Skip to main content

Full text of "On British wild flowers considered in relation to insects"

See other formats 


BIOLOGY 

LIBRARY 

G 


BY  THE  SAME  AUTHOR. 

PEACE  AND  HAPPINESS.     Crown  8vo.     (Macmillan  &  Co.,  Ltd.  * 
ON  MUNICIPAL  AND  NATIONAL  TRADING.     Third  Impres- 
sion.    8vo,  limp  cloth,  2S.  6rf.  net.    (Macmillan  &  Co.,  Ltd.) 
NOTES  ON  THE  LIFE-HISTORY  OF  BRITISH  FLOWERING 

PLANTS.     8vo,  is*,  net.    (Macmillan  &  Co.,  Ltd.) 

FREE  TRADE.  Fourth  Ed.  8vo,  2s.  6d.  net.    (Macmillan  &  Co.,  Ltd.) 
ESSAYS      AND     ADDRESSES,    1900-1903.     8vo,    7*.    6d.  net. 

(Macmillan  &  Co.,  Ltd.) 
THE  SCENERY  OF  ENGLAND,  and  the  Causes  to  which  it  is- 

Due.     Fifth  Edition.     Crown  8vo,  6s.    (Macmillan  &  Co.,  Ltd.) 

THE  SCENERY  OF  SWITZERLAND,  and  the  Causes  to  which  it 

is  Due.     Fourth  Edition.     Crown  8vo,  6s.    (Macmillan  &  Co.,  Ltd.) 
THE    USE    OF    LIFE.      One  hundred   and   forty-fifth   Thousand. 

Globe  8vo.     Popular  Edition,  is.  kd.  ;  sewed  is.     Library  Edition,  3^.  6d.  8vo, 

sewed,   (xi.     Pocket  Edition.     Fcap.    8vo,    cloth,    as.    net ;    leather,    3.1.    net. 

(Macmillan  &  Co.,  Ltd.) 
THE  BEAUTIES  OF  NATURE.    Seventy-fourth  Thousand.  Crown 

8vo,  6s.     New  Edition,  without  Illustrations.     Globe  8vo,  cloth,  is.  6d.     Paper, 
is.     Also  8vo.  sewed,  6d.     (Macmillan  &  Co.,  Ltd.) 

THE  PLEASURES  OF  LIFE.  Part  I.  24501  Thousand.  Globe 
8vo.  Popular  Edition,  is.  6d.  ;  sewed,  is.  (Macmillan  &  Co.,  Ltd.) 

THE  PLEASURES  OF  LIFE.     Part  II.     i9Qth  Thousand.     Globe 

8vo.     Popular  Edition,     is.  6d.  ;  sewed  i s.    (Macmillan  &  Co.,  Ltd.) 

THE  PLEASURES  OF  LIFE.  (Two  Parts  in  one  Vol.)  Globe 
8vo,  aj.  6d.  8vo,  sewed,  6<i.  Pocket  Edition.  Fcap.  8vo,  cloth  25.  net ; 
leather,  3^.  net.  (Macmillan  &  Co.,  Ltd.) 

SCIENTIFIC    LECTURES.      Fourth    Thousand.      8vo,    6s.    net. 

(Macmillan  &  Co.,  Ltd.) 
FIFTY  YEARS  OF  SCIENCE.     Being  the  Address  delivered  at 

York  to  the   British  Association,  August  1881.     Sixth   Edition.     8vo,   zs.   fid. 

(Macmillan  &  Co.,  Ltd.) 
BRITISH    WILD   FLOWERS   CONSIDERED  IN   RELATION 

TO    INSECTS.     With   Illustrations.    Nature  Series.      Eleventh  Thousand. 

Crown  8vo,  4J.  6d.     (Macmillan  &  Co.,  Ltd.) 
FLOWERS,  FRUITS,  AND  LEAVES.    With  Illustrations.    Nature 

Series.     Ninth  Thousand    Crown  8vo,  4*.  6<t.    (Macmillan  £  Co.,  Ltd.) 

THE  ORIGIN  AND  METAMORPHOSES  OF  INSECTS.     With 

Illustrations.       Nature    Series.       Eighth    Thousand.       Crown    8vo.    3^.    6</~ 

(Macmillan  &  Co.,  Ltd.) 
ON    SEEDLINGS.      With  690   Illustrations.     Two   Volumes   8vo, 

36*.    (Kegan,  Paul,  Trench  &  Co.) 
ON    SEEDLINGS.       Popular    Edition.       With    282    Illustrations. 

Second  Edition.     Crown  8vo,  55.    (Kegan  Paul,  Trench  &  Co.) 
ANTS,  BEES,  AND  WASPS.     With   Illustrations.     International 

Scientific  Series      ijth  Edition.     Cr.  8vo,  55.     (Kegan  Paul.  Trench  &  Co.) 

ON  THE  SENSES,  INSTINCTS,  AND  INTELLIGENCE  OF 

ANIMALS.    With  Special  Reference  to  Insects.    With  100  Illustrations.     Inter- 
national Scientific  Series,  sth  Ed.  Cr.  8vo,  55.     (Kegan  Paul,  Trench  &  Co.) 

CHAPTERS    IN    POPULAR    NATURAL    HISTORY.      I2mo. 

is.  6(t.     (National  Society.) 
MONOGRAPH  ON  THE  COLLEMBOLA  AND  THYSANURA.. 

1871.    (Ray  Society.) 
PREHISTORIC  TIMES.     As  Illustrated  by  Ancient  Remains  and 

the    Manners   and  Customs   of  Modern    Savages.     Sixth   Edition.     8vo,    i8j. 

(Williams  &  Norgate.) 

THE  ORIGIN  OF  CIVILISATION  AND  THE  PRIMITIVE 
CONDITION  OF  MAN.  Sixth  Edition.  8vo,  i8s.  (Longmans,  Green  &  Co.). 

ON  REPRESENTATION.  Eighth  Edition.  Crown  8vo,  it 
(Swan  Sonnenschein  &  Co,) 

ON  BUDS  AND  STIPULES.  International  Scientific  Series- 
(Kegan  Paul,  Trench  &  Co.) 

LA  VIE  DES  PLANTES.     8vo.     (J.  B.  Bailliere  et 


ON 


BRITISH   WILD    FLOWERS 


CONSIDERED    IN 


RELATION    TO   INSECTS. 


FIG.  43- 


FIG.  44. 


FIG.  47. 


FIG.  48. 


NATURE  SERIES 


ON 


BRITISH  WILD  FLOWERS 


CONSIDERED    IN 


RELATION  TO  INSECTS 


THE  RIGHT  HON.  LORD  AVEBURY,  P.C. 

Pres.  Soc.  Ant.  ;  For.  Sec.  R.A. ;  F.R.S..  D.C.L.  (Oxon.),  LL.D.  (CANTAB.  DUBL. 

ST.  ANDREWS  ET  EDIN.),  M.D.  (WiJRZB.),  German  Otd.  Pour  le  Merite  ;  Com. 

Legion  d'Honneur  ;  F.L.S.,  F.G.S.,  F.Z.S.,  F.S.A.,  F.E.S.,  Trust.   Brit. 

M us.;  Pres.  Roy.  Mic.  Soc.;  Pres.  Roy.  Soc.;  Assoc.  Roy.  Acad.desSci. 

Brux.  ;  Hon.  Mem.  R.  Irish  Acad.,  Amer.  Ethnol.  Soc.,  Anthrop. 

Soc.  Wash.  (U.S.),  Brux.  Firenze,  Anthrop.  Verein  Graz,  Soc. 

Entom.  de   France, '  Soc.    Gcol.    de   la    Suisse     and    Soc. 

Helvet-des  Sci.  Nat.;  Mem.  Amer.  Phil.  Soc.  Philad., 

and  Soc.  d'Ethn.  de  Paris  ;  Corresp.  Mem. 
Soc.  des.  Sci.  Nat.  de  Cherb.,  Berl.  Gesell.  fur  Anthrop. 
Soc.  Romana  di  Antrop.,  Soc.  d'Emul.  d' Abbeville  ;  For.  Mem. 
Roy.  Dan.  Acad.,  Soc.  Cient.  Argentina,  Soc.  de  Geog.  de  Lisb., 
Acad.  Nat.  Sci.  Philad.,  Numis.  and  Ant.  Soc.  Philad.,  Amer.  Entom. 
Soc.  For.  Assoc.  Mem.  Soc.  d'Anthrop.  de  Paris ;  For.  Mem.  Amer.  Antiq. 
Soc.;  For.  Mem.  Soc.  Espanolade  Hist.  Nat.,  Roy.  Soc.  of  Sci.,  Upsala  ; 
Hon.  Mem.  New  Zealand  Inst. ;  Hon.  Mem.  Soc.  de  Sociologie 
Patron  Calcutta  Historical  Soc.  ;  Vice-Patron    Royal  Anthro- 
pological Soc.  of  Australasia  ;  Lord  Rector  of  the  University 
of  St.  Andrews. 


WITH   NUMEROUS  ' 


MACMILLAN  AND  CO.,  LIMITED 

ST.  MARTIN'S  STREET,  LONDON 

1909 


\ 

BIOLOGY 
UBBARY 

« 


RICHARD  CLAY  AND  SONS,  LIMITED 

BREAD  STREET  HILL,  E.C.,  AND 

BUNGAY,  SUFFOLK. 


First  Edition,  printed  1875. 
Reprinted  1875,  1882,  unth  slight  corrections  1885,  1890,  1893   1897)  1903,  1909. 


PREFACE. 


IT  is  not  without  much  diffidence  that  I  venture  on 
the  present  publication.  For  though  as  an  entomo- 
logist I  have" necessarily  been  long  familiar  with  our 
common  wild  plants,  I  had  made  no  serious  study  of 
Botany  until  recent  researches  brought  prominently 
before  us  the  intimate  relations  which  exist  between 
flowers  and  insects.  My  observations  and  notes  on 
this  subject  were  originally  prepared  with  the  view 
of  encouraging  in  my  children  that  love  of  natural 
history  from  which  I  myself  have  derived  so  much 
happiness,  but  it  was  suggested  to  me  that  a  little 
book  such  as  the  present  might  perhaps  be  of  use 
to  others  also. 

Sprengel,  in  his  admirable  work,  "Das  entdeckte 
Geheimniss  der  Natur,"  published  as  long  ago  as  the 
year  1793,  was  the  first  to  show  how  much  plants  are 
dependent  on  the  visits  of  insects,  and  to  point  out 
that  the  forms  and  colours  of  flowers  are  adapted  to 
ensure,  and  profit  by,  those  visits.  His  work,  how- 
ever, did  not  attract  the  attention  which  it  deserved, 
and  our  knowledge  of  the  subject  made  little  pro- 
gress until  the  publication  of  Mr.  Darwin's  researches, 
to  which  I  shall  continually  have  occasion  to  refer. 
Dn  Hermann  Miiller  in  his  "  Die  Befruchtung  der 
Blumen  durch  Insekten,"  has  brought  together 
the  observations  of  previous  writers,  and  added 

7 1.7  093 


PREFACE. 


to  them  an  immense  number  pf  his  own.  Many 
other  naturalists — for  instance,  Axell,  Bennett,  Del- 
pino,  Hildebrand,  Hooker,  F.  Muller,  and  Ogle,  have 
also  published  valuable  memoirs  on  the  subject,  to 
which  I  shall  frequently  have  occasion  to  refer ;  but 
to  the  works  of  Sprengel,  Darwin,  and  Dr.  H.  Muller 
I  am  indebted  in  almost  every  page,  and  in  spite 
of  constant  references,  it  is  impossible  for  me  ade- 
quately to  acknowledge  my  obligations  to  them. 
In  the  systematic  portion,  I  have  followed  Mr.  Ben- 
tham's  excellent  "  Handbook  of  the  British  Flora." 

As  far  as  possible,  I  have  avoided  the  use  of 
technical  terms,  but  some  were  unavoidable;  refer- 
ences for  these  will  be  found  in  the  Index,  and  I  have 
aiso  given  a  Glossary  of  the  technical  terms  most  fre- 
quently employed. 

I  have  to  thank  various  friends  who  have  been 
good  enough  to  assist  me,  but  especially  Dr.  (now  Sir 
Joseph)  Hooker  and  Mr.  Busk,  who  have  been  so  very 
kind  as  to  look  through  my  proofs. 

In  conclusion,  I  must  add  that  the  subject  is  com- 
paratively new,  and  many  of  the  observations  have 
not  yet  stood  that  ordeal  of  repetition  which  they 
will  no  doubt  experience.  While,  therefore,  I  believe 
that  the  facts  will  be  found  to  be  in  the  main  correct, 
the  inferences  drawn  from  them  must,  in  many  cases, 
be  regarded  rather  as  suggestions  than  as  well  esta- 
blished theories.  The  whole  subject  is  one  which 
is  most  interesting  in  itself,  and  will  richly  repay 
those  who  devote  themselves  to  it. 

HIGH  ELMS,  DOWN,  KENT, 
September,   1874. 


CONTENTS. 

f  AGK 

LIST  OF  ILLUSTRATIONS xi 

GLOSSARY r         „          ; .  , '    +         XV 

CHAPTER  I. 

INTRODUCTION I 

CHAPTER  II. 
INTRODUCTION— (Continued) 27 

CHAPTER  III. 

DICOTYLEDONS. 

THALAMIFLOR/E 52 


CONTENTS. 


CHAPTER  IV. 

PAGE 

CALYCIFLOR.E 85 


CHAPTER  V. 

COROLLIFLOR^  *          . 115 

CHAPTER  VI. 

INCOMPLETE      .          .          . 165 

CHAPTER  VII. 

MONOCOTYLEDONS    .          .          .          .          .          .          .  1 68 


LIST  OF  ILLUSTRATIONS. 


In  all  the  figures  of  flowers,  unless  otherwise,  specified,  the  letters 
refer  to  the  same  parts,  viz.  : — pistil,  / — style,  p' — stigma,  st — 
stamen,  f—  filament,  f—  anther,  a — petals,  pe — corolla,  co — 
sepals,  s. — calyx,  ca — ovary,  o — honeygland,  h — pollen,  po. 


Fie.  J-AGE 

Geranium  sylvaticurn I 

1.  Stigma  of  the  Alder                       (after  Axell)      ...  9 

2.  Stigma  of  the  Hop                              ,,         ,,          ...  9 

3.  Stigma  of  the  Wheat                          ,,         ,,          .         .         .  9 

4.  Stigma  of  the  Willow  „         ,,          .  •••   '9 

5.  Stigma  of  the  Flax                             ,,         ,,          .         .        •  9 

6.  Stigma  of  Nuphar                               ,,         ,,          .         .         •  •      9 
7-  Section  of  Plantago  major                  ,,         ,,           .         .         .  10 

8.  Section  of  Plumbago  Europea            ,,         ,,          .         .         .  10 

9.  Section  of  Poterium  sanguisorba        ,,         ,,          .         .         .  10 

10.  Section  of  Sanguisorba  officinalis       ,,         ,,          .         .         .10 

11.  Mouth-parts  of  a  Wasp 16 

12.  Front  part  of  head  of  Prosopis,  seen  from  below,  with  the 

mouth-parts  extended  (after  Miiller)       .         .                  .  17 

13.  Prosopis  (after  F.  Smith)       . 17 

14.  Mouth-parts  of  Polistes                               (after  Miiller}          .  17 

15.  Mouth-parts  of  Andrena,  seen  from  below    ,,         ,,      .         .  18 

16.  Mouth-parts  of  Halictus                                  ,,         ,,      .        .  18 

17.  Mouth-parts  of  Panurgus                                ,,         ,,               •  18 

1 8.  Mouth-parts  of  Halictoides                             ,,         ,,               .  18 

19.  Mouth-parts  of  Chelostoma                             ,,         ,,      •         •  18 

20.  Head  of  Humble-bee  (Bombus  agroruni),  with  the  mouth- 

parts  extended          (after  Miiller) 19 

21.  Left  hind-leg  of  Prosopis      ,,         „ 

22.  Left  hind-leg  of  Sphecodes  ,,         ,, 2O 

23.  Sphecodes  (after  Westwood)          .         .         .         ...  20 


LIST  OF  ILLUSTRATIONS. 


FIG.  PACK 

24.  Right  hind-leg  of  Halictus                        (after  M  tiller)    .         .  20 

25.  Left  hind-leg  of  Panurgus  banksianus        ,,         ,,          .  21 

26.  Right  hind-leg  of  Anthophora  bimaculata  ,,         ,.  .          .21 

27.  Right  hind-leg  of  Bombus  scrimskiranus    ,,         ,,  .         .22 

28.  Right  hind- leg  of  Hive-bee                          ,,         ,.          .         .  22 

29.  Diagrammatic  section  of  Arum 32 

30.  Pink  in  the  first  (male  condition)  ......  35 

31.  Pink  in  the  second  condition,  with  mature  stigmas          .         .  3^ 

32.  Thymus  serpyllum,  in  the  first  condition,  with  ripe  stamens 

(after  Miiller)         .         . 36 

33.  Thymus  serpyUum,   in   the  second  condition,    with   mature 

stigma 36 

34.  Myosotis  versicolor,  young  flower  (from  Nature)      .         .         .  36 

35.  Myosotis  versicolor  (older  flower) 36 

36.  Cleistogamous  flower  of  Lamium  amplexicaule  (after  Hilde- 

brand) 37 

37.  Section  of  ditto  (after  Hildebrard)        .         .        .         .        .37 

38.  Primula  (long-styled  form) 38 

39.  Primula  (short-styled  form) 3& 

40.  Geranium  pratense  (after  Bentham) 4 r 

41.  Geranium  pratense,  young  flower  (after  Hildebrand)       .         .  42 
a.2.   Gfratiium  pratense  (older  flower)      „             ,,                 .         .42 

43.  Maiva  sylvestris        (after  Sower  by;       .                  ...  45 

44.  Malva  rotundifolia       „           ,,              45 

45.  Stamens  and  stigmas  of  Malva  sylvestris    (after  Miiller)         .  46 

46.  Stamens  and  stigmas  of  Malva  rotundifolia    „         ,,              .  46 

47.  Epilobium  angustifolium  (after  Sowerby)        ....  47 

48.  Epilobium  parviflorum        ,,  ,,  .         .         .         .47 

49.  Corolla  of — a,  Geranium  pratense ;  b,  G.  pyrenaicum  ;  cy  G. 

molle ;  d,  G.pusillum 4& 

50.  Lychnis  -vespertina  (after  Bentham) 5° 

51.  A  young  flower  of  Delphinium  elatum,  seen  from  in  front,  and 

after  removal  of  the  calyx                              (after  Miiller)  57 

52.  Section  of  the  same  flower  seen  from  the  side           ,,         „  57 

53.  An  older  flower,  seen  from  front,  after  removing  calyx  ,,         ,,  57 

54.  Section  of  the  same  flower,  seen  from  the  side          ,,         ,,  57 

55.  Flower  seen  from  above                                              ,,         ,,  59 

56.  Pistil  with  two  stamens,  after  the  visit  of  an  insect  ,,         ,,  59 

57.  Section  of  a  flower  of  Viola  canina 65 

58.  Stamen  of  a  flower  of  Viola  canina 65 


LIST  OF  ILL  USTRA  TIONS.  xiii 


59.  Polygala  vulgaris  (after  Bentham)          .         .         .         .         .69 

60.  Flower  of  Polygala  vulgaris yO 

61.  Section  of  ditto 70 

62.  Stellaria  graminea  (after  Bentham) 7^ 

63.  Young  flower  of  Tropeeolum  major gj 

64.  Flower  of  Tropaolum  major  in  the  second  stage     .         .  ^2 

65.  Flower  of  Tropceolum  major  in  the  third  stage       ...        83 

66.  Z0/#J  corniculatus  (after  Bentham) 87 

67.  Flower  of  Lotus  corniculatus  seen  from  the  side  and  in  front 

(after  Muller) gg 

68.  Ditto,  after  removal  of  the  standard  (after  Muller)     .        gg 

69.  Ditto,  after  removal  of  the  standard  and  wings  ,,         ,,  .        gg 

70.  Ditto,  after  removal  of  one  side  of  the  keel       ,,         ,,  .        gg 

71.  Terminal  portion  of  Fig.  70  more  magnified       ,,         ,,  .        gg 

72.  Flower  of  Sweet  Pea,  in  its  natural  position          .         .         .        gO 

73.  Ditto.  The  wings  are  depressed,  the  stamens  and  pistil  exposed        gO 

74.  Flower  of  Genista  tinctoria  unopened    .         .         .         .  g? 

75.  76.     Ditto,  opened 93 

77.  Lythrum  salicaria  (after  Bentham) IO2 

78.  Long-styled  form  of  Lythrum  salicaria  (after  Darwin)    .         .       IO3 

79.  Mid-styled  ditto  ,,         ,,         .         -103 

80.  Short- styled  ditto  ,,         ,,         .         .       103 

81.  Drosera  rotundifolia  (after  Bentham) 106 

82.  Two  leaves  of  Dionsea  :  one  open,  one  closed  upon  a  fly        .       107 

83.  Wild  Chervil  (Chcsrophyllum  sylvestre)  (after  Bentham).         .       no 

84.  Flower  of  Wild  Chervil  in  the  first  (male)  state  (after  Muller)       1 1 1 

85.  Ditto,  in  the  second  (.female)  state  .         .         .       ,,         ,,  in 

86.  Chrysanthemum  partfuniiim  (after  Bentham)          .         .         .120 

87.  Floret  of  Chrysanthemum  parthenium,  just  opened  (after  Ogle)       121 

88.  Ditto,  somewhat  more  advanced  ,,       ,,  121 

89.  Ditto,  with  the  stigmas  expanded  ,,       ,,  121 

90.  Section  of  bud  of  Campanula  medium          .         .         .         .129 

91.  Section  of  a  flower  in  the  first  (male)  condition     .         .         .129 

92.  Ditto,  in  the  second  (female)  condition          .         .         .         .129 

93.  Flower  of  Erica  tetralix  (after  Ogle) 131 

94.  Stamen  of  ditto  „         „         .  ...       131 

95.  Borago  ojficinalis          (after  Bentham)   .         .         .         .  137 

96.  Pulmonaria  officinalis     ,,  „ 139 

97.  Veronica  chamcedrys        ,,  „  .          .         .         .         .142 

98.  Verbascum  thapsus          ,,  ,,  .          .         .         .         .        143 


xiv  LIST  OF  ILL  USTRA  TIONS. 

KIG.  PAGE 

99.  Scrophularia  nodosa  (after  Bentham) r ,. 

100.  Section  of  Digitalis purpurea  (after  Ogle)    .         .         .         -145 

lor.  Ditto,  more  advanced j^c 

1 02.  Ditto,  still  more  advanced 14 1 

103.  Bartsia  odontites  (after  Bentham) !^5 

104.  Ditto.     Flower  with  a  short  pistil  (after  Miiller)  .         .         .  147 

105.  Ditto.     Flower  with  a  long  pistil      ,,,,...  147 

1 06.  Euphrasia  oj)icinalis  (after  Bentham) 148 

107.  Flower  of  ditto 148 

1 08.  PedicUaris  sylvatica  (after  Ogle) 150 

109.  Lamium  album  (after  Bentham)  .         .         .         .         .         .152 

no.  Flower  of  ditto . 153 

in.   Section  of  ditto 153 

112.  Salvia  officinalis.     Section  of  a  young  flower  (after  Ogle)      .  156 

113.  Ditto,  visited  by  a  Bee                                          ,,         ,,         .  156 

114.  Ditto,  older  flower                                                 ,,         „         .  156 

115.  Stamens  in  their  natural  position                          „         „         .  157 

116.  Stamens  when  moved  by  a  bee                             ,,         ,,         .  157 

117.  Teucrium  scorodonia,  in  the  first  state           .         .         .  J5^ 

118.  Ditto  in  the  second  state *5& 

119.  Chenopodium  bonus-henritus  (after  Bentham)        .         .         .165 

1 20.  Orchis  niascula                            ,,             ,,             .         .  I7I 

121.  Side  view  of  flower,  with  all  the  petals  and  sepals  cut  oil 

except  the  labeiium,  of  which  the  near  half  is  cut  away, 
as  well  as  the  upper  portion  of  the  near  side  of  the  nectary 

(after  Darwin)       . 172 

122.  Front  view  of  flower,  with  all  sepals  and  petals  removed 

except  the  labeiium  (after  Darwin)          ....  172 

123.  The  two  pollinia                ,,          ,, 172 

124.  Ophrys  apifera  (after  Bentham)   .         .         .         -175 

125.  Cepkalanthera  grandiflora      ,,          ,,             ....  177 

126.  Listera  ovata  ,,         ,,  .         .         .         .178 

127.  Flower  of    Cypripedium  longifolium.     Front  view       .         .  180 

128.  Ditto.     Seen  from  the  side          .         .         .         .         .         .  180 

129.  Side  veiw  of   Catasetum  saccatutn,  with  all  the  sepals  and 

petals  removed  except  the  labeiium             {after  Darwin)  182 

130.  Section  of  ditto,  with  all  the  parts  a  little  expanded  183 


GLOSSARY. 


Anemophilous  (p.  9)  plants  are  those  in  which  the  pollen  is  carried  to 

the  stigma  by  the  wind. 
Anther,  that  portion  of  the  stamen  which  contains  the  pollen. 

Calyx  (p.  27),  the  outer  whorl  of  the  flower. 

