the uniou of the sepals 
at tlie base into a eampanulate tube, round the edge of which are 
inserted the stamens, being thus much more decidedly perigynoua 
than in the rest of the group. 

The genera Psammotroplie, Eckl. & Zeyh., and Polpoda, Presl, 
with uniovulate cells to the ovary, enumerated by Fenzl among 
Molluginese, appear to have nothing to distinguish them from true 
Phytolaccacese. Adenogramma, Presl, is also a Phytolaccaceous 
plant allied to Oiesehia, where the ovary and fruit are reduced to a 
single one-seeded carpel, not compounded of 2 or 3 carpels although 
one-seeded as in Paronychiaces. Acrossantlies, on the other hand, 
both in habit and character, belongs to the apetalous Ficoideas. 

IV. Pabonychiace^. 

Without having sufficiently examined all the genera of this Order 
to ascertain their limits with respect to each other, or the order 
of their arrangement, we have, however, verified the ordinal cha- 
racters in all the following (except Cardianema) : — 

1. Corrigiola, Linn, (an exceptional genus in its prominent petals 
and alternate leaves) ; 2. Herniaria, Linn. ; 3. Illecehrum, Linn. ; 
4. Cardionema, DC. ; 5. Pentaccena, Bartl. ; 0. Paronychia, Juss. 
(including Siphonychia, Torr. et Gray, and Anychia, Eich., and 
perhaps altogether, with Cardionema and Pentaccena, artificial sec- 
tions oi Illecebrum) ; 7. TIahrosia, Fenzl; 8. Sclerocephaliig,Tioiaa.; 
9. Gymnocarpos, Forsk. ; 10. Pterantlius, Forsk. ; 11. Cometes, 
Burm. ; 12. Picheranthtis,Wehh ; 13. Pollichia, Soland. ; 14. Gitil- 
leminea, H. B. et K. ; 15. JiLniarum, Forst. ; 16. Scleranthus, Linn. ; 
and 17. Lastarriea, A. Gay. 



On the Two Forms, or Dimorphic Condition, in the Species of Pri- 
mula, and on their remarkable Sexual Halations. By Chakles 
Dabwin, M.A., F.E.S., F.L.S., &c. 

[Kead Nov. 21, 1861.] 

If a large number of Primroses or Cowslips (P. vulgaris and veris) 
be gathered, they will be found to consist, in about equal numbers, 
of two forms, obviously differing in the length of their pistils and 
stamens. Florists who cultivate the Polyanthus and Auricula 
are well aware of this difference, and call those \\hich display the 
globular stigma at the moutli of the corolla '' pin-headed " or " pin- 
eyed," and those which display the stamens "thumb-eyed." I 

M,,. Hnt- Garde!!, 

'5 00 



78 



MB. 0. BARWIS OS THK DISIORPUIC CONDITION 



will designate the two forms as long-styled and short-styled. Those 
botanists with whom I have spoken on the subject have looked at 
the case as one of mere variability, which is far from the truth. 

In the Cowslip, in the long-styled form, the stigma projects just 
above the tube of the corolla, and is externally visible ; it stands 
high above the anthers, which are situated halfway down the tube, 




iKing- styled. 



Short-styled. 



and cannot be easily seen. In the short-styled form the anthers 
are attached at the mouth of the tube, and therefore stand high 
above the stigma ; for the pistil is short, not rising above halfway 
up the tubular corolla. The corolla itself is of a difi'erent shape in 
the two forms, the throat or expanded portion above the attach- 
ment of the anthers being much longer in the long-styled than in 
the short-styled form. Village children notice this diiference, as 
they can beat make necklaces by threading and slipping the corollas 
of the long-styled flowers into each other. But there are much 
more important differences. The stigma in the long-styled plants 
is globular, in the short-styled it is depressed on the summit, so 
that the longitudinal axis of the former is sometimes nearly double 
that of the latter. The shape, however, is in some degree variable ; 
but one difference is persistent, namely, that the stigma of the 
long-styled is much rougher: in some specimens carefully com- 
pared, the papillae which render the stigmas rough were in the long- 
styled form from twice to thrice as long as in the short-styled. 
There is anotlier and more remarkable difference, namely, in the 
size of the pollen-grains. I measured with the micrometer many 



IN THE Sl'KCIES OF PRIMULA. 79 

specimens, dry and wet, taken from plants growing in difterent 
situations, and always found a palpable difference. The measure- 
ment is best made with grains distended with water, in which case, 
the usual size of the grains from short-styled flowers is seen to be 
~T6o5^ of an inch in diameter, and those from the long-styled about 
M^go of an inch, which is in the proportion of three to two ; so that 
the pollen-grains from the short stamens are plainly smaller than 
those from the long stamens which accompany the short pistil. 
When examined dry, the smaller grains from the long-styled plants 
are seen under a low power to be more transparent than the larger 
grains, and apparently in a greater degree than can be accounted 
for by their less diameter. There is also a difference in shape, 
the grains from the short-styled plants being nearly spherical, 
those from the long- styled being oblong with the angles rounded ; 
this difference in shape disappears when the grains are distended 
with water. Lastly, as we shall presentl)- see, the short- styled 
plants produce more seed than the long-styled. 

To sum up the differences : — The long-styled plants have a mucli 
longer pistil, with a globular and much rouglier stigma, standing 
high above the anthers. The stamens are short ; the grains of 
pollen smaller and oblong in shape. The upper half of the tube 
of the corolla is more expanded. The number of seeds produced is 
smaller. 

The short-styled plants have a short pistil, half the length of the 
tube of the corolla, with a smooth depressed stigma standing be- 
neath the anthers. The stamens are long ; the grains of pollen 
are spherical and larger. The tube of the corolla is of the same 
diameter tiU close to its upper end. Tlie number of seeds pro- 
duced is larger. 

I have examined a large number of flowers ; and though the 
shape of the stigma and the length of the pistil vary, especially 
in the short-styled form, I have never seen any transitional grades 
between the two forms. There is never the slightest doubt under 
wliich form to class a plant. I have never seen the two forms on tlie 
same plant. I marked many Cowslips and Primroses, and found, 
the following year, that all retained the same character, as did 
some in my garden which flowered out of their proper season in 
the autumn. Mr. W. Wooler, of Darlington, however, informs 
us that he has seen the early blossoms on Polyanthuses which 
were not long-styled, bvit which later in the season produced flowers 
of this form. Possibly the pistils may not in these cases have 
become fully developed during the early spring. An excellent 



80 MR. C. DAEWIX Oil THE DliEORPHIC CONDITIO?)" 

proof of the permanence of the two forms is seen in nursery gar- 
dens, where choice varieties of the Polyanthus are propagated by 
division ; and T found whole beds of several varieties, each consisting 
exclusively of the one or the other form. The two forms exist iu 
the wild state in about equal numbers : I collected from several 
different stations, taking every plant which grew on each spot, 
522 umbels ; 241 were long-styled, and 281 short-styled. No dif- 
ference in tint or size could be jjerceived iu the two great masses 
of ilowers. 

1 examined many cultivated Cowslips (P. veris) or Polyanthuses, 
and Oxllps ; and the two forms always presented the same differ- 
ences, including the same relative difference in tlie size of the 
pollen-grains. 

Frimula Auricula presents the two forms ; but amongst the 
improved fancy kinds the long- styled are rare, as these are less 
valued by florists, and seldomer distributed. There is a much 
greater relative inequality in the length of the pistils and stamens 
than in the Cowslip, the pistil in the long-styled form being neai-ly 
fonr times as long as in the short-styled, in which it is barely 
longer than the ovarium ; the stigma is nearly of the same shape 
in both forms, but it is rougher in the long-styled, though the 
difference is not so great as in the two forms of the Cowslip. In 
the long-st}led plants the stamens are very short, rising but little 
above the orarium. The poUen-grains of these short stamens from 
the long-styled plants, when distended with water, were barely 
gifdo of an inch in diameter, whereas those from the long stamens 
of the short-styled plants were barely g-a'aoi showing a relative 
difference of five to seven. The smaller grains of the long-styled 
plants were much more transparent, and before distention with 
water more triangular in outline than those of the other form. 
In one anomalous specimen with a long pistil, the stamens almost 
surrounded the stigma, so that they occupied the position proper 
to the stamens of the short-styled form ; but the small size of the 
pollen-grains showed that these stamens had been abnormally de- 
veloped in length, and that the anthers ought to have stood at the 
base of the corolla. 

In the two forms of Primula Sinensis, the pistil is about twice as 
long in the one as in the other. The stigma of the long-styled 
varies much in shape, but is considerably more elongated and 
rougher than that of the short-styled, the latter being nearly 
smooth and spherical, but depressed on the summit. The shape 
of the throat of the corolla in the two forms differs as in the Cow- 



IS THE SPECIES OE PMMfLA. 81 

slip, as does the length of the stamens. But it is remarkably that 
the pollen-grains of both forms, wet and dry, presented no differ- 
ence in diameter ; they vary somewhat in size, as do the pollen- 
grains of all the species, but in both forms the average diameter 
was ratlier above -^^%g of an inch. There is one remarkable dit- 
ference in the two forms of this species, namely (as we shall pre- 
sently more fully see), that the short -styled plants, if insects be 
excluded and there be no artifleial fertdization, are quite sterile, 
whereas the long-styled produce a moderate quantity of seed. But 
when both forms are properly fertilized, the short-styled flowers 
(as with Cowslips) yield more seed than the long-styled. In a lot 
of seedlings which I raised, there were thirteen long-styled and 
seven short-styled plants. 

Of Primula ciliata a long-styled specimen, and of P. ciliata, var. 
pwrpurata, a short- styled specimen, were sent me from Kew by 
Prof. Oliver. This case, however, is hardly worth giving, as the 
\axietj purpurata is said* to be a hybrid between this species and 
P. auricula ; and the height of the stamens in the one form does not 
correspond with tlio height of the stigma in the other, as they 
would have done had they been the same sjjecies. There was, 
however, the usual difference in the roughness of the stigmas in 
the two forms, and the pollen-grains, distended in water, measured 
gg^ and ^ of an inch in diameter. Single trusses were sent me 
of P. denticulata and P. Piedmontana whichi were long-styled, and 
of P. maryinata and nivalis which were shorfc-styled ; and the 
general character of the organs leaves hardly any doubt on my 
mind that these species are dimorphic. In a single flower of P. 
Sibirica, however, which was sent me from Kew, the stigma reached 
up to the base of tlie anthers ; so that this species is not dimorphic, 
or not dimorphic as far as the length of the pistil and stamens are 
concerned, unless indeed this single specimen was anomalous, like 
that mentioned of P. auricula. 

We thus see that the existence of two forms is very general, if 
not universal, in the genus Primula. The simple fact of the 
pollen-grains differing in size and outline, and the stigma, in shape 
and rouglmess, in two sets of individuals of the same species, is 
curious. But what, it may be asked, is the meaning of these 
several differences? The question seems worthy of careful inves- 
tigation, for, as far as I know, the use or meaning of dimorphism 
in plants has never been explained ; hence, I w ill give my obser- 

* Sweet's ' JHowcr Garden,' rol. v. (ab. 123. 
LINK. mOC DOTAiyY. VOL. VI. (■ 



82 



MB. C. DARWIN 0>- THE DIMOIiPHIC CO'DITIOS 



vationa in detail, tlioiigh I am far from supposing that all cases of 
dimorphism are alike. The first idea which naturally occurred 
was, that the species were tending towards a dioicous condition ; 
tliat the long-styled plants, with their rougher stigmas, were more 
feminine in nature, and would produce more seed ; that the short- 
styled plants, with their long stamens and larger pollen-grains, 
were more masculine in nature. Accordingly, in 1860, I marked 
some Cowslips of both forms growing in my garden, and others 
growing in an open field, and others in a shady wood, and gathered 
and weighed the seed. In each of these little lota the short-styled 
plants yielded, contrary to my expectation, most seed. Taking 
the lots together, the following is the result : — 





No. of 
Plants. 


No. of 1^0. of 
Umbels Capsules 
produced, produced. 


WJight of 
seed in 
grains. 


Slioi-t-styled Cowslips 
Long-styled Cowslips 


9 
13 


33 199 
51 201 


83 
91 



If we reduce these elements for comparison to similar terms, ' 
have — 





No. of 
Plants. 


Weight 

of seed in 

grains. 


No. of ^«ft 
U-l"^''- seed. 


No. ot 
Capsules. 


Weight 

of seed in 

grains. 


Short-styled Cowslips 
Long-styled Cowslips 


10 
10 


92 
70 


100 
100 


251 

178 


100 

.100 


41 i 

34 ; 



So that, by all the standards of comparison, the short-styled are 
the most fertile ; if we take the number of umbels (which is the 
fairest standard, for large and small plants are thus equalized), the 
short-styled plants produce more seed than the long-styled, in the 
proportion of four to three. 

In 1861 I tried the result in a fuller and fairer manner. I 
transplanted in the previous autumn a number of wild plants 
into a large bed in my garden, treating them all alike ; tlie result 



Short-styled Cowslips . 
Long-styled Cowslips , 



No. of I No. of 
Plants, j Umbels. 



47 

58 



I Weight of 
seed in 
grains. 



173 
208 



745 
692 



IN THE SPECIES OF PBIMULA. bS 

These figures, reduced as before, give the following proportions : — 





Number 
of 

Plants. 


Weight of 
seed in 
graiaa. 


Number 

of 
Umbels. 


Weight of 
seed in 
grains. 


Short-styled Cowslips . . . 
Long-styled Cowslips . . . 


100 
100 


1585 
1093 


100 
100 


4.30 
332 



The season was much better this year than the last, and the 
plants grew in good soil, instead of in a shady wood or struggling 
with other plants in the open field ; consequently the actual pro- 
duce of seed was considerably greater. Nevertheless we have the 
same relative result ; for the short-styled plants produced more 
seed than the long-styled in the proportion of tliree to two ; but if 
we take the fairest standard of comparison, namely, the number of 
umbels, the excess is, as in the former case, as four to three. 

I marked also some Primroses, all growing together under the 
same conditions ; and we here see the product ; — 





No. of 
Plants. 


Total 
So. of 
Cap- 
sules. 


Good -y'S''^ 

Cap- i°f?™<' 

sules. 1 '^ 

! grains. 


Or by Calcu- 
lation '• 


Good 
Cap- 
sules. 


1 
Weight 

seed. 


Short-styled Primroses 
Long-styled Primroses 


8 
9 


49 

68 


40 

50 


16 
10 


100 
100 


40 
20 



The number of Primrose plants tried was hardly sufficient, and 
the season was bad ; but we here again see (excluding the capsules 
which contained no seed) the same result in a still more marked 
manner, for the short-styled plants were twice as productive of 
seed as the long-styled plants. 

I had, of course, no means of ascertaining the relative fertility of 
the two forms of the Chinese Primrose in a natural condition, and 
the result of artificial fertilization can hardly be trusted ; but sis- 
teen capsules from long-styled flowers, properly fertilized, produce 
9'3 grains' weight of seed, whereas eight capsules of short-styled 
flowers produced 61 grains ; so that if the same number, namely, 
16 of the latter, had been fertilized, the weight of seed would have 
been 12'2, which would have been nearly in the proportion of four 
to three, as in Cowslips. 

Looking to the trials made during two successive years on the 
large number of Cowslips, and on these facts with regard to com- 
mon Primroses and Chinese Primroses, we may safely conclude 
that the short-styled forms in these species are more productive 

G 2 



84 



MH. C. DABWIN OX THE DIMOBPHIC CONDITION 



than the long-stvled forms ; consequently the anticipation that the 
plants having largely developed pistils with rougher stigmas, and 
having shorter stamens with smaller pollen-grains, would prove to 
be more feminine in their nature is exactly the reverse of the 
truth. If the species of Frimula are tending to become dioicous, 
which possibly may be the case, the future hypothetical females 
would have short pistils, and the males would have short stamens ; 
but this tendency is accompanied, as we shall presently see, by 
other conditions of the generative system of a much more singular 
nature. Anyhow, the possibility of a plant thus becoming dioicous 
by slow degrees is worthy of notice, as the fact would so easily 
escape observation. 

In 1860 I found that a few umbels of both long-styled and 
short-styled Cowslips, which were covered by a net, did not pro- 
duce seed, though other umbels on the same plants, artificially fer- 
tilized, produced an abundance of seed ; and this fact shows that 
the mere covering in itself was not injurious. Accordingly, in 
1861 I covered up under a similar net several plants just before 
they opened their flowers ; these turned out as follows : — 





No. of 

Plants. 


No. of 
Umbels 
produced, 


Product of Seed. \ 

1 


Short-styled .... 


6 

18 


2i 
74 


1-3 grains, or 50 seeds.' 
Not one seed. | 


Long-styled 



Judging from the exposed plants which grew all round in the 
same bed, and had been treated in every way exactly the same, 
except that they were exposed to the visits of insects, the six short- 
styled plants ought to have produced 92 grains' weight of seed in- 
stead of only 1-3 ; and the eighteen long-styled plants, which pro- 
duced not one seed, ought to have produced above 200 grains' 
weight. The production of the 1-3 grain of seed in the smaller 
lot was probably duo to the action of Thrips or some minute in- 
sect. This evidence is sufficient, but I may add that ten pots of 
Polyanthuses and Cowslips of both forms, protected from insects 
in my greenhouse, did not set one pod, though artificially fertilized 
flowers in other pots produced an abundance. So we see that the 
visits of insects are absolutely necessary to the fertilization of 
Cowslips. As the exposed plants produced an abundance of seed, 
the tendency to a dioicous condition, previously remarked on, 
might have been safely carried on, as we see that there is an effect- 



W THE SPECIES Or PRIMULA. 85 

ive agency already at work wliicli would have carried pollen from 
one sex to the other. 

"What insects habitually visit Cowslips, as is absolutely necessary 
for their regular fertility, I do not know. I have often watched 
them, but perhaps not long enough ; and only four times I have 
seen Humble-bees visiting them. One of these bees was gathering 
poUeu from short-styled flowers alone, another had bitten holes 
through the corolla ; and neither of these would have been effective 
in the act of fertilization : two others were sucking long-styled 
plants. I have watched Primroses more attentively during several 
years, and have never seen an insect visit tliem ; yet from their close 
similaritj' in all essential respects to Cowslips, there can hardly be 
a doubt that they require the visits of insects. Hence I am led 
to suppose that both Primroses and Cowslips are visited by motlis. 
All the species which I- have examined secrete plenty of nectar. 

In Primula Sinensis, when protected from insects and not arti- 
ficially fertilized, tiie case is somewhat, but not materially, different. 
Five short-styled plants produced up to a given period 116 flowers, 
which set only seven capsules, whereas twelve other flowers on 
the same plants artificially fertilized set ten capsules. Five long- 
styled plants produced 147 flowers, and set sixty-two capsules ; so 
that this form, relatively to the other, sets afar greater number of 
capsules : yet the long-styled protected flowers do not set nearly 
so well as when artificially fertilized ; for out of forty-four flowers 
thus treated, thirtj'-eight set. These remarks apply only to the 
early setting of tlie capsules, many of which did not continue 
swelling. With respect to the product of seed, seven protected 
short-styled plants, which bore about 160 flowers, produced only 
lialf a grain of seed ; they ought to have produced 120 grains : so 
that the short-styled plants, when protected from insects, are nearly 
as sterile as Cowslips. Thirteen long- styled plants, which bore 
about 380 flowers, and which as we have seen set many more cap- 
sules, produced 25'9 grains of seed ; they ouglit to have produced 
about 220 grains in weight': so that although far less fertile tlian 
the artificially fertilized flowers, yet the long-styled P. Sinensis, 
w'hen protected from insects, is nearly twenty-four times as fertile 
as the short-styled when protected from insects. The cause of 
this difference is, that when the corolla of the long styled plants 
falls oflf, the short stamens near the bottom of the tube are neces- 
sarily dragged over the stigma and leave pollen on it, as I saw by 
hastening the fall of nearly withered flowers ; whereas in the short- 
styled flowers, the stamens are seated at the mouth of the corolla, 



86 MB. C. DAB,WI>' 0:S THE DlilOHPHIC COXBITIOS 

and in falling off do not brush over the lowly seated stigma. In 
the Cowslip the coroUa does not fall off; and both long-styled and 
short-styled plants are equally sterile when protected from insects. 
It is a rather cvirious case, that the falling of the corolla, or its re- 
maining attached when withered, might have a considerable in- 
fluence on the numbers of a plant, during a year unfavourable to 
the visits of the proper insects. 

In three short-styled plants of Primula auricula, protected from 
insects, the flowers which I fertilized produced seed, but those 
which were not touched produced none. 

In all the species of Primula the pollen readily coheres to any 
object. In all that I have observed, though the stamens and pis- 
tils differ in length relatively to each other in the different species, 
yet, in the two forms of the same species, the stigma of the one 
form stands at exactly the same height with respect to the corolla 
as the anthers of the other form. If the proboscis of a dead 
Humble-bee, or thick bristle, or rough needle be pushed down the 
corolla, first of one form, and then of the other, as an insect would 
do in visiting the two mingled forms, it will be found that pollen 
from the long-stamened form will adhere round the base of the 
proboscis, and will be left with certainty on the stigma of the long- 
styled form ; pollen from the short stamens of the long-styled 
form wOl also adhere a little above the tip of the proboscis, and 
some wiU generally be left on the stigma of the other form. Thiis 
pollen will be carried lecipTocally from one form to the other. In 
withdrawing the proboscis from the long-styled form, with poUen 
adhering near the tip, there will be a good chance of some being 
left on the flower's own stigma, in which case there wiU he self- 
fertilization ; but this by no means always occurs. In the short- 
styled form, on the other hand (and it is important to remember 
this), in inserting the proboscis between the anthers situated at 
the mouth of the corolla, poUen, as I repeatedly found, is almost 
invariably carried down and left on the flower's own stigma. 
Moreover minute insects, such as Thrips, numbers of which I have 
observed in Primrose flowers thickly dusted with pollen, could not 
fail often to cause self-fertilization. We positively know that the 
visits of large insects are necessary to the fertilization of the species 
of Primula ; and we may infer from the facts just given that these 
visits would carry pollen reciprocally from one form to the other, 
and would likewise tend to cause self-fertilization, more especially 
in the short-styled (i. e. long-stamened) form. 

These observations led me to test the potency of the two pol- 



IN THE SPECIES OF PBIMULA.. 



87 



lens with respect to the two stigmas iu F. veris, Sinensis, and 
auricula. In each species four crosses can be tried ; namely, the 
stigma of the long-styled by its own-form jJoUen and by that of 
the short-styled, and the stigma of the short-styled by its own- 
form pollen and by that of the other form. It is necessary to use 
and remember two new terms for these crosses : when the long- 
and the short-styled stigmas are fertilized by their own-form pol- 
len the union is said to be " homomorphic ;" when the long-styled 
and short-styled stigmas are fertilized by tlie pollen of the other 
form, the union is " heteromorphic." I speak of the " own-form 
pollen," because in the following homomorphic unions, iu order 
to make the experiment perfectly fair, I never placed the pollen 
of the same flower on its own stigma, but, to avoid the possible ill 
effects of close interbreeding, I always used the pollen from an- 
other plant of the same form. In the following experiments all 
the plants were treated in exactly the same manner, and were 
carefully protected from insects as far as that is possible. I per- 
formed every manipulation myself, and weighed the seed in a che- 
mical balance. Some of the capsules contained no seed, or only 
two or three, and these are excluded in the column marked " good 
pods." First for P. Sinensis, as the simplest case. 



Primula Sinensis. — Table I. 





'S^.ri 


1 "S ri 


t-_- 


^ -. 


By Calculation. 




"a fS^ 


III! 






Good ( ^^'«'8^' of 




S eg 


tng^o 


^•o^ 


;slfe 


PodT- '«<"» 




^ "S 


g a 






( grains. 


Long-styled by own- 












form pollen (homo- 


20 


18 


13 


5-9 


or as 100 to 43 


morphic union) .... 












Long-styled by pollen' 












of short-styled (hete- • 


24 


18 


16 


9-3 


or as 100 to 58 


romorphic union)... 












Short-styled by own- 












form pollen (homo- ■ 


7 


6 


4 


0-9 


or as 100 to 22 


morphic union) 






• 






Short-styled by pollen ' 












of long-styled (hete- [• 


8 


8 


8 


61 


or as 100 to 76 


romorphic union). . . J 












Summary : 












The two homomorphic 1 
unions J 


27 


23 


17 


6-8 














The two heteromorphic 1 
unions J 


32 


26 


24 


15-4 















For the sake of comparison, we may reduce these latter figures 
as follows : — 



88 



ME, C. DABWIS 0>' THE DIMOKPHIC CO>'DITIO:S 





Number of Ufumber 
flowers of good 
fertilized. poda. 


Weight of. 
seed in ; 
grains. 


Number 
of good 
podg. 


Weight of 
seed in 
grains. 


The two homomorphic 1 
unions j 

The two heteromor- \ 
phic unions J 


100 
100 


63 

75 


25 

48 


100 
100 


40 
64 



In the first part of the xipper table, the number of flowers fer- 
tilized and the simple result is shown ; and at the right hand, for 
the sake of comparison, the calculated product of the weight of seed 
from 100 good pods of each of the four unions is given ; showing 
that in each case the heteromorphic union is more fertile than the 
homomorphic union. Beneath we have a simple summary of the 
two homomorphic and the two heteromorphic unions. And lastly, 
for the sake of comparison, a calculation has been made from this 
summary ; first, assuming that 100 flowers of both kinds of unions 
were fertilized ; and then to the right hand, assuming that 100 
good pods were produced from both unions. If we compare the 
result, we see that the flowers of the two heteromorphic unions 
produced a greater number of good pods, and a greater weight of 
seed, than the flowers of the two homomorphic unions ; and again 
(and this is the fairest element of comparison, for accidents are 
thus almost eliminated), that the good pods from the two hetero- 
morphic unions yielded more seed, in about the proportion of three 
to two, than those from the two homomorphic unions. The dif- 
ference in weight from 100 capsules of the two forms is 24 grains, 
and this is equal to at least 1200 seeds. 

Beneath we have Table 11. of P. veris, or the Cowslip. The 
upper part is exactly the same as in the Table of P. Sinensis, and 
we see ia each case that the heteromorphic is more fertile than 
the homomorphic union. The calculated results irom the sum- 
mary of the two homomorphic and the two heteromorphic unions 
are more complex than with the last species, as I wished to show 
that, however we proceed, the general result is the same. We see 
that the assumed hundred flowers, heteromorphically fertilized by 
the pollen of the other forms, yielded more capsules, more good 
capsules, and a greater weight of seed ; but I rely little on this, as 
some whole umbels perished after being fertilized. The fairest 
element of comparison is to take the good capsules alone ; and we 
here see that tlie 100 from the two heteromorphic unions yielded 
seed which in weight was as 54 to 35 from the 100 good capsules 



IIJ THE SPECIES OF PfilMULA. 



89 



of the two homomorphic unions, — that is, nearly as three to two, 
as in the Chinese Primrose. 



Primula veris. — Table II. 





111 


Total 
number of 

poda 
produced. 


Number 

of good 

pods. 




By Calculation. 

Good r ■"''■'«i'' "f 


Long-styled by own- 












form pollen (homo- 


20 


8 


5 


21 


or as 100 to 42 


morphic union) .... 












Long-styled by pollen 












of short-styled (hete- I 


22 


15 


14 


8-8 


or as 100 to 62 


romorphic union)... 












Short-styled by own- 
form pollen (homo- ^ 
morphic union) 












15 


8 


6 


1-8 


or as 100 to 30 












Short-styled br pollen ] 












of long-styled (hete- i 


la 


13 


11 


4-9 


or as 100 to 44 


romorphic union)... J 












Summary : 












The two homomorphic \ 


35 
35 


16 

27 


11 
25 


39 
13-7 




The two heteromorphic 1 
unions / 



For the sake of comparison, we may reduce these figures as fol- 
lows : — 





111 


Total 
tlumber of 

produced. 


111 
1*3 =■ 


Is. 


Total 

number of 

pods 

1 produced. 


"Ss" 




Is.- 

Ill 


The two ho- ^ 
















momorphic I 


100 


45 


31 


11 


100 


24 


100 


35 


unions 


















The two hete-] 


















romorphic K 


100 


77 


71 


39 


100 


50 


100 


54 


unions J 



















"With P. auricula I was unfortunate ; my few seedlings, except 
one poor plant, all came up short-stj'led ; and of these plants 
several died or became sick, owing to the hot weather and the dif- 
ficulty of excluding insects and ventilating the corner of my green- 
house enclosed with net. I finally got only two pods from one 
union, and three from the other. The result is given in the 
following table ; and, though worth little, we here again see that 
the heteromorphic are far more fertile than the homomorpliio 
unions. 



90 MR. C. DARWIN ON THE DIMOKPillC CONDITION 

Primula auricula, — Table III. 






Short-styled by own-form pol- 1 

len (homoru Orphic union) ., J 

Short styled by pollen of long- 1 

styled (heteromorphic union) J 




0-12 
1-50 



, Weight of 
Good } seed in 
Pods. ^ grains. 



or as 100 to 12 
or as 100 to 50 



Whoever will study these three tables, which give the result 
of 134 flowers carefully fertilized and protected, will, I think, be 
convinced that in these three species of Frinnila the so-called 
heteromorphic unions are more fertile than the homomorphic 
unions. For the sake of clearness, the general result is given in 
the following diagram, in which the dotted lines with arrows re- 
present how in the four unions pollen has been applied. 

Heteromorphic union. 
Complete fertility. 



Homomorphic 

union. 

Incomplete 

fertility. 




Homomorphic 

union. 

Incomplete 

fertility. 



"We here have a case new, as far as I know, in the animal and 
vegetable kingdoms. We see the species of Primula divided into 
two sets or bodies, which cannot be called distinct sexes, for both 
are hermaphrodites ; yet they are to a certain extent sexually 
distinct, for they require for perfect fertility reciprocal union. 
They might perhaps be called sub-dioicous hermaphrodites. As 
quadrupeds are divided into two nearly equal bodies of different 
sexes, so here we have two bodies, approximately equal in number, 



IN THE SPECIES OE PHIMULA. 91 

differing in their sexual powers and related to each other like males 
and females. There are many hermaphrodite animals which can- 
not fertilize themselves, but must unite with another hermaphro- 
dite : so it is witli numerous plants ; for the pollen is often mature 
and shed, or is mechanically protruded, before the flower's own 
stigma is ready ; so that these hermaphrodite flowers absolutely 
require for their sexual union the presence of another hermaphro- 
dite. But in Primula there is this wide difference, that one indi- 
vidual Cowslip, for instance, though it can with mechanical aid im- 
perfectly fertilize itself, for full fertility must unite with another 
individual ; but it cannot unite with any individual in the same 
manner as an hermaphrodite Snail or Earth-worm can unite with 
any other one Snail or Earth-worm ; but one form of the Cowslip, 
to be perfectly fertile, must uuite with one of tlie other form, just 
as a male quadruped must and can uuite only with a female. 

I have spoken of the heteromorphic union in Primula as result- 
ing in full fertility ; and I am fully justified, for the Cowslips thus 
fertilized actually gave rather more seed than the truly wild plants 
— a result which may be attributed to their good treatment and 
having grown separately. With respect to the lessened fertility 
of the homomorphic unions, we shall appreciate its degree best by 
the following facts. Gartner has estimated the degree of sterility 
of the union of several distinct species *, in a manner which allows 
of the strictest comparison with the result of the heteromorphic 
and homomorphic unions of Prim ida. Witli P. veris, for ewerj hun- 
dred seeds yielded by the heteromorphic unions, only sixty-four seeds 
were yielded by an equal number of good capsules from the homo- 
morphic unions. With P. Sinensis the proportion was nearly the 
same — namely, as 100 to 62. Now Glartner has shown that, on the 
calculation of Verbascum lychiitis yielding with its own pollen 
100 seeds, it yields when fertilized by the pollen of V. Piiceiiiceum 
ninety seeds ; by the pollen of V. nigrum, sixty-three seeds ; by 
that of V. llattaria, sixty-two seeds. So again, Biantlius harhatus 
fertilized by the pollen of D. superbus j-ielded eighty-one seeds, 
and by the pollen of JD. Japonicus sixty-six seeds, relatively to 
the 100 seeds produced by its own pollen. Thus we see— and the 
fact is highly remarkable — that the homomorphic unions relatively 
to the heteromorphic unions in Primula are more sterile than the 
crosses between several distinct species relatively to the pure union 
of those species. 

The meaning or use of the existence in Primula of the two 
* Versuehe iiber die Bastarderzeugung, 1849, s. 216. 



92 ilE. C. DAKWIN OK THE DIMORPHIC CONDITION 

forms in about equal numbers, with their pollen adapted for reci- 
procal union, is tolerably plain ; namely, to favour the intercross- 
ing of distinct individuals. With plants there are innumerable 
contrivances for this end ; and no one will understand the final 
cause of the structure of many flowers without attending to this 
point. I have already shown that the relative heights of the an- 
thers and stigmas in the two forms lead to insects leaving the 
pollen of the one form on the stigma of the other ; but, at the same 
time, there will be a strong probability of the flower's own pollen 
being likewise placed on the stigma. It is perfectly well known 
that if the pollen of several closely allied species be placed on the 
stigma of a distinct species, and at the same time, or even subse- 
quently, its own pollen be placed on the stigma, this wUl entirely 
destroy the simultaneous or previous action of the foreign pollen. 
So again if the pollen of several varieties, including the plant's own 
pollen, be placed on the stigma, one or more of the varieties will 
take the lead and obliterate the efiiect of the others : but I have 
not space here to give the facts on which this conclusion is 
grounded. Hence we may infer as highly probable that, in Pri- 
mula, the heteromorphic pollen which we know to be so much the 
most effective would obliterate the action of the homomorphic 
pollen when left on the flower's own stigma by insects ; and thus 
we sec how poteut the dimorphic condition of the pollen in Pri- 
mula will be in favouring the intercrossing of distinct individuals. 
The two forms, though both sexes are present in each, are in 
fact dioicous or unisexual. Whatever advantage there may bo in 
the separation of the sexes, towards which we see so frequent a 
tendency throughout nature, this advantage has been here so far 
gained, that the one form is fertilized by the other, and conversely ; 
and this is effected by the pollen of each form having less po- 
tency than that of the other on its own stigma. 

Bearing on this view of the final cause of the dimorphism of the 
Primulas, there is another curious point. If we look at the right- 
haud figures of the four first lines in the previous tables of P. Si- 
nensis and veris, we shall see that one of the homomorphic unions, 
namely, the short-styled by its own-form pollen, is considerably 
more sterile than the other ; and in P. auricula, though here there 
is no other homomorphic union as a standard of comparison, this 
union is likewise excessively sterile. That the fertility of this 
union is really less in a marked degree than in the other three 
unions, we have an independent proof in the seeds germinating less 
perfectly and much more slowly than those from the other imions. 



Ilf THE SPECIES OF PHIMtJLA, 93 

This fact is the more remarkable, because we have clearly seeu 
that tlie short-styled form in the Cowslip in a state of nature is 
the most productive of seed. This form bears its anthers close 
together at the mouth of the corolla, and I observed long before 
I had ascertained the relative fertility of the four unions, in 
passing the proboscis of a dead Humble-bee or bristle down the 
the corolla, that in this form the flower's own pollen was almost 
certain to be left on its own stigma; and, as I wrote down at the 
time, the chance of self-fertilization is much strouger in this than 
in the other form. On this view we can at once understand the 
good of the pollen of the short-styled form, relatively to its own 
stigma, being the most sterile ; for tliis sterility would be the most 
requisite to check self-fertilization, or to favour intercrossing. 
Hence, also, it would appear that there are four grades of fertility 
from the four possible unions in PrimziJa ; ot the two homomor- 
phic unions, as we have just seen, one is considerably more sterile 
than the other. In the wild state we know that the sliort-styled 
plants are more fertile than tlic long-styled ; and we may infer as 
almost certain, that in the wild state, when the flowers are visited 
by insects, as is absolutely necessary for the production of seed, 
and when pollen is freely carried from one form to the other, 
that the unions are heteromorphic ; if so, there are two degrees of 
fertility in the heteromorphic unions, making altogether four 
grades of fertility. 

Two or three other points deserve a passing notice. The ques- 
tion whether the Primrose and Cowslip (P. vulgaris and veris) are 
distinct species or varieties has been more disputed and experi- 
mented on than in any other plant. But as we now know tliat 
tlie visits of insects are indispensable to the fertilization of these 
plants, and that in all probability the heteromorphic pollen of a 
Primrose would be prepotent on the stigma of a Cowslip over the 
homomorphic poUeu of a Cowslip, the numerous experiments which 
liave been made, showing that Oilips appear amongst the seed- 
lings of Cowslips, cannot be trusted, as the parent plants do not 
appear to have been carefully protected from insects*. I am far 
from wishing to affii-m that pure Cowslips will not produce Ox- 

* Mr. Sidebotham (Phytologist, vol. iii. pp. 703-5) states that he protec^ed liis 
plants from crossing ; but as he gives in detail all the precautions which he took, 
and says nothing about artificial fertilization, we may conclude that he did not 
fertilize his plants. As he raised very numerous seedlings, he woiJd Imvchad to 
fertilize many flowers, if they had been really well guarded against the visits of 
iuseetB. Hence I conclude that his results arc not wortl)y of trust. 



94 MB. C. DAKWI^' ON THE DIMOHPHIC CONDITION 

lips, but t'urtber experiments are absolutely necessary. We may 
also suspect that the fact noticed by florists*, that the varieties 
of the Polyanthus never come true from seed, may be in part 
due to their habitually crossing with other varieties of the Poly- 
anthus. 

The simple fact of two individuals of the same undoubted species, 
when homomorphically united, being as sterile as are many distinct 
species when crossed, will surprise those who look at sterility as a 
special endowment to keep created species distinct. Hybridizers 
have shown t that individual plants of the same species vary in 
their sexual powers, so far that one individual will unite more 
readily than another individual of the same species with a distinct 
species. Seeing that we thus have a groundwork of variability in 
sexual power, and seeing that sterility of a peculiar kind has been 
acquired by the species of Primula to favour intercrossing, those 
who believe in the slow modification of specific forma will natu- 
rally ask themselves whether sterility may not have been slowly 
acquu-ed for a distinct object, namely, to prevent two forms, whilst 
being fitted for distinct lines of life, becoming blended by marriage, 
and thus less well adapted for their new habits of life. But many 
great difiicultiea would remain, even if this view could be main- 
tained. 

Whether or not the dimorphic condition of the Priinula has 
any bearing on other points in natural history, it is valuable as 
showing how nature strives, if I may so express myself, to favour 
the sexual union of distinct individuals of the same species. The 
resources of nature are illimitable ; and we know not why the 
species of Primula should have acquired this novel and curious aid 
for checking continued self-fertilization through the division of the 
individuals into two bodies of hermaphrodites with different 
sexual powers, instead of by the more common method of the 
separation of the sexes, or by the maturity of the male and female 
elements at difi'erent periods, or by other such contrivances. Nor 
do we know why nature should thus strive after the intercrossing 
of distinct individuals. We do not even in the least know the final 
cause of sexuality ; why new beings should be produced by the union 
of the two sexual elements, instead of by a process of partheno- 
genesis. When we look to the state in which young mammals 
and birds are born, we can at least see that the object gained is 

» Mr. D. Beaton, in ' Journal of Horticulture,' May 28, 1861, pp. 154, 244. 
t Giirtncr, Bastarderzeuguiig, s. 165. 



IN THE SPECIES OF PBIMULA. 96 

not, as has sometimes been maintained, mere dissemination. The 
whole subject is as yet hidden in darkness. 

I will now only add that cases of dimorphism, like that of Pri- 
mula, seem to be far from rare in the vegetable kingdom, though 
they have been little attended to. A large and important class of 
analogous facts will probably soon be discovered. Professor Asa 
Grray* informs me, that he and Dr. Torrey have described several 
Eubiaceous genera, in which some plants have exserted stamens, 
and others exserted pistils. " Mitchella offers an interesting in- 
stance of this structure from its relationship, through Nertera, to 
Coprosma, one of the few dioecious genera of Miihiacete, and in 
which the stamens are elongated in the male flowers and the styles 
in the females." The long-styled hermaphrodite ilowers of Mit- 
chella would probably be found more productive of seed tlian the 
short-styled ; in the same way, but in a reversed manner, as in 
Primula, the short-styled flowers are more productive than the 
long-styled ; from which fact I inferred that, if Primula were to 
become dioecious, the females would have short pistils and the 
males short stamens, these being the corresponding organs neces- 
sary for a heteromorphic union with full fertility. In the dioBcious 
Coprosma, on the other hand, the females have long pistils, and 
the males have long stamens. These facts probably show us 
the stages by which a dioecious condition has been acquired by 
many plants. 

Prof. A. Gray also informs me that another Eubiaceous genus 
{Knoxia) in India has been described by Dr. Wight, with a 
similar structure ; and this, I am told, is the case with Cinchona. 
Several species of North Amei-ican Plantago are dimorphic, as is 
Phamnus lanceolatus, as far as its female organs are concerned. 
In the BoraginecB, Dr. Torrey has observed a strongly marked in- 
stance in Amsinckia spectahilis : in some dried flowers sent me by 
Prof. Grray, I find tliat the pistil in the one form is more than 
twice as long as in the other, with a corresponding difference in 
the length of the stamens ; in the short -styled flowers the grains 
of pollen, as in Primula, apparently are larger, in the proportion 
of nine to seven, than in the long-styled flowers, which have the 
short stamens ; but the difiference can hardly be determined with 
safety in dried flowers. In Mertensia alpina, another member of 

* See also Prof. Asa Gray's 'Manual of the Botany of the >f . United States,' 
1856, p. 171. For Plantago, see p. 269. 



96 MR. C. DAEWIN ON THE DIMOEPHIC CONBITIOTf IN PEIMULA. 

tlie Boraginece, Prof. Gray finds a new and inexplicable case, — 
namely, some specimens witli the stamens and pistil sub-esserted, 
and other specimens with loth organs seated low down the tube of 
the corolla. Dr. Torrey and Prof. Gray have designated aU such 
plants as " diceciously dimorphous." IntheXaJiatejMr.Bentham 
informs me that several species oiyEgiphyla, and some of Mentha, 
are dimorphic like Primula. The case of Thymus is different, as I 
know from my own observations ; but I will not here enlarge on 
this genus. Again, as I hear from Mr. Bentham, numerous species 
of Oxalis are similarly dimorphic. I can add the genus Linum. 
So that we already know of species (generally several in the same 
genus) having distinct dimorphic individuals, as far as structure 
is concerned, however it may prove in function, in no less than 
eight natural orders. 

AVith respect to Linum, I will not here enter on details, as I in- 
tend to try further experiments next summer ; but I may state, 
that 1 observed many years ago two forms in Linum flavmn, with 
both the pistils and stamens differing in length. In Linum grandi- 
florum there are likewise two forms which present no difference in 
their male organs, but the pistil and stigmatic surfaces are much 
longer in the one form than in the other. The short-styled form, 
I have good reason to believe, is liighly fertile with its own pollen ; 
whether it be more fertile with the pollen of the long-styled form, 
I cannot at present say. The long-styled form, on the other hand, 
is quite sterile with its own pollen : several plants grew in my 
garden, remote from the short-styled plants ; their stigmas were 
coloured blue with their own pollen ; but although they produced 
a vast number of flowers, they did not produce a single seed- 
capsule. It seemed a hopeless experiment ; but I had so much 
confidence from my trials on Primula, tliat I put a little pollen 
from the short-styled plants on the stigmas (already blue with 
. their own pollen) of twelve flowers on two of the long-styled 
plants. From these twelve flowers I got eight remarkably fine 
seed-capsules ; the other flowers not producing a single capsule. 
The existence of plants in full health, and capable of bearing 
seed, on which their own pollen produces no more effect than 
the pollen of a plant of a different order, or than so much in- 
organic dust, is one of the most surprising facts which I have ever 
observed. 



ox THE £XISTE^'■CE OF TWO FOR:\rS ly SPECIES OF T.jyvsz. 09 

ovgans are almost concealed by the spathe and bracts. Its nearest 
known ally is probably 11. rosti-ata, Euiz and Pavou, a native of 
Peru. Dr. Antlioine desires that this noble plant should bear the 
name of tlie Empress of Eussia, -nhicli I have therefore attached 
to it. 

Helicoxia Marine, Jlook.f. Folioi-imi vaginis trimcnm elatum effov- 
mantibus, lamina oblonga petiolata ampia, spicis longe peihmciilatis 
peiuluUs, spathis erebre dense disticho-imbricatis rachin omnino velan- 
tibus late ovato-eynibiformibus rccuryis obtusis, lloribus bracteis in- 
clusis gl.abratis. 

Hah. Betami on the Sinu River (lat. S^ X.), State of Rolivar, in Neir 
Granada [Jir. A. Anthoine). 

Truncus 3—1 metr., cam foliis G nietr., etiam 10-15 centimetr., laevis, 
viridi-purpureus {Aiith,). Folia oblonga v. lineari-oblonga, obtnsa, 
3-4 ped. longa, petiolo feqnilonga, viridia. Feduncidus crass, digiti, 
curvns, glaber, sicens flexnosus, teresj intus vasibus moUibus farctus. 
Spicie li ped. longas, 3-4 poll, latue, lineares, obtnsah, eompressse. 
Spathte 60-80, dense imbrieata;, refle.va?, valde concava?, late oxato^ 
cymbiformes, glabric v. pnbescentes, lateribns erectis, basin versns sub- 
oordatae, marginibus undidatis, apice obtusiuscuUc ; iufima; rostrata; ; 
inferiorcs 1-2 distantes, 4-5 unc. longa;, rachin pubescentera non 
tegentibns ; cscterie 2-2.J vmc. longs, rachin velantcs ; superiores in- 
feriorcs amplcctentes. Flores rubri (.-I?iM.), in spatha singula 15-20, 
bracteis lineari-lanceolatis glabriusculis inclusi, reccptacvdo brevissimo 
in axilla spathoe inserti ; apieibns periantliii tantum exsertis. Bractete 
alba;, spatha breviores, ovato-lanceolatce, basi concavae, exteriores vacuiE. 
Pedicelli A" longi, crassiuscnli, vlllosnli, compressi. Ovarium trigonum. 
Perianthium 1" long., foliolis extus subtomentosis. Stylus apice in- 
eurvns. Anthera inelusne. Dnipa Citrulea (Ant/i.), 3-cocca; coccis 
oblongis, couipressis, basi antice fovea cupubcforini notatis, subrugosis, 
osseis, intus subrugosis. Semen erectum; testa membranacea, raphe 
annular! circumdata. Alhitmen snbfarinaccuni. Mmbri/o a\iUaris, gra- 
cilis, cxtreniltate radiculari panlo crassiore, germinatione foveam cocci 
perforante. 



On the existence of two forms, and on their reciprocal sexual re- 
lation, in several species of the genua JAiimn, By CitA.Kl-E3 
Dabwik, ar.A., F.E.S., F.L.S., &c. 

[Bead February 5, 1863.] 
The crimson Linum grandiflorum presents two forms, occurring 
in about equal numbor.s, which differ little in structure, but greatly 
in function. The foliage, corolla, stamens, and poUen (e-vamiued 



Mo. Bot. Garden, 

1S96. 



70 ME. DAKTVIX OJf THE I;XISTI:^*CE or TWO rOEJIS 

dry, and distended witli vrater) are alike in both forms. The 
difference is confined to the pistil : in the one form, -n-hich I will 
call "short-styled," the column formed by the united styles, and 
the short stigmas, together is about half the length of the whole 
pistil io the other and " long-styled " form. A more important ■ 
distinction is, that the five stigmas in the short-styled form diverge 
greatly from each other and pass out between the filaments of the 
stamens, and thus lie within the tube of the corolla. In the 
long-styled form the elongated stigmas stand nearly upright, and 
alternate with the anthers. In this latter form the length of the 
stigmas varies considerably, their upper extremities projecting 
even a little above the anthers, or reaching up only to about their 
middle. Nevertheless there is never the slightest difficulty in 
distinguishing between the two forms ; for, besides the difference 
in divergence, the stigmas of the short-styled form never reach 
even to the bases of the anthers. In the short-styled, the papillae 
on the stigmatic surfaces are shorter, darker-colovired, and more 
crowded together than in the long-styled form : but these differ- 
ences seem due merely to the shortening of the stigma ; for in the 
varieties of the long-styled form with shorter stigmas, the papiUa; 
are more crowded and darker-coloured than in those with the 
longer stigmas. Considering the slight and variable differences 
between the two forms of this Linum, it is not surprising that 
they have been hitherto overlooked. 