Cleistogamous  species  (p.  37),  are  those  which,  besides  the  usual  con- 

spicuous  flowers,  have  others  which   are   smaller,  and  generally 

uncoloured. 
Corolla  (p.  27),  the  second  whorl  of  the  flower.     In  most  cases  this  is 

the  coloured  part. 

Dichogamous  species  (p.  28)  are  those  in  which  the  stamens  and  pistil 

do  not  mature  simultaneously. 
Diclinous  plants  (p.   28),  are  those  in  which  all  the  flowers  are  either 

male  or  female,  that  is  to  say,  either  contain  stamens  but  no  pistil, 

or  pistil  but  no  stamens. 
Dimorphous  species  (p.  29)  are  those  in  which  there  are  two  forms  of 

flowers,  differing  in  the  relative  position  or  length  of  the  anthers 

and  stigma. 
Dioecious  species  (p.  28)  are  those  in  which  the  stamens  and  pistils  are 

situated  not  only  in  distinct  flowers,  but  also  on  separate  plants. 

Entomophilous  plants  (p.  9)  are  those  in  which  the  pollen  is  carried  to 

the  stigma  by  insects 
Epigynous,  situated  upon  the  ovary. 

Filament,  the  stalk  of  the  anther. 

Heterogamous  plants    are   those  which  have  male,  female,  and    her- 
maphrodite flowers,  or  any  two  of  them  united  in  one  head. 


xvi  GLOSSARY. 


Heteromorphous  species  are  those  in  which  there  is  more  than  one  form 

of  flower. 
Hypogynous,  situated  under  the  ovary.    ; 

Monoecious  species  (p.  28)  are  those  in  which  the  stamens  and  pistils  are 

in  separate  flowers,  but  on  the  same  plant. 
Monomorphous  species  are  those  in  which  all  the  flowers  resemble  one 

another  in  the  relative  position  of  the  stamens  and  pistil. 

Nectary,  that  part  of  the  flower  which  secretes  honey. 

Perigynous,  situated  around  the  ovary. 

Petals,  the  leaves  of  the  corolla. 

Pistil,  the  central  organ  of  the  flower.  It  generally  consists  of  one  or 
more  ovaries  and  stigmas ;  the  stigma  is  often  raised  on  a  stalk,  called 
a  "  style." 

Polygamous  species  are  those  which  have  male,  female,  and  hermaphro- 
dite flowers  on  the  same  or  on  distinct  plants. 

Proterandrous  plants  (p.  28)  are  those  in  which  the  stamens  come  to 
maturity  before  the  pistil. 

Proterogynous  plants  (p.  28)  are  those  in  which  the  pistil  comes  to 
maturity  before  the  stamens. 

Sepals  (p.  27)  the  leaves  of  the  calyx. 

Stamens  (p.  27)  the  parts  of  a  flower  which  generally  stand  next  the 

cprolla,  on  the  inner  side.      They  usually  consist  of  a  stalk  or 

filament,  and  an  "anther"  containing  the  pollen. 
Stigma  (p.   27),  that  portion  of  the  pistil  in  which  pollen  must  be 

deposited  in  order  to  fertilise  the  flowers. 
Style,  the  stalk  of  the  stigma. 

Trimorphous  species  are  those  in  which  there  are  three  forms  of  flowers, 
differing  in  the  relative  position  or  length  of  the  anthers  and  stigma. 


GERANIUM   SYLVATICVM.         Co      «  Ji '''•'*»    •''!'»«     »'» 


ON   BRITISH  WILD  FLOWERS 

CONSIDERED   IN 

RELATION    TO    INSECTS. 

CHAPTER  I.— INTRODUCTION. 

THE  flowers  of  our  gardens  differ  much  in  size  and 
colour  from  those  of  the  same  species  growing 
wild  in  their  native  woods  and  fields  :  this  is  due 
partly  to  cultivation,  but  still  more  to  the  careful 
selection  of  seeds  or  cuttings  from  those  plants,  the 
flowers  of  which  show  any  superiority  over  the  others 
in  size  or  colour. 

Even  amongst  wild    flowers,   however,  recent   re- 
searches have  proved  that  the  forms  and  colours  have 


2  IMPORTANCE  OF  INSECTS  [CHAP. 

been  modified  in  a  similar  manner :  the  observa- 
tions of  botanists,  especially  of  Sprengel  and  Darwin, 
have  shown  that  the  forms  and  colours  of  wild 
flowers  are  mainly  owing  to  the  unconscious  selec- 
tion exercised  by  insects,  although  no  doubt  the 
existence  of  a  certain  amount  of  colouring  matter 
is,  as  we  see  in  the  autumn  tints,  in  various  fungi, 
seaweeds,  &c.,  due  to  other  causes. 

Sprengel  appears  to  have  been  the  first  who  per- 
ceived the  intimate  relations  which  exist  between 
' '  i  .-jHants  landms^ets  ;  and  Geranium  sylvaticum  (see  p.  i) 
will  alway&  liave"  an  interest  as  being  the  flower  which 
;  '/first  «fecl!  faim;  to0his;  researches.  In  the  year  1787  he 
observed  that  in  trie  corolla  of  this  species  there  are 
a  number  of  delicate  hairs ;  and,  convinced,  as  he  says, 
that  "the  wise  Author  of  Nature  would  not  have 
created  even  a  hair  in  vain,"  he  endeavoured  to  ascer- 
tain the  use  of  these  hairs,  and  satisfied  himself  that 
they  served  to  protect  the  honey  from  rain. 

His  attention  having  thus  been  drawn  to  the  sub- 
ject, he  examined  numerous  other  flowers  with  great 
care,  and  was  surprised  to  find  how  many  points  in 
reference  to  them  could  be  explained  by  their  rela- 
tions to  insects. 

The  visits  of  insects  are  of  great  importance  to 
plants  in  transferring  the  pollen  from  the  stamens  to 
the  pistil.  In  many  plants  the  stamens  and  pistil  are 
situated  in  separate  flowers :  and  even  in  those  cases 
where  they  are  contained  in  the  same  flower,  self-fer- 
tilisation is  often  rendered  difficult,  or  impossible; 
sometimes  by  the  relative  position  of  the  stamens  and 
pistil,  sometimes  by  their  not  coming  to  maturity  at 


I.]  TO  FLOWERS. 


the  same  time.  Under  these  circumstances  the  trans- 
ference of  the  pollen  from  the  stamens  to  the  pistil 
is  effected  in  various  ways.  In  some  species  the 
pollen  is  carried  by  the  action  of  the  wind ;  in  some 
few  cases,  by  birds ;  but  in  the  majority,  this  im- 
portant object  is  secured  by  the  visits  of  insects, 
and  the  whole  organisation  of  such  flowers  is  adapted 
to  this  purpose. 

To  the  honey  are  due  the  visits  of  insects ;  the 
sweet  scent  and  bright  colours  of  the  flowers  attract 
them  ;  the  lines  and  circles  on  the  corolla  guide  them 
to  the  right  spot ;  and,  as  we  shall  see,  there  are  a 
number  of  curious  contrivances  all  tending  to  the  same 
object.  But  while  Sprengel's  deep  religious  feeling  thus 
gave  him  the  clue  which  has  thrown  so  much  light  on 
the  origin  and  structure  of  flowers,  the  comparatively 
low  conception  of  creative  power  which  was  in  his 
time,  and,  indeed,  until  recently,  prevalent,  led  him  to 
assume  that  each  flower  was  created  as  we  now  see  it, 
and  prevented  him  from  perceiving  the  real  signifi- 
cance of  the  facts  which  he  had  discovered  ;  while 
the  true  explanation  could  scarcely  have  escaped 
him  if  he  had  possessed  that  higher  view  of  creation 
which  we  owe  to  Mr.  Darwin.  Though  he  observed 
that  in  many  species  the  stamens  and  pistil  are  not 
mature  simultaneously,  and  that  such  plants  there- 
fore cannot  fertilise  themselves,  but  are  generally 
dependent  on  the  visits  of  insects,  he  appears  to  have 
considered  that  these  visits  were  arranged  mainly  in 
order  to  overcome  the  difficulty  of  fertilisation  thus 
resulting  ;  and  hence,  perhaps,  the  oblivion  into  which 
his  work,  though  so  interesting  and  suggestive  in 

B   2 


4  SPRE NOEL'S  OBSERVATIONS.  [CHAP. 

itself,  so  full  of  curious  and  careful  observations,  was 
allowed  to  fall.  For  there  is  an  obvious  incon- 
sistency in  the  coexistence  of  two  elaborate  sets 
of  arrangements,  one  tending  to  preclude,  the  other 
to  effect,  self-fertilisation ;  in  supposing  that  in  the 
first  place  the  stamens  and  pistil  were  so  arranged 
that  the  pollen  of  the  one  might  not  fertilise  the 
other  ;  and,  secondly,  that  elaborate  contrivances 
were  devised  to  promote  the  visits  of  insects,  and 
compel  them  to  transfer  the  pollen  from  the  stamens 
to  the  pistil:  a  result  which  might  have  been  ob- 
tained so  much  more  simply  by  a  slight  alteration 
of  the  flower  itself. 

It  is  the  more  remarkable  that  this  did  not  strike 
Sprengel,  because  he  •  expressly  observes  in  one  pas- 
sage that,  "Die  Natur  nicht  will  dass  irgend  einer 
Zwitterblume  durch  ihren  eigenen  Staub  befriichtet 
werden  solle  "  (Nature  does  not  choose  that  any  com- 
plete flower  should  be  fertilised  by  its  own  pollen). 
Yet  though  thus  so  near  the  truth,  he  failed  to  per- 
ceive the  true  importance  of  the  visits  of  insects. 
Subsequent  observers,  though  in  some  cases  recog- 
nising the  advantage  of  fertilising  one  flower  by 
pollen  from  another,  did  not  connect  these  observa- 
tions with  Sprengel's  discoveries  ;  and  our  illustrious 
countryman  Mr.  Darwin  was  the  first  to  bring  into 
prominence  the  fact  that  the  importance  of  insects  to 
flowers  consisted  in  their  transferring  the  pollen — not 
merely  from  the  stamens  to  the  pistil,  but  from  the 
stamens  of  one  plant  to  the  pistil  of  another. 

While  then  from  time  immemorial  we  have  known 
that  flowers  are  of  great  importance  to  insects,  it  is 


I.]  MR.  DARWIN'S  OBSERVATIONS. 


only  comparatively  of  late  that  we  have  realised  how 
important,  indeed  how  necessary,  insects  are  to  flowers. 
For  it  is  not  too  much  to  say,  that  if,  on  the  one  hand, 
flowers  are  in  many  cases  necessary  to  the  existence 
of  insects  ;  insects,  on  the  other  hand,  are  still  more 
indispensable  to  the  very  existence  of  flowers : — 
that,  if  insects  have  been  in  many  cases  modified  and 
adapted  with  a  view  to  obtain  honey  and  pollen  from 
flowers,  flowers  in  their  turn  owe  their  scent  and 
colour,  their  honey,  and  even  their  distinctive  forms 
to  the  action  of  insects.  There  has  thus  been  an  in- 
teraction of  insects  upon  flowers,  and  of  flowers  upon 
insects,  resulting  in  the  gradual  modification  of  both. 

If  it  be  objected  that  I  am  assuming  the  existence 
of  these  gradual  modifications,  I  must  reply  that  it 
is  not  here  my  purpose  to  discuss  the  doctrine  of 
Natural  Selection.  I  may,  however,  remind  the 
reader  that  Mr.  Darwin's  theory  is  based  on  the 
following  considerations  : — I.  That  no  two  animals  or 
plants  in  nature  are  identical  in  all  respects.  2.  That 
the  offspring  tend  to  inherit  the  peculiarities  of  their 
parents.  3.  That  of  those  which  come  into  existence, 
only  a  certain  number  reach  maturity.  4.  That  those 
which  are,  on  the  whole,  best  adapted  to  the  circum- 
stances in  which  they  are  placed,  are  most  likely  to 
leave  descendants. 

Now,  applying  these  considerations  to  flowers ;  if 
it  be  an  advantage  to  them  that  they  should  be  visited 
by  insects  (and  that  this  is  so  will  presently  be  shown), 
then  it  is  obvious  that  those  flowers  which,  either  by 
their  larger  size,  or  brighter  colour,  or  sweeter  scent, 
or  greater  richness  in  honey,  are  most  attractive  to 


6  USES  OF  INSECTS  TO  PLANTS.         [CHAP. 

insects,  will,  cceieris  paribus,  have  an  advantage  in  the 
struggle  for  existence,  and  be  most  likely  to  per- 
petuate their  race. 

Every  garden  indeed  is  a  sufficient  proof  that  in 
size  and  colour,  flowers  are  susceptible  of  great 
modifications ;  and  insects  unconsciously  produce 
changes  similar  to  those  which  man  effects  by 
design. 

Insects  are  useful  to  plants  in  various  ways.  Thus, 
a  species  of  acacia  mentioned  by  Mr.  Belt,1  if  unpro- 
tected, is  apt  to  be  stripped  of  its  leaves  by  a  leaf- 
cutting  ant,  which  uses  the  leaves,  not  directly  for 
food,  but,  according  to  Mr.  Belt,  to  grow  mushrooms 
on.  The  acacia,  however,  bears  hollow  thorns,  and 
each  leaflet  produces  honey  in  a  crater-formed  gland 
at  the  base,  and  a  small,  sweet,  pear-shaped  body  at 
the  tip.  In  consequence,  it  is  inhabited  by  myriads 
of  a  small  ant,  Pseudomyrma  bicolor,  which  nests 
in  the  hollow  thorns,  and  thus  finds  meat,  drink,  and 
lodging  all  provided  for  it.  These  ants  are  con- 
tinually roaming  over  the  plant,  and  constitute  a 
most  efficient  body-guard,  not  only  driving  off  the 
leaf-cutting  ants,  but  even  in  Mr.  Belt's  opinion,  ren- 
dering the  leaves  less  liable  to  be  eaten  by  herbivo- 
rous mammalia. 

The  principal  service,  however,  which  insects  per- 
form for  plants  is  that  of  transferring  the  pollen  from 
one  flower  to  another. 

I  will  not  now  enter  on  the  large  question  why  this 
cross-fertilisation  should  be  an  advantage  ;  but  that 

1  F.  Miiller  has  observed  similar  facts  in  Sta.  Catharina.     (Nature, 
vol.  x.  p.  1 02.) 


I.]     IMPORTANCE  OF  CROSS-FERTILISATION.        ^ 

it  is  so  has  been  clearly  proved.  Kolreuter  speaks 
with  astonishment  of  the  " statura  portentosa"  of  some 
plants  thus  raised  by  him  ;  indeed,  says  Mr.  Darwin 
("Animals  and  Plants  under  Domestication,"  ch.  xvii.), 
"  all  experimenters  have  been  struck  with  the  won- 
derful vigour,  height,  size,  tenacity  of  life,  precocity, 
and  hardiness  of  their  hybrid  productions."  Mr. 
Darwin  himself,  however,  was,  I  believe,  the  first  to 
show  that  if  a  flower  be  fertilised  by  pollen  from  a 
different  plant,  the  seedlings  so  produced  are  much 
stronger  than  if  the  plant  be  fertilised  by  its  own 
pollen.  I  have  had  the  advantage  of  seeing  several 
of  these  experiments,  and  the  difference  is  certainly 
most  striking.  For  instance,  six  crossed  and  six  self- 
fertilised  seeds  of  Ipomcea  purpurea  were  grown  in 
pairs  on  opposite  sides  of  the  same  pots ;  the  former 
reached  a  height  of  7  ft.,  while  the  others  were  on 
an  average  only  5  ft.  4  in.  The  first  also  flowered 
more  profusely.  It  is  moreover  remarkable  that  in 
many  cases  plants  are  themselves  more  fertile  if  sup- 
plied with  pollen  from  a  different  flower,  a  different 
variety,  or  even,  as  it  would  appear  in  some  instances 
(in  the  passion  flower,  for  instance),  from  a  different 
species.  Nay,  in  some  cases  pollen  has  no  effect 
whatever  unless  transferred  to  a  different  flower. 
Fritz  Miiller  has  recorded  some  species  in  which 
pollen,  if  placed  on  the  stigma  of  the  same  flower, 
has  not  only  no  more  effect  than  so  much  inorganic 
dust ;  but,  which  is  perhaps  even  more  extraordinary, 
in  others,  he  states  that  the  pollen  placed  on  the 
stigma  of  its  own  flower  acted  on  it  like  a  poison. 
This  he  noticed  in  several  species :  the  flower  faded  and 


8  TRANSFERENCE  OF  POLLEN  [CHAP. 

fell  off ;  the  pollen-grains  themselves,  and  the  stigma 
in  contact  with  them,  shrivelled  up,  turned  brown, 
and  decayed ;  while  other  flowers  on  the  same  branch, 
which  were  not  so  treated,  retained  their  freshness. 

The  transference  of  the  pollen  from  one  flower  to 
another  is,  as  I  have  already  mentioned,  effected 
principally  either  by  the  wind  or  by  insects.  In  the 
former  case  the  flower  is  rarely  conspicuous ;  indeed 
Mr.  Darwin  finds  it  "  an  invariable  rule  that  when  a 
flower  is  fertilised  by  the  wind  it  never  has  a  gaily- 
coloured  corolla."  Conifers,  grasses,  birches,  poplars, 
&c.,  belong  to  this  category. 

In  such  plants  a  much  larger  quantity  of  pollen 
is  required  than  where  fertilisation  is  effected  by 
insects.  Everyone  has  observed  the  showers  of 
yellow  pollen  produced  by  the  Scotch  fir.  It  is 
an  advantage  to  these  plants  to  flower  before  the 
leaves  are  out,  because  the  latter  would  greatly  in- 
terfere with  the  access  of  the  pollen  to  the  female 
flower.  Hence  such  plants,  as  a  rule,  flower  early  in 
the  spring.  Again,  in  such  flowers  the  filaments  of 
the  stamens  are  generally  long,  and  the  pollen  is  less 
adherent,  so  that  it  can  easily  be  detached  by  the 
wind,  which  would  manifestly  be  a  disadvantage  in 
the  case  of  those  flowers  which  are  fertilised  by 
insects.  On  the  other  hand,  it  is  an  advantage  to 
most  seeds  to  be  somewhat  tightly  attached,  because 
they  are  then  only  removed  by  a  high  wind  which  is 
capable  of  carrying  them  some  distance.  I  say  "  to 
most "  because  this  does  not  apply  to  such  seeds  as 
those  of  the  dandelion,  which  are  specially  adapted 
to  be  carried  by  the  wind. 


I.] 


BY  WIND  AND  INSECTS. 


Again,  as  Mr.  Darwin  has  pointed  out,  irregular 
flowers  appear  to  be  almost  always  fertilised  by 
insects. 

Wind-fertilised  flowers,  moreover,  generally  have 
the  stigma  more  or  less  branched  or  hairy,  which 
evidently  tends  to  increase  its  chance  of  catching  the 
pollen. 

Figs,  i  to  6,  taken  from  Axell's  work,  illustrate 


FIG.  i. 


FIG.  2. 


FIG.  3. 


FIG.  4. 


FIG.  5. 


FIG.  6. 


FIG.  i.  Stigma  of  the  Alder.  FIG.  2.— Of  the  Hop.  FIG.  3.— Of  the  Wheat ;  which 
are  anemophilous.  FIG.  4.— Of  the  Willow.  FIG.  5.— Of  the  Flax.  FIG.  6.— Of 
Nuphar  ;  which  are  entomophilous. 


this  difference.  In  the  alder  (Fig.  i),  the  hop  (Fig.  2), 
and  wheat  (Fig.  3),  the  pollen  is  wind-borne,  whence 
they  have  been  termed  by  Delpino  "  anemvphilous ;" 
while  in  the  willow  (Fig.  4),  the  flax  (Fig.  5),  and 
nuphar,  (the  yellow  water  lily)  (Fig.  6),  it  is  carried 
by  insects,  whence  such  plants  have  been  termed 
"  entomopkilous" 


10 


WIND-FERTILISED  FLOWERS. 


[CHAJ>. 


Even  in  nearly  allied  plants  this  difference  is  well 
marked,  in  illustration  of  which  Axell  gives  the 
following  figures  taken  from  Maout  and  Decaisne's 
"  Trait6  geneVale  de  Botanique  " : — Fig.  7  represents 
a  section  of  a  flower  of  Plantago  major,  which  is 
wind-fertilised  ;  Fig.  8  of  an  allied  species,  Plumbago 


FIG.  7. 


FIG. 


FIG.  7 — Section  of  Plantago  Major. 
FIG.  9.— Flower  of  Poterium  sanguisorba. 


FIG.  8.— Of  Plumbago  Europea. 
FIG.  io.— Of  Sanguisorba  officinalis 


Europea,  which  is  insect-fertilised.  Again,  Fig.  9  re- 
presents a  section  of  Poterium  sanguisorba,  which  is 
wind-fertilised  ;  Fig.  io  of  the  nearly  allied  Sangui- 
sorba officinalis,  which  is  fertilised  by  insects. 


I.]  COLOUR,  SCENT,  AND  HONEY.  11 

It  is  an  almost  invariable  rule  that  wind-fertilised 
flowers  are  inconspicuous ;  but  the  reverse  does  not 
hold  good,  and  there  are  many  flowers  which,  though 
habitually  visited  by  insects,  are  not  brightly  coloured. 
In  some  cases,  flowers  make  up  by  their  numbers  for 
the  want  of  individual  conspicuousness.  In  others, 
the  insects  are  attracted  by  scent ;  indeed,  as  has 
already  been  mentioned,  not  only  the  colour1  of 
flowers,  but  the  scent  also,  has  no  doubt  been  greatly 
developed  through  natural  selection,  as  an  attraction 
to  insects.  But  though  bright  colours  and  strong 
odours  are  sufficient  to  attract  the  attention  of  insects, 
something  more  is  required.  Flowers,  however  sweet- 
smelling  or  beautiful,  would  not  be  visited  by  insects 
unless  they  had  some  inducements  more  substantial 
to  offer.  These  advantages  are  the  pollen  and  the 
honey  ;  although  it  has  been  suggested  that  some 
flowers  beguile  insects  by  holding  out  the  expecta- 
tion of  honey  which  does  not  really  exist,  just  as 
some  animals  repel  their  enemies  by  resembling 
other  species  which  are  either  dangerous  or  dis- 
agreeable. 

Night  flowers  are  generally  white  or  pale  yellow, 
these  being  the  tints  which  render  them  most  con- 
spicuous in  the  dusk  of  evening.  Thus  Lychnis  diuma, 
which  opens  by  day,  is  red  ;  while  L.  'uespertina,  which 
opens  in  the  evening,  is  white. 

It  will  scarcely,  I  think,  be  doubted   by  any  one 

1  In  confirmation  of  this  it  is  stated  that  when  insects  are  excluded, 
the  blossoms  last  longer  than  is  otherwise  the  case  ;  that  when  flowers 
are  once  fertilised,  the  corolla  soon  drops  off,  its  function  being  per- 
formed. 


1 2  NIGHT  FLO  WERS.  [CHAP. 

that  scent  is  an  advantage  to  flowers  by  attracting 
insects.  No  wind-fertilised  flowers  are  scented.  On 
the  other  hand,  while  colour  is  as  useful  as  scent  by 
day,  at  night  it  is  of  course  less  easily  perceived. 
Hence  night  flowers  are  specially  odoriferous,  and 
there  are  some — such  as  Hesperis  matronalis,  Silene 
nutans,  &c. — which  are  very  sweet  in  the  evening 
and  yet  emit  little  or  no  odour  by  day. 

The  honey  is  secreted,  sometimes  by  one  part  of  the 
flower,  sometimes  by  another ;  and  great  variations 
may  be  found  in  this  respect  even  within  the  limits  of 
a  single  order.  Thus  in  the  Ranunculaceae  the  honey 
glands  are  situated  on  the  calyx,  in  certain  Paeonies  ; 
on  the  petals,  in  buttercups  and  hellebore  ;  on  the 
stamens,  according  to  Miiller,  in  Pulsatilla ;  and  on 
the  ovary,  in  Caltha. 

The  real  use  of  the  honey  in  flowers,  indeed,  now 
seems  so  obvious  that  it  is  remarkable  to  see  the 
various  theories  which  were  entertained  on  the  subject. 
Patrick  Blair  thought  it  absorbed  the  pollen,  and  thus 
fertilised  the  ovary.  Linnaeus  confessed  his  inability 
to  solve  the  question.  Other  botanists  considered  it 
was  useless  material  thrown  off  in  the  process  of 
growth.  Kriinitz  even  thought  he  had  observed  that 
in  meadows  much  visited  by  bees  the  plants  were 
more  healthy,  but  the  inference  he  drew  was  that  the 
honey  unless  removed  was  very  injurious,  that  the  bees 
were  of  use  in  carrying  it  off.  Sprengel  was  the  first 
to  show  that  the  real  office  of  the  honey  is  to  attract 
insects,  but  his  view  was  far  from  meeting  with  general 
consent,  and  even  so  lately  as  1833  were  altogether 
rejected  by  Kurr  who  came  to  the  conclusion  that 


I.]  THE  USES  OF  HONEY.  13 

the  secretion  of  honey  is  the  result  of  developmental 
energy,  which  afterwards  concentrates  itself  on  the 
ovary. 