In 1861 I had eleven plants growing in my garden, eight of 
which were long-styled, and only three short-styled. Two very 
fine long-styled plants grew in a bed a hundred yards off, and 
se2)arated from the others by a screen of evergreens. I marked 
twelve flowers, and put on their stigmas a little pollen from the 
short-styled plants. The pollen of the two forms is, as stated, 
identical in appearance; the stigmas of the long-styled flowers 
were already thickly covered with their own pollen — so thickly 
that I could not find one bare stigma; and it was late in the 
season, namely, September 1.3th. Altogether, to expect any result 
from this trial seemed almost childish. From my experiments, 
however, on Primula, which have been laid before this Society 
(' Journal,' vol. vi. p. 77), I had faith, and did not hesitate to make 
the trial, but certainly I did not anticipate the full result. The 
germens of these twelve flowers all swelled, and ultimately six fine 
capsules (the seed of which germinated this year) and two poor 
capsules were produced ; only four capsules shanked off. These 



Ijr SEVKBAI SPECIES OP THE OE\rs LI^-rM. 71 

two plants produced, before and after and at tlie time of tlic trin], 
a vast number of flowers, but the germens of not even one swelled. 
All these flowers, thougb their stigmas were so densely covered 
with their own pollen, were absolutely barren. 

The nine other plants, six long-styled and three short-styled, 
grew in the beds of the same flower-garden. Four of the long- 
styled produced no seed-capsules ; one produced two ; but the re- 
maining long-styled plant grew so close to a short-styled plant 
that their branches touched, and this produced twelve capsules, 
but they were poor. The case was dift'crent with the short-styled 
plants. The plant which grew in juxtaposition with the long- 
styled plant produced ninety-four imperfectly fertilized eapsides 
containing a multitude of bad seeds, with a moderate number of 
good seeds. The two other short-styled plants grew in a single 
clump, and were very small, being partly smothered by other 
plants ; they did not stand very close to any long-styled plants, 
yet they yielded together nineteen capsules. These facts seem to 
show that the short-styled plants are far more fertile with theijr 
own pollen than the long-styled. We shall immediately see that 
this is the case in a slight degree. But I suspect that in tin's 
instance the difierence in fertility between the two forms was in 
part due to a distinct cause-. I repeatedly watched the flowers, 
and only once saw a humble-bee momentarily alight on one, and 
then fly away, as if it were not to its taste. If bees had visited 
the several plants, there cannot be a doubt that the four long- 
styled plants w"hich did not produce a single capsule would have 
borne an abundance. But several times I saw small diptera suck- 
ing the flowers ; and these insects, though not visiting the flowers 
with anything like the regularity of bees, would carry a little 
pollen from one form to the other, especially wlicn growing close 
together; and the stigmas of the short-styled plants, diverging 
within the tube of the corolla, would be more likely than the up- 
right stigmas of the long-styled to receive a small quantity of 
pollen when brought by small insects. l<'rom the much greater 
number of long-styled than of short-styled flowers in the garden, 
evidently the short-styled would bo more likely to receive some 
pollen from the long-styled, than the long-styled from the short- 
styled. 

In 1S62 I raised thirty-four plants of this Linum in a hotbed ; 
and these consisted of seventeen long-styled and seventeen short- 
styled forms. Seed sown later in the flower-garden yielded seven- 
teen long-styled and twelve short-styled forms. These facts justify 



72 Jrn. bvrwis o>' titt; existexoe of two ronjts 

the st<atcment tliat the two forms are produced iu about equnl 
numbers. The fivst thirty-four plauts were kept under a net 
which excluded insects. I fertiUzed heteromorphically fourteen 
long-stylod flowers with pollen from the short-styled, and got 
eleven fine seed-capsules ; these contained on an average 8-6 seeds 
per capsule, hut only 5-6 were apparently good. It may be well to 
state tliat ten seeds is the maximum possible production for a 
capsule, and that our climate cannot bo very favourable to this 
North-African plant. On three occasions I fertilized homomor- 
phically the stigmas of altogether nearly a hundred flowers (but 
did not separately mark them) with their own pollen, but taken 
from separate plants, so as to prevent any possible ill effects 
from close interbreeding ; and many other flowers were produced, 
which, as before stated, would get plenty of their own individual 
pollen ; yet from all these flowers, borne by the seventeen long- 
styled plants, only three capsules were produced; one of these iu- 
cluded no seed, and the other two together gave only Ave good 
seeds. Kor do I feel at all sure that this miserable product of the 
two half-fertile capsules from the seventeen plants, each of which 
must have produced at least fifty or sixty flowers, is really the re- 
sult of their fertilization by their own pollen ; for I made a great 
mistake in keeping the two forms under the same net, with their 
branches often interlocking, and it is surprising that a greater 
number of flowers were not accidentally fertilized. 

Of tlie short-styled flowers I fertilized heteromorphically twelve 
witli the pollen of tlie long-styled (and to make sure of the result 
I previously castrated the majority), and obtained seven fine seed- 
capsules. Tliese included an average of 7'6 seeds, but of apparently 
good seed only 4'3 per capsule. At three separate times I ferti- 
lized homomorphically nearly a hundred flowers with their own- 
form pollen, taken from separate plants ; and numerous other 
flowers were produced, many of which must have received their 
own pollen. From all these flowers borne on the seventeen plants, 
only fifteen capsules were produced, of which only eleven con- 
tained any good seed, on an average 4-2 per capsule. xA^s remarked 
in the case of the long-styled plants, some even of these capsules 
were perhaps the product of a little pollen accidentally fallen 
from the flowers of the other form. Nevertheless the short- 
styled plants seem to be slightly more fertile with their own 
pollen, in the proportion of fifteen capsules to three, than the 
long-styled : the real proportional excess in fertility is probably 
a little greater, as the short-styled flowers, when not disturbed, do 



IK SETEHAL SPECIES OF THE OESUS LINUM. 73 

not SO surely receive tlieir own pollen as do the long-stjled. The 
greater self-fertility of the short-styled flowers was, as we have 
seen, also shown by the plants left to themselves, and but sparingly 
visited by insects, in the flower-garden in 1861, and likewise by 
those raised in 1862. 

The absolute sterility (judging from the experiments of 1861, 
and which is hardly contradicted by those of 1862) of the long- 
styled plants with their own-form pollen led me to examine into 
its apparent cause ; and the result is so curious that it will be 
worth while to give most of the experiments in detail. These ex- 
periments were tried on fresh plants, grown in pots and brought 
successively into the house. 

First. I placed pollen from a short-styled flower on the 
five stigmas of a long-styled plant, and after thirty hours found 
them deeply penetrated by a multitude of pollen-tubes, far too 
numerous to be counted ; the stigmas had become discoloured and 
twisted. I repeated this experiment on another flower, and in 18 
hours found the stigmas penetrated by a multitude of long pollen- 
tubes. All this is what might have been expected, as this is a fertile 
or heteromorphic union. I likewise tried the converse experiment, 
and placed pollen from a long-styled flower on the stigmas of a 
short-styled flower, and in 24 hours found the stigmas discoloured, 
twisted, and penetrated by numerous pollen-tubes ; and this, again, 
is what might have been expected, as this is a fertile or hetero- 
morphic union. 

Secondly. I placed pollen of a long-styled flower on all five 
stigmas of a long-styled flower on a separate plant : after 19 liours 
I rigorously dissected the stigmas, and found only a single pollen- 
grain which had emitted a very short tube. To make sure that 
the poUen was good, I took in this case, and in most other cases, 
pollen either from actually the same anther or from the same 
flower, and proved it to be good by placing it on the stigma of a 
short-styled 'plant, and seeing numerous pollen-tubes emitted. 

Thirdly. Eepeated last experiment, and placed own-form pollen 
on all five stigmas of a long-styled flower ; and, after 19i hours, 
not one single grain had emitted its tube. 

Foiirtldy. Eepeated the experiment, with the same result after 
24 hours. 

FiftJdy. Eepeated last experiment, and, after leaving pollen on 
for 19 hours, put an additional quantity of own-form poUen on 
all five stigmas. After an interval of exactly three whole days, 
I rigorously examined the stigmas, which, instead of being dis- 

LIKN. PEOC. BOTAiry, TOL. Til. O 



74. ME. DAEAVl:s Olf THE EXISTENCE "Or TWO TOEMS 

coloured and twisted, were straight and fresh-coloxired ; and only 
one grain had emitted quite a short tube, which could he drawn 
out of the stigmatic tissue without being ruptured. 
The following experiments are more striking :— 
Sixthly. I placed own-form pollen on three of the stigmas of a 
long-styled flower, and pollen from a short-styled flower on the 
other two stigmas. After 22 hours these two stigmas were dis- 
coloured, and slightly twisted, and penetrated by the tubes of 
numerous pollen-grains : the other three stigmas, covered with 
their own-form pollen, were fresh, and aU the poUen-graias were 
loose ; but I did not dissect the whole stigma rigorously. 

SevenMy. Experiment repeated iu the same manner, with the 
same result. 

Eiffhthly. Experiment repeated, but the stigmas were carefully 
examined after an iaterval of only 5i hours. The two stigmas with 
pollen from a short-styled flower were penetrated by innumerable 
tubes; but these were as yet short, and the stigmas themselves 
were not at all discoloured. The three stigmas covered with their 
own-form pollen were not penetrated by a single pollen-tube. 

Ninthly. Put pollen of short-styled on one stigma, and own- 
form pollen on the other four stigmas ; after 24 hours, found the one 
stigma somewhat discolotired, and twisted, and penetrated by many 
long tubes : the other four stigmas were quite straight and fi-esh ; 
but on dissecting their whole lengths I found that three pollen- 
grains had protruded quite short tubes into the tissue. 

Tenfhly. Eepeated the experiment, with the same result after 24 
hours, excepting that only two own-form grains had penetrated the 
stigmatic tissue with their tubes, to a very short depth ; the one 
stigma, which was deeply penetrated by a multitude of tubes from 
the short-styled pollen, presented a conspicuous difference in com- 
parison with the other four straight and bright pink stigmas, in 
being much curled, half-shrivelled, and discoloured. 

I could add a few other experiments ; but those now given amply 
suffice to show that the pollen-grains of a short-styled flower placed 
on the stigmas of a long-styled flower emit a multitude of tubes 
after an interval of from five to six houi-s, and penetrate the tissue 
ultimately to a great depth, and that after twenty-four hours the 
stigmas thus penetrated change colour, become twisted, and appear 
half- withered. On the other hand, the pollen-grains of the long- 
styled flowers placed on their own stigmas, after an interval of a 
day, or even three days, do not emit their tubes, or at most only 
three or four grains out of a multitude emit their tubes ; and these 



IN SEVERAL SPECIES OF THE GENUS LINUM. 75 

apparently never penetrate the stigmatic tissue deeply, and the 
stigmas themselves do not become discoloured and twisted. 

This seems to me a remarkable physiological fact. The pollen- 
grains of the two forms are undistinguishable under the micro- 
scope ; the stigmas dift'er only in length, degree of divergence, and 
in the size, shade of colour, and approximation of their papilte, these 
latter differences being variable and apparently simply due to the 
elongation of the stigma. Yet we plainly see that the two pollens 
and the two stigmas are widely dissimilar in action — the stigmas of 
each form being almost powerless on their own pollen, but causing, 
through some mysterious influence, by simple contact (for I could 
detect no viscid secretion), the pollen-grains of the opposite fonn 
to protrude their tubes. It may be said that the two pollens and 
the two stigmas by some means mutually recognize each other. 
Taking fertility as the criterion of distinctness, it is no exaggera- 
tion to say that the poUen of the long-styled Linum grandiflorum 
(and conversely of the other form) has been diilerentiated, with 
respect to the stigmas of all the flowers of the same form, to a 
degree corresponding with that of distinct species of the same 
genus, or even of species of distinct genera. 

Linum perenne. — The dimorphism is here more conspicuous, and 
has been noticed by several authors. In the long-styled form the 
pistil is nearly twice as long as in short-styled ; in the latter the 
stigmas are smaller and, diverging more, pass out between the fila- 
ments of the stamens. I could detect no difierence in the size of 
the stigmatic papillae ; in the long-styled form alone the stigmatic 
surfaces turn round so as to face the circumference of the flower : 
but to this point we shall presently return. Difterently from what 
occurs in L. grandiflorum, the long-styled flowers have stamens 
hardly more than half the length of those of the short-styled. The 
size of the pollen-grains is rather variable ; after some doubt, I have 
come to the conclusion that there is no uniform difierence between 
the pollen of the two forms. The long stamens in the short-styled 
form project to some height above the corolla, and, apparently from 
exposure to the light, the filaments are coloured blue. These longer 
stamens correspond in height with the lower part of the stigmas 
of the long-styled flowers ; and the shorter stamens of the latter 
form correspond in the same manner in height with the shorter 
stigmas of the short-styled flowers. 

I raised from seed twenty-six plants, wliich proved to be twelve 
long-styled and fourteen short-styled. They flowered well, but 
were not large plants. As I did not expect them to flower so 

02 



76 MB. DAEWIN OH TUE EXISTENCE OF TWO rOEMS 

soon, I did not transplant them, and they -unfortunately grew with 
their branches closely interlocked. All the plants were covered 
by a net, excepting one of each form. First, of the long-st^ded 
flowers, twelve were homomorphicaUy fertilized by their own-form 
pollen, taken in every case from a separate plant ; and not one 
flower set a seed-capsule : twelve other flowers were heteromor- 
phicaUy fertilized by pollen from short-styled flowers ; and they set 
nine pods, each including on an average seven good seeds : as 
before, ten seeds is the maximum possible production. Secondly, 
of the short-styled flowers, twelve were homomorphicaUy fertilized 
by own-form pollen, and they yielded one capsule, including only 
three good seeds ; twelve other flowers were hoteromorphically 
fertilized by pollen of long-styled flowers, and these produced nine 
capsules, hut one was bad ; the eight good capsules contained on 
an average exactly eight good seeds each. 

The many flowers on the eleven long-styled plants under the 
net, which were not fertilized, produced only three capsules 
(including 8, 4, and 1 good seeds) ; whetlier, owing to the inter- 
locking of the branches, these accidentally received pollen from 
the other form, I will not pretend to conjecture. The single long- 
styled plant which was uncovered, and grew close by the uncovered 
short-styled plant, produced five good pods ; but it was a very poor 
and small plant. 

The flowers borne on the thirteen short-styled plants under the 
net, which were not fertilized, produced twelve capsules (containing 
5'6 seeds on average) : as some of these capsules were very fine, and 
five wore borne on one twig, I suspect tliat they had been visited 
by some minute insect which had accidentally got under the net 
and had carried pollen from the other form. The one uncovered 
short-styled plant yielded exactly the same number of capsules, 
namely, twelve. 

Prom these facts we have some evidence, as in the case of L. 
grand iflwmn, that the short-styled plants are in a very slight 
degree more fertile with their own pollen than are the long-styled 
plants. And we have the clearest evidence, from the result of the 
forty-eight flowers artificially fertilized, that the stigmas of each 
form require pollen from the stamens of corresponding height 
produced by the opposite form. 

In contrast with the case of L.grandiflormn, it is a singular fact 
that the pollen-grains of both forms of X. perenne when placed on 
their own-form stigmas, though not causing fertility, yet emit their 
tubes; and these tubes I found, after an interval of eighteen 



IS" SETEHAL SPECIES OE THE OEXUS LI^-USI. 77 

hours, had penetrated the stigmatic tissue, but to what depth I 
did not ascertain. In this case the inaction of the pollen-grains on 
their own stigmas must be due either to tlio tubes not reaching 
the ovules, or reaching them and not efficiently acting on thorn. 
In the case of Li/thrum Salicaria, which I hope at some future 
time to lay before the Society, there are three distinct forms, each 
of whicli produces two kinds of pollen ; but neither 2)ollen, when 
placed on its own stigma, causes fertility, except occasionally and 
in a vevj moderate degree ; yet the pollen-tubes in each case freely 
penetrate the stigmatic tissue. 

The plants of L. perenne and oi L. grandiflorum grew, as stated, 
with their branches interlocked, and with scores of flowers of the 
two forms close together ; they wore covered by an open net, 
through which the wind, when high, passed ; and such minute in- 
sects as Thrips could not, of course, be excluded ; yet we liave 
seen that the utmost possible amount of accidental fertilization on 
seventeen long-styled plants in the one case, and on eleven plants 
in the other case, was the production, in eacli, of three poor cap- 
sules ; so that we may infer that, when the proper insects are ex- 
cluded, the wind does hardly anything in the way of carrying 
pollen from plant to plant. I allude to this fact because botanists, 
in speaking of the fertilization of plants or of the production of 
hybrids, often refer to the wind or to insects as if the alternative 
were indifferent. This view, according to my experience, is en- 
tirely erroneous. "When the wind is the agent in carrying pollen, 
either from one separated sex to the other, or from hermaphrodite 
to hermaphrodite (which latter case seems to be almost equally 
important for the ultimate welfare of the species, though occurring 
perhaps only at long intervals of time), we can recognize structure 
as manifestly adapted to the action of the wind as to that of 
insects when they are the carriers. We see adaptation to the 
wind in the incoherence of the pollen, in the inordinate quantity 
produced (as in the Coniferse, Spinage, &c.), in the dangling anthers 
well fitted to shake out the pollen, in the absence or small size of 
the perianth or in the protrusion of the stigmas at the period of 
fertilization, in the flowers being produced before they are hidden 
by the leaves, in the stigmas being downy or plumose (as in the 
Gramineai, Docks, and other plants) so as to secure the cliance- 
blown grains. In plants which are fertilized by the wind, the 
flowers do not secrete nectar, their pollen is too incoherent to be 
easily collected by insects, they have not bright-coloured corollas 
to serve as guides, and they are not, as far as I have seen, visited 



78 ilK. BAEWiy OS THE EXISTENCE OF TWO TOHMS 

by insects. When insects are the agents of fertilization (and this 
is incomparably the more frequent case both with plants having 
separated sexes and with hermaphrodites), the wind plays no part, 
but we see an endless number of adaptations to ensure the safe 
transport of the pollen by the living workers. We can recognize 
these adaptations most easily in iiTeguIar flowers ; but they do not 
the less occur in perfectly regular flowers, of which those of Linum 
offer an instance, as I will almost immediately endeavour to show. 

I have already alluded to the rotation of each separate stigma in 
the long-styled form alone oi Linum perenne. In the other species 
examined by me, and in both forms when the species are dimor- 
phic, the stigmatic surfaces face the centre of the flower, and the 
furrowed backs of the stigmas, to which the styles are attached, face 
the circumference. This is the case, in the bud, with the stigmas of 
the long-styled flowers of L. perenne. But by the time the flower 
in this form has expanded, the five stigmas, by the torsion of that 
part of the style which lies beneath the stigma, twist round and 
face the circumference. I should state that the five stigmas do 
not always perfectly turn round, two or three often facing only 
obliquely towards the circumference. My observations were made 
during October ; and it is not improbable that earlier in the season 
the torsion would have been more perfect ; for after two or three 
cold and wet days the movement was very incomplete. The flowers 
etould be examined shortly after their expansion ; for their dura- 
tion is brief, and, as soon as they begin to wither, the styles be- 
come spirally twisted together, and the original position of the 
parts is lost. 

He who will compare the structure of the whole flower in both 
forms of L. perenne wiA. grandiflorum, and, I may add, of L.flavum, 
will, I think, entertain no doubt about the meaning of this torsion 
of the styles in the one form alone of L. perenne, as well as the 
meaning of the divergence of the stigmas in the short-styled forms 
of all three species. It is absolutely necessary, as we now know, 
that insects should reciprocally carry pollen from the flowers of 
the one form to those of the other. Insects are attracted by five 
drops of nectar, secreted exteriorly at the base of the stamens, so 
that to reach these drops they must insert their proboscides outside 
the ring of broad filaments, between them and the petals. In the 
short-styled form of the above three species, the stigmas face the 
axis of the flower ; and had the styles retained their original up- 
right and central position, not only would tlie stigmas have pre- 
sented their backs to insects as they sucked the flowers, but they 



IK SETEBAL SPECIES OF THE OEJfUS LmUM. 



70 



would have been separated from them by the ring of broad fila- 
ments, and could never have been fertilized. As it is, the styles 
diverge greatly and pass out between the filaments. The stigmas, 
being short, lie within the tube of the corolla ; and their papillous 
faces, after the divergence of the styles, being turned upwards are 
necessarily brushed by every entering insect, and thus receive the 
required pollen. 

In the long-styled form of L. grandijiorum, the parallel anthers 
and stigmas, slightly diverging from the axis of the flower, project 
only a little above the tube of the somewhat concave corolla ; and 
they stand directly over the open space leading to the drops of 
nectar. Consequently when insects visit the flowers of either 
form (for the stamens in this species occupy the same position in 
both forms), they will get their proboscides well dusted with the 
coherent pollen. As soon as the insect inserts its proboscis to a 
little depth into the flower of the long-styled form, it will neces- 
sarily leave poUen on the faces and margins of the long stigmas ; 
and as soon as the insect inserts its proboscis to a rather greater 
depth into the short-styled flowers, it will leave pollen on their 
upturned stigmatic surfaces. Thus the stigmas of both forma 
wiU indifferently receive the pollen of both forms ; but we know 
that the pollen alone of the opposite form will produce any eflect 
and cause fertilization. 




Long-efyled form of L. perenae, var. Atislriacum, with the petals and calvi 
removed on the near side. 

In the case of L. perenne, aifairs are arranged a little more per- 
fectly ; for the stamens in the two forma stand at different heights, 



80 MB. DAEWIK OJf THE EXISTElfCE Or TWO EOEMS 

and pollen will adhere to different parts of an insect's body, and 
will generally be brushed off by the stigmas of corresponding 
height, to which stigmas each kind of pollen is adapted. In this 
species, the corolla is flatter, and in the one form the stigmas and 
in the other form the anthers stand at some height above the 
mouth of the corolla*. These longer stigmas and longer stamens 
do not diverge greatly ; hence insects, especially rather small ones, 
will not insert their proboscides between the stigmas or between 
the anthers, but will strike against them, at nearly right angles, 
with the backs of their head or thorax. JSTow, in the long-styled 
.flowers oi L. perenne, if each stigma had not rotated on its axis, 
insects in visiting them would have struck their heads against the 
backs of tlio stigmas ; as it is, they strike against the papillous 
fronts of the stigmas, and, their heads being already charged with 
the proper coherent pollen from the stamens of corresponding 
height borne by the flowers of the other form, fertilization is per- 
fectly efiected. 

Thus we can understand the meaning of the torsion of the 
styles in the long-styled flowers alone, as well as their divergence 
in the short-styled flowers. 

One other point is worth a passing notice. In botanical works 
many flowers are said to be fertilized in the bud. This rests 
solely, as far as I can discover, on the anthers opening in the bud ; 
no evidence is adduced that the stigma is at this period mature, 
or that, if then penetrated by pollen-tubes, it is not subsequently, 
after the expansion of the flower, acted on by pollen brought from 
other flowers. In the case of Ceplialanthera graniiflora I have 
shown t by experiment that insufiicient precocious self-fertiliza- 
tion, together with subsequent full fertilization, is the regular 
course of events. The belief that flowers of any plant are habitu- 
ally fertilized in the bud, or are perpetually self-fertilized, is a 
most effectual bar to really understanding their structure. I am 
far from wishing to say that some flowers, in certain seasons, are 
not fertilized in the bud : I have reason to believe that some 
flowers are frequently fertilized without expanding ; but my ob- 
servations lead me to disbelieve that this is ever the invariable 

* I neglected to get drawings made from fresh flowers of the two forms. 
Mr. Fitch has made the above sketch of a long-styled flower from dried speci- 
mens and published engrarings : his well-known skill ensures accuracy in the 
proportional size of the parts ; and I believe their relative position is true. 

+ Fertilization of Orcliids, p. 108. 



15" SETEEAI/ SPECIES OF THE OEXL'S 'LmVil. 81 

course witli all the flowers of any species wliatever. As it is dif- 
ficult to prove without troublesome experiments the falsity of the 
belief of regular fertilization in the bud, I here notice this subject. 
An estimable and laborious observer*, resting his belief on the 
usual kind of evidence, states that in L. Austriacnm (which is 
dimorphic and is considered by Planchon as a variety of L. 
perenne) the anthers open the evening before the expansion of the 
flowers, and tJiat the long-stjled stigmas are then almost ahvaj's 
fertilized. He asks whether this precocious fertilization in tlio 
several species of Linum and in other plants is not one cause of 
the sliort duration of their flowers. ^o\x we know positively that, 
so far from Linum perenne being fertilized by its own pollen in 
the bud, its own pollen is as powerless on the stigma as so much 
inorganic dust. 

Linum flavum. — To recur to our more immediate subject, in 
the long-styled form of this species the pistil is nearly twice as 
long as in the short-styled form ; and the stigmas are longer with 
the papillas coarser. In the short-styled form the stigmas diverge 
and pass out between the filaments. The stamens in the two forms 
differ in height, and, what is singular, the anthers of the longer 
stamens are sliorter ; so that in the short-styled form botli stigmas 
and anthers are shorter than in the other form. The pollen of 
the two forms does not difler. I have not been able to try any 
experiments on this species ; but a careful observer, Mr. W. C. 
Crocker, intends proving tiieir reciprocal fertility next summer. 
As this plant is propagated hj cuttings, I have generally found 
that all the plants in the same garden belong to the same form. 
On inquiry I have never heard of its seeding in this country ; but 
to anyone wishing to raise seedlings, in all probability the path is 
now open, namely, by carrying pollen from one form to the other. 
I have now shown that three species of Linum are dimoi-phic, 
besides several races of L. perenne, esteemed by some botanists to 
be distinct species, such as L. montanum, L. Sihiricum, and L. Aus- 
triaeicm. According to Vaucherf, L. GalUcmn, L. maritimwm, and 
Z. strictinn are in the same manner dimorphic, as likewise is, ac- 
cording to PlauchonJ, L saholoides. This latter botanist is the 
only one who seems to have been struck with the importance of 
the subject ; and he acutely asks whether this dimorphism has not 
some influence on the manner of fertilization. We thus know of 

* feudes 8ur la Geograph. Bot., par Prof. H. Lecoq, 1850, torn. T. p. 325. 
t Iliet. Physiolog. dcs Plantes d'Europe, 1841, torn. i. p, 401. 
X Hooker's London Joum. of Botany, 1848, vol. vii. p. 171. 



82 0>" THE EXISTENCE OF TWO TOEMS IN SPECIES OP IISTII. 

seven dimorphic species of Linum ; but as this structure has been, 
overlooked in such common garden-fiowers as L. grandiflorum and 
L.flavum, it is probably of frequent occurrence. 

All the species, however, are certainly not thus characterized. I 
have examined many specimens of L. catliarticum, and found in 
all that the stamens and stigmas were of nearly equal height and 
the same in all the plants. So, again, I looked, near Torquay, at 
many ilowers of the wild L. usitatissimum or angustifolium (I 
know not which), and there was no trace of dimorphism. Again, 
I raised 111 plants from seed sent me from Kew, incorrectly 
named L. Austriacmn ; the plants were tall and straight, having a 
rather different aspect from the wild species seen at Torquay, with 
extremely fugacious blue flowers : in all these plants the stigmas 
stood on a level with the anthers or projected a very little above 
them. I protected the flowers from insects ; but every one of the 
111 plants produced plenty of seed. I mention this fact because it 
had occurred to me that possibly a species might be dimorphic in 
function, though not in structure. 

Lastly, Linum Lewisii, which is ranked by Planchon as a variety 
of L. perenne, but which, now that we know the meaning of re- 
ciprocal dimorphism, surely deserves specific honours, must not bo 
passed over. According to Planchon*, the same plant bears some 
flowers with anthers and stigmas of the same height, and others 
with styles either longer or shorter than the stamens ; so that the 
same individual plant is trimorphic. This, as far as I know, is a 
unique case. Prom analogy we may pretty safely predict the 
function of the three kinds of flowers: those with stigmas' and 
anthers of the same height will be self-fertile ; those with these 
organs of unequal height will require reciprocal fertilization. A 
plant of L. grandiflorum or of the other dimorphic species, grow- 
ing hy itself, could no more perpetuate its race than could one 
sex of a dioecious plant, nor could any number of plants without 
the aid of insects. A single plant of Linum Lewisii, on the other 
hand, in all probability could propagate itself, even if no insects 
were present, as probably sometimes occurs in its Arctic home. 
If insects visited the plant, the flowers which were dimorphic 
would be fertile one with another or with those on any neighbour- 
ing plant. Thus the plant would receive the advantage of a cross. 

* Ilooker's London Joum. of Botany, 1848, vol. vii. p. 175. It is not im- 
probable that the allied genus Sugonia is dimorphic ; for (p. 525) one species is 
described " staminibus exsertis ; " another has " stamina 5, majora, stylos longe 
siiperantia ; " and another is furnished " stylis staminibus longioribus." 



FOEM OF THE TASCULAK FASCICULI IS BKITISII FEEXS. 83 

That this is an advantage, and is one great end gained by reciprocal 
dimorphism, I can entertain no doubt. That in some cases this 
dimorphism may be a step towards a complete separation of the 
sexes, I wiU not dispute ; but good reasons could be assigned 
to show that there is uo necessary connexion between reciprocal 
dimorphism and a tendency to dioecious structure. Although good 
is gained by the inevitable crossing of the dimorphic flowers, yet 
numerous other analogous facts lead me to conclude that some 
other quite unknown law of nature is here dimly indicated to us. 



On the Form of the Vascular Fasciculi in certain British Ferns. 
By AaiHiTE H. Chuech, B.A. Oxon. Communicated by 
W. Feancis, Ph.D., F.L.S. 

[Bead Dec. 18, 1862.] 

The distribution of the vascular tissues in the stem and stipes of 
the British species of Ferns has been made the subject of much in- 
teresting and accurate study by Dr. Ogilvie*. His papers are to 
be found in the ' Annals and Magazine of Natural History ' for 
December 1859 and November 1860. My own long-continued 
examination of the living plants has not enabled me to detect any 
but the most trivial mistakes in these full and admirable memoirs. 
I have therefore only to propose a few slight alterations in Dr. 
Ogihie's conclusions, and to make one or two additional remarks 
on certain species and varieties which he omits to notice. The 
present communication may be deemed the first instalment of 
such supplementary observations. I may also here state that I 

* The following list of papers includes nearly all those in which the vascular 
tissues of Ferns have been discussed : — 

Presl. Tentamen Pteridographise. Pragse : 1836. 

Ff?e. Die Gefassbiindel im Stipes der Fame. Praga; : 1847. 

OgUyie, Dr. Ann. & Mag. Nat. Hist. 1859 and 1860. 

Duval-Joure, J. Etudes sur le Petiole des Fougferes. In BUlot's Archives 

de la Flore de France ; pp. 57 & 149. 
King. On Sigillaria. Edinburgh PhU. Trans. 1844. 
Leighton, Eev. W. A. Hints on a new character in Ferns. Phyt. n. s. i. 

p. 256. 
Moore, T. The Tascular Bundles of the Stipes of Ferns. Phyt. n. s. i. p. 378. 
Eeicbardt, H. W. tJeber der Gefassbiindel Vertheilung im Stammc und 

Stipes der Fame. Denksehriften der Kaiserlichcn Akademie der Wissen- 

schaften, xvii'" Band. Wien : 1859. 



84 iiE. ciincn o>" the roEii or the 

can confirm the general accuracy of Duval-Jouve'a figures so far 
as they relate to species found in Britain. 

To discuss the difficult question of the nomenclature of these 
plants is beside my purpose ; I shaU therefore do no more than 
designate each form named by two or three of its best-known 
synonyms. At the same time, it seems that the results of such 
inquiries as the present, as possibly affording criteria of generic if 
not of sjjccific difference, cannot be wholly disregarded, and may 
ultimately aid us in arriving at a more consistent classification 
for the FUices. 

The genera Foli/stichum and Lastrea as understood by Moore 
and many other authors are respectively coextensive (so far as 
our native ferns are concerned) with the genera Aspidium and 
Nephrodium adopted by Hooker in his 'British Ferns' (1862). 
I have examined transverse sections of the stipes of all the gene- 
rally received species and many of the varieties included under 
these generic ai)pellations, and in two species only did I find any 
material departure from tliat one particular arrangement of the 
vascular fasciculi which is disclosed by a transverse stipital section 
of such a form as IMoore's Lastrea Filix-mas or Polystichmn Lon- 
cJiUis. In Nephrodium Filix-mas, N. rigidum, N. cristatum, I^. 
spinulosum a. tipinnatum, (3. dilatatum, y. cdmulum, i. dwmeforum, 
Aspidium aciileatum a. lohatum, (i. infermeditim, y. angulare of 
Hooker, and also in the forms Lopliodium glandulosum, L. uligi- 
nosum, L. nanum, and L. collinum of Newman, the same disposi- 
tion of the vascular tissue occurs. The two notable exceptions to 
which I have before alluded are found in Neplirodiwm Thelypteris 
and N. Ormpferis of Hooker, identical with tbo Lastrea Thely- 
pteris and L. montana of Moore and the ILemestheum Thelypteris 
and Lastrea (JlemestJieum) montana of Newman. In fig. 1 the 
prevalent arrangement is shown ; in fig. 2 that wbicb occurs in 
the mountain fern ; while fig. 3 represents that of the marsh fern, 
which I will now more particularly describe. In all cases the 
sections noticed are those of tlie stipes, not of the stem ; and I 
have freely availed myself of the use of a very weak solution of 
perchloride of iron, in order that the tracts containing tannin 
might be distinctly marked out. 

Nephrodium Thelypteris, Hooker. 
Hemestlieiim Thelypteris, Newman. 
Lastrea Thelypteris, Moore. 

The present plaut is not only closely connected in many of its 



OK THE FUETILIZAT10^• Oi? LYTIIKUM SALICAItlA. IGO 

Integra, glabra, supra luciiia; nervi laterales 12-15 utrinque costaque 
utraque pagina promiuuli ; petiolus usque poUicem fere longus, teres, 
glaber. Amenta axiliaria, gemiuata, rarius abortu solitaria, breviter 
(3 poll.) peduuculata, subtus nuda, supra floribus niasculis ilensissirae 
obrlucta, fosmiueis paueis niulto majoribus iiiterniixtis. Bracteolaj 
trigono-peltata;, minuta;, pilosulos, ciliolata3, viriiles. Floras sessilcs, 
compaeti, viridiusculi, dein albescentes. Sepala florum masc. basi in 
tubiim brevem coiinata, cxtus pilosula, ea flor. fcem, libera, exteriora 
pubera, dein hirtella, interiora la;via, teneriora. Achajnium pisi majoris 
magnitudine, stylo persistente auctum, perigonio birtello inclusuin, 
inatiirescens contactu etiam levi elastice (ad 6 metr.) exsiliens. 

In sylvis Sumatrte; in prov. Palcmbang; inprov. Padangpropc Lurautet 
ad littora })rope Siboga, Teljsmann, Ins. Singapora, T. Anderson, M.D. 

Nom. vernac. Kapinie. 

Synon. Artoearpus elongatus, Miq. Fl. hid. Bat. Suppl. p. 172 et-lli). 

Tab. XIII. tig. 1. Ramus florifervis magnit. nat. ; fig. 2. Flos <? et ? 
auct. ut fig. sequent. ; fig. 3. Sepalum exter. fl. § a dorso ; fig. 4. 
Sepal, inter, fl. J ; fig. 5. Ovarium ; fig. 6. idem, vertiealiter transsect. ; 
fig. 7. Semen, tegmento remote. 



On the Sexual Kelations of the Three Forma of LijtJirum salicaria. 

By CiiAHLES PAitwiy, F.E.S., F.L.S., &c. 

[Read JuS^le, 1864.] 

SoiiE of the species of LytJirum offer in their manner of ferti- 
lization a more remarkable case than can, perhaps, be found in 
any other plant or animal. In Lythrum salicaria three plainly 
iliiFerent forma occur.- each of these is an hermaphrodite, eacli 
is distinct in its female organs from the other two fonns, and 
each is furnished with two sets of stamens or males difl'ering 
from each other in appearance and function. Altogetlicr there 
are three females and three sets of males, aU as distinct from 
each other as if they belonged to dificrent species ; and if smaller 
functional differences are considered, there are five distinct sets 
of males. Two of the three hermaphrodites must coexist, and the 
pollen be carried by insects reciprocally from one to the other, 
in order that either of the two shoitld be fully fertile ; but unless 
all three forms coexist, there will be waste of two sets of stamens, 
and the organization of the species, as a whole, will be imperfect. 
On the other hand, when aU three hermaphrodites coexist, and 
the pollen is carried from one to the other, the scheme is perfect ; 
there is no waste of pollen and no false co-adaptation. In short, 
nature has ordained a most complex marriage-arrangement, 
namely a triple union between three hermaprodites, — each her- 

Mo. Bot. Garden, 



170 MB. C. DABWIN ON" THE SEXUAL HET.ATIOXS OF 

mapliroJite being in its female organ quite distinct from the 
other two hermaphrodites and partially distinct in its male 
organs, and each furnished with two sets of males. 

The three forms may be conveniently called, from the unequal 
lengths of their pistils, the long-stijled, mid-styled, and sJiort-styUd. 
Their existence and diilereuces were first observed by Vaucher*, 
and subsequently more carefully by Wirtgeu ; but, not being guided 
by any theory, neither author perceived some of the most curious 
points of difference. I will first briefly describe the three forms 
by the aid of the accompanying accurate diagram, which shows 
the flowers, six times magnified, in their natural position, with 
their petals and the near side of the calyx removed. 

Long-styled form. — This can at once bo recognized by the 
length of the pistil, which is (including the ovarium) fully one- 
third longer than that of the mid-styled, and more than thrice 
as long as that of the short-styled form. It is so dispropor- 
tionately long, comjiared with the flower, that it projects in 
the bud through the unfolded petals. It stands out consi- 
derably beyond the longer stamens ; its terminal portion de- 
pends a little, but the stigma itself is slightly upturned : the 
globular stigma is considerably larger than that of the other 
two forms. The six longer stamens project about two-thirds 
of the length of the pistil, and correspond in length with the 
pistil of the mid-styled form. The correspondence with the 
pistil in length in this and the two following cases is generally 
very close ; the difference, where there is any, being usually in a 
slight excess of length in the stamens. The six shorter stamens 
(each of which alternates with a longer one) lie concealed within 
the calyx ; their ends are upturned, and they are graduated in 
length, so as to form a triple row — ^both which characters are 
here much more marked than with the longer stamens, which 
vary in these respects. The anthers of the shorter stamens are 
smaller than those of the longer stamens. Knowing that the 
pollen differs greatly in the longer and shorter stamens of the two 
other forms, I carefully compared that of the two sets of stamens 
in this form : in both the pollen-grains are yellow, but they are a 
little larger in the longer than in the shorter stamens. The dif- 
ference is slight, so that I convinced myself of its reality only by 
putting two small heaps close together under the compovmd mi- 
* Hist. Phys. des Plantes d'Europe, torn, ii., 1841, p. 371. Wii-tgen, " Ueber 
Lythrum salicaria und dessen.Formen," Vcrfiand. des naturhist. Vereins der 
prcuss. Rhcinl,, 5. Jahrgaug, 1848, S. 7. 



THE THKET: poems or LTTHKir^r SATiTf'AETA. 



171 




Diagrams of the flowers of the three forms of Lythmn mlicaria. in their 
natural position, with the petals removed and with the near side of the elayi 
cut away : enlarged six times. 

The dotted lines with the arrows show wliioh pollen must be applied to each 
stigma to cause full fertility. 



173 >[R. C. DARWIN O:^ THE SEXtlAI. r.ET.ATIOyS OF 

croseoxje, and I found I could always (with one exception) distin- 
guisli them : I then showed the specimens to two other persons, 
and they likewise distinguished the two kinds and pointed out 
which was the largest. The capsules of this form contain, on an 
average, 93 seeds : how this average was obtained will presently 
be explained. I repeatedly observed that the seed, when cleaned, 
seemed larger than that from the mid-styled or short-styled 
forms ; consequently I placed 100 loug-stylod seeds in a good 
balance, and by the double method of weighing found that they 
equalled 121 seeds of the mid-styled and 142 of the short-styled ; 
or, in short, that five long-styled seeds equalled six mid-styled and 
seven short-styled seeds. These slight diiferences in the weight of 
the seed, and, as we shall soon see, in the average number produced, 
are worth recording, as they characterize not mere varieties but 
coexisting forms of the same species. 

3Iid-styled form. — The pistil occupies the position represented 
in the diagram, with its extremity considerably, but in a variable 
degree, upturned ; the stigma is seated between the anthers of 
the long and the short stamens. The six longer stamens correspond 
in length with the pistil of the long-styled form ; their filaments 
are coloured bright pink ; the anthers are dark-coloured, but 
from containing bright green pollen and from their early de- 
hiscence they appear emerald-green. Hence the general appear- 
ance of these stamens is remai'kably dissimilar from that of the 
longer stamens of the long-styled form. The six shorter stamens, 
enclosed within the calyx, resemble in all respects the shorter 
stamens of the long-styled form, and both correspond in length 
with the short pistil of the short-styled form. The green pollen- 
grains of the longer stamens are plainly larger than the yellow 
pollen-grains of the shorter anthers : this fact was conspicuous in 
several camera-lucida drawings made for me by my sou, Mr. W. E. 
Danvin. There is some variability in size, but y-J-J^ of an inch 
may be taken as about the average diameter of the green pollen- 
grains when distended mth water, and y-^ij aa the diameter of 
the yellow grains of the shorter stamens ; so that the difi'ercnce 
in diameter is in about the proportion of four to three. The cap- 
sules contain, on an average, 132 seeds ; but, perhaps, as we shall 
see, this is rather too high an average. The seeds themselves are 
smaller than those of the long-styled form. 

Short-styled form. — The pistil is here very short, not one-third 
of the length of that of the long-styled form. It is enclosed 
within the calyx, which, differently from in the other two forms. 



THE THEEE rOEilS OF LTTHRUil SAT.ICAKIA. IvJJ 

does not enclose any anthers. The end of the pistil is generally 
bent upwards at right angles. The six longer stamens, with their 
pink filaments and green pollen, resemble in size of the grains 
and in all respects the longer stamens of the mid-styled form, and 
both correspond in length with the long-styled pistd. The six 
shorter stamens, with their uncoloured iilaments and yellow pollen, 
resemble in size of the grains and in all respects the longer 
stamens of the long-styled form, and both correspond in length 
with the mid-styled pistil. The capsules contain fewer seeds on 
an average than in eitlior of the preceding forms, namely 83'5, and 
they are considerably smaller in size. In this latter respect, but 
not in number, there is a gradation parallel to that of the length 
of tlie pistil, the long-styled having the largest, the mid-styled the 
next in size, and the short-styled the smallest seed. 

From this description we see that there are three distinct 
female organs, or rather females as they are borne on distinct indi- 
viduals, diifering in the length and curvature of the style, in the 
size of the stigma, and in the number and size of the seed. In the 
three forms, taken together, there are thirty-six stamens or males, 
and these can be divided into three sets of a dozen each, differing 
from each other in length, curvature, and colour of the filaments, 
in the size of the anthers, and especially in the colour and 
diameter of the pollen-grains. Each of the three forms bcar,^ 
half-a-dozcn of one kind of stamens and half-a-dozen of another 
kind, but not all three kinds. The three kinds correspond in 
length with the three pistils : the correspondence is always be- 
tween half the stamens borne by two forms with the pistil of a 
third form. These remarks apply to the structure, and not, as yet, 
to the functions, of the reproductive organs. 

I ascertained the average number of seed by counting them in 
eight fine selected capsides taken from plants of the three fonns 
growing wild, and the result was, as we have seen, for the long- 
styled (neglecting decimals) 93, mid-styled 132, and short-styled 
83. I should not have trusted this result, but I had a number 
of plants in my garden which, from their youth, did not yield the 
full complement of seed, but they were of exactly the same age 
and grew under exactly the same conditions, and were freely 
visited by bees. I took six fine capsules from each, and found 
the average to be for the long-styled 80, for the mid-styled 97, 
and for the short-styled 61. Lastly, I made numerous artificial 
unions, and, as may be seen in the following Tables, these gave 
in the long-styled an average of 90 seeds, in the mid-styled 117, 



17J: 



MB. C. DABWIJf ON THE SEXUAT. BKLATIONS OF 



and in the short-styled 71. So that we have good concurrent 
evidence of the different average production of seed by the three 
forms. To show that the artiiicial fertilizations, presently to he 
described, produced their full effect and may be trusted, I may 
state that one mid-styled capsule yielded 151 good seeds, which 
is the exact number of the finest wild capsule examined by me. 
Artificially fertilized short- and long-styled capsules actually pro- 
duced a greater number of seeds than I have found in wild plants, 
but then I did not examine many of the latter. This Lythrum, 
I may add, offers a remarkable instance, how profoundly ignorant 
we are of the life-conditions of each species : naturally it grows 
" in wet ditches, watery places, and especially on the banks of 
streams," and though it produces so many minute seeds, it never 
spreads on the adjoining land ; yet, planted in my garden, on 
clayey soil lying over the chalk, and which is so dry that a rush 
cannot be found, it thrives luxuriantly, grows to above six feet iu 
height, produces self-sown seedlings, and (which is a severer test) 
is fully as fertile as in a state of nature. Nevertheless it would 
be almost a miracle to find this plant spontaneously growing on 
such land as my garden, though under its native climate. 

According to Vaucher and Wirtgen, the three forms coexist in 
all parts of Europe. Some friends gathered for me in North 
Wales a number of twigs from separate plants growing near each 
other, and then classified them. My son did the same in Hamp- 
shire, and here is the result : — 



! 


Long-styled. 


Slid-stylcd. 


1 
Sliort-styled. j 


Total. 


\ XortliWale.s 
1 Hampshire . 


95 
53 


97 

38 


72 ! 
3?^ i 


204 
129 


1 Total. . . . 


l-t-S 


135 


110 ; 


393 



If twice or thrice the number had been collected, probably the 
three forms would have been found nearly equal ; I infer this 
from considering the above figures, and from my son telling me 
that if he had collected in another spot, he felt sure that the 
mid-styled plants would have been in excess. I several times 
sowed small parcels of seed, and raised all three forms ; but I 
neglected to record the parent form, except in one instance, in 
which I raised from short-styled seed twelve plants, of which only 
one turned out long- styled, four mid-styled, and seven short- 
styled. 



THE THREE FORMS OF I.TTHBTIM SALTCARIA. 175 

Insects are neccssan- for the fertilization of this Lytlirum. 
During two years I kept two plants of each form protected, and 
in the autumn they presented a remarkable contrast in appear- 
ance with the adjoining uncovered plants, which were densely 
covered with capsules. In 1863 a protected long-styled plant pro- 
duced only five poor capsules ; two mid-styled plants produced the 
same number ; and two short-styled plants between them produced 
only one : these capsules contained very few seed ; yet the plants 
were fully productive when artificially fertilized under the net. 
In a state of nature the flowers are incessantly visited for their 
nectar by hive- and liumble-bees and various Diptera. The nectar 
is secreted all round the base of the ovarium ; but a passage is 
formed along the upper and inner side of the calyx by the lateral 
deflection (not represented in the diagram) of the basal portions 
of the filaments ; so that insects invariably alight on the upper 
side of the flowers, on the projecting stamens and pistil, and insert 
their probosces along the ujjper inner margin of the calyx. "We 
can now see why the ends of the stamens with their anthers, and 
the ends of the pistils with their stigma, are a little upturned, in 
order that they may brush against the lower hairy surfaces of the 
insects' bodies. The short stamens which lie enclosed within the 
calyx of the long- and mid-styled forms can be touched only by 
the proboscis and the narrow chin of the sucking bee ; hence they 
have their ends more upturned, and they are graduated in length, 
so as to fall into a narrow file, three deep, sure to be raked by 
the thin intruding proboscis. The anthers of the longer stamens 
stand laterally further apart and are more nearly of the same 
length, for they have to brush against the whole breadth of the 
insect's body. I may here incidentally remark, that in very 
many flowers the pistil, or the stamens, or both, are rectangularly 
bent to one side of the flower : this bending may be permanent, 
as with Lytlirum and many others, or may be efiected (as in 
Dictamnus fraxineUa and many others) by a temporary move- 
ment which occurs in the stamens when the anthers dehisce, 
and in the pistil when the stigma is mature ; but these two 
movements are by no means always contemporaneous in the 
same flower. iN'ow I have found no exception to the rule, that 
when the stamens and pistil are bent, the bending is exactly to 
that side of the flower which secretes nectar (even though there 
be a rudimentary nectary of large size on the opposite side, as m 
some species of Cori/dalis) ; or, when nectar is secreted on all 
IIKN. PBOC. — BOTAirr, TOI. Till. ^ 



176 MB. C. DAEWIN OS" THE SEXUAL KELATIOyS OP 

sides, to that side where the structure of the flowers allows the 
easiest access to it, as in Lyihrum, Papilionaceous flowers, and 
many others. The rule consequently is that when the pistil and 
stamens are bent, the stigma and anthers are brought into the 
pathway towards the nectary. There are a few cases which seein 
to be exceptions, but they are not so in truth : for instance, in the 
Grloriosa lily, the stigma of the grotesque and rectangularly bent 
pistil is brought, not into the pathway from the open air towards 
the nectar-secreting recesses of the flower, but into the circular 
route from one nectajpy to the other ; in Scrophularia aquatica 
the pistil is bent downwards from the mouth of the flower, but 
it thus strikes the pollen-dusted breasts of the wasps which 
habitually visit these iU-scented blooms. In the above rule we see 
one more instance of the supreme dominating power of insects 
over all the minor structural details of flowers, especially of those 
which have irregular corollas. Elowers which are fertilized by 
the wind must of course be excepted, but I do not know of a 
single instance of an irregular flower which is fertilized or crossed 
by this means. 