No  doubt,  however,  seems  any  longer  to  exist  that 
Sprengel  is  right  in  considering  that  the  object  is  to 
attract  insects,  and  thus  to  secure  cross-fertilisation. 
Thus  most  of  the  Rosaceae  are  fertilised  by  insects, 
and  possess  nectaries,  but,  as  Delpino  has  pointed  out, 
the  genus  Poterium,  is  anemophilous,  or  wind-fertilised, 
and  possesses  no  honey.  As  also  the  Maples  are 
almost  4all  fertilised  by  insects  and  produce  honey, 
but  Acer  negundo  is  anemophilous  and  honey  less.  So 
also  among  the  Polygonaceae,  some  species  are 
insect-fertilised  and  melliferous,  while,  on  the  other 
hand,  certain  genera,  Rumex  and  Oxyria,  have  no 
honey  and  are  fertilised  by  the  wind.  At  first 
sight  it  might  appear  an  objection  to  this  view  that 
some  plants  secrete  honey  on  other  parts  than  the 
flowers. 

Belt  and  Delpino  have,  I  think,  suggested  the  true 
function  of  these  extra  floral  nectaries.  The  former 
of  these  excellent  observers  describes  a  South  Ameri- 
can species  of  acacia :  this  tree,  if  unprotected,  is  apt 
to  be  stripped  of  the  leaves  by  a  leaf-cutting  ant,  which 
uses  them,  not  directly  for  food,  but,  according  to  Mr. 
Belt,  to  grow  mushrooms  on.  The  acacia,  however, 
bears  hollow  thorns,  while  each  leaflet  produces  honey 
in  a  crater-formed  gland  at  the  base,  and  a  small, 
sweet,  pear-shaped  body  at  the  tip.  In  consequence, 
it  is  inhabited  by  myriads  of  a  small  ant,  which  nests 
in  the  hollow  thorns,  and  thus  finds  meat,  drink,  and 
lodging  all  provided  for  it.  These  ants  are  continually 


14  POLLEN.  [CHAP. 

roaming  over  the  plant  and  constitute  a  most  efficient 
bodyguard,  not  only  driving  off  the  leaf-cutting  ants, 
but,  in  Belt's  opinion,  rendering  the  leaves  less  liable 
to  be  eaten  by  herbivorous  mammalia.  Delpino 
mentions  that  on  one  occasion  he  was  gathering 
a  flower  of  Clerodendrons  fragrans,  when  he  was 
suddenly  attacked  by  a  whole  army  of  small  ants. 
M.  Boissier  also  makes  the  interesting  observation  that 
many  plants  produce  honey  in  some  countries  and 
not  in  others.  Thus  Potentilla  tormentilla  and  Geum 
urbanum  give  honey  in  Norway,  and  none,  or  hardly 
any,  near  Paris.  Indeed  a  careful  comparison  showed 
that  most  plants  gave  more  honey  in  Norway  than  at 
Paris.  No  doubt,  in  consequence  of  this,  some  plants 
which  are  visited  by  insects  in  the  north  are  neglected 
in  the  south.  Thus  he  observed  five  species  of  Hier- 
acum  to  be  frequented  both  by  bees  and  humble- 
bees  in  Denmark,  while  near  Paris  they  are  never 
visited  by  those  insects. 

M.  Boissier  found  that  by  watering  a  plant  copiously 
he  could  increase  the  supply  of  honey ;  nay,  more, 
that  he  could  even  cause  some  species  to  give  honey 
which  do  not  generally  do  so. 

The  pollen  of  course,  though  very  useful  to  insects, 
is  also  essential  to  the  flower  itself;  but  the  scent 
and  the  honey,  at  least  in  their  present  development, 
are  mainly  useful  in  securing  the  visits  of  insects, 
though  the  honey  is  also  sometimes  of  service  in 
causing  the  pollen  to  adhere  to  the  proboscis  of  the 
insect. 

Bees  rarely  visit  flowers  unless  for  some  real  advant- 
age. The  Diptera  (flies)  appear  to  be  less  intelligent, 


i.]  BEES  AND  COLOURS.  15 

and  among  fly-flowers  we  find  not  only  those  which 
attract  the  insects  by  honey  or  pollen,  but  also  trap- 
flowers,  as,  for  instance,  the  Arum ;  and  deceptive 
flowers,  such  as  Parnassia,  where  five  of  the  stamens 
terminate  in  a  number  of  beautiful  yellow  glands 
which  look  like  drops  of  honey,  or  Stapelia,  in  which 
the  flowers  both  in  colour  and  smell  resemble  decay- 
ing meat. 

That  bees  are  attracted  by,  and  can  distinguish, 
colours,  was  no  doubt  a  just  inference  from  the 
observations  on  their  relation  to  flowers,  but  I  am 
not  cognisant  of  any  direct  evidence  on  the  subject. 
I  thought  it  therefore  worth  while  to  make  some  ex- 
periments ;  and  a  selection  from  them  will  be  recorded 
in  the  forthcoming  volume  of  the  Journal  of  the 
Linnean  Society.  I  placed  slips  of  glass  with  honey, 
on  papers  of  various  colours,  accustoming  different 
bees  to  visit  special  colours,  and  when  they  had  made 
a  few  visits  to  honey  on  paper  of  a  particular  colour, 
I  found  that  if  the  papers  were  transposed  the  bees 
followed  the  colour. 

But  if  flowers  have  been  modified  with  reference 
to  the  visits  of  insects,  insects  also  have  in  some  cases 
been  gradually  modified,  so  as  to  profit  by  their  visits 
to  flowers.  This  is  specially  the  case  with  reference 
to  two  groups  of  insects,  namely,  Bees  and  Butter- 
flies, which  have  been  specially  studied  by  H.  Miiller 
with  reference  to  this  point ;  and  from  his  works  the 
following  facts  are  mainly  taken.  Although  the 
whole  organisation  of  the  insect  might  be  said  to 
have  reference  to  these  relations,  still  the  parts  which 
have  been  the  most  profoundly  altered  are  the  mouth 


1 6    AD  APT  A  TIONS  O  F  INSECTS  TO  FL  O  WERS.    [CH. 

and  the  legs.  If  we  are  asked  why  we  assume 
that  in  these  cases  the  mouth  and  legs  have  been 
modified,  the  answer  is,  that  they  depart  greatly 
from  the  type  found  in  allied  insects,  and  that  be- 
tween this  original  type  and  the  most  modified 
examples,  various  gradations  are  to  be  found. 

The  mouth  of  an  insect  is  composed  of  (i)  an 
upper  lip  (Fig.  1 1  a),  (2)  an  under  lip  (Fig.  1 1  d) 
(3)  a  pair  of  anterior  jaws  or  mandibles  (Fig.  1 1  b), 
and  (4)  a  pair  of  posterior  jaws  or  maxillae  (Fig. 
1 1  c\  These  two  pairs  of  jaws  work  laterally, 


d 

FlG.  it. — Mouth-parts  of  a  Wasp,  a,  labrum  or  upper  lip  ;  b,  mandibles  ;  c,  maxillae  ; 
d,  labium  or  lower  lip  ;  xx,  palpi. 

that  is  to  say,  from  side  to  side,  and  not,  as  in  man 
and  other  mammalia,  upwards  and  downwards.  The 
lower  lip  and  maxillae  are  each  provided  with  a  pair 
of  feelers  or  palpi  (Fig.  n,  c  and  d,  x).  The  above 
figures  represent  the  mouth  parts  of  a  wasp,  in  which, 
as  is  very  usually  the  case,  the  mandibles  are  hard 
and  horny,  while  the  maxillae  are  delicate  and  mem- 
branous. In  the  different  groups  of  insects,  these 
organs  present  almost  infinite  variations. 


I.J 


MOUTH  OF  WASP. 


•pa 


Fig.  12  represents  the  mouth  parts  of  a  bee,  Prosopis 
(Fig.  13),  seen  from  below  ;  md  being  the  mandibles  ; 
pm,  the  palpi  of  the  maxillae  la, 
//,  those  of  the  lower  lip. 

The  bees  belonging  to  this 
genus  construct  their  cells  in 
sand,  or  in  the  centre  of  dry 
bramble  sticks,  lining  them  with 
a  transparent  mucus,  which  they 
smooth  down  with  their  trowel- 
like  lower  lip  (Fig.  12  /*),  and 
which  hardens  into  a  thin  mem- 
brane (Smith  "  Catalogue  of 
Brit.  Hymenoptera,"  p.  7). 

That  the  mouth  of  Prosopis 
probably  represents  the  condi- 
tion of  that  of  the  ancestors  of 
the  Hive-bees,  before  the  mouth-parts  underwent  spe- 
cial modifications,  may  be  inferred  from  the  fact  that 
the  same  type  occurs  in  allied  groups,  as  is  shown  in 
Fig.  14,  which  represents  the  mouth  of  a  wasp  (Polistes) 


FIG.  12. — Front  part  of  head  of 
Prosopis,  seen  from  below, 
with  the  mouth -parts  ex- 
tended, pa,  paraglossae;  It, 
ligula  ;  //,  labial  palpi ;  pm< 
maxillary  palpi;  mt,  men- 
turn  ;  st,  stipes ;  mdt  man  - 
dibles  ;  c,  cardo  ;  o,  eye. 


FIG.  i3.-ProsoPis.  f,G.  14-— Mouth-parts  of  Poliste*. 

also  seen  from  below.  We  may  therefore  consider 
that  Prosopis  shows  in  this  respect  no  special  adap- 
tation for  the  acquirement  of  honey,  and  in  fact, 


iS 


MOUTH  OF  SOLITARY  BEES.  [CHAP. 


though  the  bees  belonging  to  this  genus  feed  their 
young  on  honey  and  pollen,  they  can  only  get  the 


FIG.  15. 


FIG.  17. 


•pm 


FIG.  18. 


FIG.  19. 


FIG.  15. — Mouth-parts  of  Andrena,  seen  from  below— •/«,  paraglossae;  li,  ligula; 
pi,  labial  palpi :  pm,  maxillary  palpi ;  mt,  mentum  ;  st,  stipes  ;  c,  cardo ;  a,  eye 
FIG.  16.— Of  Halictus.  FIG.  17.— Of  Panurgus.  FIG.  18.— Of  Halictoides.  FIG. 
19. — Of  Chelostoma. 

former  from   those   flowers  in    which   it    is    on    the 
surface.      In   Andrena  (Fig   15),  Halictus   (Fig.   1 6), 


I.] 


MOUTH  OF  HUMBLE-BEE. 


Panurgus  (Fig.  17),  Halictoides  (Fig.  18),  and  Chelos- 
toma  (Fig.  19),  we  see  various  stages  in  the  elon- 
gation of  the  lower  lip,  until  at  length  it  reaches 
the  remarkable  and  extreme  form  which  it  no\v 
presents  in  the  hive  and  humble  bees  (Fig.  20),  and 


FIG.  20. — Head  of  Humble-bee  (Botnbus  agrorum),  with  the  mouth-parts  extended. 
pa,  paraglossse  ;  It,  ligula  ;  //,  labial  palpi ;  pm,  maxiliary  palpi ;  la,  lamina  01 
ditto ;  tut,  mentum  ;  ft,  stipes  ',  ntd,  mandibles ;  c,  cardo  ;  0,  eye. 


which  enables  them  to  extract  the  honey  from 
almost  all  our  wild  flowers.  No  bees,  however, 
have  the  proboscis  so  much  elongated  as  is  the 
case  with  some  butterflies  and  moths ;  perhaps, 
as  Hermann  Miiller  has  suggested,  because  the 

C    2 


20 


HIND-LEGS  OF  BEES. 


[CHAP. 


necessity  of  using  their  mouth  for  certain  domestic 
purposes  has  limited  its  specialisation  in  this  parti- 
cular direction. 

If,  again,  we  examine  the  hind-legs  of  bees,  we 
shall  find  gradations  similar  to  those  already  men- 
tioned in  the  lower  lip.  In  Prosopis  (Fig.  21)  they 
do  not  differ  materially  from  those  of  genera  which 
supply  their  young  with  animal  food.  Portions  of 
the  leg,  indeed,  bear  stiff  hairs,  the  original  use  of 


FIG.  21. 


FIG.  23. 


FIG.  24. 


FIG.  21.— Left  hind-leg  of  Prosopis.         FIG.  22.— Lef^hmd-leg  of  Sphecodes. 

"*"""  '      J-let 


FIG.  23. — Sphecodes. 


FIG.  24. — Right  hind-leg  of  Halictus. 


which,  probably,  was  to  clean  these  burrowing  insects 
from  particles  of  sand  and  earth,  but  which  in  Pro- 
sopis assist  also  in  the  collection  of  pollen. 

Fig.  22  represents  the  hind  leg  of  Sphecodes  (Fig. 
23),  a  genus  in  which  the  tongue  resembles  in  form 
that  of  Halictus.  Here  we  see  the  hairs  decidedly 
more  developed,  a  modification  which  has  advanced 
still  further  in  Halictus  (Fig.  24),  in  which  the  de- 


I.]        HALICTUS,  PANURGUS,  ANTHOPHORA.        21 


velopment  of  the  hairs  is  most  marked  on  those  seg- 
ments of  the  hind  legs  which  are  most  conveniently 
situated  for  the  collection  and  transport  of  pollen.  In 
Panurgus,  the  same  change  is  still  more  marked  (Fig. 
25)  and  the  pollen-bearing  apparatus  is  confined  to 
the  tibia,  and  first  segment  of  the  tarsus,  a  differen- 
tiation which  is  even  more  apparent  in  Anthophora 
(Fig.  26).  In  all  these  bees  the  pollen  is  simply  en- 
tangled in  the  hairs  of  the  leg,  as  in  a  brush,  but  there 


FIG.  25. — Left  hind-leg  of  Panurgus 
banksianus. 


FIG.  26. — Right  hind-leg  of  Antho- 
phora bimaculata. 


are  other  genera,  of  which  the  humble  bees  and  the  hive 
bees  are  the  only  British  representatives,  which  moisten 
the  pollen  with  honey,  and  thus  form  it  into  a  sticky 
mass,  which  is  much  more  easy  to  carry,  and  is  borne 
not  round  the  leg,  but  on  one  side  of  it.  In  the 
Humble-bee  (Bombus,  Fig.  27)  for  instance,  the 
honey  is  borne  on  the  outer  side  of  the  hinder  tibiae, 
which  are  flattened,  smoothed,  and  bordered  by  a 
row  of  stiff  curved  hairs,  thus  forming  a  sort  of 


22  BOMBUS,  APIS— HAIRS  ON  BODY.       [CHAP. 

little  basket.  Lastly  in  the  Hive-bee  (Fig.  28)  the 
adaptation  is  still  more  complete,  the  hairs  on  the 
first  tarsal  segment  are  no  longer  scattered,  but  are 
arranged  in  regular  rows,  and  the  tibial  spurs,  inherited 
by  Bombus  from  far  distant  ancestors,  have  entirely 
disappeared. 

In  some  bees  the  pollen  is  collected  on  the  body, 
and  here  also  we  find  a  remarkable  gradation  from 
Prosopis  (Fig.  13)  which  has  only  simple  hairs  like  a 


FIG.  27.— Right  hind-leg  of  Bombus  FIG.  28.— Right  hind-leg  of  Hive-bee. 

Scrimshiranus. 

wasp  ;  through  Sphecodes  and  Nomada,  in  which  the 
longer  hairs  are  still  few  and  generally  simple  (though 
some  few  are  feathered)  ;  to  Andrena  and  Halictus 
where  the  hairs  are  much  more  developed  ;  a  change 
which  is  still  more  marked  in  Saropoda,  Colletes, 
and  Megachile ;  still  more  so  in  Osmia  and  An- 
thophora ;  until  we  come  to  the  Humble-bees,  in 
which  the  whole  body  h  covered  with  long  feathered 
hairs. 

It  is  difficult   to   account  for  the  relations  which 


L]       BEHAVIOUR  OF  INSECTS  TO  FLOWERS.       23 

exist  between  flowers  and  insects,  by  the  hypothesis 
of  a  mere  blind  instinct  on  the  part  of  the  latter. 

Thus  Sarcophaga  carnaria  visits  Polygonum  Bistorta 
in  search  of  honey,  although  that  flower  does  not 
contain  any.  Genista  tinctoria  again,  though  not  mel- 
liferous, is  visited  by  the  males  of  several  species  of 
bees  in  search  of  honey.  The  same  is  the  case  with 
Ononis.  H.  Miiller  records  a  case  in  which  he  watched 
a  female  Humble-bee  (B.  terrestris)  examining  an 
Aquilegia;  she  made  several  vain  attempts  to  suck  the 
honey,  but  after  awhile,  having  apparently  satisfied 
herself  that  she  was  unable  to  do  so,  bit  a  hole 
through  the  corolla.  Having  thus  secured  the  honey, 
she  visited  several  other  flowers,  biting  holes  through 
them,  without  making  any  attempt  to  suck  them  first ; 
conscious  apparently  that  she  was  unable  to  do  so 
He  also  observed  a  similar  instance  in  relation  to 
Primula  elatior.  In  Vicia  cracca  and  some  other 
species,  Bombus  terrestris  habitually  obtains  access  to 
the  honey  by  biting  a  hole  at  the  base  of  the  flower  ; 
and  these  holes  are  then  subsequently  used  by  other 
bees.  Indeed  anyone  who  has  watched  bees  in  green- 
houses will  see  that  they  are  neither  confined  by 
original  instinct  to  special  flowers,  nor  do  they  visit 
all  flowers  indifferently. 

It  would  also  appear  that  individual  bees  differ 
somewhat  in  their  mode  of  treating  flowers.  Some 
Humble-bees  suck  the  honey  of  the  French  bean  and 
Scarlet  runner  in  the  legitimate  manner,  while  others 
cut  a  hole  in  the  tube  and  thus  reach  it,  so  to  say 
surreptitiously  ;  and  Dr.  Ogle  has  observed  that  the 
same  bee  always  proceeded  in  the  same  manner 


24  SPECIAL  RELATIONS.  [CHAP. 

some  always  by  the  mouth  of  the  flower,  others 
always  cutting  a  hole.  He  particularly  mentions 
that  this  was  the  case  with  bees  of  one  and  the 
same  species,  and  infers,  therefore,  that  the  different 
individuals  differ  from  one  another  in  their  degrees 
of  intelligence ;  these  observations,  though  of  course 
not  conclusive,  are  interesting  and  suggestive. 

Lastly,  some  insects  confine  themselves  to  particu- 
lar flowers.     Thus,  according  to  H.  Miiller — • 

Andrena  florea  ^  ..    Bryonia  dioica 


Halictoides 
Andrena  hattorfiana 
Cilissa  melanura 
Macropis  labiata 
Osmia  adunca 


Species  of  Campanula, 
Scabiosa  arvensis. 
Lythrum  Salicaria. 
Lysimachia  vulgaris. 
.  Echium. 


The  arrangements  to  which  I  have  hitherto  called 
attention  are  for  the  most  part  of  such  a  nature  as  to 
adapt  the  flowers  to  the  visits  of  insects.  There  are 
others,  however,  of  much  interest  which  serve  to  pro- 
tect them  from  unwelcome  visitors,  such  as  ants, 
who  would  rob  them  of  their  honey  without  fulfilling 
any  useful  purpose  in  return.  Some  plants  are  pro- 
tected by  downward  pointing  hairs,  others  by  viscid 
glandular  hairs,  others  by  the  extreme  smoothness  of 
their  surface.  In  other  cases  the  flower  is  closed  by 
barriers,  which  only  leave  sufficient  space  for  the 
slender  proboscis  of  the  bees,  while  others  again,  such 
as  the  Foxglove,  are  closed  boxes  which  bees  only  are 
able  to  enter. 

Another  remarkable  peculiarity  of  plants,  which 
may  I  think  possibly  have  reference  to  their  rela- 


I.]  SLEEP  OF  FLOWERS  25 

t 

tions  with  insects,  is  the  habit  of  "  sleeping,"  which 
characterises  certain  species. 

Many  flowers  close  their  petals  during  rain,  which 
is  obviously  an  advantage,  since  it  prevents  the  honey 
and  pollen  from  being  spoilt  or  washed  away.  Every- 
body, however,  has  observed  that  even  in  fine  weather 
certain  flowers  close  at  particular  hours.  This  habit 
of  going  to  sleep  is  surely  very  curious.  Why  should 
flowers  do  so  ? 

In  animals  we  can  understand  it  ;  they  are  tired 
and  require  rest.  But  why  should  flowers  sleep  ? 
Why  should  some  flowers  do  so,  and  not  others  ? 
Moreover,  different  flowers  keep  different  hours.  The 
Daisy  opens  at  sunrise  and  closes  at  sunset,  whence 
its  name  "  day's-eye."  The  Dandelion  (Leontodon 
taraxacum)  is  said  to  open  about  seven  and  close 
about  five  ;  Arenaria  rubra  to  be  open  from  nine  to 
three  ; 1  Nymphcza  alba  from  about  seven  to  four  ;  the 
common  Mouse-ear  Hawkweed  (Hieracium  Piloselld) 
from  eight  to  three ;  the  Scarlet  Pimpernel  (Ana- 
gallis  arvensis)  to  waken  at  seven  and  close  soon 
after  two  ;  Tragopogon  pratensis  to  open  at  four  in 
the  morning,  and  close  just  before  twelve,  whence 
its  English  name,  "John  go  to  bed  at  noon."  Far- 
mers' boys  in  some  parts  are  said  to  regulate  their 
dinner-time  by  it.  Other  flowers,  on  the  contrary, 
open  in  the  evening.1 

Now,  it  is  obvious  that  flowers  which  are  fertilised 
by  night-flying  insects  would  derive  no  advantage  from 

1  In  my  own  observations  the  opening  and  closing  was  more  gradual 
and  more  dependent  on  the  weather  than  I  should  have  expected  from 
the  statements  quoted  above. 


26  HOURS  OF  INSECTS.  [CHAP.  i. 

being  open  by  day  ;  and  on  the  other  hand,  that  those 
which  are  fertilised  by  bees  would  gain  nothing  by 
being  open  at  night.  Nay,  it  would  be  a  distinct  dis- 
advantage, because  it  would  render  them  liable  to  be 
robbed  of  their  honey  and  pollen,  by  insects  which 
are  not  capable  of  fertilising  them.  I  would  venture 
to  suggest,  then,  that  the  closing  of  flowers  may 
have  reference  to  the  habits  of  insects,  and  it  may  be 
observed  also  in  support  of  this  that  wind-fertilised 
flowers  do  not  sleep  ;  and  that  some  of  those  flowers 
which  attract  insects  by  smell,  emit  their  scent 
at  particular  hours ;  thus,  Hesperis  matronalis  and 
Lychnis  vespertina  smell  in  the  evening,  and  Orchis 
bifolia  is  particularly  sweet  at  night. 

Bees  appear,  moreover,  to  be  skilful  in  adapting  the 
hour  of  their  visits  to  the  habits  of  the  plants.  Thus 
M.  Boissier  tells  us  ("Les  Nectaires,"  p.  166),  that  he 
observed  some  species  of  Sempervivum  (S.  tectorum, 
S.  arachnoideum^  S.  montanum,  S.  reflexum,  and  .S. 
maximum]  growing  abundantly  on  rocks,  which 
secreted  honey  in  the  morning  only.  These  plants 
were  much  frequented  by  bees  up  to  midday,  but 
quite  deserted  in  the  afternoon.  He  has  also  ob- 
served that  some  bees  which  specially  frequented 
Limes  and  a  field  of  Clover  (Trifolium  repens), 
went  to  the  former  in  the  early  morning,  and  did 
not  commence  visiting  the  clover  until  the  dew  was 
off.  During  the  height  of  summer  in  Provence,  the 
flowers,  he  tells  us,  secrete  no  honey  in  the  heat  of  the 
day ;  and  the  bees  also  remain  at  home.  Mr.  Todd  even 
assures  us  that  at  Blidah  in  Algeria  the  bees  during 
summer  do  not  work  after  eight  in  the  morning. 


LYTHRUM    SALICARIA. 


CHAPTER    II. 

I  NOW  pass  to  the  structure  and  modifications  oi 
flowers.  A  complete  flower  consists  of  (i)  an  outer 
envelope  or  calyx,  sometimes  tubular,  sometimes  con- 
sisting of  separate  leaves  called  sepals ;  (2)  an  inner 
envelope  or  corolla,  which  is  generally  more  or  less 
coloured,  and  which,  like  the  calyx,  is  sometimes 
tubular,  sometimes  composed  of  separate  leaves,  called 
petals ;  (3)  of  one  or  more  stamens,  consisting  of  a 
stalk  or  filament,  and  a  head  or  anther,  in  which  the 
pollen  is  produced ;  and  (4)  a  pistil  or  an  ovary,  which 
is  situated  in  the  centre  of  the  flower,  and  contains 
one  or  more  seeds  or  ovules.  The  pistil  consists  of  a 
stalk  or  style ;  and  a  stigma,  to  which  the  pollen  must 
find  its  way  in  order  to  fertilize  the  flower,  and  which 


28  THE  PARTS  OF  A  FLOWER.  [CHAR 

in  many  familiar  instances  forms  a  small  head  at  the 
top  of  the  style.  In  some  cases  the  style  is  absent, 
and  the  stigma  is  consequently  sessile. 

Thus,  the  pistil  is  normally  surrounded  by  a  row  of 
stamens,  and  it  would  seem  at  first  sight  a  very 
simple  matter  that  the  pollen  of  the  latter  should 
fall  on  the  former.  This  in  fact  does  happen  in 
many  instances,  and  flowers  which  thus  fertilize 
themselves  have  evidently  one  great  advantage — 
few  remain  sterile  for  want  of  pollen. 