I have delayed too long on these points, but I must allude to 
one other. We have seen that the three pistils of different 
lengths have each two half-dozen sets of stamens of correspond- 
ing length. When bees suck the flowers, the longest stamens, 
bearing the green pollen, rub against the abdomen and the iate- 
rior sides of the posterior legs, as does likewise the stigma of the 
long-styled form. The stamens of middle length and the stigma 
of the mid-styled form rub against the under side of the thorax 
and between the front pair of legs. The shortest stamens and 
the stigma of the short-styled form must rub against the pro- 
boscis and chin ; for the bees in sucking insert only the front of 
their heads into the calyx. On catching bees, I observed much 
green poUen on the inner sides of the hind legs and on the abdo- 
men, and much yellow poUen on the under side of the thorax. 
There was also pollen on the chin, and, it may be piresumed, on 
the proboscis, but this was difficult to observe. I had, however, 
independent proof that pollen is carried on the proboscis ; for in 
a protected short-styled plant (which produced only two cap- 
sules) one small branch was accidentally left during many days 
pressing against the iine net, and bees were seen inserting their 
probosces through the meshes, and in consequence numerous 
capsules were formed on this one small branch. From these 
several fects it foUows that insecta would chiefly carry to the 



THE THREE FOHMS OF TA-THBUM SALICAEIA. 177 

stigma of each form pollen from the stamens of corresponding 
length ; and we shall presently see the importance of this adapta- 
tion. It must not, however, be supposed that the bees do not 
get more or loss dusted aU over with the several kinds of poUen ; 
they certainly do, as could be seen with the green pollen from 
the longest stamens. Moreover, a case wiU presently be given of 
a long-styled plant which grew absolutely by itself, and produced 
an abundance of capsules, which must have been fertilized by its 
own two kinds of pollen ; but these capsules contained a very 
poor average of seed. Hence insects, and chieily bees, act both 
as general carriers of pollen, and as special carriers of the right 
kind *. 

Variability. — Before passing on to more important topics, I 
must say a few words on this head. Wirtgcn remarks t on the 
variability in the branching of the stem, .in the length of the 
bractcaa, size of the petals, and in several other respects. The 
plants now growing in my garden have their leaves arranged op- 
positely, alternately, and in whorls of three, and differ greatly in 
shape. The stems of the plants bearing leaves in whorls are 
hexagonal ; those of the other plants are quadrangular. But we 
are concerned only with the reproductive organs : the upward 
bending of the pistil is variable, and in a remarkable degree jn 
the short-styled form, in which it is sometimes straight, Tsome- 
times slightly curved, but generally upturned at right angles. 
The stigma of the long-styled pistil frequently has longer papillaa 
or is rougher than that of the mid-styled, and this than that of 
the short-styled form ; but this character, though fixed and uni- 
form with the two forms of Primula, is here variable, and I have 

* In my paper ou the two forms of Frimula (Journal Proc. Linn. Soc. 1862, 
p. 85) I stated that I had only occasionally seen Immble-bes sucking the flowers 
of the Cowshp (P. veris). Since then I have had some beds in my garden 
eontauiing nearly 700 plants, and these were incessantly visited by Bomlua 
hortornm and S. muscormn. I caught some of these bees, and I found (as I 
had anticipated in my paper, p. 86) that a vast majority of the poUen-grains 
which adhered to the base of the proboscis were large-sized and had come from 
the long stamens of the short-styled form, and were thus placed ready to ferti- 
lize the stigma of the long-styled form. On the other hand, on the middle, and 
near tlie tip of the proboscis, a very large proportion of the pollen -grams were 
of the small size, and had come from the short stamens of the long-styled form. 
My son caught, also, a moth (CuciilUa wriasci) hovering over the bed, and I 
found on its proboscis a similar distribution of the two kinds of pollen-grains. 
I give these facts as a further illustration of the importance of the relative 
lengths of the stamens and pistil. 

t Vei-hand. des iiaturiiiet. Vereins, 5. Jahrgang, 1848, S. 11^ 13. 

p2 



178 MK. C. DAB-niX Oy THE SESI'AL KELATION'S OF 

seeu mid-st}4ed stigmas rougher than those of the long-styled. 
The degree to which the longer and middle stamens are graduated 
in length and are upturned at their ends is variable ; sometimes 
all are equal. The colour of the green pollen in the long stamens 
is Tariable *, and is sometimes pale greenish yellow ; in one short- 
styled plant it was almost white. The grains vary a little in. 
size : I osamiued one short-styled plant witli the grains above 
the average size ; and I have seen a long-styled plant with un- 
distinguishable grains from the longer and shorter anthers. "VVe 
have here considerable fluctuations of character; and if any of 
these slight structural diiferences Avere of direct service to the 
plant, or wore correlated with useful functional diflerences, we 
can perceive that the species is just in that state in which natural 
selection might readily do much for its modification. 

To return to our proper subject — we see that there are three 
kinds of females and three kinds of males, each kind of the latter 
being borne by half-dozens on two of the three forms. It remains 
to discover whether these several sexes or sexual organs differ from 
each other in function. Nothing brings more prominently forward 
the complexity of the reproductive system of this extraordinary 
plant, than the necessity, in order to ascertain the above fact, of 
artificially making eighteen distinct unions. Thus the long-styled 
form had to be fertilized with pollen from its own two distinct 
kinds of anthers, from the two in the mid-styled, and from the two 
in the short-styled form. The same process had to be repeated 
with both the mid- and short-styled forms. It might have been 
thought sufficient to have tried on each stigma the green pollen, 
for instance, from either the mid- or short-styled longer stamens, 
and not from both ; but the result proves that this would have ■ 
been insuificient, and that it was necessary to try all six kinds of 
pollen on each stigma. As in artificial fertilizations there wiU 
always be some failures, it would have been advisable to have 

* Lagerstrcemia Indica, one of the Lythraoeie, is strangely variable in its 
stamens — I presume in part due to its growth in a hothouse. The most per- 
fect flowers produced with me fire very long stamens with thick flesh-coloured 
filaments and green pollen, and from nineteen to tw-enty-nine short stamens with 
yellow pollen ; hut many flowers produced only one, two, three, or four long 
stamens with green pollen, which in some of the anthers was wholly replaced 
by yellow pollen ; one anther offered the singular case of half, or one cell being 
filled with bright green, and the other cell with bright yellow pollen. One petal 
had a furrow near its base, which contained poUen. Accordmg to analogy with 
Lt/thrum, this species would produce three forms ; if so, the above plant was a 
mid-3tyled form : it was quite sterile with its own two kinds of pollen. 



THE THHEE FOltMS 01' LXTHEVJI SALIL'AKIA. 179 

repeated each of the eighteen unions a score of times ; but the 
labour would have been too great ; as it was, I made 223 artificial 
unions ; i. e., I fertilized, on an average, above a dozen flowers in 
the eighteen dilFerent methods. Each flower was castrated; the 
adjoining buds had to be removed, that the marking-tliread, wool, 
&c. might be safely secured ; and after each fertilization the 
stigma had to be examined with a lens to see that there was suf- 
ficient pollen. Plants of all three forms were protected during 
two years by large nets on a framework ; two plants were used 
during one or both years, in order to avoid any individual pecu- 
liarity in any one plant. As soon as the flowers withered, the 
nets ^YCTO removed ; and in the autumn tlie capsules were daily 
inspected ; when the seeds were ripe they were counted under 
the microscope. I have given these details that confidence may 
be placed in the following Tables, and as some eseuse for two 
blunders which, I believe, I made. These blunders are referred 
to, with tlieir probable causes, in two notes to the Tables ; the 
erroneous numbers, however, are entered in tlie Tables, that it 
may not be supposed that I have in any one instance tampered 
with the results. 

A few words explanatory of the three Tables must be given. 
Each is devoted to one form, and is divided into six compartments. 
The two upper ones in each table give the product of good seed 
from the application of pollen from the two sets of stamens which 
correspond in lengtli with the pistil of that form. The two next 
lower compartments show the result of pollen from the other two 
sets of stamens, which do not correspond in length with the pistil, 
and which are borne by the same two forms. The two lowest 
compartments show the result of the application of each form's 
own two kinds of pollen. The term "own pollen," used here and 
in the Tables, does not mean pollen from the flower to be fertilized 
— for this was never used — but from another flower on the same 
plant, or more commonly from a distinct plant of the same form. 
In the result given, " " generally means that no capsule was 
produced, or that the capsule contained no good seed. In some 
part of each row of figures in each compartment, a short hori- 
zontal line mav be seen ; the unions above this line were made in 
1862, and below it in 1803. It is of importance to observe this, 
as it shows that the same general result ensued in two successive 
years ; but more especially because 1863 was a very hot and dry 
season, and the plants had occasionally to bo watered. This did 
not prevent the full complement of seed being produced from 



180 



Mil. 0. BAEWIN ON" TUB SEXUAL HEIATIONS OF 



the more fertile 'imions ; but it rendered the less fertile imions 
even more sterile than they otherwise would have been. I have 
seen striking instances of this same fact in making homomorphie 
and heteromorphic unions in Primula * ; and it is well known 
that the conditions of life must be highly favourable to give any 
chance of producing hybrids from species which cross with diiB- 
culty. 

Table I. — LoNG-STiiED Fosm. 



I. 

13 flowers fertilized hy the longer 
stamens of the mid-styled. T/iese 
damms equal in length the pistil of 
the loiig-styhd. 

Product of good seed in each capsule. 
36 53 

81 







— 

45 
41 
38 per cent, of these flowers yield- 
ed capsYiles. Each capsule contain- 
ed, on an average, 51-2 seed. 



II. 

13 flowers fertilized by the longer 
stamens of the short-styled. These 
stamens equal in length the pistil of 
the long-styled. 

Product of good seed in each capsule. 
159 104 

43 119 

96 poor seed. 96 
103 





99 
131 
116 



114 



84 per cent, of these flowers yield- 
ed capsules. Each capsule con- 
tained, on an average, 107'3 seed. 



* In the spring of 1862 I crossed forty Cowslip flowers {P. veris) hetero- 
morphieally and homomorphicaUy. The plants were accideutaUy exposed in 
the greenhouse to too hot a sun, and a numher of umbels perished. Some, 
however, remained in moderately good health, and on these there were twelve 
flowers which had been fertflized hotcromorphically and eleven which had been 
fertiliised homomorphicaUy. The twelve heteromorpliio miions yielded seven fine 
capsules, containing on an average 57'3 good seed. Now mark the difference : 
the eleven homomorphie unions yielded only two capsules, of which one con- 
tained 39 seeds, but so poor, that I do not suppose one would have germinated, 
and the other only 17 fairly good seed. It would be superiluous to give any 
more details on this experiment, or on some which I made at the same time on 
P. Sinensis, after the appearance of Mr. John Scott's admirable paper on the 
various dimorphic species of Primula, in which he confirms my former results, 
and adds many original and valuable observations. Dr. Hddebrand has also 
(Botanischo Zeitung, 1864, Jan. 1, S. 3) confirmed my general residts with respect 
to P. Sinensis, and has corrected an error into which in some unaccountable 
manner I feU, namely, that the poflen-grains from the long- and short-styled 
forms -were of the same size. Dr. Ilildebrand has added a series of new and 
important experiments, for he fertflized homomorphicaUy a number of flowers 
with poUen from the same form, and likewise from the same individual flower. 
These latter he found were thus rendered rather more sterfle. This experiment, 
I believe, has never been systematically tried before. 



THE THBEE FOBMS OF LTTHBTJM SAMCAHIA. 



181 



Table I. — Lono-sttlbd Foem {continued). 


in. 


IV. 


14 flowera fertUized by the short 


12 flowers fertilized by the shorter 


stamens of the mid-styled. 


stamens of the short-styled. 


3 


20 























— 


— 


a 











Too sterile for any average. 


Too sterile for any average. 




V. 


VI. 


15 flowers fertilized by oivn longer 


15 flowers fertilized by miM shorter 


stamens. 


stamens. 


2 — 


4 — 


10 


8 


23 


4 


. 





























Too sterile for any average. ' 


Too sterile for any average. 



I fertilized a considerable number of flowers with pollen, taken by a 
camel's-hair brush,fi-om both the long and short stamens of their own (long- 
styled) form ; but I did not examine with a lens (as I did in the cases in 
the Tables) whether suflicient pollen had been placed on the stigma : only 
5 capsules were produced, and these jielded on an average 14'5 seed. In 
186.3 I tried a much better experiment : a long-styled plant was grown 
by itself, miles away from an}' other plant, so that its stigmas could have 
received only the two kinds of pollen proper to this form. The flowers 
were incessantly visited by bees, so that the stigmas must have received 
on the most favourable days, and at the most favourable hours, successive 
applications of pollen : aU who have crossed plants know that this highly 
favours fertilization. This plant produced an abundant crop of capsules ; 
I took by chance 20, and these (excluding one poor one) contained seed as 
below:— 20 20 35 21 19 

20 24 12 23 10 

7 30 27 29 13 

20 12 29 19 35 

This gives an average of 21-5 seed per capsule ; and as we know that this 
form, when standing near plants of the other two forms and fertilized by 
insects, produces an average of 934 seed per capsule, we see that the 
long-styled form fertilized by its own two poUens j-ields only between 
one-fourth and one-fifth of the full number of seed. I have spoken as if 
this plant had received both its own kinds of pollen, and this is, of course, 
possible ; but, from the enclosed position of the shorter stamens, it is 
much more probable that the stigma received almost exclusively the pollen 
from its own longer stamens. 



182 



MH. C. DAB1TIX OJf TUB SEXUAL BELATIO'S OF 



Table II. — Mid-sttt,ed FoHir. 



12 flowers fertilized by the longer 
stamens of the long-styled. Them 
stamens equal in length the pistil of 
the mid-styled. 
Product of good seed in each capsule. 

138 122 

140 50 
1-17 151 
100 119 
133 138 

141 

92 per cent, of the tiowers (pro- 
hably 100 per cent.) yielded cap- 
sules. Eachjjapsule contained, on 
an average, 127'3 seed. 



II. 
12 flowers fertilized by the shorter 
stamens of the short-styled. These 
stamens equal in length the pistil of 
the mid-stgled. 
Product of good seed in each capsule. 

112 109 

180 143 

143 124 

100 145 

33 12 

— 141 

104 
100 per cent, of the flowers yielded 
capsules. Each capsule contained, 
on an average, 108 '0 seed ; or, ex- 
cluding capsules with less than 20 
seed, the average is 110'7 seed. 



III. 
13 flowers fertilized by the short 
stamens of the long-stvled. 
83 12 

r, a- (seed small 

U CO -> , 

Q ' and poor. 






44 
44 
45 







54 per cent, of the flowers yielded 
capsules. Each capsule contained, 
on an average, 47-4 seed; or, ex- 
cluding capsules with less than 20 
seed, the average is CO-2 seed. 



IV. 

15 flowers fertilized by the longer 
stamens of the short-styled. 
130 86 

115 113 

14 29 

6 17 

2 113 

9 79 

— 128 

132 

03 per ceni. of tie flowers yielded 
capsules. Each capsule contained, 
on an average, 69-5 seed ; or, ex- 
cluding capsules with less than 20 
seed, the average is 102'8. 



12 flowers fertilized by oirn longer 
stamens. 

02 

9 

C3 

— 

130 ? * 




Excluding the capsule with 136 
seed, 25 per cent, of the flowers 
yielded capsules, and each capsule 
contained, on an average, 54-0 seed ; 
or, excluding capsules with less than 
20 seed, the average is 77'5. 



VI. 

12 flowers fertilized by om-m shorter 
stamens. 







— 






per cent, of the flowers yielded 
capsules. 



* I have hardly any doubt that this result of 136 seed is due to a gross error. 
The flowers to be fertilized by their own longer stamens were fii-st marked by 



THE THREE TOHMS OF LTTHBTJil SAIICAHIA. 



183 



I fertilized a considerable number of flowers with pollen, taken by a 
camel's-hair brush, fi-om both the long and short stamens of their own 
(shoi-t-styled) fomi ; but I did not examine -n-ith a lens (as I did in the 
cases in the Tables) whether sufficient pollen had been placed on the 
stigma : only 5 capsules were produced, and these yielded, on an ayerage, 
11-0 seed. 



Table III. — Stiobt-sttled romr. 



I. 

12 flowers fertilized bj^ the shorter 
stamens of the long-styled. These 
stamens equal in length the pistil of 
the short-styled. 



61 


88 


88 


112 


66 


111 





62 





lOO 



83 per cent, of the flowers yielded 
capsules. Each capsule contained, 
on an ayerajre, 81-3 seed. 



II. 

13 flowers fertilized by the shorter 
stamens of the mid-styled. 'Iltese 
stamens equal in length the pistil of 
the short-styled. 



93 
77 
48 
43 





ca 

09 
o3 
9 






61 per cent, of the flowers yielded 
capsules. Each capsule contained, 
on an ayerage, G4'6 seed. 



HI. 

10 flowers fertilized by the longer 
stamens of the long-styled. 
14 







— 

23 
Too sterile for any ayerage. 



10 flowers fertilized by the longer 
stamens of the mid-styled. 
" 







— 


Too sterile for any average. 



"white thread," and those by the longer stamens of the long-styled form by 
" white silk ; " a flower fertilized in the latter manner would have yielded about 
136 seed, and it may be observed that one such pod is missing, viz., at the bottom 
of compartment 1. Therefore I have hardly any doubt that I fertilized a 
flower marked with " white thread," as if it had been marked with " white silk." 
With respect to the capsifle which yielded 9^ seed, in the same column with that 
which yielded 136, I do not know what to think. I endeavoured to prevent 
pollen dropping from an upper to any lower flower, and I tried to remember 
to wipe the pincers carefully after each fertilization ; but in making eighteen 
different crosses, sometimes on windy days, and pestered by bees and flies buzzing 
about, some few errors could hardly be avoided. One day I had to keep a 
third man by me all the time to prevent the bees visiting the uncovered plants, 
for in a tew seconds' time they might have done irreparable mischief. It was 
also extremely difSoult to exclude minute Diptcra from the net. In 1862 I 
made the great mistake of placing a mid-styled and long-styled under the same 
huge net : in 1863 I avoided this error. 



184 ' MH, C. DAHWIN OJf THE SEXUAL BELATIONS OF 

Table III. — Short-stxled Fobm {continued). 



V. 


VI. 


10 flowers fertilized by mm longer 


lOflowers fertilizeij by oiun shorter 


stamens. 


stamens. 





64?* 














— 


— 





21 





9 


Too sterile for any average. 


Too sterile for any average. 



I fertilized a number of flowers without particular care with their own 
two pollens, but they did not produce a single capsule ; the position of 
the stigma within the calyx renders the fertilization without some care 
difficult. 

Summary of the three preceding Tables. 

Long-styled form. — Twenty-six flowers fertilized by the stamens 
of corresponding length, borne by the mid- and short-styled forms, 
yielded Cl-5 per cent, of capsules, which contained, on an average, 
89-7 seed. 

Twenty-six flowers fertilized by the other and shorter stamens 
of the mid- and short-styled forms yielded only two very poor 
capsules. 

Thirty flowers fertilized by this form's own two sets of stamens 
yielded only eight very jjoor capsules ; but flowers well fertilized 
by bees by one or both of their own kinds of pollen produced 
numerous capsules containing, on an average, 21-5 seed. 

Short-styled form. — Twenty -five flowers fertilized by the stamens 
of corresponding length, borne by the long- and mid-styled forms, 
yielded 72 per cent, of capsules, which (excluding one capsule 
with only nine seeds) contained, on an average, 70'8 seed. 

Twenty flowers fertilized by the longer stamens of the long- 
and mid-styled forms yielded only two very poor capsules. 

Twenty flowers fertilized by both their own two sets of stamens 
yielded only two poor (or perhaps three) capsules. 

Mid-styled form. — Twenty -four flowers fertilized by the stamens 
of corresponding length, borne by the long- and short-styled 
forms, yielded 96 (probably 100) per cent, of capsules, which con- 

* I suspect that, by mistake, I fertilized this flower with the pollen of the 
shorter stamens of the long-styled form, and it would then have yielded about 
64 seed. Flowers to be thus fertilized were marked with black silk ; those with 
the poUcn of the shorter stamens of the short-styled with black thread ; and thus, 
I suspect, the mistake arose. 



THE THBEE FOEIIS OP LTTHBUM SAIICAHIA. 185 

tained (excluding one capsule with 12 seed), on an average, 117-2 
seed. 

Fifteen flowers fertilized by the longer stamens of the short- 
styled form yielded 93 per cent, of capsules, which (excluding 
four capsules with less than 20 seed) contained, on an average, 
102-8 seed. 

Thirteen flowers fertilized by the shorter stamens of the long- 
styled form yielded 54 per cent, of capsules, which capsules (ex- 
cluding one with 19 seed) contained, on an average, 60-2 seed. 

Twelve flowers fertilized by own longer stamens j'iolded 25 per 
cent, of capsules, which (excluding one with 9 seed) contained, on 
an average, 77-5 seed. 

Twelve flowers fertUized by own shorter stamens yielded not a 
single capsule. 

Considering the three Tables and this summary, we may safely 
draw the following conclusions. First, that, as in structure so in 
function, there are three females or female organs : this is mani- 
fest ; for when all three receive the very same pollen, they are 
acted on most difiierently. So conversely with the thirty-six sta- 
mens, we know that they consist of three separate sets of a dozen 
each, dilTering in various respects ; and in function the pollen of 
these three sets when applied to one and the same stigma acts 
most differently, as a glance at the Tables proves. But we shall 
presently see that the action of the pollen of the whole dozen 
longest and of the whole dozen shortest stamens is not identical. 
Secondly, wo see that only the longest stamens fully fertilize 
the longest pistil, the middle stamens the middle pistil, and the 
shortest stamens the shortest pistil. And now we can compre- 
hend the meaning of the almost exact correspondence in length 
between the pistil of each form and the two half-dozen sets of 
stamens borne by the two other forms ; for the stigma of each 
form is thus rubbed against the same spot of the insect's body, 
which becomes most charged with the proper pollen. In all tliree 
forms, the female organ is but feebly, or not at aU, acted on by its 
own two kinds of pollen. In my papers on the dimorphism of 
Primula and Linum, I used the terms " heteromorphic " for the 
fully fertile unions between the female element of the one form 
and the male element of the other, and " homomorphic " for the 
less fertile or quite sterile unions between the female and male 
elements of the same form. The principle involved in these terms 
holds good with Lythrum, but is insufficient ; for though in each 
of the three forms the fertile unions are all heteromorphic, the ap- 



186 MR. C. DABWIS- Oy THE SEXUAL EELATIOITS OJ? 

propriate pollen coming from the stamens of corresponding length 
borne by the other two forms, and though the homamorpUc unions 
of the females with their own two sets of males are always more 
or less sterile, there remain in each case two other sterile unions, 
not included in these two terms. Hence it will be found con- 
venient to designate the two unions of each female with the two 
sets of stamens of corresponding length, which are fully fertile, as 
legitimate tmions, and the four other, more or less sterile, unions 
of each female with the four other sets of stamens as illegitimate 
unions. Consequently, of the eighteen possible unions between 
the three forms, six are legitimate and twelve are illegitimate. 

Another and curious conclusion cannot be considered as proved, 
but is rendered highly probable, by the Tables. The unions of 
the pistils and stamens of equal length are alone fully fertile. 
Now with the several illegitimate unions it will be found that the 
greater the inequality in length between the pistil and stamens, 
the greater the sterility of the result. There is no exception to 
this rule. Thus, with the long-styled form, its own shorter sta- 
mens are far less equal in length to the pistil than its own longer 
stamens ; and the capsules fertilized by the pollen of the shorter 
stamens yielded fewer seeds : the same comparative result follows 
from the use of the pollen of the shorter stamens of the mid-styled 
form, which arc much shorter than the shorter stamens of the short- 
styled (see diagram), and therefore less equal in length to the long- 
styled pistil. We shall see exactly the same result if we look to 
the four illegitimate unions under the mid- and short-styled forms. 
Certainly the difference in sterility in these several cases is very 
slight, but the sterility always increases with the increasing 
inequality of length between the pistU and the stamens which are 
used. Therefore I believe in the above rule ; but a vast number 
of artificial unions would be requisite to prove it. If the rule be 
true, we must look at it as an incidental and useless result of the 
gradational changes through which this species has passed in 
arriving at its present condition. On the other hand, the corre- 
spondence in length between the pistil of each form and those 
stamens which alone give full fertility is clearly of service to the 
species, and is probably the result of direct adaptation. 

Some of the illegitimate unions yielded, as may be seen in the 
Tables, during neither year a single seed ; but, judging from the 
case of the long-styled plant, it is probable, if such unions could 
be effected repeatedly under the most favourable conditions, some 
few seeds would be produced. Anyhow, I can state that in all 



THE THEEE F0EM3 OF XTTHBrjI SALICAHIA, 187 

the eighteen possible vinions the polleu-tubes penetrated, after 
eighteen hours, the stigma. I have reason to believe that the 
ofispring from the illegitimate unions present some singular 
characteristics ; but until my observations on this head are re- 
peated, I must be silent. At first I thought that perhaps two 
kinds of pollen placed together on the same stigma would give 
more fertility than any one kind ; but we have seen that this is 
not the case with each form's own two kinds of pollen ; nor is it 
probable in any case, as I occasionally got, by the use of single 
kinds of pollen, fully as many seed as I have seen in a capsule 
naturally fertilized. Moreover the proper pollen from a single 
anther is more tlian sufficient to fully fertilize each stigma ; hence, 
in this as in so many other cases, at least twelve times as much 
of each kind of pollen is produced as is necessary to ensure full 
fertilization. From the dusted condition of the whole body of 
those bees which I caught on these flowers, it is probable that 
some pollen of all kinds is deposited on each stigma ; but there 
can hardly be a doubt that the pollen of the stamens of corre- 
sponding length will be prepotent and will wholly obliterate any 
eft'cct from tho other kinds of pollen, even if previously deposited 
on the stigma. I infer this partly from the fact ascertained by 
Glirtner tliat each species' own pollen is so prepotent over that of 
any other species, that if put on the stigma many hours subse- 
quently, it will entirely obliterate the action of the foreign pollen. 
But I draw the above inference especially from the following 
experiment : I fertilized homomorphically or illegitimately some 
long-styled Cowslip flowers (^Primula veris) with their own pollen, 
and exactly twenty-four hours subsequently I fertilized these 
same stigmas heteromorphically or legitimately with pollen from 
a short-styled dark-red Polyanthus. I must premise that I have 
raised many seedlings from crossed Cowslips and Polyanthus, and 
know their peculiar appearance ; and I further know, by the test 
of the fertility of the mongrels inter se, and with both parent 
forms, that the Polyanthus is a variety of the Cowslip, and not of 
the Primrose (P. vulgaris) as some authors have supposed. iS^ow 
from the long-styled Cowslip twice fertilized in the manner ex- 
plained, I raised twenty-nine seedlings, and every one of them 
had flowers coloured more or less red ; so that the heteromorphic 
Polyanthus-pollen wholly obliterated the influence of the homo- 
morphic pure Cowslip-pollen, which bad been placed on the 
stigmas twenty-four hours previously, and not a single pure 
Cowslip was produced. 



188 ME. C. DAEWTS OS THE BEXrAL HELATIOHS OE 

The last conclusion which may be deduced from the Tables, 
even from a glance at them, is that the mid-styled form differs 
from both the others in its much higher capacity for fertilization. 
Not only did the twenty-four flowers fertilized by the stamens of 
corresponding lengths, all, or all but one, yield capsules rich in 
seed ; but of the other four illegitimate unions, that by the longer 
stamens of the short-styled form was highly fertile, though less 
than in the two legitimate unions, and that by the short stamens 
of the long-styled form was fertile to a considerable degree ; the 
two unions with this form's own pollen were sterile, but in dif- 
ferent degrees. So that the mid-styled form, when fertilized by 
the sis kinds of pollen, evinces five different grades of fertility. 
By comparing compartments 3 and 6 in Table II. we learn a re- 
markable fact, namely, that though the pollen from the short 
stamens of the long-styled and from this form's own (mid-styled) 
short stamens, used in these two unions, is identical in aU respects, 
yet that its action is widely difi'erent ; in the one case above half 
the fertilized flowers yielded capsules containing a fair number of 
seed ; in the other case not one single capsule was produced. So, 
again, the green, large-grained pollen from the long stamens of 
the short-styled and from this form's own (mid-styled) long sta- 
mens is identical in aU respects, but its action, as may be seen in 
compartments 4 and 5, is widely different. In both these cases 
the difference in action is bo plain that it cannot be mistaken, but 
it can be corroborated. If we look to Table III., to the legiti- 
mate action of the short stamens of the long- and mid-styled 
forms on the pistil of the short-styled form, wo again see a similar 
but slighter difference, the poUen of the short stamens of the 
mid-styled form yielding a smaller average of seed during the 
two years of 1862 and 1863 than that from the short stamens of 
the long-styled form. Again, if we look to Table I., to the legi- 
timate action of the green pollen of the two sets of long stamens, 
we shall find exactly the same result, viz. that the pollen of the 
long stamens of the mid-styled form yielded during both years 
fewer seeds than that from the long stamens from the short-styled 
form. Hence it is certain that the two kinds of pollen produced 
by the mid-styled form are less potent than the similar pollens 
produced by the corresponding stamens of the two other forms. 

When we see that the capsules of the mid-styled form yield 
a considerably larger average number of seed than those of 
the 6ther two forms, — ^ivhen we see how surely the flowers are 
fertilized in the legitima,te unions, and how much more productive 



THB THHEE TOEMS OP LYTHBUM SAllCAEIA. 18& 

the illegitimate unions are than those of the other two forms, we 
are led to consider the mid-styled form as eminently feminine in 
its nature. And although it is impossible to consider as rudi- 
mentary or aborted the two perfectly developed sets of stamens 
of the mid-styled form which produce an abundance of perfectly 
well-developed pollen, yet we can hardly avoid connecting, as 
balanced, the higher efficiency of the female organ with the lesser 
potency of the two mid-styled pollens. 

Friially, it is proved by the Tables that Lythrum salicaria 
habitually produces or consists of three females difierent in 
structure and widely different in function ; that it produces or 
consists of three sets of males -\videly dift'erent in structure and 
function ; and that two of the three sets of males are subdivided 
into subgroups of half a dozen each, differing in a marked manner 
in potency, so that regularly five kiads of pollen are elaborated 
by this one species of LytJirum. 

Lythrwn Grcefferi. — I must now say a few words about some of 
the other species of the genus. I have examined numerous dried 
flowers of L. Grafferi, each from a separate jjlant, kindly sent 
me from Kew. This species, like X. salicaria, is trimorphic, and 
the three forms apparently occur in about equal numbers. In 
the long-styled form the pistil projects about one-third of the 
length of the calyx beyond its mouth, and is therefore shorter 
than in L. salicaria ; the globose and hirsute stigma is larger than 
that of the other two forms ; the longer stamens, which are 
graduated in length, have their anthers standing just above and 
just beneath the mouth of the calyx; the half-dozen shorter 
stamens rise rather above the middle of the calyx. In the mid- 
styled form the stigma projects just above the mouth of the 
calyx, and stands almost on a level with the longer stamens of 
the previous form ; its own longer stamens project well above the 
mouth of the calyx and stand a little above the level of the stigma 
of the long-styled form; the shorter stamens correspond in all 
respects with the shorter ones in the pre^dous form. In the 
short-styled form the stigma of the pistil is nearly on a level with 
the anthers of the shorter stamens in the two preceding forms ; 
and the longer stamens correspond with the longer stamens of 
the mid-styled form, and the shorter stamens with the longer 
stamens of the long-styled form. In short, there is a close general 
correspondence in structure between this species and L. salicaria, 
but w-ith some differences in the proportional lengths of the parts. 
Nevertheless the fact of each of the three pistils having two sets 



190 Mn. C. DAHWIX ON THE SEXrAL EEEATIONS OP 

of stamens, borne bj tlie two other forms, of corresponding lengths, 
comes out conspicuously. In the mid-styled form the distended 
pollen-grains from the longer stamens had nearly double the 
diameter of those from the shorter stamens ; so that there is a 
greater difference in this respect than in L. salicaria. In the 
long-styled form, also, the ditforence in diameter between the 
pollen-grains of the longer and shorter stamens was plainer than 
in L. salicaria. These comparisons, however, must be received 
with caution, as they were made on specimens long kept in a 
dried condition. 

Ly thrum tJujmifolia. — This form, according to Vaucher*, is 
dimorphic like Primula, and therefore presents only two forms. 
I received two dried flowers from Kew, which presented two 
forms : in the oue form the stigma projected far beyond the calyx, 
in the other it was included within the calj's ; in this latter form 
the style was only one-fourth of the length of the style of the 
other form. There are ojily six stamens ; these are somewhat 
graduated in length, and in the short-styled form the anthers 
stand a little above the stigma, but yet the stamens by no means 
equal in length the pistil of the long-styled form ; in the long- 
styled form the stamens are rather shorter than in the other 
form. Tliese six stamens alternate with the petals, and corre- 
spond homologically with the longer stamens of L. salicaria and 
i. Qrmfferi. As there are only six stamens, it is scarcely possible 
that this species can be trimorphic. 

Lyihrum Tiyssopifolia. — This species is said by Vaucher, but I 
believe erroneously, to be dimorphic. I have examined dried 
flowers from twenty-two separate plants from various localities, 
kindly sent to me by Mr. Hewett C. Watson, Prof. Babington, and 
others. These were all essentially alike. Hence the species cannot 
be dimorphic. The pistil varies somewhat in length, but when un- 
usually long the stamens are likewise generally long ; in the bud the 
stamens are short : perhaps these circumstances deceived Vaucher. 
There are from six to nine stamens, graduated in length ; the sta- 
mens which are variable in being present or absent correspond with 
the six shorter stamens of L. salicaria and with the six which are 
absent in Z. thymifolia. The stigma is included within the calyx, 
and stands in the midst of the anthers, and would generally be 
fertilized by them ; but as the stigma and anthers are upturned, 
and as, according to Vaucher, there is a passage left in the upper 
side of the flower to the nectary, there can hardly be a doubt that 
* Hist. Phya. dos Hantes d'Europe, torn, ii. (1841) pp. 369, 371. 



THE THRKE FOKJIS Or LTTURrSr SALICAEIA. 191 

the flowers are visited by insects, wiiieli would occasiojially bring 
IJoUeu from other ilowers of the same or of any adjoining plant, 
as surely as occurs witli the short-styled L. salicaria, of which 
the pistil and corresponding stamens closely resemble those of 
L. Jiijssopifolia. According to Vaucher and Leco(i*, this species, 
■n-hich is an annual, generally grows almost solitarily, whereas the 
three preceding species are social ; and this alone would almost 
have convinced me that L. liijssopifolia cannot be dimorphic, as 
such plants cannot habitually live by themselves any better than 
one sex of a dioecious species. 

Ncsaea verticillata. — I raised a number of plants from seed sent 
me by Professor Asa Grray, and they presented three forms. These 
differed from each other in the proportional lengths of their organs 
of fructification and in all respects in very nearly the same way as 
the three forms of LytTirum Grwffcri. The green pollen-grains from 
the longest stamens, measured along their greater axis and not 
distended with water, were j-^jnj- of an inch in lengtli ; those from 
the stamens ot middle length Yi>^%'> ^^^'^ those {com. the sliortcst 
stamens ififoxj of an inch. 

We have seen that the genus Li/thrum affords trimorphic, dimor- 
phic, and monomorphic species. 

The inquiry naturally arises, why do these species differ so 
remarkably in their sexual relations ? of what service can reci- 
procal dimorphism or trimorphism be to certain species, whilst 
other species of the same genus present, like the great majority of 
plants, only one form ? I have elsewhere given too brieiiyt the 

* Geograph. Bot. de rEurope, tom. vi. (1857) p. 157. 

t ' Origin of Species,' 3rd edit., p. 101. Hugo von Mold has recently (Bot. 
Zeituug, 1863, S. 309, 321), in a most interesting paper, advanced the case of the 
minute, imperfectly developed, closed and self-fertile flowers borne by Viola, 
Oxalis, Impatiens, Campanula, &c., as an argument against my doctrine that no 
species is self-fertilized for perpetuity. I may state that in the spring of 1862 I 
examined some of tliese flowers, and saw, tliough less thoroughly, all that 
H. von Mobl has so well described. I can add only one remark, which I 
believe is correct, that in V. canina there is an open channel for the pollen- 
tubes from the extremity of the stigma to the ovarium ; for I gently pressed a 
minute bubble of air repeatedly backwards and forwards from end to end. 
Though the imperfectly developed and the perfect flowers are so different in 
structure, it is a rather cm-ious case of correlation, that in the double purple 
Violet (r. odorata) the minute imperfect flowers are double to the very core, 
so that a section appears like the head of a cabbage when cut through. There 
can be, as vou Mold asserts, no doubt tliat these flowers are always self-fertilized ; 
they are moreover specially adapted for this end, as may be seen in the remark- 
able difference in the shape of the pi^til in V. caiuna (and in a less degree iu 
V. hirla and the single V. odorata) as compared with that of the perfect flower ; 

IINJT. PEOC. — BOT.VNi' VOL. Ylir, 4 



192 MH. C. DABWIN ON THE SEXUAL EEIATIOITS OF 

general grounds of my belief that with all organic beings distinct in- 
dividuals at least occasionally cross together, and reciprocal dimor- 
phism is plainly one most efficient means for ensuring this result. 

and in the pollen-tubes which proceed from the grains within the anthers in 
V. canina, and from within the lower anthers of Oxalis acetoseJla, having the 
wonderful power of directing their course to the stigma. If these plants had 
produced the minute closed flowers alone, the proof would have been perfect 
that they could never have crossed with other iiulividuals. I am aware that 
in some of these cases it has been stated that the perfect flowers never produce 
any seed ; as far as jimphicarfma is concerned, I hear from Professor Asa Gray 
that the petaliferous flowers certainly sometimes yield seed. The completely 
enclosed flowers of that curious grass, the Leersia on/zoides, as described by M. 
Duval-Jouve (BuU. Soc. Bot. de France, tom. x. 1863, p. 194), apparently offer 
the best case of perpetual self-fertilization ; for when perfect flowers arc pro- 
truded from the culms, they are, as far as is yet known, always sterile. In a 
number of plants kept by me in pots in water, not one single perfect flower has 
protruded, but the enclosed flowers produced plenty of seed. Without wishing 
to throw any doubt on M. Duval- Jouve's excellent observations, I may add that 
witli the enclosed flowers borne by my plants, the act of fertiUzation, that is, 
the penetration of the stigma by the poUen-tubes, took place in the air and not 
in fluid within tlie glumes. With the exception of the Leersia^ as the case now 
stands, I cannot see how the production of the small, imperfect flowers invali- 
dates my doctrine that no species is perpetually self-fertilized, more than the 
multiplication of many plants by bulbs, stolons, &c. As I observe that the pro- 
duction of seed by the perfect flowers of Viola is spoken of as something capri- 
cious and accidental, I may state that, although it varies much in diflerent years, 
it depends exclusively on the visits of bees ; I ascertained this by marking many 
flowers thus visited, and finding that they produced capsules, and by covering up 
many flowers which (excepting a few that I artificially fertiUzed) did not, when 
thus protected, produce a single capsule. After bees have visited these flowers, the 
pollen may be seen scattered on the papiUfe and on the stigma itself, and they can 
liardly fail thus to cross distinct individuals. These remarks apply to V. canina, 
Mrta, and odorata ; with V. tricolor the case is somewhat different ; but I 
must not enlarge any more on this subject. The production by so many plant.s 
of perfect and expanded, as well as of imperfect and closed flowers, seems to me 
to throw much light on many points; it shows how extraordinarily little 
pollen is necessary for fuU fertilization, for I ascertained with V. canina that the 
perfect and imperfect flowers (tlie latter producing so few pollen-grains) yielded 
the same average number of seeds ; it shows us that fertilization can be perfected 
in closed flowers ; it shows us that large, liighly coloured petals, perfume, and 
the secretion of nectar are by no means indispensable for this act, even in those 
species which properly possess these characters. It seems to me that the neces- 
sity of an occasional cross with a distinct individual of the same species explains 
the universal presence of at least some expanded flowers, at the expense of injury 
from rain and the loss of much pollen by innumerable pollen-robbing insects ; 
it explains the enormous superfluity of pollen from its Uabdity to loss from these 
causes and during conveyance from flower to flower ; it explains the use of a 
gaily coloured corolla, perfume, and nectar, namely, to attract insects, except in 
those comparatively few eases in which wmd is the agent, and in these the last- 
named attributes are deficient. 



THE THREE EOKMB OF LTTnnUji SALICAEIA. 193 

This result would appear to be one of high importance, for with 
dimorphic plants it is ensured at the risk of occasional sterility ; 
not only is the pollen of each plant useless or nearly useless to 
that individual, but so is the pollen of all the plants of the same 
form, that is, of half the total number of individual plants. In 
that extensive class of plants called by C. K. Sprengel dieho- 
gams, in which the jjollen of each flower is shed before its own 
stigma is ready, or in which the stigma (though this ease occurs 
more rarely) is mature before the flower's own pollen is ready 
sterility can hardly fail to be the occasional result ; and it would 
be the inevitable result with both dichogamous and reciprocally 
dimorjjliic flowers unless pollen were carried by insects (and in 
some few species by the wind) from one flower or plant to the 
other. As with reciprocal dimorphism so with dichogamy, 
within the same genus some of the species are and some are not 
thus characterized. Again, in the same genus, as in that of 
Trifolium, some species absolutely require insect-aid to produce 
seed, others are fertile without any such aid ; now when insects are 
requisite for fertilization, pollen will generally be carried from one 
flower to the other. We thus see, by means of reciprocal dimor- 
phism, of dichogamy, and of insect-aid, that some species require, 
or at least receive, incessant crosses with other individuals of the 
same species ; whereas other species of the same genera can be, 
and probably are often fertilized during long periods by the 
pollen of their own flowers. Why this wide difference in the 
frequency of crosses should occur we are profoundly ignorant. I 
will only further remark on this head, that it would be a great 
mistake to suppose that many flowers, which are neither reci- 
procally dimorphic nor dichogamous, nor require insect-aid for 
their fertilization, nor show any particular adaptation in their 
structure for the visits of insects, are not habitually crossed with 
the pollen of other individuals ; this occurs, for instance, habitually 
with cabbages, radishes, and onions, which nevertheless are per- 
fectly fertile (as I know by trial) with their own pollen without 
aid of any kind. 

But it may be further asked, granting that reciprocal dimor- 
phism is of service by ensuring at each generation a cross (but I 
am far from pretending that it may not have some additional 
unknown signification), why did not dimorphism suffice for 
L. salicaria and Grafferi ? why were they rendered reciprocally 
trimorphic, entailing such complicated sexual relations P Wo 
cannot answer, except perhaps so far : — if we suppose two xflants of 

«J2 



101 'Sni. C. DABWFN OJ.' TIIF SEXUAL RELATIONS OF 

tlio X. saJicfiria to grow by themselves, then if the species were 
dimorphic it would only be an equal chance in fovour of the two 
turning out different forms and consequently both being fertile ; 
but as tlio species is trimorphic and each form can fertilize the 
two other forms, it is two to one iu favour of the two turning out 
different forms and being consequently both fertile. Wo thus 
sec liow reciprocal trimorphisui must bo an advantage ; aud 
probably it would be more advantageous to this Lythrum, whicli 
commouly grows in almost a single row along the banks of 
streams, than it would bo to Primroses or Cowslips which have 
neighbours On all sides. But even if trimorphism etfected fio 
good beyond that gained by dimorphism, we ought not to feel 
mvich surprised at its occurrence, for we continually see throughout 
nature the same end gained by the most complicp^tod as well as by 
the most simple moans : to give one instance : — in maliy dioecious 
plants pollen is carried from the male to the fem.ile by the wind, 
which is perhaps the simplest method conceivable, or by the 
adherence of the grains to the hairy bodies of insects, which is a 
method only a little less simple ; but in Catasetiim the conveyance 
is effected by the most complex machinery ; for in this orchid we 
have sensitive liorns which when touched cause a mombrano to 
rupture, and this sets free certain springs by which the pollen- 
masses are shot forth like an arrow, and they adhere to the 
insect's body by a peculiar viscid matter, and then bj^the breaking 
of an elastic thread of the right strength the pollen is left sticking 
to the stigma of the female plant. The complexity of the means 
used in this and in many other eases, in fact depends on all the 
previous stages through whicli the species has passed, and on the 
successive adaptations of each part during each stage to changed 
conditions of life. 

As some authors consider reciprocal dimorphism to be the first 
step towards dicEciousness, the difficulty of understanding how a 
trimorphic plant like Lythrum salicaria could become dioecious 
should be noticed; and as dimorphism and trimorphism are so 
closely allied, it is not probable that either state is necessarily 
in any way related to a separation of the sexes — though it may 
occasionally load to this end. As far as Lythrum salicaria is con- 
cerned, the one tendency which we can discover is towards the 
abortion of the two sets of stamens in the mid-styled form. This 
tendency is evinced by its pollen, though abundant and apparently 
good, yielding a smaller percentage of seed than docs the pollen 
of the corrospoudiug stamens in the other two forms ; and this 



THE TirUEE FORMS OF I.YTUErM SALTCAI!rA. 195 

fact is iu itself curious, and shows by wliat insensibly graduated 
steps nature moves. If this tendency were carried out the 
mid-styled form would becomo a female, depending for its fer- 
tilization on two sets of stamens in the long- and sliort-styled 
forms ; and these two forms would reci[)rocally fertilize each other 
like the two forms of Priiinda or Linum ; but tlicre would be no 
approach to a dioecious condition. 

As the case of the trimorphie species of Lythrum is so com- 
plicated, and as it is easier to perceiYO the relations of the sexes 
in the animal than in the vegetable kingdom, it may be worth 
while to give, before concluding, a somewhat elaborate simile. 
We may take the case of a species of Ant, and suppose all the 
individuals invariably to live in three kinds of communities ; in 
the first, a large-sized female (not to specify other difterenccs) 
living with six middle-sized and six small-sized males ; in the 
second, a middle-sized female witli six large- and six small-sized 
males ; and in the third community, a small-sized female with six 
large- and six middle-sized males. Each one of these three 
females, though enabled to unite with any male, would be nearly 
sterile with her own two seta of males, and likewise with two 
other sets of males living in the other two communities ; for she 
would be fully fertile only when paired with a male of her own 
size. Hence the thirty-six males, distributed by- half-dozens iu 
the three communities, woiild be divided into three sets of a 
dozen each ; and these sets, as well as the three females, would 
differ from each other sexually in exactly the same manner as 
distinct species of the same genus. Moreover the two sets of 
males living in the community of the extraordinarily fertile 
middle-sized female would be less potent sexually than the males 
of corresponding size in the two other communities. Lastly, we 
should find that from the eggs laid by each of the three females, 
all three sorts of females and all three sorts of males were 
habitually reared^X)roving to demonstration that all belonged to 
one and the same species. 