Such  cases,  however,  are  much  less  frequent  than 
might  at  first  be  supposed,  and  there  are  three  prin- 
cipal modes  by  which  self-fertilization  is  prevented. 
Firstly,  in  many  species,  the  stamens  and  pistil  are 
situated  in  different  flowers  ;  such  species  are  called 
diclinous ;  when  the  male  and  female  flowers  are  on 
the  same  plant,  they  are  termed  monoecious ;  when  on 
different  plants,  dicecious. 

Secondly,  in  other  instances,  as  was  first  discovered 
by  Sprengel,  though  the  stamens  and  pistil  are  both 
situated  in  one  flower,  they  are  not  mature  at  the 
same  time,  and  the  pollen,  therefore,  cannot  fertilize 
the  stigma.  These  plants  are  called  dichogamous. 
Sometimes,  as  in  the  Arum,  the  pistil  matures  before 
the  anther,  and  these  plants  are  called  proterogynous  ; 
but  much  more  frequently  the  anther  matures  before 
the  pistil  ;  and  such  plants  are  called  proterandrous. 

Thirdly,  there  are  some  plants  in  which,  as  was  first 
discovered  by  Mr.  Darwin,  the  same  object  is  secured 
by  the  existence,  within  the  limits  of  the  same  species, 
of  two  or  more  kinds  of  flowers,  differing  in  the  rela- 
tive position  of  the  stamens  and  pistil,  which  are  so 
placed  as  to  favour  the  transference  by  insects  of  the 


II.]  MODES  OF  CROSS-FERTILISATION.  29 

pollen  from  the  anther  of  the  one  form  to  the  pistil  of 
the  other.  These  plants  are  termed  heteromorphous  ; 
some  of  them  have  two  kinds  of  flowers,  and  are 
called  dimorphous  ;  while  others  have  three  forms,  and 
are  called  trimorphous. 

But  even  in  plants  which  belong  to  none  of  these 
categories  we  find  minor  modifications  which  tend 
to  prevent  self-fertilization  ;  and  Mr.  Darwin  is  pro- 
bably right  in  his  opinion  that  no  plant  invariably 
fertilizes  itself.  Thus  in  some  species  where  the 
stamens  surround  the  pistil,  and  which  might,  there- 
fore, be  supposed  to  be  arranged  in  such  a  man- 
ner as  to  ensure  self-fertilization,  the  anthers  do  not 
open  towards  the  pistil,  but  on  the  sides,  and  by  no 
means  therefore  in  a  favourable  position  with  reference 
to  the  transference  of  the  pollen.  In  most,  if  not  all 
the  Cruciferae,  the  anthers  in  young  flowers  have  the 
side  which  opens  turned  towards  the  pistil  ;  but  be- 
fore the  anthers  come  to  maturity  they  twist  them- 
selves round,  so  as  to  turn  their  backs  to  the  stigma. 
Again,  in  pendent  flowers,  where  the  pistil  hangs 
below  the  anthers,  the  stigmatic  surface  is  never  the 
upper  one,  which  would  catch  any  falling  pollen  ;  but 
on  the  contrary,  the  lower  one,  which  could  hardly  be 
touched  by  the  pollen  of  the  same  flower,  but  which 
is  so  placed  as  to  come  in  contact  with  any  insect 
or  other  body  approaching  the  flower  from  below. 

It  is  also  probable  that  many  cases  will  be  found  to 
exist,  in  which,  though  the  pollen  necessarily  comes  in 
contact  with  the  pistil  of  the  same  plant,  fertilization 
does  not  take  place.  However  improbable  this  might 
^priori  appear,  it  is  nevertheless  said  by  Hildebrand 


30  TRANSFERENCE  OF  POLLEN.  [CHAP. 

to  be  the  case  in  Corydalis  cava  and  Pulmonaria 
(Fig.  96),  by  Gartner  in  Verbascum  nigrum  (Fig.  98), 
and  Lobelia  fulgens  ;  by  Scott  in  Primula  verticillata, 
Oncidium,  Sac. 

Other  cases  are  recorded  in  which  plants  are  more 
or  less  insusceptible  of  fertilization  by  their  own 
pollen.  Moreover,  even  where  plants  are  capable  of 
self-fertilization,  the  pollen  from  another  flower  is 
often  more  effective  than  their  own,  whence  it  fol- 
lows that  if  a  supply  of  pollen  from  another  plant 
be  secured,  it  is  comparatively  unimportant  to  ex- 
clude the  pollen  of  the  plant  itself;  for  in  such  cases 
the  latter  is  neutralized  by  the  more  powerful  effect  of 
the  former. 

Everyone  who  has  watched  flowers,  and  has  ob- 
served how  assiduously  they  are  visited  by  insects, 
will  admit  that  these  insects  must  often  deposit 
on  the  stigma  pollen  brought  from  other  plants, 
generally  those  of  the  same  species  ;  for  it  is  a  re- 
markable fact,  as  Aristotle  long  ago  mentioned,  that  in 
most  cases  bees  confine  themselves  in  each  journey  to 
a  single  species  of  plant ;  though  in  the  case  of  some 
very  nearly  allied  forms  this  is  not  so ;  for  instance, 
it  is  stated,  on  good  authority,  that  Ranunculus  acris, 
R.  repens,  and  R.  bulbosus,  are  not  distinguished  by 
the  bees,  or  at  least  are  visited  indifferently  by  them, 
as  is  also  the  case  with  two  of  the  species  of  clover, 
Trifolium  fragiferum  and  T.  repens. 

Even  in  the  simplest  and  most  regular  flowers, 
where  the  stamens  surround  the  pistil,  and  both  are 
mature  at  the  same  time,  insects  may  visit  the  flower, 
and  yet  not  fertilise  it  with  its  own  pollen,  because 


IL]  DICLINOUS  PLANTS.  31 

they  touch  the  anther  with  one  side  of  the  proboscis 
and  the  stigma  with  the  other.  There  are,  however 
in  flowers  a  great  many  admirable  and  beautiful 
contrivances,  tending  to  prevent  the  fertilization  of  a 
flower"  by  its  own  pollen  ;  in  consequence  of  which 
insects  habitually  carry  the  pollen  from  the  anthers 
of  one  flower  to  the  stigma  of  another. 

As  already  mentioned,  there  are  three  principal 
modes  in  which  self-fertilisation  is  prevented.  Firstly, 
by  the  stamens  and  pistil  being  situated  in  different 
flowers,  either  on  the  same  plant,  or,  more  commonly, 
in  different  plants.  These  differences  form  the  char- 
acteristics of  the  classes,  Monoecia,  Dioecia,  and  Poly- 
gamia,  of  Linnaeus  ;  but  it  is  obvious  that  such  classes 
are  not  natural,  since  we  have  in  very  nearly  allied 
species,  even  within  the  limits  of  what  is  generally 
considered  a  single  genus,  cases  in  which  the  one  is 
diclinous,  that  is  to  say,  has  the  stamens  and  pistil 
in  separate  flowers,  while  in  the  other,  the  flowers 
contain  both. 

Secondly,  in  other  cases,  the  self-fertilization  of 
plants,  as  was  first  observed  by  Sprengel  in  Epilobium 
angustifolium  in  the  year  1790,  is  guarded  against 
by  the  fact  that  the  stamens  and  pistils  do  not  ripen 
at  the  same  time. 

In  some  few  cases  the  pistil  ripens  before  the  sta- 
mens ;  these  species  are  called  " proterogynous?  Thus 
the  Aristolochia  has  a  flower  which  consists  of  a  long 
tube  with  a  narrow  opening  closed  by  stiff  hairs  which 
point  backwards,  so  that  it  much  resembles  an  ordi- 
nary eel-trap.  Small  flies  enter  the  tube  in  search  of 
honey,  which  from  the  direction  of  the  hairs  they  can 


DICHOGAMOUS  PLANTS. 


[CHAP. 


do  easily,  though  on  the  other  hand,  from  the  same 
cause,  it  is  impossible  for  them  to  return.  Thus  they 
are  imprisoned  in  the  flower ;  gradually,  however,  the 
pistil  passes  maturity,  and  the  stigma  ceases  to  be  capa- 
ble of  fertilisation,  while  the  stamens  ripen  and  shed 
their  pollen,  by  which  the  flies  get  thoroughly  dusted. 
Then  the  hairs  of  the  tube  shrivel  up  and  release  the 
prisoners,  which  carry  the  pollen  to  another  flower. 

Again,  in  the  common  Arum,  we  find 
a  somewhat  similar  mode  of  fertilisation. 
The  well-known  green  leaf,  as  shown  in 
the  annexed  diagrammatic  figure  (Fig. 
29),  encloses  a  central  pillar  which  sup- 
ports a  number  of  stigmas  (Fig.  29,  st.) 
near  the  base,  and  of  anthers  (a)  some- 
what higher.  Now  in  this  case  nothing 
would  at  first  sight  seem  easier  or  more 
natural  than  that  the  pollen  from  the 
anthers  should  fall  on,  and  fertilise,  the 
pistils.  This,  however,  is  not  what  occurs. 
The  stigmas  mature  before  the  anthers, 
and  by  the  time  the  pollen  is  shed,  have 
become  incapable  of  fertilisation.  It 
FIG.  29.— Diagram-  is  impossible,  therefore,  that  the  plant 
should  fertilise  itself.  Nor  can  the  pol- 
len be  carried  by  wind  When  it  is 
shed  it  drops  to  the  bottom  of  the  tube, 
where  it  is  so  effectually  sheltered  that  nothing  short 
of  a  hurricane  could  dislodge  it ;  and  although  Arum 
is  common  enough,  still  the  chances  against  any  of 
the  pollen  so  dislodged  being  blown  into  the  tube 
of  another  plant  would  be  immense. 


*' 


u.]  ARUM,  ARISTOLOCHIA.  33 

As,  however,  in  Aristolochia,  so  also  in  Arum,  small 
insects  which,  attracted  by  the  showy  central  spadix, 
the  prospect  of  shelter  or  of  honey,  enter  the  tube  while 
the  stigmas  are  mature,  find  themselves  imprisoned, 
by  the  fringe  of  hairs  (Fig.  29,  k],  which,  while  per- 
mitting their  entrance,  prevent  them  from  returning. 
After  a  while,  however,  the  period  of  maturity  of  the 
stigmas  is  over,  and  each  secretes  a  drop  of  honey^ 
thus  repaying  the  insects  for  their  captivity.  The 
anthers  then  ripen  and  shed  their  pollen,  which  falls 
on  and  adheres  to  the  insects.  Then  the  hairs 
gradually  shrivel  up  and  set  the  insects  free,  which 
carry  the  pollen  with  them,  so  that  those  which  then 
visit  another  plant  can  hardly  fail  to  deposit  some  of 
it  on  the  stigmas.  Sometimes  more  than  a  hundred 
small  flies  will  be  found  in  a  single  Arum.  In  these 
two  cases  there  is  obviously  a  great  advantage  in 
the  fact  that  the  stigmas  arrive  at  maturity  before 
the  anthers. 

Our  common  Scrophularia  nodosa,  some  species  of 
Plantago,  &c.,  are  also  proterogynous,  but  such  cases 
are  comparatively  rare. 

The  advantage  to  Scrophularia  of  being  proter- 
ogynous, as  Mr.  Wilson  ("  Nature,"  September  5,  1878) 
has  ingeniously  pointed  out,  arises  from  the  fact  of  its 
being  fertilised  by  wasps,  which  generally  begin  with 
the  upper  flower  and  work  downwards,  while  bees  begin 
below  and  work  upwards.  The  lower  flowers  are  the 
older.  Hence  a  bee  coming  from  another  plant  of  the 
same  species  fertilises  the  lower  flowers,  and  then  carries 
off  a  fresh  supply  of  pollen  from  the  upper  and  younger 
ones.  On  the  other  hand,  as  wasps  commence  from  above 

n 


34  PINKS,   THYME.  [CHAP. 

it  is  an  advantage  that  the  flowers  should  be  proter- 
ogynous,  because  the  consequence  is  that  the  wasp 
fertilises  the  upper  flowers,  and  then  carries  off  a  fresh 
supply  of  pollen  from  the  lower  and  older  ones. 

On  the  other  hand  those  in  which  the  anthers  come 
to  maturity  before  the  pistil  are  much  more  numerous. 
To  the  category  of  these  plants,  which  are  called 
proterandrous,  belong  some  species  of  Thyme,  Pinks, 
Epilobium  (Figs.  47,  48),  Geranium  (Fig.  40),  Malva 
(Figs.  43,  44),  (Mallow),  Impatiens,  Gentians,  many 
of  the  Labiatae,  the  Umbellifers,  most  of  the 
Composites,  of  the  Lobeliaceae,  and  Campanulaceae. 
In  fact,  the  greater  number  of  flowers  which  contain 
both  stamens  and  pistil,  are  more  or  less  pro- 
terandrous. 

Fig.  30  represents  a  flower  of  the  Pink  in  the  first, 
or  male  condition.  The  stamens  are  mature,  and  pro- 
ject above  the  disk  of  the  flower,  while  the  pistil  is 
still  concealed  within  the  tube.  On  the  other  hand 
Fig.  3 1  represents  the  same  flower  in  a  more  advanced 
condition  ;  the  stamens  have  shrivelled  up,  while  the 
pistil  now  occupies  their  place. 

Again,  Fig.  32  represents  a  flower  of  the  Thyme 
(Thymus  serpyllum)  and  shows  the  four  mature  sta- 
mens, aa,  and  the  short,  as  yet  undeveloped  pistil, 
p.  Fig.  33,  on  the  contrary,  represents  a  somewhat 
older  flower,  in  which  the  stamens  are  past  maturity, 
while  the  pistil,  py  on  the  other  hand,  is  considerably 
elongated,  and  is  ready  for  the  reception  of  the 
pollen. 

Here  it  is  at  once  obvious  that  insects  alighting  on 
the  younger  (male)  flowers  would  dust  themselves  with 


II.] 


PINK,  MYOSOTIS. 


35 


pollen,  some  of  which,  if  they  subsequently  alighted 
on  an  older  flower,  they  could  not  fail  to  deposit  on 
the  stigma.1  In  some  cases  flowers  which  are  first 
male  and  then  female,  are  male  on  the  first  day  of 
opening,  female  on  the  second.  In  others  the  period 
is  longer.  Thus  Nigella,  according  to  Sprengel,  is 
male  for  six  days,  after  which  the  stigma  comes  to 


FIG.  30.— Pink  in  the  first  (male) 
condition. 


FIG.  31. — Pink  in  the  second  condition, 
with  mature  stigmas. 


maturity  and  lasts  for  three  or  four.     ("  Das  endeckte 
Geheimniss  der  Natur,"  p.  287.) 

Fig.  34  represents  a  flower  of  Myosotis  versicolor  (a 
species  often  known  as  the  Forget-me-not),  when  just 
opened.  It  will  be  observed  that  the  pistil  projects 
above  the  corolla  and  stamens,  so  that  it  must  be  first 
touched  by  any  insect  alighting  on  the  flower. 
Gradually,  however,  the  corolla  elongates,  carrying 

1  In  the  Thymes  there  are  likewise  some  small  flowers  which  contain 
no  stamens. 

D   2 


36 


MYOSOTIS. 


[CHAP. 


up  the   stamens  with  it,  until   at   length  they  come 
opposite  the  stigma,  as  shown  in  Fig.  35.     Thus,  if 


a 


FIG.  32.—  Thymus  serpyllum,   in   the 
first  condition,  with  ripe  stamens. 


FIG.    ^.—  Thymus    serpyllum,    in   the 
second  condition,  with  mature  stigma, 


FIG.    SA.—  Myosotis    versi 
flower). 


FIG.   35. — Myosotis  versicolor    (older 
flower). 


the  flower  has  not  already  been  fertilised  by  insects,  it 
is  almost  sure  to  fertilise  itself. 

I  now  pass  to  the  third  of  the  principal  modes  by 


ii.]  DIMORPHOUS  PLANTS.  37 

which  self- fertilisation  is  prevented.  In  the  flowers 
hitherto  described,  while  the  several  species  offer  the 
most  diverse  arrangements,  we  have  met  with  no 
differences  within  the  limits  of  the  same  species,  ex- 
cepting those  dependent  upon  sex.  But  there  are 
other  species  which  possess  flowers  of  two  or  more 
kinds,  sometimes,  as  in  the  violet,  adapted  to  dif- 
ferent conditions,  but  more  frequently  so  constituted 
as  to  ensure  cross-fertilisation.  In  some  of  the  violets 
(  V.  odorata,  canina,  &c.),  besides  the  blue  flowers  with 


FIG.  36.— Cleistogamous  flower  of  FIG.  37.— Section  of  ditto 

Lamium  amplexicaule. 

which  we  are  all  so  familiar,  there  are  other,  autumnal, 
flowers  almost  without  petals  and  stamens  ;  which 
indeed  have  scarcely  the  appearance  of  true  flowers, 
but  in  which  numerous  seeds  are  produced.  "  Cleis- 
togamous "  flowers,  as  these  have  been  called,  occur 
also  in  Lamium  amplexicaule  (Figs.  36  and  37),  Oxalis 
acetosella,  Trifolium  subterraneum,  and  other  plants 
belonging  to  very  different  groups.  They  were,  I 
believe,  first  observed  by  Dillenius  in  Ruellia  ("  Hortus 


CLEISTOGAMOUS  FLOWERS. 


[CHAP. 


Elthamensis,"  vol.  ii.  p.  239).  As,  however,  they  have  no 
relation  to  our  present  subject,  I  shall  not  now  dwell 
upon  them. 

I  pass  on,  therefore,  to  the  genus  Primula.  If  a 
number  of  specimens  of  primroses  or  of  cowslips  be 
examined,  we  shall  find  that  about  half  of  them 
have  the  pistil  at  the  top  of  the  tube,  and  the 
stamens  half-way  down  (as  is  shown  in  Fig.  38), 
while  the  other  half  have,  on  the  contrary,  the 
stamens  at  the  top  of  the  tube,  and  the  pistil  half- 
way down  (as  shown  in  Fig.  39).  Corresponding 


CO 


Oo  00 
0   0 


x  aso 

FIG.  38.— Primula  (long-styled  form).  FIG.  39.— Primula  (short-styled  form). 

differences  occur  in  Polyanthus  and  Auricula,  and 
have  long  been  known  to  gardeners,  and  even  to 
schoolchildren,  by  whom  the  two  forms  are  distin- 
guished as  "  thrum-eyed  "  and  "  pin-eyed."  As 
already  mentioned,  plants  which  present  these  differ- 
ences are  known  as  Heteromorphous  (in  opposition  to 
those  which  are  Homomorphous,  or  have  only  one 
kind  of  flower),  while  those  with  two  forms  are  called 
Dimorphous,  those  with  three,  Trimorphous. 

Sprengel  himself  had  noticed  a  case  of  Dimorphism 


II.]  HETEROMORPHOUS  FLOWERS.  39 

in  Hottonia,  and  shrewdly  observed  that  there  was 
probably  some  reason  for  it,  but  was  unable  to 
suggest  any  explanation. 

In  Lythrum  the  existence  of  different  forms  had 
been  observed  by  Vaucher  in  1841,  and  in  the  genus 
Oxalis  by  Jacquin,  who  regarded  them  as  indicative 
of  different  species ;  but  it  was  reserved  for  the  genius 
and  perseverance  of  Mr.  Darwin  to  explain  ("  Jour. 
Linn.  Soc."  1862,  p.  77)  the  significance  of  this  curious 
phenomenon,  and  the  important  part  it  plays  in  the 
economy  of  the  flower.  Now  that  Mr.  Darwin  has 
pointed  this  out,  it  is  sufficiently  obvious  :  An  insect 
thrusting  its  proboscis  down  a  primrose  of  the  long- 
styled  form  (Fig.  38)  would  dust  its  proboscis  at  a 
part  which,  when  it  visited  a  short-styled  flower 
(Fig.  39),  would  come  just  opposite  the  head  of  the 
pistil,  and  could  not  fail  to  deposit  some  of  the 
pollen  on  the  stigma.  Conversely,  an  insect  visiting 
a  short-styled  plant,  would  dust  its  proboscis  at  a 
part  further  from  the  tip  ;  which,  when  the  insect  sub- 
sequently visited  a  long-styled  flower,  would  again 
come  just  opposite  to  the  head  of  the  pistil.  Hence 
we  see  that  by  this  beautiful  arrangement,  insects 
must  carry  the  pollen  of  the  long-styled  form  to  the 
short-styled,  and  vice  versd. 

There  are  other  points  in  which  the  two  forms  differ 
from  one  another ;  for  instance,  the  stigma  of  the  long- 
styled  form  is  globular  and  rough,  while  that  of  the 
short-styled  is  smoother,  and  somewhat  depressed. 
The  pollen  of  the  two  forms  (Figs.  38  and  39)  is 
also  dissimilar ;  that  of  the  long-styled  being  con- 
siderably smaller  than  the  other — TQ^  of  an  inch  in 


40  PRIMROSE,  LY THRUM,  [CHAP. 


diameter  against  -finnr*  or  nearly  in  the  proportion  of 
three  to  two  ;  a  difference,  the  importance  of  which 
is  probably  due  to  the  fact  that  each  grain  has  to 
give  rise  to  a  tube  which  penetrates  the  whole  length 
of  the  style,  from  the  stigma  to  the  base  of  the  flower; 
and  the  tube  which  penetrates  the  long-styled  pistil 
must  therefore  be  nearly  twice  as  long  as  in  the 
other.  Mr.  Darwin  has  shown  that  much  more  seed 
is  set,  if  pollen  from  the  one  form  be  placed  on  the 
pistil  of  the  other,  than  if  the  flower  be  fertilised  by 
pollen  of  the  same  form,  even  taken  from  a  dif- 
ferent plant.  Nay,  what  is  most  remarkable,  such 
unions  in  Primula  are  more  sterile  than  crosses 
between  some  nearly  allied,  though  distinct  species 
of  plants. 

The  majority  of  species  of  the  genus  Primula 
appear  to  be  dimorphous,  but  this  is  not  the  case. 
(Scott,  "  Proc.  Linn.  Soc."  vol.  viii.  1864,  p.  80.) 

Mr.  Darwin  has  since  pointed  out  ("Jour.  Linn. 
Soc."  1863)  that  several  species  of  Linum  are  di- 
morphous, in  the  same  manner  as  those  of  Primula; 
and  has  shown  that  the  existence  of  three  forms  in 
Lythrum  (Figs.  77 — 80)  already  observed  by  Vaucher, 
is  to  be  explained  in  the  same  manner.  I  shall  refer 
to  this  case  more  in  detail  when  we  come  to  that 
family.  Nor  are  these  by  any  means  the  only  cases 
of  Heteromorphism  now  known.  I  have  already 
mentioned  that  of  Oxalis,  and  Hildebrand  gives  the 
following  list  of  genera  as  containing  Heteromorphous 
species,  viz.,  Hottonia,  Primula,  Linum,  Lythrum, 
Pulmonaria,  Cinchona,  Mitchella,  Plantago,  Rhamnus, 
Amsinckia,  Mertensia,  Leucosmia,  Drymospermum, 


II.]    MOVEMENTS  OF  STAMENS  AND  PISTIL.      41 


Menyanthes,  and  Polygonum.  It  will  be  observed 
that  these  genera  belong  to  very  different  groups, 
while  on  the  other  hand,  in  several  cases,  as  in 
Primula  itself  (Scott,  "  Proc.  Linn.  Soc."  vol.  viii.),  we 
find  monomorphous  and  heteromorphous  species  in 
the  same  genus. 

Another  point  of  great  interest  is  the  spontaneous 


FIG.  40. — Geranium pratense. 


movement  of  the  stamens  and  pistil  in  dichogamous 
plants,  first  observed  by  Kolreuter  in  Ruta  graveo- 
lens;  he,  however,  supposed  that  the  object  was  to 
bring  the  stamens  in  contact  with  the  pistil ;  whereas 
the  real  advantage,  as  Sprengel  pointed  out,  is  that 
in  consequence  the  stamens  and  pistil  successively 
occupy  the  same  spot  in  the  flower,  and  thus  come  in 


FOXGLOVE,  VALISNERIA 


[CHAP. 


contact  with  the  same  part  of  the  insect.  For  instance, 
in  Geranium  pratense  (Fig.  40),  when  the  flower  first 
opens,  the  stamens  lie  on  the  petals,  at  right  angles 
with  the  upright  pistils.  As,  however,  they  come  to 
maturity  they  raise  themselves  (Fig.  41  a),  parallel 
and  close  to  the  pistil  (Fig.  41  £),  which,  however,  is 
not  as  yet  capable  of  fertilisation.  After  they  have 
shed  their  pollen,  they  return  to  their  original  position 
(Fig.  42),  and  the  stigmas  unfurl  themselves.  More 


FIG.  41. — Geranium  pratense  (young 
flower).  Five  of  the  stamens  are 
erect. 


Fie.  42. — Geranium  pratense  (older 
flower).  The  stamens  have  retired, 
and  the  stigmas  are  expanded. 


or  less  similar  movements  have  been  observed  in 
various  other  flowers.  Thus  the  cells  of  the  anthers 
of  the  Foxglove  (Digitalis  pur purea)  (Figs.  100 — 102), 
which  are  at  first  transverse,  become  longitudinal  as 
they  ripen. 