To appreciate fully this remarkable case of the reciprocally tri- 
morphie species of Lytlirmn, wc may take a glance at the two great 
kingdoms of nature and search for anything analogous. With 
animals we have the most astonishing diversity of structure iu 
the so-called cases of alternate generation, but as such animals 
have not arrived at maturity, they are not properly comparable 
with the forma of Lythrum. With mature animals we have 
extreme differences Ln structure iu the two sexes; we have in 



190 MB. C. DAHWI^- OS ITTHHUM S.VITCABTA. 

some of the lower animals males, females, and hermaphrodites 
of the same species ; we have tlie somewhat more curious case 
of certain Cirripedos which are hermaphrodites, but are sexually 
aided by whole clusters of what I have called complemcntal 
males ; we have, as Mr. Wallace has lately shown, the fp^-ilos of 
certain Lepidoptera existing under three distinct fon s ; but in 
none of these cases is there any reason to suspect iu. *' there 
is more than one female or one male sexual element. With 
certain insects, as with Ants, in which there exist, besides 
males and femiales, two or three castes of workers, we have a 
slightly nearer approach to our case, for the workers are so far 
sexually affected as to have been rendered sterile. With plants, 
at least with phanerogamic plants, we have not that wonderful 
series of successive developmental forms so common with animals ; 
nor could this bo expected, as plants are fixed to one spot from 
their birth, and must be adapted throughout life to the same 
conditions. With plants wc have sexual differences in structure, 
but apparently less strongly marked than with animals, from 
causes which are in part intelligible, such as there being no 
sexual selection ; again, we have that class of dimorphic flowers 
80 ably discussed recently by Hugo von Mohl, in which some 
of the flowers are minute, imperfectly developed, and neces- 
sarily self-fertile, whilst others are perfect and capable of 
crossing with other flowers of the same species; but in these 
several cases wo have no reason to suspect that there is more 
than one female or one male sexual element. When we come to 
the class of reciprocally dimorphic plants, such as Prvmula, Linum, 
&c., we first meet with two masculine and two feminine sexes. 
But these cases, which seemed only a short time since so strange, 
now sink almost into insignificance before that of the trimorphic 
species of Lythrmn. 

Naturalists are so much accustomed to behold great diversities 
of structure associated with the two sexes, that they feel no 
surprise at the fact ; but differences in sexual nature have been 
thought to be the very touchstone of specific distinction. We 
now see that such sexual differences — the greater or less power 
of fertilizing and being fertilized— may characterize and keep 
separate the coexisting individuals of the same species, in the 
same manner as they characterize and have kept separate those 
groups of individuals, produced from common parents during the 
lapse of ages or in different regions, which we rank and deno- 
minate as distinct species. 



[Fn»n the A>raALS axd Magazine of Natural History for 
Hfpfi-mher 18G9.] 



barat;ii, 



NOTES 



TTTE FERTILIZATION OF ORCHIDS. 

BY 

CHARLES DAEWIN, M.A., F.R.S. 



To the Editors of the Annah and Magazine of Natural Ilistofy. 

<Jf.\tlemen, 

Having drawn up sonic notes for a Frencli translation of 
my work ' On the various contrivances by which British and 
Foreign Orchids are Fertilized by Insects ' (1862), it has ap- 
peared to me that these notes would be worth publishing in 
English. I have thus been able to bring up the literature of 
the subject to the present day, by giving references to, together 
with very brief abstracts of, all the papers published since my 
work appeared. These papers contain, on the one hand, cor- 
rections of some serious errors into which I had fallen, and, 
on the other hand, confirmations of many of my statements. 
I have also been able to add, from my own observations and 
those of others, a few new facts of interest. A heading is 
given to each note, which will show the nature of the correc- 
tion or addition, without any reference to my book ; but I have 
added in a parenthesis the page to which the note ought to be 
appended. 

Gentlemen, 
Down, Becketiham, Kent. Your obedient Servant, 

July 23, 1869. Chai;les Da R W I \. 

Orchis or Anacamptis pyramirlnlis (p. 20). — The late Prof. 
Treviranus has confirmed (Botanische Zeitung, 1863, p. 241) 
my observations on this remarkable species ; but he differs from 
me in one or two minor points. 

Oft the kinds of Insects loMch hahitually visit and fertilize 
some of the common British species (/Orchis (p. 35). — I believe 

A 



2 ]Mr. C. Darwin on the Fertilization of Orcliids. 

that it may be safely predicated that orchids with very long 
nectaries, such as the Anacamptis, Gymnadenia, and Platan- 
thera, are habitually fertilized by Lepidoptera, whilst those 
with only moderately long nectaries are fertilized by bees and 
Diptera — in short, that the length of the nectary is correlated 
with that of the proboscis of the insect which visits the plant. 
I have now seen Orchis morio fertilized by various kinds of 
bees, namely: — by the hive-bee {Apis mellijica), to some of 
which from ten to sixteen pollen-masses were attached ; by 
Bomhus muscorum, with several pollen-masses attached to the 
bare surface close above the mandibles ; by Eucera longi- 
corntSj with eleven pollen-masses attached to its head ; and 
by Osmia rufa. These bees, and the other Hymenoptera 
mentioned throughout these notes, have been named for me by 
our highest authority, Mr. Frederick Smith, of the British 
Museum. The Diptera have been named by Mr. F. Walker, 
of the same establishment. In Northern Germany, Dr. H. 
Miillcr of Lippstadt found pollen-masses of Orchis morio at- 
tached to Bombus silvarum, lapidariuSj confusus, and pra- 
tonnn. The same excellent observer found the pollen-masses 
of Orchis latifolia attached to a Bomhis ; but this orchis is 
also frequented by Diptera. A friend watched for me Orchis 
mascula, and saw several flowers visited by a Bombus, 
apparently B. rnuscorum ; but it is surprising how seldom 
any insect can be seen visiting this common species. With 
respect to Orchis maculata, my son, Mr. George Darwin, has 
clearly made out the manner of its fertilization. He saw many 
specimens of a fly [Empis livida) inserting their proboscides into 
the nectary ; and subsequently I saw the same occurrence. 
lie brought home six specimens of this Enqiis, with pollinia 
attached to their spherical eyes, on a level with the bases of 
the antennie. The pollinia had undergone the movement of 
depression, and stood a little above and parallel to the pro- 
boscis : hence they were in a position excellently adapted to 
strike the stigma. Six pollinia were thus attached to one spe- 
cimen, and three to another. My son also saw another and 
smaller species (Empis pennipes) inserting its proboscis into 
the nectary ; but this species did not act so well or so regu- 
larly as the other in fertilizing the flowers. One specimen of 
this latter Empis had five pollinia, and a second had three 
pollinia, attached to the dorsal surface of the convex thorax. 
.. On nectar being secreted and contained between the outer 
and inner membranes of the nectary in several sj^ecies o/Orchis 
(p. 51).— I have repeated my observations on the nectaries of 
some of our common species, and especially on those of Orchis 
morio, at the time irhen carious bees irere continually visiting 



ilr. C. Darwin on the Fertilization of Orchids. 3 

the flowers ; but I could never see the minutest drop of nectar 
within the nectary. Each bee remained a considerable time 
with its proboscis in constant movement whilst inserted into 
the nectary. I observed the same fact with Empis in the case 
of Orchis mmulata ; and in this orchis I could occasionally 
detect minute brown specks, where punctures had been made. 
Hence the view suggested by me that insects puncture the 
inner lining of the nectary and suck the fluid contained be- 
tween the two coats may be safely accepted. I have said in 
my work that this hypothesis was a bold one, as no instance 
was known of Lepidoptera penetrating with their delicate pro- 
boscides any membrane ; but I now hear from Mr. E. Trimen 
tliat at the Cape of Good Hope moths and butterflies do much 
injury to peaches and plums by penetrating the skin, in parts 
which have not been in the least broken. 

Since the appearance of my loork, the following observations 
have been published on other species o/Orchis and on certain allied 
forms (p. 53) . — Mr. J. Traherne Moggridge has given ( Journ. 
Linn. Soc. vol. viii. Botany, 1865, p. 2o&) a very interesting 
account of the structure and manner of fertilization of Orchis 
or Aceras longibracteata. Both pollinia, as in Anacampfis 
pi/ramidalis, are attached to the same viscid disk ; but, differ- 
ently from those in that species, after being removed from the 
anther-cases, they first converge and then undergo the move- 
ment of depression. But the most interesting peculiarity in 
this species is that insects suck nectar out of minute open cells 
in the honeycombed surface of the labellum. Mr. Moggridge 
saw this plant fertilized by a large bee, the Xylocopa violacea. 
He adds some observations on Orchis hircina, and describes 
the structure and manner of fertilization of Serapias cordicjera 
by another bee, viz. the Ceratina aJbilahris. In this Serapias 
both pollinia are attached to the same viscid disk ; when first 
withdrawn, they are bent backwards, but soon afterwards 
move forwards and downwards in the usual manner. As the 
stigmatic cavity is narrow, the pollinia are guided into it by 
two guiding plates. 

Mr. Moggridge sent me from Northern Italy living plants 
oWrchis or Neotinea tntacta, together with excellent drawings 
and a full account of the structure of the flower.^ He informed 
me that this species is remarkable for producing seed with- 
out the aid of insects ; and I ascertained that when insects 
were carefuUv excluded, almost all the flowers produced cap- 
sules. Their fertilization follows from the pollen being ex- 
tremely incoherent, and spontaneously falling on the stigma. 
Nevertheless a short nectary is present, the pollinia possess 

a2 



4 Mr. C. Darwin on the Fertilization of Orchids. 

small viscid disks, and all the parts arc so arranged that, if 
insects were to visit the flowers, the pollen-masses would pro- 
bably be removed and then carried to another flower, but not 
so effectually as with most other orchids. We shall hereafter 
find a few other cases of orchids which have structiu-al pecu- 
liarities adapted both for self-fertilization and for crossing. I 
may here also refer to a paper by Mr. R. Trimen ( Journ. Linn. 
Soc. voL vii. Botany, 1863, p. 144) on the beautiful Disa 
grandijlora of the Cape of Good Hope. This orchid presents 
several remarkable characteristics, one of these being that the 
pollinia do not spontaneously undergo any movement of de- 
pression, the weight of the pollen-masses sufficing to bend the 
caudicle into the proper curvature for the act of fertilization. 
Another peculiarity is that the posterior sepal secretes nectar, 
and is developed into a spur-like nectary, ilr. Trimen in- 
forms me that he has seen a Dipterous insect, allied to Bom- 
hyliusj frequenting the flowers. I may add that Mr. Trimen 
has sent me descriptions and specimens of various other South- 
African orchids, which confirm the general conclusions at 
which I have arrived in my work. 

On the movement of the pollinia o/Ophrys muscifera (p. 56). 
— ^Ir. T. H. Farrer, who has lately been attending to the fer- 
tilization of various plants, has convinced me that I have 
erred, and that the pollinia of this Ophrys do undergo a move- 
ment of depression. Hence my remarks on the correlation of 
the various parts of the flower are to a certain extent invali- 
dated ; but there can be no doubt that the naturally bent 
caudicle plays an important part in placing the pollen-mass 
in a proper position for striking the stigma. I have continued 
occasionally to watch the flowers of this species, but have 
never succeeded in seeing insects visit them ; but I have been 
led to suspect that they puncture or gnaw the small lustrous 
prominences beneatli the viscid disks, which, I may add, arc 
likewise present in several allied species. I have observed 
very minute punctures on these prominences, but I could not 
decide whether these had been made by insects or whether 
superficial cells had spontaneously burst. 

Ophrys aranifera (p. 63). — F. Delpino states (Fecondazione 
nellePiante&c, Firenze, 1867, p. 19) that he has examined in 
Italy thousands of specimens of this Oj)hrys, and that it sel- 
dom produces capsules. It does not secrete any nectar. Al- 
though he never saw an insect on the flowers (excepting once 
a green locust), nevertheless they are fertilized by insects ; for 
he found pollen on the stigmas of some flowers, which liad tlieir 
own pollinia still within the anther-cases. The pollinia never 



Mr. C. Darwin on the Fertilization of Orchids. 5 

spontaneously fell out. He a])])ear3 to tliink that I infer that 
this Ophrys fertilizes itself, wiiicli is an error. 

Ophrys apifera (p. 71). — Prof. Treviranus at first douhtcd 
(Botanische Zeitung, 1862, p. 11) the aceuracy of my account of 
this Ophrys, and of the differences between it and 0. arach- 
nites ■ but he has subsequently (Bot. Zeit. 1863, p. 241) fully 
confirmed all that I have stated. 

_ (Jphrys arachiites (p. 72). — I liave now examined several ad- 
ditional living specimens of this Ophrys, and can confirm my 
statement that the pollinia do not fall out of the anther-cases, 
even when the spikes are strongly shaken ; nor do they fall 
out when the spikes are kept standing in water for a week. 
Mr. J. Moggridge has made (Journ. Linn. Soc, Bot. vol. viii. 
1865, p. 258) a remarkable observation on 0. scolopax, which 
is closely allied to 0. arachnites, — namely, that at Mentone it 
never exhibits any tendency to self-fertilization, whilst at 
Cannes all the flowers fertilize themselves, owing to a slight 
modification in the curvature of the anther, which causes the 
pollinia to fall out. This botanist has given, in his ' Flora of 
Mentone,' a full description, with excellent figures, of 0. scolo- 
2>ax, arachnites, aranifera, and apifera; and he believes, from 
the number of intermediate forms, that they must all be 
ranked as varieties of a single species, and that their differ- 
ences are intimately connected with their period of flowering. 
It does not appear that these forms in England, judging from 
their distribution, are liable to pass into each other, within any 
moderate or observable period of time. 

On the fertilization of Ilerminium monorchis (p. 74). — My 
son, Mr. George Darwin, has fully observed the manner of 
fertilization of this minute and rare orchis. It differs trom 
that of any other genus known to me. He saw the flowers 
entered by various niinute insects, and brought home no less 
than twenty-seven specimens with pollinia (generally with only 
one, but sometimes with two) attached to them. These insects 
consisted of minute Hymenoptera (of which Tetrastichus dia- 
2>hantus was the commonest), of Diptera and Coleoptera, the 
latter being Malthodes brevicollis. The one indispensable 
point appears to be that the insect should be of very minute 
size, the largest being only the -^-^ of an incli in length. It 
is an extraordinary fact that in all the specimens tlie pollinia 
were attached to the same peculiar spot, namely, to the outer 
side of one of tlie two front legs, to the projection formed by 
the articulation of the femur with the coxa. In one instance 
alone a poUinium was attached to the outside of the femur 
a little beneath the articulation. The cause of this peculiar 
manner of attaelaneut is sullieientlv clear : the middle part 



6 Mr. C. Darwin on the Fertilization of Orchids. 

of tlie laLellum stands so close to the anther and stigma, that 
insects always enter the flower at one corner, between the 
margin of the labellum and one of the upper petals ; they also 
almost always crawl in with their backs turned directly or 
obliqviely towards the labellum. My son saw several which 
had begun to crawl into the flower in a different position ; but 
they came out and changed their position. Thus, standing in 
either corner of the flower, with their backs turned towards 
the labellum, they inserted their heads and fore legs into the 
short nectary, which is seated between the two widely sepa- 
rated viscid disks. I ascertained that they stand in this po- 
sition by finding three dead insects, which had been per- 
manently glued to the disks. Whilst sucking the nectar, 
which occupies about two or three minutes, the projecting 
joint of the femur stands under the large helmet-like viscid 
disk on either side ; and \vhen the insect retreats, the disk 
exactly fits on, and is glued to, the prominent joint. The 
movement of depression in the caudicle then takes place, and 
the mass of pollen-grains projects just beyond the tibia ; so 
that the insect, when entering another flower, can hardly fail 
to fertilize the stigma, which is situated directly beneath the 
disk on either side. I know of hardly any other case in 
Avhich the whole structure of the flower is more beaiitifully 
correlated than in the Herminium for a most peculiar manner 
of fertilization. 

On the movement of the pollinia in Peristylus viridis (p. 76). 
— Mr. T. H. Farrer infortns me that the pollinia certainly un- 
dergo a movement of depression, but that this does not take 
place until twenty or thirty minutes have elapsed after their 
removal from the anther-cases. This length of time probably 
accounts for my oversight. He asserts that, after the move- 
ment of depression, the pollinia become much better adapted 
to strike the stigmatic surface. He suggests that insects may 
take a long time to lick up the nectar from the two naked 
spots on the labelhim, and through the narrow slit-like open- 
ing into the nectary — and that during this time the polli- 
nium becomes fiiinly attached, by the slow hardening of the 
viscid matter, to the insect's body, so as to be subsequently 
ready to fertilize another flower when visited by the same 
insect. 

On the Lejtidoptera which fertilize the Gymnadenia conopsea, 
and on the divergence of the pollinia (p. 82). — Mr. George 
Darwin went at night to a bank where this species grows 
plentifully, and soon caught Plusia chrysitts with six pollinia, 
P. gamma with three, Anaitis plagiata with five, and Tri- 
phcenapronidtaviith seven pollinia attaclicd to their ])roboscides. 



Mr. C. Darwin on the Fertilization of Orclilds. 7 

I may add tliat he cauglit the first-named motli, bearhig the 
pollinia of this orchis, in my flower-garden, ahhough more 
than a quarter of a mile distant from any spot where the plant 
grows. I state in my work that I do not understand the cause 
of the divergence of the pollinia so that they are enabled to 
strike the lateral stigmatic surfaces ; but the explanation is 
simjile. The upper margin of the nectary is arched, being 
formed on one side by the disk of one pollinium, and on the 
other side by the other disk. Now if a moth inserts its pro- 
boscis obliquely, and there are no guiding-ridges by which, as 
in Anacamptls pyramidalls, a moth is compelled to insert its 
proboscis directly in front, or if a bristle be inserted obliquely, 
one pollinium alone is removed. In this case the pollinium 
becomes attached a little on one side of the bristle or proboscis ; 
and its extremity, after the vertical movement of depression, 
occupies a proper position ior striking the lateral stigma on 
the same side. 

On the Gymnadenia tridentata of North America (p. 83). — 
Prof. Asa G-ray has published (American Journal of Science, 
vol. xxxiv. 1862, p. 426, and footnote p. 260 ; and vol. xxxvi. 
1863, p. 293) some interesting notes on the Gymnadenia 
tridentata. The anther opens in the bud, and some of the 
pollen invariably falls on the naked cellular tip of the rostel- 
lum ; and this part, strange to say, is penetrated by the pollen- 
tubes, so that the flowers are self-fertilized. Nevertheless 
"all the an-angements for the removal of the pollinia by insects 
(including the movement of depressien) are as perfect as in the 
species which depend upon insect aid." Hence there can be 
little doubt that this species is occasionally crossed. 

Hahenarla or Platanthera hlfoUa (p. 88). — According to 
Dr. H. Miiller, of Lippstadt, PI. blfolia of English authors is 
the PL solstitlalis of Boenninghausen ; and he fully agrees 
with me that it must be ranked as specifically distinct from 
PI. cMorantha. Dr. llliller states that this latter species is 
connected by a series oi gradations witli another form which 
in Germany is called PI. blfolia. He gives a very full and 
valuable account of the variability of these species of Platan- 
thera and of their structure in relation to their manner of fer- 
tilization. (See Yerhandl. d. Nat. Verein. Jahrg. xxv. III. 
Folge, V. Bd. pp. 36-38.) 

American species of Platanthera (p. 91). — Prof. Asa Gray 
has described (American Journal of Science, vol. xxxiv. 1862, 
pp. 143, 259, & 424, and vol. xxxvi. 1863, p. 292) the stmc- 
ture of ten American species of Platanthera. Most of these 
resemble in their manner of fertilization the two British spe- 
cies described by me ; but some of them, in which the viscid 



Mr. C Darwin on the Fertilization of Orchids. 



disks do not stand tar apart, have curious contrivances, such 
as a channelled laljelliun, lateral shields, &c., compelling 
moths to insert their proLoscides directly in front. PI. Ifookerij 
on the other hand {ibid. vol. xxxiv. 18C2, p. 143), differs in a 
very interesting manner : the two viscid disks stand widely 
separated from each other ; consequently a moth, unless of 
gigantic size, would be able to suck the copious nectar without 
touching either disk ; but this risk is avoided in the following 
manner : — The central line of the stigma is prominent, and the 
labellum, instead of hanging down, as in most of the other 
species, is curved upwards, so that the front of the liower is 
made somewhat tubular and is divided into two halves. Thus 
a moth is compelled to go to one or the other side, and its 
face will almost certaiidy be brought into contact witli one of 
the disks. The drum of the poUinium, when removed, con- 
tracts in the same maimer as I have described under PL chlo- 
raidha. Prof. Gray has seen a butterfly from Canada with 
the pollinia of this species attached to each eye. In the case 
of Platanthera Jlava (American Journal of Science, vol. xxxvi. 
1863, p. 292), moths arc compelled in a different manner to 
enter the nectary on one side. A narrow but strong jjrotubc- 
rance, risuig from the base of the labellum, projects upwards 
and backwards, so as almost to touch the column ; thus the 
moth, being forced to go to either side, is almost sure to 
withdraw one of the viscid disks. In the allied and wonderful 
Bonatea s]>eciosu of the Cape of Good Hope there is a similar 
contrivance for the same.pur])ose. 

Platanthera hi/jyerhorea and dilatata have been regarded 
by some botanists as varieties of the same species ; and Prof. 
Asa Gray says (Amer. Journ. of Science, vol. xxxiv. 1862, 
pp. 259 & 425) that he has often been tempted to come to the 
same conclusion ; but now, on closer examination, he finds, 
besides other characters, a remarkable physiological difference, 
namely, that PL dilatata, like its congeners, requires insect aid 
and cannot fertilize itself; whilst in PL hyperlorea the pollen- 
masses commonly fall out of the anther-cells whilst the flower 
is very young or in bud, and thus the stigma is self-fertilized. 
Nevertheless the various structures adapted for crossing are 
still present. 

Fertilization of Epipactis palustris (p. 102). — My son, Mr. 
W. E.Darwin, has carefully observed for me this plant in the 
Isle of Wight. I live-bees seem to be the chief agents in fer- 
tilization ; for he saw about a score of flowers visited by these 
insects, many of which had pollen-masses attached to their 
foreheads, just above the mandibles. I had su))posed that in- 
sects crawled into the flowers ; but hive-bees are too large to 



Mr. C. Darwin on the Ftrt'dization of Orchids. 9 

do tliis ; tliey always clung, wliilst sucking the nectar, to the 
distal and hinged half of the lahelium, which was thus pressed 
do\ynwards. Owing to this part being elastic and tending to 
spring up, the bees, as they left the flowers, seemed to fly 
rather upwards ; and this would favour, in the manner explained 
by me, the complete withdrawal of the pollen-masses, quite as 
well as an insect crawling out of the flower in an upward 
direction. Perhaps, however, this upward movement may not 
be so necessary as I had supposed; for, judging from the point 
at which tJie pollen-masses were attached to the bees, the 
back part of tlie head would press against, and thus lift up, the 
blunt, solid, upper end of tlie anther, thus freeing the pollen- 
masses. 

Various other insects besides hive-bees visit this Epqiactiti. 
My son saw several large flies {Sarcojdiaga carnosa) haunting 
tiie flowcTS ,• but they did not enter in so neat and regular a 
manner as the hive-bees ; nevertheless two had pollen-masses 
attached to their foreheads. Several smaller flies [Coslopa 
friffida) were also seen entering and leaving the flowers, with 
pollen-masses adliering rather irregularly to the dorsal surface 
of the thorax. Three or four distinct kinds of Ilymenoptera 
(one of small size being Grahro hrevis) likewise visited the 
flowers ; and three of these Ilymenoptera had pollen-masses 
attached to their backs. Other still more miimte Diptera, 
Coleoptera, and ants were seen sucking the nectar ; but these 
insects appeared to bo too small to transport the pollen-masses. 
It is remarkable that some of the foregoing insects should 
visit these flowers ; for Mr. F. Walker informs me that the 
Sarcophaga frequents decaying animal matter, and the Gwlopa 
haunts seaweed, occasionally settling on flowers ; the Cral/ro 
also, as I hear from Mr. F. Snnth, collects small beetles (//«/- 
ticce) for provisioning its nest. It is equally remarkable, see- 
ing how many kinds of insects visit this EpijxtctiSj that, al- 
though my son watched for some hours on three occasions 
hundreds of plajits, not a single humble-bee alighted on a 
flower, though many were flying about. In a footnote I have 
given the results of experiments made by Mr. More, by cutting 
oflf the distal and hinged half of the labellum, in order to as- 
certain how far this part is important. lie has now repeated 
the experiment on nine additional flowers : of these, three did 
not produce seed-capsules; but this may have been accidental. 
Of six capsules which were produced, two contained about as 
many seeds as the capsules of unmutilated flowers on the same 
jdant; but four capsules contained much fewer seeds. The 
seeds themselves were well-formed. These experiments, as 
far as they go, support the view that the distal part of the 



10 Mr. C. Darwin on the Fertilization of Orchids. 

labellum plays an important part in leading insects to enter 
and leave the flower in a proper manner for fertilization. 