In  aquatic  plants,  the  blossoms  habitually  come  to 
the  surface.  In  Valisneria  spiralis  the  female  flower 
has  a  long  spiral  stalk  which  enables  it  to  rise  to 
the  top  of  the  water.  The  male  flowers  which  are 


II.]  FORMS  OF  POLLEN.  43 

small,  very  numerous,  and  attached  lower  down, 
separate  themselves  altogether  from  the  plant,  rise 
to  the  surface,  and  fertilise  the  female  flowers,  among 
which  they  float.  When  this  is  effected,  the  spiral 
stalk  of  the  female  flower  again  contracts,  and  draws 
it  down  below  the  surface. 

While  the  pollen  grains  from  each  flower  agree  very 
closely  with  one  another,  those  of  different  species 
differ  greatly  in  form,  size,  character  of  surface,  &c. 
Doubtless  there  are  reasons  for  these  differences,  but 
the  subject  is  one  with  reference  to  which  we  have 
as  yet  very  little  information. 

According  to  Sprengel,  the  pollen  of  wind-fertilised 
flowers  is  drier,  and  therefore  more  easily  carried  by 
the  wind,  than  that  of  most  insect-fertilised  flowers. 
I  say  of  most,  because  in  some  cases,  for  instance 
in  the  violet,  as  will  be  shown  presently,  it  is  as 
necessary  that  the  pollen  should  separate  readily 
from  the  anthers,  as  in  wind-fertilised  flowers. 

Mr.  Bennett  states  that  the  pollen  of  wind-fertilised 
flowers  is  generally  spherical ;  while  that  of  insect- 
fertilised  flowers  is  usually  furrowed,  the  furrows 
running  along  the  longer  axis  of  the  grain. 

In  Dimorphous  species  the  pollen  of  the  short- 
styled  form  is  generally  larger  than  that  of  the  long- 
styled  form,  but  in  Linum,  according  to  Hildebrand, 
("Die  Ges.  Verth.  bei  den  Pflanzen,"  p.  37)  it  is  of  the 
same  size  in  both  forms. 

In  Faramea,  another  Dimorphous  group,  the  sur- 
face of  the  pollen  grains  is  different  in  the  two  forms 
(Thome*  "Das  Gesetz  der  vermiedenen  Selbstbe- 
fruchtung  bei  den  hoheren  Pflanzen,"  1870),  the 


44  FORM  AND  QUANTITY  OF  POLLEN.     [CHAP. 


smaller  grains  of  the  long-styled  form  are  studded 
with  small  points ;  in  consequence  of  which  the  pol- 
len-grains are  less  easily  detached  from  the  anther ; 
this  difference  possibly  has  reference  to  the  different 
position  of  the  two  forms  ;  the  smooth  ones  being 
sheltered  by  the  flower ;  while  the  larger  pollen- 
grains,  which  are  produced  in  the  anthers  of  the 
long  stamens,  and  are  therefore  more  exposed  to  the 
wind,  are,  in  consequence  of  their  roughness,  less 
liable  to  be  blown  away  and  wasted. 

According  to  D.  Miiller  ("Bot.  Zeit,"  1857)  the  pollen 
of  the  small  flowers  of  Viola  elatoir  and  V.  lancifolia 
is  minute  and  round.  Herr  von  Mohl,  however,  found 
no  difference  between  the  pollen  of  the  large  and 
small  flowers  in  V.  mimM/is^'Eot  Zeit,"  1863).  The 
number  of  grains  in  these  flowers  is  very  small.  So 
also  in  the  cleistogamous  flowers  of  Oxalis  acetosella, 
there  are  not  above  two  dozen  pollen-grains  in  each 
of  the  five  larger  anthers,  and  one  dozen  in  each  of 
the  five  smaller  ones.  The  ovules  are  about  twenty 
in  number. 

It  is  interesting  to  notice  that  the  contrivances  by 
which  cross-fertilisation  is  favoured,  or  ensured,  are 
probably  of  a  very  different  geological  antiquity.  Thus 
as  Miiller  has  pointed  out,  the  special  peculiarities  of 
the  Umbelliferae  and  Compositae  have  been  inherited 
respectively  from  the  ancestral  forms  of  those  orders ; 
those  of  Delphinium,  Aquilegia,  Linaria,  and  Pedicu- 
laris,  from  the  ancestral  forms  of  the  respective 
genera ;  those  of  Pofygvnnm  Fagopyrum,  P.  Bistorta, 
Lonicera  Caprifoliutn,  &c.,  from  the  ancestors  of  those 
species ;  while  in  Lysimachia  vulgaris>  Rkinantkus 


II.]      GEOLOGICAL  ANTIQUITY  OF  FLOWERS.       45 


Cristagalli,  Veronica  spicata,  Euphrasia  Odontites,  and 
E.  officinalis,  we  find  that  differences  have  arisen  even 
within  the  limits  of  one  and  the  same  species. 

In  some  species,  for  instance,  we  find  two  varieties, 
one  with  larger  flowers,  which  are  fertilised  by 
insects,  and  others  with  smaller  flowers,  which  are 
self-fertile. 

In  other  cases  the  differences  between  the  two  kinds 
of  flowers  are  so  marked,  and  have  become  so  fixed, 


FIG.  ^.—Malva  sylvestris  FIG.  ^.—Malva.  rotundifolia. 

that  the  two  kinds  are  usually  considered  to  be  dis- 
tinct species ;  while  in  yet  other  cases  the  differentia- 
tion is  still  more  complete. 

Among  other  obvious  evidences  that  the  beauty 
of  flowers  is  useful  to  them,  in  consequence  of  its 
attracting  insects,  we  may  adduce  those  cases  in 
which  the  transference  of  the  pollen  is  effected  in 
different  manners  in  nearly  allied  plants,  some- 
times even  in  different  species  belonging  to  the 
same  genus. 


46  DIFFERENCES  BETWEEN  ALLIED  SPECIES.  [CH. 


Thus,  as  Miiller  has  pointed  out,  Malva  sylvestris 
(Fig.  43)  and  Malva  rotundifolia  (Fig.  44),  which  grow 
in  the  same  localities,  and  therefore  must  come  into 
competition,  are  nevertheless  nearly  equally  common. 
In  both  species  the  young  flower  contains  a  pyramidal 
group  of  stamens  which  surround  the  stigma,  and 
produce  a  large  quantity  of  pollen,  which  cannot  fail 
to  dust  any  insect  visiting  the  flower  for  the  sake  of  its 
honey.  In  Malva  sylvestris  (Fig.  43),  where  the  branches 
of  the  stigma  are  so  arranged  (Fig.  45),  that  the  plant 
cannot  fertilise  itself,  the  petals  are  large  and  conspi- 
cuous, so  that  the  plant  is  visited  by  numerous  insects ; 


FIG.  45.—  Stamens  and  stigmas  of  Malva        FIG.  46.—  Ditto  of  Malva  rotundifoli 


while  in  Malva  rotundifolia  (Fig.  44),  the  flowers  of 
which  are  comparatively  small  and  rarely  visited  by 
insects,  the  branches  of  the  stigma  are  elongated 
and  twine  themselves  (Fig.  46)  among  the  stamens, 
so  that  the  flower  can  hardly  fail  to  fertilise  itself. 

Another  remarkable  instance  occurs  in  the  genus 
Epilobium,  which  is,  moreover,  specially  interesting, 
because  in  E.  angustifolium,  as  I  have  already  men- 


II.]        RELA  TION  OF  THE  SIZE  OF  FLO  WER          47 

tioned,  the  curious  fact  was  first  noticed  that  the  pistil 
did  not  mature  until  the  stamens  had  shed  their  pollen. 
E.  angustifolium  (Fig.  47)  has  conspicuous  purplish- 
red  flowers,  in  long  terminal  bunches  or  racemes,  and 
is  much  frequented  by  insects  ;  E.  parviflorum  (Fig. 
48),  on  the  contrary,  has  small  solitary  flowers,  and  is 
seldom  visited  by  insects.  Now,  to  the  former  species 
the  visits  of  insects  are  necessary,  since  the  stamens 
ripen  before  the  pistil,  and  the  flower  has  consequently 
lost  the  power  of  self-fertilisation.  In  the  latter,  on 
the  contrary,  the  stamens  and  pistil  come  to  maturity 
at  the  same  time,  and  the  flower  can  therefore 


FIG.   47. — Epilobium  angustifolium.       FIG.  48. — Epilobium  parvijlorum. 

fertilise  itself.  It  is,  however,  no  doubt  sometimes 
crossed  by  the  agency  of  insects ;  and  indeed  I  am 
disposed  to  believe  that  this  is  true  of  all  the  flowers 
which  are  either  coloured  or  sweet  scented. 

The  genus  Geranium  also  affords  us  an  instructive 
example.  There  are  a  number  of  species  which,  as 
will  be  seen  in  Fig.  49,  differ  much  in  the  size  of  the 
flowers.  Thus  those  (Fig.  49  a)  of  Geranium  pratense 


48         TO  THE  DEPENDENCE  ON  INSECTS.     [CHAP 

(Fig.  40)  are  nearly  twice  as  large  as  those  of  G.  pyre- 
naicum  (Fig.  49  b\  which  again  are  much  larger  than 
those  of  G.  molle  (Fig.  49  c\  while  those  of  G.pusillum 
(Fig.  49  d]  are  still  smaller.  These  differences  of 
size  appear  to  be  connected  with  other  remarkable 
differences  between  these  species.  Fig.  41,  as  already 
mentioned,  represents  a  flower  of  G.  pratenze  when 
first  opened.  Five  of  the  stamens  have  raised  them- 
selves and  stand  upright,  and  surround  the  still 
immature  pistil.  When  they  have 
shed  their  pollen  they  sink  back  and 
shrivel  up,  when  the  other  five  raise 
themselves.  At  a  later  stage  these 
in  their  turn  fall  back  and  shrivel  up, 
but  the  stigma  does  not  become  ma- 
ture (Fig.  42),  until  all  the  stamens 
have  shed  their  pollen.  Under  these 
circumstances  G.  pratense  has  lost 
the  power  of  self-fertilisation,  and  is 
absolutely  dependent  on  the  visits  of 


FIG.  49.—  Corolla  of—  a, 
Geranium  pratense  i  _  .  .  . 

t,  G.  tyrenaicum;  c,       G.  pyrenatcum  (Fig.  AQ  &)  is  also  pro- 

G.  molle;  d,  G.  f>u-  . 

siiium.  terandrous  ;  but  while  in   G.  pratense 

the  pistil  is  not  mature  until  the  sta- 
mens have  shed  all  their  pollen  and  fallen  back,  in 
G.pyrenaicum  the  second  series  of  stamens  are  still 
upright  when  the  stigmatic  lobes  unfurl  ;  the  flower  is 
consequently  less  absolutely  dependent  on  insects,  and 
we  see  that  the  corolla  is  much  smaller. 

In  the  third  species,  G.  molle  (Fig.  49  c),  the  pistil 
matures  before  the  second  series  of  stamens,  and  the 
corolla  is  still  smaller  ;  while  in  G.pusillum  (Fig.  49  d) 


II.] 


LINES  AND  MARKS  ON  FLOWERS. 


49 


the  pistil  matures  before  any  of  the  stamens.  Thus 
then  these  four  species  may  be  arranged  in  a  table  as 
below : — 


GERANIUM 

GERANIUM 

GERANIUM 

GERANIUM 

FRATENSE. 

PYRENAICUM. 

MOLLE. 

PUSILLUM. 

Flower  large. 

Flower  small. 

Flower  smaller. 

Flower  smallest 

First  exclusively 
male,  then  ex- 
clusively fe- 
male. 

First  exclusively 
male,  then  her- 
maphrodite. 

First  exclusively 
male,  then  her- 
maphrodite. 

First  exclusively  j 
female,     soon 
becoming  her- 
maphrodite. 

Incapable  of  self- 
fertilization. 

Generally  fertil- 
ised by  insects. 

Often  self-fertil- 
ised. 

Generally     self- 
fertilised. 

Indeed,  though  further  observations  on  the  point 
are  no  doubt  required,  it  would  seem  that,  as  a  general 
rule,  where  we  find  within  the  limits  of  one  genus  some 
species  which  are  much  more  conspicuous  than  others, 
we  may  suspect  that  they  are  also  more  dependent 
on  the  visits  of  insects. 

Sprengel  also  suggests,  and,  as  it  would  appear, 
with  reason,  that  the  lines  and  bands  by  which  so 
many  flowers  are  ornamented  have  reference  to  the 
position  of  the  honey  ; 1  and  it  may  be  observed  that 
these  honey-guides  are  absent  in  night-flowers,  where 
of  course  they  would  not  be  visible,  and  would  there- 
fore be  useless,  as,  for  instance,  in  Lychnis  vespertina 
(Fig.  50),  or  Silene  nutans.  Night-flowers,  moreover, 

1  I  did  not  realise  the  importance  of  these  guiding  marks  until,  by 
experiments  on  bees,  I  saw  how  much  time  they  lose  if  honey,  which 
is  put  out  for  them,  is  moved  even  slightly  from  its  usual  place. 


50    IMPORTANCE  OF  INSECTS  TO  FLOWERS.   [CH. 

are  generally  pale  ;  for  instance,  Lychnis  vespertina 
is  white,  while  Lychnis  diurna,  which  flowers  by  day, 
is  red.  Brown  flowers,  such  as  Scrophularia,  some 
species  of  Epipactis,  of  Lonicera,  &c.,  perhaps  owe 
their  hue  to  the  selective  influence  of  wasps.  Fly 
flowers  also  are  often  livid  or  flesh-coloured. 

I  have  been  good-humouredly  accused  of  attacking 
the  Bee,  because  I  have  ventured  to  suggest  that  she 


Fie.  50. — Lychnis  vesfierffna. 

does  not  possess  all  the  high  qualities  which  have 
been  popularly  and  poetically  ascribed  to  her.  But  if 
scientific  observations  do  not  altogether  support  the 
moral  and  intellectual  eminence  which  has  been 
ascribed  to  Bees,  they  have  made  known  to  us  in  the 
economy  of  the  hive  many  curious  peculiarities  which 
no  poet  had  dreamt  of,  and  have  shown  that  bees 
and  other  insects  have  an  importance  as  regards 
flowers  which  had  been  previously  unsuspected.  To 


n]     IMPORTANCE  OF  INSECTS  TO  FLOWERS.     51 

them  we  owe  the  beauty  of  our  gardens,  the  sweet- 
ness of  our  fields.  To  them  flowers  are  indebted  for 
their  scent  and  colour  ;  nay,  for  their  very  existence 
in  its  present  form.  Not  only  have  the  present  shape 
and  outlines,  the  brilliant  colours,  the  sweet  scent 
and  the  honey  of  flowers,  been  gradually  developed 
through  the  unconscious  selection  exercised  by  insects ; 
but  the  very  arrangement  of  the  colours,  the  circular 
bands  and  radiating  lines,  the  form,  size,  and  position 
of  the  petals,  the  relative  situations  of  the  stamens 
and  pistil,  are  all  arranged  with  reference  to  the 
visits  of  insects,  and  in  such  a  manner  as  to  ensure 
the  grand  object  which  these  visits  are  destined  to 
effect. 


LYCHNIS    VESPERTINA. 

CHAPTER  III. 

DICOTYLEDONS. 

THALAMIFLOR.E. 

IN  the  preceding  chapters  1  have  endeavoured  to  give 
a  general  sketch  of  the  relations  existing  between 
flowers  and  insects.  I  shall  now  proceed  to  de- 
scribe particular  instances  more  in  detail,  following  in 
general  the  classification  adopted  in  Mr.  Bentham's 
admirable  "  Handbook  of  the  British  Flora,"  from 
which  also  many  of  my  facts  and  illustrations  have 
been  borrowed.  I  propose  to  go  through  the  English 
Flora,  in  the  order  of  Mr.  Bentham's  work,  calling  at- 
tention to  those  facts,  bearing  on  our  present  subject, 
which  strike  me  as  most  interesting.  The  present 
chapter  is  devoted  to  the  thalamifloral  division  of  the 
Dicotyledons. 


CH.  in.]       CLASS1FICA  TION  OF  PLANTS.  53 

The  vegetable  kingdom  may  be  divided  into 
flowering  and  flowerless  plants ;  while  flowering  plants 
again  fall  into  two  divisions,  known  as  Dicotyle- 
dons or  Exogens  and  Monocotyledons  or  Endogens. 
Dicotyledonous  or  exogenous  plants  are  those  in 
which,  when  the  seed  germinates,  the  "plumule"  or 
bud  arises  between  two  (rarely  more)  seed-leaves  or 
cotyledons  of  the  embryo,  or  from  a  terminal  notch. 
In  this  class  the  leaves  have  their  nerves  branched, 
forming  a  sort  of  network,  as  in  the  oak,  beech, 
clover,  violet,  &c.  In  their  growth  they  increase  by 
forming  new  woody  tissue  over  the  old,  whence  the 
term  "  Exogenous."  In  a  Dicotyledonous  or  exo- 
genous tree,  therefore,  we  find  a  number  of  con- 
centric circles,  each  representing  a  period  of  growth, 
and  indicating,  though  roughly,  its  age  in  years. 
Monocotyledonous  or  endogenous  plants,  on  the  con- 
trary, are  those  in  which  the  plumule  or  bud  is  de- 
veloped from  a  sheath-like  cavity  on  one  side  of  the 
cotyledon.  The  leaves  have  parallel  nerves,  as  for 
instance  in  grasses,  orchids,  lilies,  palms,  &c.  In  a 
cross-section  the  wood  shows  no  concentric  circles, 
but  consists  of  bundles  of  woody  fibre  irregularly 
imbedded  in  cellular  tissue.  Both  these  classes  have 
flowers. 

Cryptogams,  on  the  contrary  (ferns,  mosses,  sea 
weeds,    lichens,    fungi,    &c.),  have   no    flowers,    and 
multiply  by  bodies  called  spores. 

That  the  colour  of  the  corolla  has  reference  to  the 
visits  of  insects  is  also  well  shown  by  the  case  of  those 
rtowers,  which — as,  for  instance,  the  ray  or  outside 
florets  of  Centaurea — have  neither  stamens  nor  pistils, 


54        CLASSIFICATION  OF  DICOTYLEDONS.   [CHAP. 

and  merely  serve,  therefore,  to  render  the  flower-head 
more  conspicuous.  The  calyx,  moreover,  is  usually 
green ;  but  when  the  position  of  the  flower  is  such 
that  it  is  much  exposed,  it  becomes  brightly  coloured, 
as,  for  instance,  in  the  Berberry  or  Larkspur 

The  above  characters,  though  true  in  the  main,  do 
not  hold  good  in  all  cases.  For  instance  the  genus 
Arum,  though  a  Monocotyledon,  has  reticulated 
nerves,  but  its  stem  is  endogenous,  and  its  embryo 
has  only  one  cotyledon. 

The  class  of  Dicotyledons  is  divisible  into  four  sub- 
classes, which  may  be  thus  characterised  : — 

Thalamiflorce.  Petals  distinct  from  the  calyx  and 
from  each  other,  seldom  wanting.  Stamens 
usually  hypogynous  (i.e.  attached  under  the 
ovary),  so  that  if  the  calyx  be  torn  away  the 
stamens  remain. 

Calyciflora.    Petals    usually    distinct.      Stamens 
perigynous  (i.e.  attached  round  the  ovary),  or 
epigynous  (i.e.  placed  upon  the  ovary). 
Corolliflorce  or   Monopetalce.      Petals   united  (at 

least,  at  the  base)  into  a  single  corolla. 
Incomplete  or  Monochlamydece.     Perianth  or  floral 
envelope,  really  or  apparently  simple  ;  or  none. 
These  subclasses  may  be  tabulated  as  follows : — 

Perianth  /  single  or  none Monochlamydeae. 

or  floral  /  i  corolla  of  united  petals  ....     Corolliflone. 

envelope    double  j  i_          \ 

)'     ,£ZS     yP°"    Thalamiflone. 
I  corolla  of  dis-/     gy11008     '    '  ' 
tinct  petals     \  stamens  perigy.  j 

nous  or  epigy-  >  Calycifloras. 
nous     .     .     .  ) 


Hi.]  RANUNCULUS,  CLEMATIS.  55 

RANUNCULACE^E. 

This  order  contains  fourteen  British  genera,  in- 
cluding the  Clematis,  Ranunculus  (Buttercup),  Ane- 
mone, Columbine,  Hellebore,  Larkspur,  Paeony,  &c. 

In  the  Buttercup  (Ranunculus  acris),  the  anthers 
commence  to  discharge  their  pollen,  as  soon  as  the 
flower  opens,  beginning  from  the  outside.  The 
stigmas,  however,  are  not  as  yet  mature,  nor  do  the 
stamens  open  on  the  side  which  is  turned  towards 
them,  but  on  the  contrary,  on  their  edges;  moreover 
as  each  stamen  ripens,  it  generally  turns  outwards. 
The  result  of  this  is  that  bees  and  other  insects,  which 
visit  the  flowers  in  search  of  honey,  are  almost  sure 
to  dust  themselves  with  pollen  ;  which  they  carry 
away  with  them,  and  are  then  very  likely  to  deposit 
it  on  another  flower.  The  stigmas  are  mature  before 
the  inner  stamens  have  shed  all  their  pollen,  and  self- 
fertilisation  must  often  take  place,  both  by  means  of 
the  small  insects  which  may  almost  invariably  be  found 
wandering  about  the  flower,  and  because  the  inner 
stamens  often  touch  some  of  the  stigmas.  Larger 
insects,  however,  which  fly  from  flower  to  flower,  must 
habitually  carry  the  pollen  from  the  younger  flowers, 
and  deposit  it  on  the  stigmas  of  those  more  advanced. 

Clematis  recta  produces  no  honey,  but  is  visited  for 
the  sake  of  the  pollen.  It  is  proterandrous  (see  p.  28), 
but  not  very  decidedly  so  ;  for  as  in  other  flowers 
which  do  not  produce  honey,  if  the  stamens  had  shed 
all  their  pollen  before  the  pistil  came  to  maturity, 
insects  would  cease  to  visit  the  flowers  before  the 
stigma  had  attained  maturity,  and  had  thus  become 
susceptible  of  fertilisation. 


56  CALTHA,  HELLEBORUS,  ANEMONE.    [CHAP. 

Like  Clematis,  Thalictrum  produces  no  honey.  The 
petals  are  absent  and  the  sepals  minute,  but  the 
stamens  are  numerous  and  brightly  coloured. 

Caltha  palustris  has  large  yellow  sepals,  but 
no  true  petals.  In  the  Hellebore  also  the  petals 
are  minute,  but  secrete  honey.  The  species  of  this 
genus  are  said  by  Hildebrand  to  be  proterogynous 
(See  p.  28.) 

In  Anemone  nemorosa  the  colouring  is  given  not  by 
the  corolla,  but  by  the  calyx.  The  flower  does  not 
appear  to  produce  honey,  but  bees  are  said  to  pierce 
the  base  of  the  flower,  and  lick  the  sap.  Van 
Tieghem  however  states  that  it  gives  off  honey  from 
the  whole  surface  of  the  receptacle. 

Delphinium  (the  Larkspur)  and  D.  elatum  (Figs.  5 1 
— 54)  have  been  well  described  by  H.  Miiller.  The 
five  sepals  are  brightly  coloured  ;  the  upper  one  is 
produced  into  a  long  spur  (x  x).  The  two  upper 
petals  are  also  produced  into  spurs  which  lie  within 
the  former,  and  secrete  honey.  In  order  to  reach 
this  it  is  necessary  for  the  bee  to  press  its  proboscis 
between  the  upper  and  lower  petals,  through  the 
interval  (Figs.  51,  53  ;;z).  The  lower  wall  of  this 
orifice  is  in  front  closed  by  the  lower  petals  (Figs.  5 1, 
53  Pe  Pe\  which  are  turned  upwards  and  sideways, 
so  as  to  form  the  lower  wall  of  the  orifice  leading 
to  the  nectary,  and  to  cover  the  stamens  and  pistils. 
Immediately  behind  the  entrance  to  the  tube,  how- 
ever, these  petals  contract  so  as  to  leave  a  space  (m\ 
The  stamens  (a)  and  pistil  lie  below  this  space,  and  as 
the  stamens  ripen,  they  successively  raise  themselves 
and  their  anthers  pass  through  this  space,  as  shown  in 


III.] 


DELPHINIUM. 


57 


Fig.  5 1  a'y  so  that  the  proboscis  of  the  bee,  in  passing 
down  to  the  honey  can  hardly  fail  to  come  in  contact 
with  them.  After  shedding  their  pollen,  they  turn 
down  again,  and  when  each  anther  has  thus  raised 
itself  and  again  retired,  the  pistil  in  its  turn  takes  pos- 

FIG.  54 


FIG.  53.  FIG.  52. 

FIG.  51.— A  young  flower  of  Delphinium  elatum,  seen  from  the  front,  and  after  re- 

moval  of  the  calyx. 

FIG.  52.  — Section  of  the  same  flower  seen  from  the  side. 
FIG.  53. — An  older  flower,  seen  from  the  front,  after  removing  the  calyx. 
FIG.  54. — Section  of  the  same  flower,  seen  from  the  side. 

session  of  the  place,  as  shown  in  Fig.  53,  and  54  st\ 
and  is  thus  so  placed,  that  a  bee  which  has  visited 
a  younger  flower  and  there  dusted  its  proboscis,  can 
hardly  fail  to  deposit  some  of  the  pollen  on  the 


58  RANUNCULACE&.  [CHAP. 

^stigma.  Fig  51  represents  a  young  flower  seen 
from  the  front,  and  after  the  removal  of  the  calyx ; 
it  shows  the  entrance  leading  to  the  nectary,  in 
which  are  seen  the  heads  of  two  mature  stamens,  a't 
while  the  others,  a  a,  are  situated  in  a  cluster  below. 
Fig.  52  represents  a  section  of  the  same  flower. 
Fig.  53  represents  a  somewhat  older  flower,  in  the 
same  position  as  Fig.  51.  In  this  case  the  stamens 
have  all  shed  their  pollen  and  retired,  while  the  stig- 
mas st,  on  the  contrary,  have  risen  up,  and  are  seen 
projecting  into  the  space  m.  Fig.  54  represents  a 
side  view  in  section  of  this  flower.  Anthophora pilipes 
and  Bombus  hortorum  are  the  only  two  North 
European  insects,  which  have  a  proboscis  long  enough 
to  reach  to  the  end  of  the  spur  of  Delphinium  elatum. 
A .  pilipes,  however,  is  a  spring  insect,  and  has  already 
disappeared,  before  the  Delphinium  comes  into  flower, 
which,  in  the  neighbourhood  of  Lippstatt,  appears  to 
depend  for  its  fertilisation  entirely  on  Bombus  hor- 
torwn,  though  Boissier  assures  us  that  in  France  and 
in  the  Alps  it  is  visited  by  several  other  species. 

It  will  be  seen  that  the  Ranunculaceae  offer  very 
remarkable  differences  in  the  manner  of  their  adap- 
tation to  insects.  Honey  is  secreted  by  the  sepals 
in  certain  Paeonies  ;  by  the  petals  in  Ranunculus, 
Delphinium,  Helleborus,  &c. ;  by  the  stamens  in  Pul- 
satilla ;  by  the  ovary  in  Caltha  ;  while  it  is  entirely 
absent  in  Clematis,  Anemone,  and  Thalictrum.  The 
conspicuousness  of  the  flower  is  due  to  the  corolla  in 
Ranunculus ;  to  the  calyx  in  Anemone,  Caltha,  and 
Helleborus  ;  to  both  in  Aquilegia  and  Delphinium  ; 
to  the  stamens  in  Thalictrum.  The  honey  is  in  some 
cases  easily  accessible,  in  others  it  is  situated  at  the 


III.] 


BERBERIDE^E. 


59 


end  of  a  long  spur.  The  former  species  are  capable 
of  self-fertilisation,  the  latter  are  said  by  H.  Miiller 
to  have  lost  their  power. 

BERBERIDE^E. 

The  common  Berberry  is  the  only  British  representa- 
tive of  this  order,  though  Epimedium  alpinum  has 
by  some  been  considered  to  be  indigenous  ;  as  Mr. 
Bentham  thinks,  on  insufficient  grounds. 

In  the  common  Berberry  (Berberis  vulgaris),  the 
stamens  (Figs.  55  //,  56  a)  lie  close  to  the  petals  and 
almost  at  right  angles  to  the  pistil,  as  shown  in 


FIG.  55. 


FIG.  56. 


FIG.  55. — Flower  seen  from  above. 

FIG.  56. — Pistil  with  two  stamens,  after  the  visit  of  an  insect. 

55-  The  honey-glands  (nri)  are  twelve  in 
number,  situated  in  pairs  at  the  base  of  the  petals, 
so  that  the  honey  occupies  the  angle  between  the 
bases  of  the  stamens  and  of  the  pistil.  The  papil- 
lary edge  of  the  summit  of  the  pistil  (e)  is  the 
stigma.  In  open  flowers  of  this  kind  it  is  of  course 


60  NYMPH^EA  CE&,  PAPA  VERA  CEJE.      [CHAP. 

obvious  that  insects  will  dust  themselves  with  the 
pollen  and  then  carry  it  with  them  to  other  flowers. 
In  Berberis,  however,  both  advantages,  the  dusting 
and  the  cross-fertilisation,  are  promoted  by  a  very 
curious  contrivance.  The  bases  of  the  stamens  are 
highly  irritable,  and  when  an  insect  touches  them  the 
stamens  spring  forward  to  the  position  shown  in 
Fig.  56  and  strike  the  insect.  The  effect  of  this  is 
not  only  to  shed  the  pollen  over  the  insect,  but  also 
in  some  cases  to  startle  it  and  drive  it  away,  so  that  it 
carries  the  pollen,  thus  acquired,  to  another  flower. 

NYMPH^EACE^E. 

This  order  is  represented  by  two  British  species. 
Nymphaa  alba,  the  White  Waterlily;  and  Nuphar 
lutea,  the  Yellow  Waterlily.  According  to  Delpino, 
N.  alba  is  fertilised  by  beetles.  Sprengel  contrasts 
the  large  size  of  the  pistil  and  the  great  number  of 
the  stamens  in  N.  lutea,  where  the  fertilisation  is,  as  it 
were,  a  matter  of  accident,  with  the  small  pistil  and 
four  stamens  of  a  Labiate  ;  such,  for  instance,  as  the 
common  Dead  Nettle,  which,  as  we  shall  see,  are  so 
beautifully  arranged  with  reference  to  one  another,  and 
where  consequently  so  much  less  pollen  is  required. 

PAPAVERACE^E. 

Of  this  family  the  Common  Poppy  is  the  best 
known  representative,  though  the  Celandine  is  also 
common  on  roadsides,  especially  near  villages.  The 
Poppy  has  two  sepals,  which  drop  off  as  the  flower 
expands  ;  four  petals ;  numerous  stamens,  forming 


in.]  FUMARIACE^E.  61 

a  ring  round  a  globular  or  ovoid  pistil,  which  is 
crowned  by  a  circular  disk,  on  which  the  stigmas 
radiate  from  the  centre.  The  flowers  secrete  no 
honey,  but  are  visited  for  the  sake  of  the  pollen. 
Owing  to  the  weakness  of  the  petals,  insects  naturally 
alight  on  the  stigma,  which  forms  a  most  convenient 
stage  for  them  in  the  centre  of  the  stamens,  and  they 
thus  naturally  carry  the  pollen  from  one  flower  to 
another. 

FUMARIACE^E. 

This  natural  order  contains  only  two  British  genera, 
Fumaria  and  Corydalis.  The  flowers  of  Fumaria 
have  not  yet,  I  think,  been  satisfactorily  explained. 
Their  form  and  arrangement  are  very  singular,  but 
they  are  not  very  conspicuous,  and  are  said  to  be 
little  visited  by  insects,  being,  according  to  Miiller, 
self-fertile. 

In  Corydalis,  on  the  contrary,  the  flowers  are  much 
larger,  more  conspicuous,  and,  at  least  in  C.  cava, 
are  said  to  have  lost  the  power  of  self -fertilisation, 
Hildebrand  has  found  (Ueber  die  Bestaiibungs  Vorrich- 
tungen  bei  den  Fumariaceen)  that  they  are  absolutely 
sterile  with  their  own  pollen,  and  only  imperfectly 
fertile  with  that  from  other  flowers  of  the  same  plant, 
so  that  they  can  only  be  completely  fertilised  by  that 
from  a  different  plant.  The  tube  of  the  flower  is 
12  millimetres  long,  and  as  the  honey  only  occupies 
at  most  4 — 5  millimetres,  it  is  inaccessible  to  the 
Hive  bee,  whose  proboscis  is  only  6  mm.  long,  and 
almost  so  to  the  common  humble  bee,  in  which  it 
is  7 — 9,  or  at  most  10  mm.  long.  The  latter  can 


62  CORYDALIS.  [CHAP. 

reach  the  honey,  but  not  lap  it  conveniently.  She 
however,  is  in  the  habit  of  biting  a  hole  through  the 
tube,  by  which  means  she  obtains  access  to  the  honey, 
and  in  some  plants  the  greater  number  of  flowers 
will  be  found  to  have  been  treated  in  this  manner. 
Several  other  bees,  for  instance,  the  hive  bee,  Andrena 
albicanSy  K. ;  A.  nitida,  Fourc. ;  Sphecodes  gibbus,  L. ; 
and  Nomada  fabricana,  L.,  have  been  observed  by 
Muller  to  make  use  of  the  entrance  thus  prepared  for 
them.  Moreover,  though  the  hive  bees  are  unable  to 
suck  the  flowers  in  their  natural  condition,  the  flowers 
are  visited  by  them  for  the  sake  of  their  pollen. 

The  upper  petal  is  produced  into  a  long  spur. 
The  two  middle  petals  form  a  sort  of  sheath,  sur- 
rounding the  stamens  and  pistil ;  at  about  a  third 
of  their  length  from  the  base  is  a  peculiar  fold  of 
the  edge,  which  acts  as  a  sort  of  hinge,  so  that  the 
terminal  part,  which  forms  a  sort  of  sheath  or  cap  to 
the  anthers  and  stigma  is  somewhat  moveable.  The 
stamens  are  united  into  an  upper  and  lower  group. 
The  upper  basal  edge  of  the  upper  group  is  produced 
into  a  long  spur,  which  lies  in  the  spur  of  the  upper 
petal,  and  the  tip  of  which  secretes  honey.  When  a 
bee  visits  the  flower,  she  depresses  the  anther  cap,  and 
the  anthers  and  pistil  thus  exposed  rub  against  her 
breast.  When  the  pressure  is  removed  the  cap 
resumes  its  place  and  again  protects  the  anthers  and 
pistil.  Our  common  English  Fumaria  officinalis  is 
formed  on  the  same  plan  as  Corydalis  cava>  the  spur, 
however,  being  quite  short.  It  appears,  moreover,  to 
be  self-fertile,  and  in  spite  of  its  complex  organisation 
seems  to  be  but  rarely  visited,  at  least  by  day. 


HI.]  CRUCIFER^E.  63 

Hildebrand  never  saw  an  insect  on  the  flowers. 
H.  Miiller  saw  them  occasionally  visited  by  the  honey 
bee.  In  F.  officinalis,  as  in  C.  cava,  the  anther  cap  is 
elastic,  and  on  the  departure  of  the  insect  resumes 
its  original  place.  It  is  interesting  that  in  other 
species  of  each  genus  (none  of  which  however  are 
English),  as  for  instance  C.  ochroleuca  and  F.  spicata, 
the  pillar  formed  by  the  stamens  and  pistil  is  in  a 
state  of  tension,  but  is  retained  in  its  place  by  the 
two  petals  forming  the  cap.  These  are  as  it  were 
locked  together,  but  when  once  separated  by  the  pres- 
sure of  the  bee,  the  pillar  formed  by  the  stamens  and 
pistil  is  set  free,  and  springs  up,  thus  dusting  the 
insect.  This  process  only  happens  once  in  each 
flower.  Though  these  species  are  not  British,  I  men- 
tion this  here,  because  we  shall  find  a  very  similar 
process  in  some  of  the  Leguminosae  (p.  86),  and  it  is 
most  interesting  to  find  such  a  remarkable  arrange- 
ment thus  repeated  in  very  different  groups. 

CRUCIFER^:. 

4 

The  Wallflower,  Stock,  Cabbage,  Shepherd's  Purse, 
Watercress,  &c.,  belong  to  this  group. 

The  Cruciferse  are  easily  distinguished  from  other 
orders  by  their  four  sepals  and  petals,  and  six  stamens ; 
but  the  genera  into  which  they  are  divided  are  by  no 
means  so  well  marked,  and  are  to  a  great  extent 
distinguished  by  differences  in  the  pods  and  seeds. 
The  general  structure  of  the  flower  is  more  or  less 
similar  throughout  the  order,  but  the  number  and 
position  of  the  honey-glands  differ  in  almost  every 
species.  Hesperis  matronalis  is  one  of  those  plants 


64  *  RESEDACE&,  CISTINE&.  [CHAP. 

which  are  specially  odoriferous  in  the  evenings,  and  is 
therefore  probably  in  most  cases  fertilised  by  moths, 
though  it  is  also  visited  by  day-insects,  as  for  instance 
by  the  hive  bee,  the  white  butterflies  (Pieris  brassier, 
P.  rapi,  and  P.  napt),  Halictus  leucopus,  Andrena 
albicans,  Volucella  pellucens,  Rhingia  rostrata,  &c. 

But  though  the  colour,  honey,  and  scent  of  the 
Cruciferae  have  evident  reference  to  the  visits  of 
insects,  this  order  does  not  offer  so  many  special  and 
specific  adaptations  as  we  shall  meet  with  in  other 
groups  ;  and  the  majority  of  species,  at  any  rate,  ap- 
pear to  have  retained  the  power  of  self-fertilisation. 

RESEDACE^E. 

Flowers  bisexual,  small,  greenish,  sometimes  scent- 
ed irregular.  Sepals  and  petals  4-7.  Stamens  many 
inserted  on  a  broad  disk.  Pistil  one,  with  2-3  stigmas. 

This  order  is  represented  in  Britain  by  one  genus 
Reseda  (the  Mignonette),  containing  three  species. 
In  the  common  garden  mignonette  the  upper  half  of 
the  base  of  the  flower  raises  itself  between  the 
stamens  and  the  sepals  into  a  quadrangular,  perpen- 
dicular plate,  which  is  first  yellowish,  and  after  the 
flower  has  faded,  brown.  It  is  enclosed  in  a  sort  of 
box,  the  three  upper  petals  forming  the  lid.  Its 
hinder  surface  secretes  honey.  The  mignonette  is 
said  to  be  specially  frequented  by  bees  of  the  genus 
Prosopis. 

CISTINE^. 

This  order  contains  only  a  single  British  genus, 
Helianthemum,  with  four  species.  The  flowers  do 


HI.]  VIOLACE&.  65 


not  secrete  honey.  The  stamens  are  numerous.  As 
the  pistil  projects  above  them,  insects,  in  alighting  on 
the  flower,  generally  touch  the  pistil  before  the 
stamens  ;  and  cross-fertilisation  must  therefore  often 
take  place.  At  the  same  time,  if  from  any  cause 
insect-visits  are  deferred,  the  flower  is  almost  sure  to 
fertilise  itself. 

VIOLACE^E. 

This  order  is  limited  in  Europe  to  the  single  genus 
Viola,  of  which  we  have,  according  to  Bentham,  five 
English  species.  Besides  the  showy,  coloured  flowers 
with  which  we  are  all  familiar,  most  of  the  species 
possess  minute  flowers,  which,  however,  produce  abun- 
dance of  seed.  These  appear  later  in  the  year, 
and  are  not  only  much  smaller  than  the  others, 
but  almost  without  petals.  In  fact,  according  to  Ben- 
tham, the  Pansy  ( V.  tricolor)  is  the  only  one  of  our 
English  species  in  which  the  showy  flowers  generally 
produce  seed.  The  presence  of  these  two  totally 
different  kinds  of  flowers  is  a  very  interesting  fact ; 
and  as  the  smaller,  or  as  they  are  called,  "  cleisto- 
gamous"  flowers  are  sufficient  to  reproduce  the 
species,  and  of  course  have  the  advantage  of 
requiring  much  less  expenditure  of  material,  the 
persistence  of  the  showy  ones  can  only,  I  think,  be 
accounted  for  by  the  fact  that  the  ordinary  flowers 
are  useful  in  securing  an  occasional  cross,  as  the 
cleistogamous  flowers  habitually  fertilise  themselves. 

Viola  canina.  The  structure  of  the  coloured  flowers 
is  very  curious,  and  has  been  well  described  by 
Sprengel.  The  petals  are  five  in  number,  and  irregular 
in  form ;  the  median  one  being  produced  into  a 

F 


66 


VIOLA. 


[CHAP. 


hollow  spur  (Fig.  57  /),  the  entrance  to  which  is 
protected  partly  by  the  stigma,  partly  by  two  tufts  of 
hairs,  or  rather  of  delicate  lobular  processes,  situated 
on  the  two  median  petals.  The  stamens  consist  of 
a  short  filament,  to  which  the  anther  is  attached,  and 
a  terminal  membranous  expansion,  while  the  two 


FIG.  57- 


FIG.  58. 


FIG.  57.— Section  of  a  flower  of  Violet  (Viola  canina). 
FIG.  58. — Stamen  of  ditto. 


lower  stamens  also  send  out  each  a  long  spur 
(Fig.  58  ri),  which  lies  within  the  spur  of  the  median 
petal,  and  secretes  honey  at  its  fleshy  end.  The 
terminal  membranous  expansions  of  the  five  stamens 
slightly  overlap  one  another,  and  their  points  touch 
the  pistil,  so  that  they  enclose  a  hollow  space.  The 
pollen  differs  from  that  of  most  insect-fertilised 
flowers,  in  being  drier,  and  more  easily  detached 
from  the  anthers ;  consequently,  when  the  latter 


in.]  VIOLA.  67 

open,  the  pollen  drops  out ;  and  as  the  flower  is 
reversed  and  hangs  down,  the  pollen  falls  into  the 
closed  space  between  the  pistil  and  the  membranous 
terminations  of  the  stamens.  The  pistil  is  peculiar, 
the  base  of  the  style  not  being  straight  as  usual, 
but  thin  and  bent  (Fig.  57).  The  stigma  st  is  the 
enlarged  end  of  the  pistil ;  and  shows  several  small 
fleshy  projections.  It  will  be  obvious  from  the  above 
description  that  when  a  bee  visits  the  flower,  her 
head  will  come  in  contact  with  and  shake  the  stigma, 
thus  opening,  as  it  were,  the  box  containing  the 
pollen,  and  allowing  it  to  fall  on  the  head  of  the  bee. 
It  is  thus  carried  away,  and  some  can  hardly  fail  to 
be  deposited  on  the  stigma  of  the  next  violet  which 
the  bee  visits. 

Sprengel,  in  his  description  of  V.  odorata,  gives  the 
following  list  of  questions  and  answers  as  regards  this 
species  ;  passing  over,  however,  the  more  general  points, 
such  as  the  secretion  of  honey,  the  colour  of  the  corolla, 
the  radiating  lines  on  the  petals,  and  the  smell 

1.  Why  is   the    flower   situated  on   a   long  stalk^ 
which  is  upright,  but  curved  downwards  at  the  free 
end  ? — In   order   that   it   may  hang   down ;    which, 
firstly,  prevents   rain   from   obtaining   access   to  the 
honey ;  and,  secondly,  places  the  stamens  in  such  a 
position  that  the  pollen    falls   into   the   open  space 
between  the  pistil  and  the  free  ends  of  the  stamens. 
If  the  flower  were  upright,  the  pollen  would  fall  into  .the 
space  between  the  base  of  the  stamen  and  the  base  of 
the  pistil,  and  would  not  come  in  contact  with  the  bee. 

2.  Why  does  the  pollen  differ  from  that  of  most 
other    insect-fertilised    flowers  ? — In    most    of    such 
flowers   the   insects   themselves    remove    the   pollen 

F   2 


VIOLA.  [CHAP. 


from  the  anthers ;  and  it  is  therefore  important  that 
the  pollen  should  not  easily  be  detached  and  carried 
away  by  the  wind.  In  the  present  case,  on  the  con- 
trary, it  is  desirable  that  it  should  be  looser  and  drier, 
so  that  it  may  easily  fall  into  the  space  between  the 
stamens  and  the  pistil.  If  it  remained  attached  to 
the  anther,  it  would  not  be  touched  by  the  bee,  and 
the  flower  would  remain  unfertilised. 

3.  Why  is  the  base  of  the  style  so  thin  ? — In  order 
that  the  bee  may  be  more  easily  able  to  bend  the  style. 

4.  Why  is  the  base  of  the  style  bent  ? — For  the 
same   reason.     The  result  of  the   curvature   is   that 
the  pistil  is  much  more   easily  bent  than  would  be 
the  case  if  the  style  were  straight. 

5.  Finally,   why    does    the   membranous    termina- 
tion of  the  upper  filament  overlap  the  correspond- 
ing portions  of  the  two  middle  stamens  ? — Because 
this  enables  the  bee  to  move  the  pistil,  and  thereby 
to  set  free  the  pollen   more  easily  than  would  be  the 
case  under  the  reverse  arrangement. 

In  Viola  tricolor,  the  form  of  the  stigma  is  very 
different  from  that  of  V.  canina^  but  the  reason  of 
the  difference  has  not  been  satisfactorily  explained. 
Mr.  Bennett  considers  that  this  species  is  fertilised  by 
Thrips.  Mr.  Darwin,  however,  has  satisfied  himself 
that  when  bees  are  excluded,  it  is  comparatively 
infertile,  and  he  has  favoured  me  with  the  following 
memorandum  on  the  subject. 

"  When,"  he  says,  "  I  formerly  covered  up  a  fine, 
large,  cultivated  variety,  it  set  only  18  capsules,  and 
most  of  them  contained  very  few  good  seeds,  several 
from  only  I  to  3  ;  whereas  an  equally  fine  uncovered 
plant,  growing  close  by,  produced  105  fine  capsules. 


Hi.]  POLYGALACE^E.  69 

The  few  capsules  which  are  produced  when  insects 
are  excluded  are  probably  due  to  the  curling  up  of 
the  petals  (as  Fermond  and  F.  Miiller  remark)  as 
they  wither,  by  which  process  pollen-grains  adhering 
to  the  papillae  may  be  inserted  into  the  cavity  of  the 
stigma.  The  moth  Plusia  is  said  to  visit  the  flowers 
largely.  Humble-bees  are  common  agents  in  fertil- 
ising these  flowers ;  but  I  have  seen  more  than  once 
a  fly  (Rhyngia  rostratd)  with  the  under  side  of  its 
body,  head,  and  legs  dusted  with  the  pollen  of 
this  plant,  and  having  marked  the  flowers  which 
they  had  visited,  found,  after  a  few  days,  that  they 
had  all  been  fertilised. 

"  It  is  curious  in  this  case,  as  in  many  others,  how 
long  the  flowers  may  be  watched  without  seeing 
one  visited  by  an  insect.  During  one  summer,  I 
repeatedly  watched  some  large  clumps  of  heartsease, 
many  times  daily,  for  a  fortnight,  before  I  saw  a 
humble-bee  at  work.  During  another  summer  I 
did  the  same,  and  then  one  day,  as  well  as  on  two 
succeeding  days,  I  saw  a  dark-coloured  humble-bee 
visiting  almost  every  flower  in  several  clumps  ;  and 
after  a  few  days  almost  all  the  flowers  suddenly 
withered,  and  produced  fine  capsules.  A  certain 
state  of  the  atmosphere  seems  to  be  necessary  for 
the  secretion  of  nectar,  and  as  soon  as  this  occurs,  it 
is  perceived  by  various  insects,  I  presume  by  the 
odour  emitted  by  the  flowers,  and  these  are 
immediately  visited." 

POLYGALACE^E. 

This  order  contains,  according  to  Bentham,  but  one 
British  species,  which,  however,  is  very  common,  the 


POLYGALA. 


[CHAP, 


Milkwort  (Poly gala  vulgaris\  Fig.  59.  The  structure 
of  the  flower  is  curious,  and  was  first  explained  by 
Hildebrand,  whose  account,  however,  does  not  seem 
to  me  entirely  complete  or  satisfactory.  There  are 
five  sepals  (Figs.  60,  61  s  s),  of  which  three  are  small, 
linear,  and  greenish ;  the  other  two  much  larger, 
coloured  like  the  petals,  and  obovate  or  oblong.  The 


FIG.  59.  —PoiygaUi  vulgans. 

petals  form  a  tube  to  the  inside  of  which  the  stamens 
are  attached  in  two  bundles  (Fig.  6 1  a\  and  which 
contains  a  m  a? her  of  white  hairs  pointing  downwards, 
while  near  the  upper  end  are  two  groups  of  finger- 
like  lobes.  The  pistil  (Fig.  61  st)  occupies  the  axis  of 
the  flower,  and  ends  in  a  spoon-shaped  hollow.  The 
short  stamens  lie  just  over  this  hollow,  and  shed  their 
pollen  into  it,  after  which  they  withdraw  a  little  to  the 
side.  Close  behind  the  hollow  is  a  projection  which 


III.] 


CAR  YOPHYLLA  CE^E. 


terminates  in  a  very  viscid  disk.  When  the  proboscis 
of  an  insect  is  forced  down  the  tube  in  search  of 
honey,  it  comes  in  contact  with  this  viscid  disk,  and 
being  thus  rendered  adhesive,  when  it  is  withdrawn 
carries  some  of  the  pollen  with  it,  and  thus  conveys 
it  to  the  next  flower,  where  it  is  stripped  off  the 
retreating  proboscis  by  the  edge  of  the  viscid  disk, 


FlG.  60. — Flower  of  Polygala  vulgaris. 


FIG.  &.— Section  of  ditt*. 


and  is  thus  accumulated  in  the  stigmatic  hollow. 
Polygala  vulgaris  is  sometimes  blue  and  sometimes 
pink ;  why  is  this?  It  is,  moreover,  a  variable  species 
in  other  respects,  as  for  instance  in  the  size  and  pro- 
portions of  the  different  leaves.  The  use  of  the 
curious  finger- formed  processes  has  not,  I  think,  been 
satisfactorily  explained. 


CARYOPHYLLACE^:. 


This  is  a  large  family  and  contains  fourteen  British 
genera ;  Dianthus  (the  wild  Pink),  Saponaria,  Silene, 
Lychnis  (Fig.  50),  Sagina,  Cherleria,  Arenaria,  Maen- 


72  PINK,  LYCHNIS.  [CHAP. 

chia,  Holosteum,  Cerastium,  Stellaria  (Fig.  62),  Sper- 
gularia,  Spergula,  and  Polycarpon. 