Fertilization o/Epipactis latifolia (p. 104). — Altliougli tliis 
orchis is not common in the vicinity of Down, by a fortunate 
chance several plants sprang up in a gravel walk close to my 
house, so that I have been able to observe them during several 
years, and have thus discovered how they are fertilized. Al- 
though hive-bees and humble-bees of many kinds were con- 
stantly flying over the plants, I never saw a bee or any Dip- 
terous insect visit the flowers ; whilst, on the other hand, I 
repeatedly observed each year the common wasp ( Vespa syl- 
vesfris) sucking the nectar out of the open cup-shaped label- 
lum. I thus saw the act of fertilization eflicted by the pollen- 
masses being removed and carried on the foreheads of the 
wasps to other flowers. Mr. Oxenden also informs me that 
a large bed of E. purpurata (which is considered by some 
botanists a distinct species, and by others a variety) was 
frequented by " swarms of wasps." It is very remarkable 
that the sweet nectar of this Epipactis should not be attractive 
to any kind of bee. If wasps were to become extinct in any 
district, so would the Epipactis latifolia. 

Dr. H. Miiller of Lippstadt has published ( Verhandl. d. Xat. 
Ver. Jahrg. xxv. III. Folge, v. Bd. pp. 7-36) some very im- 
portant observations on the difl^erences in structure and in the 
manner of fertilization, as well as on the connecting gradations, 
between Epipactis riLhiginosa, microphylla, and viridifora. 
The latter species is highly remarkable by the absence of a 
rostellum, and by being regularly self-fertilized. This latter 
circumstance follows from the incoherent pollen of the lowerpart 
of the pollen-masses emitting, whilst still within the anther- 
cells, pollen-tubes, which penetrate the stigma ; and this oc- 
curred even in the bud state. This species, however, is probably 
visited by insects, and occasionally crossed ; for the labellum 
contains nectar. E. microphylla is equally remarkable, by 
being intermediate in structure between E. latifolia, which is 
always fertilized by the aid of insects, and E. viridifora, 
which does not necessarily require any such aid. The whole 
of this memoir by Dr. H. Miiller deserves to be attentively 
studied. 

Cephalanthera grandijlora (p. 108). — During the year 1862, 
the flowers of this orchis appeared to have been visited much 
less frequently by insects than dm-ing the previous years ; for 
the masses of pollen were seldom broken down. Although I 
have repeatedly examined the flowers, I have never seen a 
trace of nectar ; but some appearances lead me to suspect that 
the ridges within the base of the labellum arc attractive to 



Mr. C. Danvin on the Fertilizatiun of Orchiih. 11 

insects, and are gnawed by them, as in the case of many 
Vandeas and other exotic orcliids. 

Goodyera rejJens (p. 114). — Mr. K. B. Tliomson informs me 
that in the north of Scotland lie saw many humble-bees visit- 
ing the flowers and removing the pollen-masses, which were 
attached to their proboscides. The bee sent was Bomhus jjra- 
torum. This species grow.s also in the United States ; and 
Prof. Gray (Amer. Journ. of Science, vol. xxxiv. 1862, p. 427) 
confirms my account of its structure and manner of fertiliza- 
tion, which is likewise applicable to another and very dis- 
tinct species, namely, Goody era pubescens. Prof. Grray states 
that the passage into the flower, which is at first very nan-ow, 
becomes, as I suspected, more open during its older state. 
Prof. Gray believes, however, that it is the column, and not 
the labelhun, wliicii changes its position. 

Sjnranthes autumnalis (p. 123). — As in the case of the 
Goodyera, Prof. Gray feels confident that it is the column which 
moves from the labellum as the flower grows older, and not, 
as I had supposed, the labellum which moves from the column. 
He adds that this change of position, which plays so important 
a p)art in the fertilization of the flower, " is so striking that 
we ^vender how we overlooked it" (Amer. Journ. of Science, 
vol. xxxiv. p. 427). 

On the rosteUum o/Listera ovata not exploding spontaneoiisly 
(p. 149). — 1 have covered up some additional plants, and found 
that the rostellum lost its po\\-er of explosion in about four days, 
the viscid matter tlien turning brown within the loculi of the 
rostellum. The weather at the time was unusually hot, and 
this may have hastened the process. After the four days had 
elapsed, the pollen had become very incoherent and some had 
fallen on the two corners, or even o\-er the wlsole surface, of 
the stigma, which was j^enetrated by the pollen-tubes. Hence, 
if insects should fail to remove the pollinia by causing the 
explosion of the rostellinn, this orchid certainly seems capable 
of occasional self-fertilization. But the scattering of the in- 
coherent pollen was largely aided by, and perhajjs wholly de- 
pended on, the presence of Thrip^ — insects so minute that 
they could not be excluded by any net. 

Listera cordata (p. 152). — Prof. Dickie has been so good as 
to observe the flowers on living plants. He informs me that, 
when the pollen is mature, the crest of the rostellum is di- 
rected towards the labellum, and that, as soon as touched, the 
viscid matter explodes, the poUinia becoming attached to the 
touching object ; after the explosion, the rostellum bends 
downwards and spreads out, thus ]n-otecting the virgin stig- 
matic surface ; subsequently the rostellum rises and exposes 



12 Mr. C. Danviii on the Fertiiizutioii of Ofchids. 

the stigma ; so that everything here goes on as I have de- 
scribed under Listera ovata. I'lie tiowers are frequented by 
iniiiutc Diptera and Ilymenoptera. 

On thii self-fertilization of Neottia nidus-avis, and on the 
rostellum not exploding spontaneously (p. 153). — 1 covered up 
with a not several plants, and after four days fomid that tiie 
rostellum had not spontaneously exploded, and had already 
almost lost this power. The pollen had become incoherent, 
and in all the flowers much had fallen on the stigmatic sur- 
faces, which were penetrated by pollen-tubes. The spreading 
of the pollen seemed to be in part caused by the presence of 
Thrijis^ many of which minute insects were crawling about 
dusted all over with pollen. The covercd-up plants produced 
plenty of capsules, but these were much smaller and contained 
much fewer seeds than the capsules jiroduced by tlie adjoining 
uiicovered plants. I may here add that I detected on the crest 
of the rostellum some minute rough points, which seemed 
particularly sensitive in causing the rostellum to explode. 

Dr. H. Miiller, of Lippstadt, informs me that he has seen 
Diptera sucking the nectar and removing the pollinia of this 
plant. 

On the selffertilization of certain Epidendreffi (p. 166). — 
Dr. Criiger says (Journ. Linn. Soc. vol. viii. Botany, 1864, 
p. 131) that "we have in Trinidad three plants belonging to 
the Epidendrea! (a Schovihurghia, Gattleya, and Epidendron) 
which rarely open their flowers, and are invariably impreg- 
nated when they do open them. In these cases it is easily 
seen tliat the pollen-masses have been acted on by the stig- 
matic fluid, and that the pollen-tubes descend from the pollen- 
masses in situ down into the ovarian canal." Mr. Anderson, 
a skilful cultivator of orchids in Scotland, infonns me (see also 
' Cottage Gardener,' 1863, p. 206) that with him the flowers 
of Dendrohium cretaceum never expand, and yet produce 
capsules with plenty of seed, which, when examined by me, 
■was found to be perfectly good. These orchids make a near 
approach to those dimorphic plants (as Oxalis, Ononis, and 
Viola) which habitually produce open and perfect, as well as 
closed and imperfect flowers. 

On the slow movement of the piolh'nia -in Oncidium (p. 189). 
— Mr. Cliarles Wright, in a letter to Prof. Asa Gray, states 
that he observed in Cuba a pollhiiiim of an Oncidium attached 
to a Bomhus, and he concluded at first that I was completely 
mistaken about the movement of depression ; but after several 
hours the polliniunr moved into the proper position for fertilizing 
the flower. 

Mannur qfftrlilizaiion of various exotic Orchids (p. 189). 



ilr. C. Danvin on the Fertili-.ation of Orchids. 13 

— I may here rcniavk that Deljjiiio (Fccondazione nolle Piaiitc, 
Firenze, 1867, p. 19) says ]ie h&s examined Howers of Vandu, 
Epidendron, Fhaius, Oncidium, and Dendrohium, and con- 
firms my general statements. The late Prof. Bronn, in his 
German translation of this work (18(32, p. 221), gives a de- 
scription of the structure and manner of fertilization of Staii- 
hopea devoniensis, 

&a-<?s o/'Acropera notfsbparated['^. 206). — I have committed 
a great error about this genus, in supposing that the sexes 
were separate. Mr. J, Scott, of the Eoyal Botanic Garden of 
Edinburgh, soon convinced me that it was an hermajjhrodite, 
by sending me capsules containing good seed, which he had 
obtained by fertilizing some flowers with pollen from the same 
plant. He succeeded in doing this by cutting open the stig- 
matic chamber, and inserting the pollen-masses. My error 
arose from my ignorance of the remarkable fact that, as sliown 
by Dr. Hildebrand ( Botanische Zeitung, 1863, Oct. 30 eJ, 
seq., and Aug. 4, 1865), in many orchids the ovules are not 
developed until several weeks or even months after the pollen- 
tubes have penetrated the stigma. No doubt if I had exa- 
mined the ovaria of Acrojpera some time after the flowers had 
withered, I should have found well-developed ovules. In 
many exotic orchids besides Acrojjera (namely, in Gongora, 
Cirrhcea, Acineta, Stdnhojyea, &c.), the entrance into the stig- 
matic chamber is so narrow tliat the pollen-masses cannot be 
inserted without tlie greatest difficulty. How fertilization is 
effected in these cases is not yet known. That insects are the 
agents there can be no doubt ■ for Dr. Criiger saw a bee {Etc- 
glossa) with a pollinium of a Stanhopea attached to its back ; 
and bees of the same genus continually visit Gongora. Fritz 
iliiller has observed, in the case oi Cirrhina (Bot. Zeitung, 
Sept. 1868, p. 630), that if one end of the pollen-mass be in- 
serted into the narrow entrance of the stigmatic chamber, this 
part, from being bathed by the stigmatic fluid, swells, and the 
whole pollen-mass is thus gradually drawn into the stigmatic 
entrance. But, from observations whieli I liave made on 
Acropera and Btanliopea in my own hot-house, I suspect that, 
with many of these orchids, the pedicel with the nan-ow end 
of the pollinium, and not the broad end, is ordinarily inserted 
into the stigmatic chamber. By thus ])lacing the pollinium, 
I have occasionally succeeded in fertilizing some of these 
orchids, and have obtained seed-capsules. 

Structure and fertilization of the Vandea; &c. of Brazil 
(p. 210). — Fritz ]\Iuller has sent me many letters containing an 
astimishing number of new and curious observations on the 
structure and manner of cross-fertilization of various orchids 



14 Mr. C. Darwin on the Fertilization of Orchidn. 

inhabiting South Brazil. I much regret that I have not here 
space or time to give an abstract of his many discoveries, 
which support the general conclusions given in mj work; 
but I hope that he will some day be induced to publish a full 
account of his observations. 

Fertilization of Catasctum (p. 211). — It has been highly 
satisfactory to me that my observations and predictive coriclu- 
sions in regard to Cafasetum have been fully confirmed by the 
late Dr. Crilger, the Director of the Botanic Gardens of' Tri- 
nidad, in letters to me and in his paper in the ' Journal of the 
Lmnean Society ' (vol. viii. Bot. 1864, p. 127). He sent me 
specimens of the bees, belonging to three species of Eughssa, 
winch he saw gnawing the inside of the labellum. The pol- 
Imia, when ejected, become attached to, and lie flat on, the 
backs of the bees, on the hairy surface of the thorax. Dr. 
Cruger has also proved that I was correct in asserting that 
the sexes of Catasetum are separate, for he fertilized female 
flowers with pollen from the male plants ; and Fritz MuUer 
effected the same thing with Catasetum mentosum in South 
Brazil. _ Nevertlieiess, from two accounts which I have re- 
ceived. It appears that Catasetum tridentatum^ though a male 
plant, occasionally produces seed-capsules ; but every botanist 
knows that this occasionally occurs with the males of other 
difficious plants._ Fritz MiiUer has given (Botanische Zeitung, 
Sept. 1868, p. 630) a most interesting account, agreeing with 
mine, of the state of the minute pollinia in the female plant : 
the anther never opens, and the pollen-masses arc not attached 
to the viscid disks, so that they cannot be removed by any 
natural means. The pollen-grains, as so generally occurs with 
rudimentary organs, are extremely variable in size and shape. 
Nevertheless the grains of the rudimentary pollen-masses be- 
longing to the female plant, when applied (which can never 
naturally occur) to the stigmatic surface, emitted their pollen- 
tubes ! This appears to me a very curious instance of the 
slow and gradual manner in which structures are modified • 
for the female pollen-masses, included within an anther which 
never opens, are seen still partially to retain their former 
powers and function. 

Morniodes luxatum (p. 265). — I have now examined another 
species of Mormodes, the rare M. luxatum, and I find that the 
chief points of structure, and the action of the different parts, 
including the sensitiveness of the filament, are the same as 
in AI. ignea.^ The cup of the labellum, however, is much 
larger, and is not pressed down firmly on the filament on the 
summit of the column. This cup probably serves to attract 
insects, and, as in Catasetum, is gnawed bv them. The flowers 



Mr. C. Darwin on the Fertilization of Orchids. 15 

are asymmetrical to an extraordinary degree, the right-hand 
and left-hand sides differing mncli in shajie. 

Cycnoches ventricosuni (p. 265). — The plant described in my 
work as a second species of Mormodes proves to be Cycnoches 
ventricosuni. I first received from Mr. Veitch some flower-buds, 
from which the section (fig. xxx.) was taken ; but subsequently 
he sent me some perfect flowers. The yellowish-green petals 
and sepals are reflexed ; the thick labellum is singularly shaped, 
with its upper surface convex, like a shallow basin turned 
upside down. The thin column is of extraordinary length, and 
arches like the neck of a swan over the labellum ,• so that the 
whole flower presents a very singular appearance. In the sec- 
tion of the flower, given in my work, we see the elastic pedicel 
of the poUinium bowed, as in Gatasetum or Mormodes • but at 
the period of growth represented in the figure the pedicel was 
still united to the rostellum, the future line of separation being 
shown by a layer of hyaline tissue indistinct towards the upper 
end of the disk. The disk is of gigantic size, and its lower 
end is produced into a great fringed curtain, which hangs in 
front of the stigmatic chamber. The viscid matter of the disk 
sets liard very quickly, and changes colour. The disk ad- 
heres to any object with surprising strength. The anther is 
very different in shape from that of Gatasetum or Mormodes, 
and apparently would retain the pollen-masses with greater 
force. A part of the filament of the anther, lying between 
two little leaf-like appendages, is sensitive ; and when tliis 
part is touched, the poUinium is swung upwards, as in Mor- 
modes, and with sufficient force, if no object stands in the 
way, to throw it to the distance of an inch. An insect of 
large size alights probably on the labellum, for the sake of 
gnawing the convex surface, or perhaps on the extremity of 
the arched and depending column, and then, by touching the 
sensitive point, causes the ejection of the pollen-masses, which 
are affixed to its body and thus transported to another flower 
or plant. 

Fertilization of the Arethuseaj (p. 269). — Ejnpogium Grnelini 
has been the subject of an admirable memoir (Ueber den Blii- 
thenbau, &c., (iottingen, 1866) by Dr. P. Kohrbach, who 
has shown how the flowers are fertilized by Bombus lucorum. 
With respect to another genus belonging to this same tribe, 
namely Pogonia, Dr. Scudder of the United States has de- 
scribed (Proc. Boston Nat. Hist. Soc. vol.ix. 186.?, p. 182) 
the manner in which it is fertilized by the aid of insects. 

Cypripedium (p. 274). — Prof. Asa Gray, after examining 
several American species of Gypripedium, wrote to me (see 
also Amer. Journ. of Science, vol. xxxiv. 1SG2, p. 427) that 



18 



16 ilr. C. Davwin on the Fertilization of Orchiih. 

he wa3 convinced tliat I was in error, and tliat tlie flowers 
are fertilized by small insects entering the labellum througli 
the large opening on tlio njipcr surface, and crawling out in- 
one of the two small oritices close to either anther' and the 
stigma. Accordingly I caught a very small bee wliich seemed 
ot about the right size, namely the Andrena parvula (and this 
by a strange chance proved, as we shall presently see, to be 
the right genus), and placed it in the labellum through the 
upiier large opening. The bee vainly endeavoured to crawl 
out again the same way, but always fell backwards, owino- to 
the margins being inflected. The labellum thus acts like one 
ot those conical traps with the edges turned inwards, which are 
so .1 to catch beetles and cockroaches in the London kitchens. 
Uitimately the little bee forced its way out through one of the 
small orifices close to one of the anthers, and was found when 
caught to be smeared with the glutinous pollen. I then ao-ain 
put tlie same bee into the labellum ; and again it crawled^out 
through one of the small orifices. I repeated the operation 
tiv-e times, always with the same result. I tlien cut away the 
labellum, so as to examine the stigma, and found it vA\ 
smeared over with pollen. Delpino (Fecondazione &c. 1SG7, 
p. 20) with much sagacity foresaw that some insect would be 
c iscovered to act m the manner just described ; for he argued 
tliat it an insect were to insert its proboscis, as I had supposed, 
from the outside through one of the small orifices close to one 
ot the anthers, the stigma would be fertilized by the plant's 
own pollen ; and in this he did not believe, from havino- 
confidence m what I have often insisted on— namely, that all 
the contrivances for fertilization are arranged so that the 
stigma shall receive pollen from a distinct flower or plant 
JJut these speculations are now all superfluous ; for, owing to 
the admirable observations of Dr. H. Miiller, of Lippstadt 
(\ erh d A at. Ver. Jahrg. xxv. III. Folge, v. Bd. p. 1) we 
actually know that Cypripedium calceolus in a state of nature 
IS fertilized by two species oi Andrena, in the manner above 
supposed. 

On the relation between the more or less viscid condition of 
the pollen and stigma in Cypripedium (p. 276).— The relation 
between the state of the pollen and stigma, which I have 
pointed out m my work, is strongly confirmed by Prof Gray's 
statement (Amer. Journ. of Science, vol. xxxiv. 1862 p 428) 
namely, that in C. acaule the pollen is much more granular or 
less viscid than m other American species of the genus, and in 
this species alone the stigma is slightly concave and viscid' 
Ur. Lrray adds that m most of the species the broad stigma 
presents another remarkable peculiarity, " in being closely 



Mr. C. Darwin on the Fertilization of Orchids. 1 7 

beset with minute, rigid, sliarp-pointed papilla, all directed 
forwards, which are excellently adapted to brush off the pollen 
from an insect's head or back." 

The u.ie of the copious fluid contained within the Jahellum 
o/Coryanthes (p. 278). — The Goryanthes macrantha is per- 
haps tlie most wonderful of all known orcliids, even more 
wonderful in structure and function than Catasetum. Its 
manner of fej-tilization has been described bj Dr. Criiger in 
the 'Journal of the Linnean Society' (vol. viii. Bot. 1864, 
p. 130) , and in letters to me. He sent me bees, belonging to 
the genus Eiiglossa, which he saw at work. The fluid in the 
bucket formed by the basal part of the labellum is not nectar 
and does not attract insects, but serves, by wetting their 
wings, to prevent them from crawling out except through the 
small passages close to the anther and stigma. Thus the 
secretion of fluid in this orchis serves exactly the same end as 
the inflected margins of the labellum in Cypripedium. 

On the evidence that Insects visit many exotic Orchids in order 
to gnato parts of the labellum., and not for the sake of nectar 
(p. 284). — It has been highly satisfactory to me that this hypo- 
thesis has been fully confirmed. In the West Indies, Dr. Criiger 
witnessed humble-bees of the genus Euglossa gnawing the 
labellum of Catasetum, Goryanthes, Gongora, and Stanhopea ; 
and Fritz Miiller has repeatedly found, in South Brazil, the 
prominences on the labellum of Oncidium gnawed. We are 
thus enabled to understand the meaning of the various extra- 
ordinary crests and projections on the labellum of various 
exotic orchids ; for they invariably stand in such a position 
that insects, whilst gnawing them, will be almost sure to 
touch the viscid disks of the pollinia, and thus remove them. 

Bonatea speciosa (p. 30.5). — T!ie manner oi fertilization oi 
this extraordinary orchis has now been frdly described by Mr. 
E. Trimen in the 'Journal of the Linnean Society' (vol. ix. 
Bot. 1865, p. 156). A projection rising from the base of the 
labellum is one of its most remarkable peculiarities, as an in- 
sect is thus compelled to insert its proboscis on one side, and 
thus to touch one of the two widely separated and projecting 
viscid disks. Mr. J. P. Mansel Weale has also published 
[ibid. vol. X. 1869, p. 470) analogous observations on a second 
species, viz. Bonatea Darwinii. Mr. Weale caught a skipper- 
butterfly {Pyrgus ehno) quite embarrassed by the number of 
pollinia belonging to this orchis which adhered to its sternum. 
I do not know of any other case in which the pollinia adhere 
to the sternum of a Lepidopterous insect. 

On the nature of the contraction which causes the pollinia, 
after their removal from the anther, to change their position 

B 



18 Mr. C. Darwin on the Fertilization of Orchids. 

(p. 338). — ^In Orchis hircina, I clearly saw, under the micro- 
scope, the whole front of the viscid disk become depressed as the 
two pollinia together miderwent the movement of depression. 
Number of seeds (p. 344). — The number of seeds produced 
by Orchis macidata, as given in my work, is small in com- 
parison with that produced by some foreign species. I have 
shown (Variation of Animals and Plants under Domestication, 
vol. ii. 1868, p. 379), on the authority of Mr. Scott, that a 
single capsule of Acropera contained 371,250 seeds ; and the 
species produces so many flowers and racemes, that a single 
plant probably sometimes produces as many as 74 millions of 
seeds in the course of a single year. Fritz Mullev carefully 
estimated, by weighing, the number of seeds in a single capsule 
of a Maxillaria in South Brazil, and found the number 
1,756,440. The same plant sometimes produces half-a-dozen 
capsules. 

Number of jwUen-grcdns (p. 355). — I have endeavoured to 
estimate the number of pollen-grains produced by a single 
flower of Orchis mascida. There are two pollen-masses; in 
one of these I counted 153 packets of pollen ; each packet 
contains, as far as I could count, by carefully breaking it up 
under the microscope, nearly 100 compound grains ; and each 
compound grain is formed of four grains. By multiplying 
these figures together, the product for a single flower is about 
120,000 pollen-grains. Now we have seen that In the allied 
0. maculata a single capsule produced about 6,200 seeds ; so 
that there are nearly twenty pollen-grains for each ovule or 
seed. As a single flower of a Maxillaria produced 1,756,000 
seeds, it would produce, according to the above ratio, nearly 
34 million pollen-grains, each of which, no doubt, includes 
the elements for the reproduction of every single character in 
the mature plant ! 

Enumeration of the Orchidea which, as at present known, 
habitually fertilize themselves (p. 358). — We have now seen 
that self-fertilization habitually occurs, in a more or less perfect 
manner, in one of the species of Ophrys, of Neotinea, Gymna- 
denia, Platanthera, Epipactis, Cephalanthera, Neottia, and in 
those Epidendrece and in Dendrobium which often produce 
flowers that never expand. No doubt other cases will here- 
after be discovered. Self-fertilization seems to be more per- 
fectly secured in Ophrys apifera and in Neotinea intacta than 
in the other species. But it deserves especial notice that in 
all these orchids structures are still present, not in a rudimen- 
tarj' condition, which are manifestly adapted for the transport 
by insects of the pollen-masses from one flower to another. 
As I have elsewhere remarked, some plants, both indigenous 



Jlr. C. riarwin on the Fertilization of Orchids. 19 

and naturalized, rarely or never bear Howers, or, if they do bear 
tiowers, tlicse never produce seed. But no one doubts that 
it is a general law of nature that phanerogamic plants should 
produce floirers, and tliat these flowers should produce seed. 
When they fail to do this, we believe that such plants would 
perform tJieir proper functions under different conditions, or 
that they formerly did so and will do so again. On analogical 
grounds I believe that the few orchids which do not now inter- 
cross, either did formerly intercross (the means for effecting 
this being still retained) or that they will do so at some 
future period under different conditions, unless, indeed, they 
become extinct from the evil effects of long-continued close 
interbreedino-.