In  Dianthus,  of  which  we  may  take  D.  deltoides* 
the  Maiden  Pink,  as  an  illustration,  the  stamens 
are  united  with  the  petals  at  the  base,  and  form  a 
yellow,  fleshy,  swelling  which  secretes  honey.  The 
tube  of  the  flower  is  so  narrow,  and  so  nearly  closed 
by  the  stamens  and  pistil,  that  the  proboscis  of 
Lepidoptera  alone  can  reach  the  honey,  though  flies 
and  other  insects  visit  it  for  the  pollen.  The  upper 
surface  of  the  flower  forms  a  flat  disk,  pink  or  spotted 
with  white.  The  stamens  are  ten  in  number.  Soon 
after  the  flower  opens,  five  of  them  emerge  from  the 
tube,  ripen,  and  the  anthers  open.  When  they  have 
shed  their  pollen,  the  other  five  do  the  same.  During 
this  period  the  pistil  is  concealed  in  the  tube,  but 
after  the  anthers  have  ripened  and  shed  most  of  their 
pollen,  it  also  emerges  and  the  two  long  stigmas 
expand  themselves.  These  two  stages  have  been 
already  referred  to  (see  Figs.  30  and  31).  Under 
these  circumstances  the  butterflies  can  hardly  fail  to 
carry  the  pollen  from  the  anthers  of  young  flowers 
to  the  stigmas  of  older  ones.  Flies  also  visit  this 
species  to  feed  on  the  pollen,  and  though  they  cannot 
obtain  any  nourishment  from  flowers  in  the  latter 
condition,  still  they  sometimes  come  to  them,  appa- 
rently by  mistake,  and,  must  therefore  occasionally 
fertilise  them.  This  species  appears  to  have  lost  the 
power  of  self- fertilisation. 

I  have  already  referred  to  Lychnis  vespertina  and 
L.  diurna  in  the  first  chapter.  L  Gitkago,  like 
Dianthus,  is  adapted  to  butterflies.  It  agrees  with 
the  flowers  of  that  genus  in  the  narrowness  of  the 


in.]  SILENE,  STELLARIA.  73 

tube,  in  the  position  of  the  honey,  and  in  being 
distinctly  proterandrous. 

Silene  nutans  is  a  very  interesting  species.  The 
life  of  the  flower  lasts  three  days,  or  rather,  three 
nights.  The  first  evening  it  opens  towards  dusk, 
becomes  very  fragrant,  and  expands  its  petals, 
while  five  of  the  ten  anthers  burst  and  expose  their 
pollen.  So  it  remains  all  night.  Towards  morning, 
however,  the  odour  ceases,  the  petals  shrivel  and  roll 
up,  the  stamens  drop,  and  the  flower  looks  dead. 
The  next  evening,  however,  it  again  opens,  again 
emits  a  sweet  scent,  and  the  second  series  of  five 
anthers  open.  Towards  morning  it  again  loses  its 
smell,  and  again  closes.  The  third  evening  it  opens 
as  before,  but  now  the  pistil  has  come  to  maturity, 
and  the  stigmas  occupy  the  position,  which  the  two 
previous  nights  had  been  filled  by  the  anthers. 

In  Silene  inflata  (the  Bladder  Campion)  there  are, 
according  to  Axell  ("  Om  Anord.  for  de  Fan.  Vax.  Bef." 
p.  46),  three  kinds  of  flowers  ;  some  with  stamens 
only,  some  with  a  pistil  only,  some  with  both. 

In  Stellaria  graminea  (Fig.  62)  the  honey-glands 
are  situated  at  the  base  of  the  five  outer  stamens. 
The  flowers  pass  through  three  stages ;  firstly ,  that 
in  which  the  five  outer  stamens  are  mature,  and 
incline  towards  the  middle  of  the  flower.  In  the 
second,  the  five  inner  stamens  are  mature.  Lastly, 
the  stigmas  rise  and  expand  themselves,  while  the 
stamens  gradually  shorten  and  shrivel  up.  Before 
this  is  accomplished,  however,  the  stigmas  have 
curled  over  and  come  into  contact  with  the  anthers, 
so  that  if  the  visits  of  insects  are  deferred,  the  flower 
fertilises  itself.  Stellaria  Holostea  is  more  conspicuous, 


74 


STELLARIA,  CERASTIUM. 


[CHA?. 


and  the  three  periods  are  more  distinct,  but  the  flower 
still  retains  the  power  of  self-fertilisation. 

In  5.  media  (the  Chick  weed)  the  flowers  are  less 
conspicuous,  and  the  five  inner  stamens  are  often 
rudimentary  or  entirely  absent ;  nay,  two  of  the 
five  outer  'ones  are  sometimes  also  rudimentary, 
though  their  honey-gland  is  always  present.  It  is 
also  proterandrous. 


FIG.  62. — Stellana  grammea. 

Cerastium  arvense  agrees  with  Stellar ia  Holostea  in 
the  position  of  the  honey-glands,  and  in  the  sequence 
of  development  of  the  stamens  and  pistil.  It  is 
much  frequented  by  insects.  In  other  forms  of  this 
genus,  as,  for  instance,  in  C.  semidecandrum  (which 
Bentham  regards  as  a  variety  of  C.  vulgatum),  the 
flowers  are  less  conspicuous,  and  in  consequence  the 
visits  of  insects  are  fewer,  the  priority  of  the  stamens 
is  less  marked,  and  self-fertilisation  is  more  frequent. 


in.]  STELLARIA,  HYPERICACE^E.  75 

The  inner,  honeyless  stamens,  which  in  Stellaria 
minor  are  often  wanting,  are  in  this  form  always 
rudimentary,  according  to  Miiller,  while  Bentham 
says  that  the  whole  number  is  often  present.  Both 
observers  are  so  correct,  that  there  is  probably  a 
difference  in  this  respect  between  English  and  German 
specimens. 

Sagina  nodosa  is  also  proterandrous  ;  while  Mceh- 
ringia  trinervia  is,  on  the  contrary,  proterogynous. 

The  Caryophyllaceae  constitute  therefore  a  very 
interesting  and  varied  order.  As  a  general  rule  the 
more  conspicuous  the  flower,  the  more  decided  the 
dichogamy  ;  conversely,  the  smaller  the  flowers,  and 
therefore  the  less  frequent  the  visits  of  insects,  the 
greater  are  the  chances  of  self-fertilisation.  The 
order  also  presents  us  with  an  interesting  series 
commencing  with  open-flowered  species,  the  honey 
of  which  is  accessible  even  to  beetles,  and  short- 
tongued  flies,  through  those  which  are  adapted  to 
certain  flies  (Rhingia)  and  Bees ;  to  the  species  of 
Diantkus,  Saponaria,  and  Lychnis  Githago,  the  honey 
of  which  is  accessible  to  Lepidoptera  only. 

HYPERICACEiE. 

There  is  only  one  British  genus  of  this  order,  the 
well-known  Hypericum,  which,  however,  contains 
eleven  British  species.  The  stamens  are  united  into 
bundles  ;  the  styles  are  generally  three  in  number, 
alternating  with  the  bundles  of  stamens.  In  the 
large-flowered  Hypericum,  however  (H.  calycinum), 
the  styles  are  five  in  number,  and  are  raised  above 


76  LINAGES.  [CHAP. 

the  stamens.  Hypericum  perforatum  (the  Common 
Hypericum)  is  so  named  from  the  remarkable  pecu- 
liarity of  having  the  leaves  studded  by  pellucid 
dots ;  and  several  of  the  species  have  the  sepals 
fringed  with  black  or  red  glands.  The  flowers 
belonging  to  this  genus  are  generally  very  con- 
spicuous, both  from  their  bright  yellow  colour  and 
from  their  association  in  clusters.  They  secrete  no 
honey,  but  are  frequently  visited  by  insects,  partly 
for  the  sake  of  the  pollen,  partly  perhaps  in  a  vain 
search  for  honey.  Under  these  circumstances,  cross- 
fertilisation  must  frequently  occur,  though  no  doubt 
the  flowers  often  fertilise  themselves. 


LINAGES. 

This  order  contains  two  British  genera,  Linum,  and 
Radiola  ;  the  former  is  the  well-known  flax,  the  latter 
a  minute  erect  annual,  which  grows  on  heaths  and 
sandy  places.  The  genus  Linum  contains  five  British 
species,  which  differ  considerably  in  the  size  of  their 
flowers,  from  the  beautiful,  blue,  common  flax,  to  the 
minute  L.  catharticum,  the  petals  of  which  are  but 
little  longer  than  the  calyx,  and  which  yet  secretes 
honey,  from  five  minute  glands  situated  on  the  outer 
side,  and  near  the  base  of  the  five  stamens.  It  is 
therefore,  in  spite  of  its  minute  size,  frequently  visited 
by  insects,  though  in  their  absence  it  is  capable  of 
self-impregnation.  So  far  as  has  been  hitherto 
observed  L.  usitatissimum,  though  differing  so  much 
from  L.  catharticum  in  the  size  of  the  flowers,  agrees 


in.]  LINAGES.  77 

in  general  arrangement,  and  is  also  capable  of  self- 
fertilisation. 

The  crimson  L.  grandiflorum,  on  the  contrary, 
as  Mr.  Darwin  has  shown  (Jour.  Linn.  Soc.y  Feb. 
1863)  presents  two  forms,  which  occur  in  about 
equal  numbers,  and  differ  little  in  structure,  though 
greatly  in  function.  In  the  one  form,  the  column 
formed  by  the  united  styles  and  the  short  stigmas, 
is  about  half  the  length  of  the  whole  pistil  in 
the  other  or  "  long-styled  "  form.  The  stigmas  also 
of  the  short-styled  form  diverge  greatly  from  each 
other,  and  pass  out  between  the  filaments  of  the 
stamens,  thus  lying  within  the  tube  of  the  corolla, 
while  in  the  long-styled  form  the  elongated  stig- 
mas stand  nearly  upright,  and  alternate  with  the 
anthers. 

By  a  series  of  careful  and  elaborate  experiments 
Mr.  Darwin  has  shown  that  this  species  is  almost 
entirely  sterile  with  pollen  of  its  own  form.  He 
repeatedly  placed  pollen  of  long-styled  flowers  on 
the  stigmas  of  the  same  kind,  and  pollen  of  short- 
styled  flowers  on  stigmas  of  short-styled  flowers,  but 
without  effect ;  while  if  pollen  of  a  long-styled  flower 
is  placed  on  a  short-styled  stigma,  or  vice  versd, 
abundance  of  seed  is  produced.  In  short,  the  pollen 
of  the  L.grandiflorum  is  differentiated,  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  is  also  dimorphous,  and  the  differ 
ence  between  the  two  forms  is  more  conspicuous. 


78  MALVACEAE,  TILIACE^E.  [CHAP. 


MALVACEAE. 

Of  this  order  we  have  three  British  genera,  Lava- 
tera,  Althaea  and  Malva,  with  respectively  one,  two, 
and  three  specific  forms.  In  the  intoductory  chapter, 
I  have  already  called  attention  to  the  structure  of  the 
Mallow,  with  especial  reference  to  the  differences 
existing  between  Malva  sylvestris  (Figs.  43  and  45) 
and  M.  rotundifolia  (Figs.  44  and  46).  The  honey 
glands  are  five  in  number,  at  the  base  of  the  flower. 
Althaea  and  Lavatera  are  said  to  agree  in  general 
structure  with  Malva. 


TILIACE^. 

Of  this  order  we  have  in  England  only  one  species, 
the  Common  Lime  (Tilia  Europtza),  which,  however, 
is  not  a  native  species.  The  flowers  are  very  sweet, 
and  great  favourites  with  bees.  Their  abundance 
and  the  size  of  the  tree  render  colour  unnecessary. 
The  honey  is  secreted  by  the  sepals,  and  is  accessible 
even  to  short-lipped  insects ;  while,  as  the  flowers 
hang  down,  it  is  completely  protected  from  rain. 
The  stamens  are  numerous,  but,  as  Hildebrand  has 
pointed  out,  they  have  shed  their  pollen  before  the 
stigma  is  mature,  and  the  flower  is  therefore  incapable 
of  self-fertilisation.  The  visits  of  insects  are  very 
numerous,  and  yet  in  this  country  the  Lime  seldom 
produces  ripe  seed. 


in.]  GERANIACE^E.  79 


GERANIACE.E. 

This  order  contains  four  British  genera  ;  Geranium, 
Erodium,  Oxalis,  and  Impatiens. 

The  genus  Geranium  possesses  a  peculiar  interest 
in  the  history  of  the  present  subject,  because,  as 
Sprengel  tells  us,  the  hairs  in  the  corolla  of  G. 
sylvaticum  (See  p.  i),  attracted  his  attention,  and  led 
to  the  researches  which  are  so  well  described  in  his 
interesting  work. 

The  flowers  of  the  species  of  Geranium  differ  con- 
siderably in  size  :  the  larger  flowered  species,  such  as 
G.  sanguineum,  G.phceum,  G.pratense(F\gs.  40  and  42), 
and  G.  sylvaticum,  being  perennial,  the  smaller  ones 
annual,  or  biennial.  Geranium  palustre,  with  which  G. 
firatense,  G.  sylvaticum,  and  G.  sanguineum,  closely 
agree,  is  taken  by  Sprengel  as  a  type  of  the  large 
flowered  species.  The  honey  glands  are  five  in  number, 
situated  near  the  base  and  at  the  outer  side  of  the 
outer  stamens ;  and  are  effectually  protected  by 
fringes  of  hairs  arranged  just  above  them,  so  as  to 
prevent  any  rain  from  obtaining  access  to  them. 

The  stamens  are  ten  in  number,  of  which  one  half 
are  longer  than  the  remainder  :  the  pistil  terminates 
in  five  lobes,  the  upper  surfaces  of  which  constitute 
the  stigmas.  The  flower  opens  widely  by  day,  hangs 
down,  on  the  contrary,  and  partially  closes  at  night. 
The  petals  are  ornamented  by  purple  lines,  which 
serve  as  honey-guides,  pointing  to  the  honey  glands. 
When  the  flower  first  opens  (Fig.  41)  the  stigma  is 
immature,  and  the  five  lobes  are  closely  pressed 


8o  GERANIUM.  [CHAP. 

together  (b),  so  that  the  stigmatic  surfaces  are  not  ex- 
posed. Nor  do  they  separate  (Fig.  42),  or  become 
susceptible  of  fertilisation,  until  after  the  anthers  have 
all  shed  their  pollen.  The  flower,  in  fact,  passes 
through  three  distinct  stages  :  first,  the  five  outer 
stamens  open,  and  shed  their  pollen  ;  then  the  five 
inner  ones;  and  lastly,  after  the  pollen  is  all  shed, 
the  stigmatic  surfaces  expand  and  attain  maturity. 
The  flower  therefore  cannot  fertilise  itself. 

On  the  other  hand,  in  the  smaller  species  of 
Geranium  the  stigmas  come  to  maturity  before  the 
stamens  have  shed  all  their  pollen ;  hence  the  visits 
of  insects  are  not  so  necessary,  and  hence,  probably, 
the  smaller  size  of  their  flowers.  (See  anti  p.  48.) 

There  is  also  another  difference,  to  which  I  will  call 
attention.  G.  Robertianum  does  not  possess  the 
fringes  of  hairs  by  which  the  honey  is  in  G.  sylvaticum 
protected  against  the  access  of  rain  ;  on  the  contrary, 
the  petals  are  entirely  glabrous.  This  difference  is 
apparently  connected  with  the  form  of  the  flower, 
which  is  less  open  than  is  the  case  with  G.  sylvaticum 
On  the  contrary,  it  forms  a  distinct  tube,  the  entrance 
to  which  is  sufficiently  protected  against  rain  by  the 
stamens  and  pistil. 

The  smaller  flowered  species  moreover  offer  remark- 
able differences  among  themselves.  Thus  G.  molle 
and  G.  pusillum  are  at  first  sight  very  similar,  and,  as 
Bentham  observes,  are  no  doubt  sometimes  confused  ; 
yet  they  differ  remarkably.  When  G.  molle  first 
opens,  the  pistil  is  immature,  and  the  stigmatic 
surfaces  are  closely  appressed.  The  outer  anthers 
then  begin  to  open  one  after  the  other,  so  that  the 


in.]  SIZE  OF  COROLLA.  81 

flower  is  for  some  time  merely  male.  Before,  however, 
the  first  five  anthers  have  completely  shed  their 
pollen,  the  stigmatic  surfaces  arrive  at  maturity  and 
expand  ;  so  that,  during  the  second  period,  the  flower 
is  both  male  and  female. 

In  G.  pusillum,  on  the  contrary,  when  the  flower 
first  opens,  the  stigmatic  surfaces  are  mature  and 
expanded,  but  the  anthers,  are  not  yet  ripe ;  the 
flower  consequently  is  merely  female,  and  can  only 
be  fertilised  by  pollen  from  an  older  flower.  Soon, 


FIG.  63. — Young  flower  of  Tropceolum  mayor.     Neither  the  anthers  nor  the  stigma 
are  yet  mature. 


however,  the  anthers  of  the  five  outer  stamens  ripen, 
and  open,  so  that  the  flower  is  both  male  and 
female.  Another  remarkable  difference  is,  that  in 
G.  pusillum,  as  in  the  allied  genus  Erodium,  the  five 
inner  stamens  produce  no  pollen. 

In  the  genus  Erodium,  as  in  G.  pusillum,  the  five 
inner  stamens  are  rudimentary,  and  produce  no  pollen. 
The  stamens  ripen,  however,  before  the  stigma,  though 
if  the  visits  of  insects  be  deferred,  the  flower  is 
capable  of  self-fertilisation. 

G 


82  TROP^EOLUM.  [CHAP. 

To  this  family  also  belongs  Tropaeolum,  the  com- 
mon Nasturtium  of  our  gardens.  Here  the  honey  is 
contained  in  a  long  spur.  The  flower  passes  through 
three  well  marked  stages  (Figs.  63—65).  When  it 
first  opens,  as  shown  in  Fig.  63,  the  anthers  (a)  are 
unripe,  the  pistil  (/)  is  short  and  immature.  Soon, 
however,  one  of  the  anthers  ripens,  opens,  and 
turns  up,  as  shown  in  Fig.  64  a,  a,  so  as  to  stand 
directly  in  front  of  the  opening  to  the  tube;  a 
humble  bee,  therefore,  or  other  insect  of  similar  size, 


FIG.  64. — Flower  of  Trofeeolum  major  in  the  second  stage.     Some  of  the  anthers 
are  now  mature,  and  stand  upright  in  front  of  the  entrance  to  the  spur. 

visiting  the  flower  for  the  sake  of  its  honey,  could 
not  fail  to  rub  some  of  the  pollen  off  on  to  her  breast. 
Shortly  afterwards  a  second  stamen  ripens,  and 
assumes  the  same  position,  with  the  same  result,  and 
the  rest  gradually  follow.  In  flowers  which  I  have 
watched,  this  process  occupies  from  three  to  seven 
days,  by  which  time  the  stamens  have  all  come  to 
maturity,  after  which  the  anthers  drop  off,  and  the 
filaments  turn  down  as  shown  in  Fig.  65,  so  as  to  be 
well  out  of  the  way.  It  is  now  the  turn  of  the  pistil, 


in.]  OXALIS,  83 

which  in  the  meantime  has  elongated,  and  assumes  the 
position  which  the  stamens  had  successively  occupied  ; 
the  result  of  which  is,  that  a  bee  which  had  pre- 
viously visited  a  younger  flower  and  dusted  her 
breast  with  pollen  could  not  fail  to  deposit  some  of 
the  pollen  on  the  stigma.  It  will  be  observed  that 
the  lines  on  the  flower  as  usual  point  to  the  honey. 
The  three  lower  petals  bear  a  number  of  lanceolate 
processes,  which,  as  Sprengel  has  pointed  out,  serve 


FlG»  65.—  Flower  of  Tropaolum  major  in  the  third  stage.  The  anthers  have  all  shed 
their  pollen,  and  the  pistil  now  occupies  the  position  in  front  of  the  entrance  to 
the  spur. 

to  prevent  rain  from  obtaining  access  to  the  tube, 
and  also  perhaps  in  guiding  the  insects,  so  as  to 
bring  their  breasts  truly  against  the  anther  or  stigma. 
The  calyx,  which  from  the  position  of  the  flower  is 
almost  as  much  exposed  as  the  corolla,  is  of  the 
same  colour  as  the  petals. 

Oxalis  acetosella  is  one  of  the  species  which  produces 
"  cleistogamous "  flowers  (see  anti  p.  36).  This  was 
first,  I  believe,  observed  by  Michelet  (Bull.  Soc.  Bot. 
de  France,  1860,  p.  465). 

G   2 


84  IMPATIENS.  [CH.  m. 

Hildebrand  has  shown  that  of  the  foreign  species 
of  Oxalis  some  are  dimorphous,  some  trimorphous, 
This  is,  however,  not  the  case  with  either  of  our 
English  species,  and  I  will  therefore  postpone  any 
remarks  on  this  curious  arrangement  until  we  come 
to  some  of  the  English  species  in  which  it  occurs. 

Impatiens  noli  me  tangere  is  proterandrous,  and  the 
larger  flowers  cannot  fertilise  themselves.  This  species, 
however,  also  produces  cleistogamous  flowers.  (Mohl. 
"  Bot.  Zeit,"  1863.  Bennett,  "  Linn.  Jour.,"  vol.  xiii.) 
The  seed  capsules,  when  ripe,  burst  open  if  touched. 


DROSERA  KOTUN'ttlFOLlA. 

C  H  AP  T  E  R     IV. 

CALYCIFLOR^i. 


THIS  subclass  contains  those  Dicotyledons  in  which 
the  perianth  is  double,  the  petals  separate,  and  the 
stamens  either  perigynous  or  epigynous. 


CELASTRACE^:. 

This  order  contains  orre  British  species,  the  Common 
Spindle  Tree,  Euonymus  Europeans.  The  flowers 
secrete  honey,  and  are  frequented  by  Diptera  (Flies) 
and  Hymenoptera,  especially  the  former.  They  are 
proterandrous. 

RHAMNACE^:. 

The  Vine  and  the  Virginian  Creeper  belong  to  this 
order ;  but  we  have  only  one  British  genus,  Rhamnus, 


36  RHAMNACE&,  LEGUMINOS&.          [CHAP. 

(the  Buckthorn)  with  two  species,  Rhamnus  cathar- 
ticus  (the  common  Buckthorn  and  Rhamnus  franguld), 
the  Alder  Buckthorn.  The  two  species  differ  con- 
siderably. In  Rkamnus  frangula,  the  sepals,  petals 
and  stamens  are  five  in  number ;  the  petals  are 
very  small.  The  stamens  open  before  the  stigma 
is  fully  developed,  and  probably  even  before  it  is 
capable  of  fertilisation.  The  pistil  is  in  the  centre, 
and  insects  which  visit  the  flower  for  the  sake  of 
the  honey  necessarily  touch  the  stamens  with  one 
side  of  the  proboscis  and  the  pistil  with  the  other. 
They  must,  therefore,  often  convey  the  pollen  from 
one  flower  to  another.  In  the  absence  of  insects, 
however,  R.  frangula  is  capable  of  self-fertilisation. 

In  R.  catharticusy  on  the  contrary,  the  flowers  have 
four  petals,  and  are  dioecious ;  the  male  flowers  have  a 
rudimentary  pistil,  and  the  female  flowers  bear  minute 
stamens.  The  individual  flowers  are  very  small,  they 
are  rendered  conspicuous  by  being  associated  in 
clusters,  while  those  of  R.  frangula  are  in  twos  or 
threes. 

R.  lanceolatus,  which,  however,  is  not  an  English 
species,  has  been  shown  by  Mr.  Darwin  to  be  dioecious 
(Jour.  Linn.  Soc.,  v.  vi.,  1862,  p.  95.) 


LEGUMINOS^E. 

This  is  a  very  extensive  order,  containing  eighteen 
British  genera ;  the  Peas,  Vetches,  Brooms,  Clovers, 
Furze,  Sac.  belong  to  it. 

It    is    probable   that   all   flowers   which    have  an 


IV.] 


LOTUS. 


irregular  corolla  are  fertilised  by  insects.  The  advan- 
tage of  the  irregularity  is  that  it  compels  the  insects 
to  visit  the  nectary  in  one  particular  manner.  In  the 
present  group  the  result  is  that  insects  necessarily 
alight  on  a  particular  part  of  the  flower,  when  their 
weight  in  many  cases  causes  certain  mechanical 
effects  by  which  the  pollen  is  transferred  to  the  body 
of  the  insect,  and  thus  carried  from  one  flower  to 


FIG.  66. — Lotus  corniculatus. 


another.  The  corolla  in  the  Leguminosae  consists  of 
five  petals ;  an  upper  one,  usually  called  the  "  Stan- 
dard," two  lateral  ones,  or  "  Wings  ; "  and  two  lower 
ones,  united  at  their  edges  into  a  boat-shaped  organ, 


or 


keel." 


The  bases  of  the  stamens  coalesce  into  a  hollow 
tube  (Fig.  70  and  71  t)  the  inner  walls  of  which,  at 
their  base,  secrete  honey  in  some  species,  though  not 


LOTUS. 


[CHAP. 


in  all.     In  the  former,  one  or  more  of  the  stamens  is 
detached,  as  in  the  Lotus  (Fig.  70  b\  or  atrophied,  so  as 


FIG.  67. 


FIG.  68. 


FIG.  71. 

FIG.  67. — Flower  of  Lotus  corniculatus  seen  from  the  side  and  in  front. 

FIG.  68. — Ditto,  after  removal  of  the  standard. 

FIG.  69.  —Ditto,  after  removal  of  the  standard  and  wings. 

FIG.  70. — Ditto,  after  removal  of  one  side  of  the  keel. 

FIG.  71.  ^Terminal  portion  of  Fig.  70  more  magnified. 

et  entrance  to  the  honey;  d,   the  free  stamen;    c,   the  place  where  the 

wings  lock  with  the  keel ;  / ',  expanded  ends  of  stamens  ;  /,  filaments  of 

stamens  ;  gt  tip  of  keel ;  po,  pollen  ;  st,  stigma. 

to  leave  a  space  through  which  bees  can  introduce 


iv.]  LOTUS.  89 

their  proboscis  into  the  tube.  In  those  species  which 
do  not  secrete  honey  this  is  unnecessary,  and  the 
stamens  are  all  fully  developed  and  united. 

In  the  Common  Birdsfoot  Trefoil  (Lotus  cornicula- 
tus)  the  anthers  burst  and  emit  their  pollen  before 
the  flower  opens,  and  indeed  before  the  petals  have 
attained  their  full  size.  At  this  time  the  ten  stamens 
form  two  groups,  five  of  them  being  longer  than  the 
others  ;  but  by  the  time  the  flower  opens  they  arc 
all  of  the  same  length,  though  the  five  outer  ones  are 
somewhat  swollen  at  the  end  ;  a  difference  which  sub- 
sequently becomes  still  more  marked.  The  pointed 
end  of  the  keel  is  now  filled  by  a  mass  of  pollen 
(Fig.  70  and  71  po),  while  the  anthers,  having  dis- 
charged their  contents,  commence  to  shrivel  up.  The 
free  ends  of  the  five  outer  stamens  continue,  however, 
to  increase  in  size  ;  so  that,  with  the  pollen  mass,  they 
completely  fill  up  the  cavity  of  the  keel.  When  the 
flower  opens  the  pistil,  stamens,  and  pollen  occupy 
the  position  shown  in  Figs.  70  and  71. 

The  five  inner  stamens,  having  discharged  their 
pollen  have  become  useless,  shrivelled  up,  and  lie  in 
the  broader  part  of  the  keel ;  the  five  outer  ones,  on 
the  contrary  (Fig.  70  e),  which  still  have  an  important 
function  to  perform,  lie  behind  the  pollen  mass,  and 
keep  it  in  its  place. 

Insects  do  not  generally  alight  directly  on  the  keel, 
but  rather  on  the  wings,  which  are  more  conveniently 
situated  ;  the  two,  however,  are  relatively  so  arranged, 
that  when  a  bee  alights  on  the  wings,  she  presses 
down  the  keel,  which  is  locked  with  the  two  wings  by 
a  projection  and  corresponding  depression,  as  shown 


90  SWEET  PEA.  [CHAP. 

in  Figs.  68  and  69  c  ;  thus  a  portion  of  the  pollen  and 
also  the  tip  of-the  pistil  are  forced  out  at  the  point 
of  the  keel,  and  against  the  breast  of  the  bee,  until 
on  the  removal  of  the  pressure  the  elasticity  of  the 
flower  causes  the  various  organs  to  resume  their 
former  position  ;  an  obvious  advantage,  which  pre- 
vents the  pollen  from  being  wasted.  The  union  of  the 
stamens  at  their  base  has  probably  reference  to  this,  as 
Sprengel  has  suggested.  From  the  manner  in  which 


FIG.  72.— Flower  of  Sweet  Pea,  in  its        FIG.    73.— Ditto.     The    wings    are    de- 
natural  position.  pressed,  the  stamens  and  pistil  exposed. 

these  flowers  are  evidently  arranged  with  a  view  to 
the  visits  of  insects,  we  can  hardly  doubt  but  that 
these  visits  are  of  importance  to  the  plant, 

In  the  Sweet  Pea  (Figs.  72  and  73),  on  account  of 
its  larger  size  the  action  is  still  more  easily  visible. 
Fig.  72  represents  a  flower  in  the  natural  position. 
Now  if  the  two  ends  of  the  wings  be  taken  between 
the  finger  and  thumb,  and  pressed  down,  so  as  to 
imitate  the  effect  produced  by  the  pressure  of  an 
insect,  the  keel  is  depressed  with  the  wings,  while 


iv.]  CLOVER,  ANTHYLLIS,  ONONIS.  91 

the  pistil  and  stamens  are  thus  partly  uncovered,  as 
shown  in  Fig.  73.  When  the  pressure  is  removed, 
the  flower  resumes  its  former  position. 

Trifolium  repens  (the  White  Clover)  agrees  with 
Lotus  in  its  general  structure,  but  is  somewhat 
simpler.  The  wings  are  actually  united  to  the  keel  at 
one  point.  In  T.  pratense  the  flowers  are  longer,  and 
the  honey  is  only  accessible  to  those  bees  which  have 
a  very  long  proboscis.  As  in  other  such  cases,  however, 
Bombus  terrestris  obtains  access  to  it  by  eating  a  hole 
through  the  side  of  the  flower.  According  to  Darwin 
this  species  is  only  fertilised  by  humble  bees,  but 
Delpino  disputes  this.  Trifolium  subterraneum  has 
small  cleistogamous  flowers  (Mohl.  Bot.  Zeit.,  1863) 
besides  the  usual  ones. 

Anthyllis  vulneraria  also  agrees  with  Lotus  in  its 
general  arrangement.  The  tube  of  the  flower  is,  how- 
ever, elongated  ;  and  in  consequence,  this  species  is 
only  visited  by  bees  with  long  tongues.  In  the  young 
flower,  though  the  pistil  is  in  the  keel,  and  neces- 
sarily in  contact  with  the  pollen,  H.  Miiller  has 
observed  that  the  stigma  is  dry,  arid  that  no  pollen 
adheres  to  it.  Subsequently,  however,  when  most,  or 
all,  of  the  pollen  has  been  removed,  the  stigma 
becomes  sticky,  and  pollen  adheres  closely  to  it. 

In  Ononis  (the  Restharrow)  the  general  arrange- 
ment is  very  similar.  There  are,  however,  several 
important  differences.  Ononis  does  not  secrete  honey, 
and  consequently  there  is  no  need  for  the  separation 
of  the  upper  stamen,  which  in  this  genus  is  attached 
to  the  rest.  Again,  in  Ononis  all  the  stamens  are 
thickened  at  the  end  ;  the  outer  ones,  however,  much 


92  ONOBRYCHIS,  GENISTA.  [CHAP, 

more  so  than  the  inner  ones.  The  inner  ones,  on  the 
contrary,  produce  much  more  pollen  than  the  others ; 
a  difference  of  function  which  is  even  more  marked 
in  the  Lupins. 

Ononis  is  exclusively  fertilised  by  bees,  and  H. 
Miiller  has  repeatedly  seen  male  bees  visiting  this 
species  in  a  vain  search  for  honey. 

Onobrychis  sativa  (the  Common  Sainfoin)  agrees  with 
Trifolium  repens  (Clover)  in  its  general  structure ;  but 
the  wings  are  greatly  reduced  in  size  and  appear  to 
serve  only  in  preventing  the  honey  being  reached  from 
the  side,  or  at  least  in  rendering  this  more  difficult. 
This  species  is  sufficiently  conspicuous,  and  as  the 
honey  is  accessible  even  to  insects  with  a  short  pro- 
boscis, it  is  much  visited.  When  mature,  the  stigma 
projects  I  to  ij  m.  beyond  the  keel,  and  according 
to  H.  Miiller  the  flower  has  lost  the  power  of  self- 
fertilisation. 

In  Genista  tinctoria  the  ten  anthers  lie  in  two  dis- 
tinct rows.  While  the  flower  is  still  in  the  bud,  the 
four  upper  anthers  of  the  outer  row  are  already  on  the 
point  of  opening,  while  those  of  the  inner  circle  have 
not  nearly  reached  their  full  size.  These  four  anthers 
now  open  and  shed  their  pollen  into  the  space  at  the 
apex  of  the  keel,  after  which  they  shrivel  up.  The 
fifth,  although  it  has  attained  its  full  size,  remains 
closed.  The  next  process  is  that  this  anther  and 
those  of  the  second  row  also  open,  and  the  pollen 
occupies  the  end  of  the  keel  between  the  anthers  and 
the  stigma,  as  in  Lotus.  While,  however,  in  Lotus 
when  the  insect  leaves  the  flower  and  the  pres- 
sure is  thus  removed,  the  keel  resumes  its  position, 


iv.]  FURZE,  93 

and  the  stamens  and  pistil  are  again  protected  ;  in 
Genista  tinctoria,  on  the  contrary,  the  flower  opens 
once  for  all.  The  keel  is  at  first  nearly  parallel  to 
the  standard  (Fig.  74).  This  position  is,  however, 
one  of  tension  ;  the  keel  is  retained  in  it  by  the  union 
of  its  upper  margins,  which  inclose  and  retain  the 
curved  pistil  which  presses  against  them  like  a  spring. 
The  sides  of  the  keel  have  near  the  base  a  projecting 
lobe  (Fig.  76  m),  which  locks  with  one  at  the  corre- 
sponding part  of  the  wing.  When  an  insect,  alighting 
on  the  flower  presses  open  the  keel  in  search  of  pollen, 
as  soon  as  the  curved  end  of  the  pistil  is  set  free,  it 


FIG.  74. — Flower  of  Genista  tinctorta  unopened. 

FIGS.  75,  76. — Ditto,  opened,  std,  standard ;  iv,  wing  ;  k,  keel ;  m,  projection  on  keel. 


springs  up  with  a  jerk,  the  keel,  on  the  contrary, 
springs  back  (Figs.  75  and  76),  and  the  pollen  is  ejected 
in  a  shower.  It  appears  that  the  flowers  do  not  open 
of  themselves  if  insects  are  prevented  from  visit- 
ing them  (Henslow,  your.  Linn.  Soc.t  v.  x.  p.  468). 

Genista  tinctoria  contains  no  honey,  and  yet  it  is 
visited  by  several  insects  which  do  not  consume  pollen. 

The  flowers  of  the  Common  Furze  (Ulex  Europceus] 
agree  in  essentials  with  those  of  the  preceding  species. 
The  calyx,  however,  is  larger,  and  coloured ;  the 
wings  are  longei  in  proportion  and  project  beyond  the 


94  BROOM,  MEDIC  AGO.  [CHAP. 

keel.  They  also  lock  at  the  base  with  the  keel,  and 
when  they  are  pressed  downwards  the  flower  bursts 
open.  The  Furze  has,  like  Cytisus  and  the  Broom, 
on  the  outer  part  of  the  staminal  lobe  a  honey- 
containing  tissue. 

In  the  Laburnum,  the  tip  of  the  pistil  is  protected 
from  its  own  pollen  by  a  ring  of  close  hairs ;  when, 
however,  the  pistil  has  grown  to  the  very  point  of 
the  keel,  these  hairs  shrivel  and  turn  outwards,  so  as 
to  expose  the  tip  of  the  pistil,  which  thus  comes  in 
direct  contact  with  the  breast  of  any  bee  which  may 
alight  on  the  flower. 

In  the  Broom  (Sarothamnus  scoparius]  the  flowers 
also  explode.  If,  however,  the  bee  alights  on  a  newly- 
opened  blossom,  the  shorter  stamens  only  emerge 
and  dust  the  abdomen  of  the  insect.  If,  on  the  con- 
trary, the  flower  is  a  day  or  two  older,  the  pistil  and 
longer  stamens  spring  out,  and  the  hairs  on  the  pistil 
deposit  pollen  on  the  bee's  back.  The  pistil  gradually 
curls,  and  the  stigmatic  surface  turns  up,  so  as  to 
stand  close  to  the  anthers  of  the  shorter  stamens. 
In  this  position  it  is  so  placed  that  it  would  come  in 
contact  with  the  abdomen  of  the  bee.  "  Thus,"  says 
Mr.  Darwin,  "both  the  upper  and  lower  surface  of 
the  bee  get  dusted  with  pollen,  which  will  be  trans- 
ferred to  the  stigma  at  two  different  periods."  (Linn. 
Jour.  v.  ix.  p.  358.) 

In  Medicago  sativa,  as  in  Genista  and  the  Broom, 
the  flowers  open  once  for  all ;  but  the  elastic  power 
is  confined  to  the  upper  stamens.  In  the  Broom  and 
in  Genista,  the  resistance  is  obtained  by  the  union  of 
the  upper  edges  of  the  keel.  These  are  also  united 
in  Medicago,  but  even  if  they  are  separated  no  ex- 


IV.]  PEA,  SCARLET  RUNNER.  95 

plosion  takes  place;  the  flower  being  still  locked 
together  by  four  processes,  two  of  which  point  forwards 
and  two  backwards.  These  fit  so  beautifully  that 
the  proboscis  of  a  humble  bee  is  sufficient  to  unlock 
them,  and  release  the  stamens  ;  though,  according  to 
Henslow,  (Linn.  Jour.  1866,  p.  328)  the  hive  bee  is 
unable  to  do  so.  Hildebrand,  however,  has  observed 
that  in  the  absence  of  insects,  it  fertilises  itself.  In 
M.  lupulina  the  elasticity  is  much  less  than  in  M. 
sativa.  Medicago  is  a  honey-bearing  genus. 

In  the  Leguminosae  hitherto  mentioned,  when  the 
keel  is  forced  open,  both  stamens  and  pistil  emerge 
from  it.  In  Lathyrus  (the  Pea),  however,  this  is  not 
the  case.  In  L.  pratensis,  for  instance,  the  stamens 
do  not  leave  the  keel,  but  the  pistil  is  provided  with 
a  brush  of  hairs,  which  sweep  the  pollen  before  them. 

In  the  Scarlet  Runner  (Phaseolus  communis]  which 
has  been  described  by  Farrer  (A  nn.  and-  Mag.  of  Nat. 
His.  1868,  p.  255),  the  keel  is  spiral,  as  well  as  the 
stamens  and  pistil.  The  former  are  weak,  and  never 
protrude  ;  while  the  pistil,  on  the  contrary,  is  stout, 
strong,  and  very  elastic.  In  the  natural  position,  the 
stigma  just  protrudes  out  of  the  mouth  of  the  keel, 
while  the  terminal  portion  of  the  style  within  the 
tube  is  covered  with  fine  hairs.  When,  therefore,  the 
bee  alights  on  a  flower,  and  inserts  her  proboscis  into 
it,  the  stigma  will  come  in  contact  with  the  base  of 
the  proboscis,  and  will  sweep  off  any  pollen  which 
may  be  adhering  to  it.  As,  however,  the  bee  presses 
more  on  the  flower,  in  its  efforts  to  get  the  honey, 
the  pistil  comes  further  out  of  the  flower ;  the  stigma 
turns  upwards,  away  from  the  insect,  and  the  brush 
of  hairs,  which  has  swept  the  sticky  honey  out  of  the 


96      GENERAL  REMARKS  ON  LEGUMINOS^E.    [CH. 

anthers,  and  is  consequently  covered  with  it,  rubs 
against  the  head  of  the  bee  and  the  base  of  the 
proboscis,  on  which  it  deposits  a  certain  quantity  of 
the  pollen,  to  be  again  transferred  to  the  stigma  of 
the  next  flower  which  the  bee  visits. 

The  Common  Pea  (Pisum  sativuni)  is  said  not  to 
be  well  adapted  to  our  British  bees.  Its  structure, 
probably,  has  reference  to  some  of  the  larger  southern 
species. 

In  Vicia  cracca  each  wing  is  united  to  the  keel 
in  two  places.  Though  the  parts  of  the  flower  fit 
closely  to  one  another,  still  from  the  smallness  of  its 
size  the  honey  is  accessible  to  most  bees  ;  and,  owing 
to  the  conspicuousness  of  its  bunches,  it  is  much 
visited  by  them.  From  their  arrangement  and  elas- 
ticity, the  various  parts  of  the  flower  resume  their 
original  position  after  each  visit. 

Vicia  septum,  in  general  characters,  agrees  with  V. 
cracca,  though  the  arrangement  of  the  hairs  on  the 
pistil  is  very  different.  The  insects  by  which  it  is 
visited  are,  however,  much  fewer.  Its  larger  size, 
coupled  with  other  minor  differences,  excludes  flies, 
Lepidoptera,  and  the  smaller  bees.  Even  Bombus  ter- 
restris  (the  Common  Humble  Bee)  does  not  attempt 
to  suck  it,  but  bites  a  hole  through  the  side.  In 
V.  faba  the  wings  and  keel  are  less  closely  united, 
and  the  honey  is  more  easily  accessible.  The  flower 
also  is  less  elastic,  and  if  opened  widely  does  not 
again  resume  its  original  form. 

It  appears  then  that  the  Leguminosae  are  all 
adapted  to  fertilisation  by  bees,  and,  as  Delpino 
has  pointed  out,  the  flowers  fall  into  four  series. 


iv.]  ROSACES.  97 

1.  Those  in  which  the  pressure  of  the  bee  pumps 
out,  as  it   were,   a  certain    quantity  of  pollen  ;    the 
flower  resuming  its  original  form  when  the  pressure 
is  removed.     (Lotus,  Anthyllis,  Ononis,  and  Lupinus.) 

2.  Those  in  which  not  only  the  pollen,  but  also  some 
of  the  stamens  are  pressed  out ;  the  flower  resuming 
its  form  on  the  removal  of  the  pressure,  as  in  the  first 
division.     (Melilotus,  Trifolium,  Onobrychis.) 

3.  Those  in  which  the  flower  bursts  on  pressure  and 
ejects  the  pollen.     (Medicago,  Genista,  Sarothamnus.) 

4.  Those  in  which,  on  the  pressure  of  the  bee,  the 
pollen  is  swept  out  by  a  brush  of  hairs  situated  on 
the  pistil.     (Lathyrus,  Vicia,  Pisum,  Phaseolus.) 

The  power  of  self- fertilisation  seems  to  be  lost  in 
some  species  of  Phaseolus,  Onobrychis,  and  Saro- 
thamnus ;  and  to  be  much  diminished  in  others,  as  in 
Trifolium  repens  and  Vicia  faba. 

ROSACES. 

This  order  contains  seventeen  British  genera,  includ- 
ing Prunus  (the  Cherry,  &c.),  Spiraea,  Geum,  Rubus 
(Blackberry,  &c.),  Fragaria  (Strawberry),  Potentilla, 
Alchemilla,  Sanguisorba,  Poterium,  Agrimonia,  Rosa, 
Pyrus,  Crataegus,  &c. 

Prunus.  Our  three  species  of  this  genus  differ 
somewhat  in  the  relations  of  the  anthers  to  the 
stigma.  In  P.  cerasus  (the  Cherry)  both  mature  at 
the  same  time,  while  in  P.  spinosa  (the  Black- thorn) 
and  P.  padus  (the  Bird  Cherry)  the  stigma  reaches 
maturity  before  the  anthers  :  though  as  it  retains  the 
capability  of  fertilisation  after  the  anthers  have  opened 
the  flowers  are  doubtless  often  self-fertilised  ;  which 

H 


98  GEUM,  RUBUS.  [CHAP. 

from  the  position  of  the  anthers  probably  happens 
more  frequently  in  the  Bird  Cherry  than  in  the  Black- 
thorn. The  flowers  are  melliferous.  The  British 
species  of  Spiraea,  on  the  contrary,  contain  no  honey, 
but  are  rich  in  pollen  and  are  consequently  visited  by 
insects ;  which,  from  the  weakness  of  the  petals, 
generally  alight  on  the  stigma,  and  thus  effect  cross- 
fertilisation  ;  though  the  flowers,  if  not  visited  by 
insects,  fertilise  themselves.  Among  the  foreign 
species  of  this  genus,  several  are  melliferous. 

Both  our  English  species  of  Geum  (G.  rivale  and 
G.  urbanunt)  are  melliferous :  but  the  flowers  of  G. 
rivale  are  much  larger  than  those  of  G.  urbanum,  and 
more  frequently  visited  by  insects.  Miiller  mentions 
that  Primula  elatior  is  deserted  by  bees  as  soon  as 
Geum  rivale  comes  into  flower.  Van  Tieghem  states 
that  while  G.  urbanum  produces  honey  in  the  north, 
this  is  not  the  case  in  France,  at  least,  near  Paris. 

The  genus  Rubus  is  very  variable,  and  there  are 
great  differences  of  opinion  among  botanists  as  to  the 
specific  limits,  and  the  number  of  species.  Bentham 
admits  five,  though  even  these,  he  adds,  "will  very 
frequently  be  found  to  pass  imperceptibly  one  into 
the  other."  The  Raspberry  (Rubus  idaus)  is  so  called 
because  it  is  said  to  be  very  frequent  on  Mount  Ida, 
where  in  1872  Mr.  (now  Sir  M.  E.)  Grant  Duff  and  I 
found  in  abundance  a  species,  which  if  not  identical  with, 
was  very  near,  our  R.  idczus.  This  species,  though  it 
secretes  honey,  is  not  apparently  a  great  favourite  with 
insects,  and  frequently  fertilises  itself.  The  flowers  of 
the  Blackberry  (R.fruticosus\  on  the  contrary,  are  much 
more  conspicuous,  and  the  stamens  are  turned  more  out- 
wards, so  as  to  leave  more  room  between  themselves 


IV.]  STRAWBERRY,  AGRIMONY.  99 

and  the  pistil.  They  are  very  much  frequented  by 
insects,  and  as  the  stamens  ripen  gradually,  and  from 
the  outside  inwards,  there  is  a  considerable  interval 
during  which,  though  the  pistil  is  mature,  and  some  of 
the  anthens  are  ripe,  self-fertilisation  is  difficult ;  while 
from  the  great  frequency  of  insect  visits,  fertilisation  is 
generally  effected  before  the  inner  anthers  are  mature. 

In  the  Strawberry  (Fragaria  vesca)  also,  the  stigma 
arrives  at  maturity  some  time  before  the  anthers,  so 
that  cross-fertilisation  generally  takes  place.  The 
species  of  Potentilla  agree  with  Fragaria  in  habit, 
foliage,  and  flowers,  but  the  fruit  is  not  succulent. 
The  honey,  however,  is  not  secreted  in  drops,  but 
forms  a  thin  layer.  According  to  Van  Tieghem,  P. 
tormentilla  produces  honey  abundantly  in  the  north, 
but  scarcely  any  in  the  neighbourhood  of  Paris.  Agri- 
monia  Eupatoria  appears  to  secrete  no  honey,  and  is 
but  seldom  visited  by  insects.  Alchemilla  vulgaris  is 
remarkable  for  variability.  The  honey  is  scanty,  so 
that  it  is  little  visited  by  long-lipped  insects ;  while, 
from  its  greenish  colour,  it  is  not  attractive  to  beetles, 
or  other  colour-loving  species.  Self-fertilisation  is, 
however,  comparatively  rare,  since  the  flowers  seldom 
possess  both  anthers  and  stigmas;  one  or  the  other 
being  generally  more  or  less  rudimentary.  This  plant, 
therefore,  may  be  considered  to  be  becoming  dioecious. 

The  next  two  genera  of  Rosacese,  Sanguisorba  and 
Poterium,  each  of  which  contains  a  single  British 
species,  have  been  already  alluded  to  in  the  opening 
chapter  (ante,  p.  10).  Sanguisorba  (Fig.  10)  officinalis 
is  monoecious  and  fertilised  by  insects.  In  Poterium 
sanguisorba  (Fig.  9)  some  flowers  are  mal.e,  some 
female,  and  some  hermaphrodite,  and  the  pollen  is 

H    2 


ioo  ROSE,  APPLE,  ONAGRACE&.  [CHAP. 

said  to  be  wind-borne.  In  other  respects  these  two 
plants  are  curiously  similar. 

There  is  almost  as  much  difference  of  opinion  with 
reference  to  the  specific  limits  in  the  genus  Rosa  as 
is  the  case  in  Rubus.  Bentham  admits  five  British 
species,  while  others,  as,  for  instance,  Babington,  ex- 
tend the  number  to  fifteen  or  twenty.  The  flowers  do 
not  appear  to  secrete  honey,  but  are  much  visited  by 
insects  for  the  sake  of  the  pollen.  The  numerous 
stamens  ripen  at  the  same  time  as  the  pistil,  but 
from  the  convenient  position  of  the  latter,  insects 
very  frequently  alight  upon  it,  and  thus  fertilise  it 
with  pollen  from  other  flowers,  though  self-fertilisa- 
tion probably  often  occurs. 

Pyrus  malus  (the  Apple),  on  the  contrary,  and  Cra- 
tcegus  oxyacantha  (the  Hawthorn)  are  melliferous,  and 
the  stigma  comes  to  maturity  before  the  anthers. 

ONAGRACE^E 

This  order  contains  six  English  genera,  Epilobium 
CEnothera,  Ludwigia,  Circaea,  Myriophyllum,  and 
Hippuris. 

The  instructive  differences  which  exist  between  the 
different  species  of  Epilobium  have  already  been 
referred  to  in  the  introductory  chapter.  CEnothera 
biennis  is  really  a  North  American  plant,  though 
now  naturalized  in  some  parts  of  England.  As  its 
name  denotes  (Evening  Primrose)  it  is  a  yellow  night 
flower ;  it  secretes  honey,  and  is  probably  fertilised  by 
moths,  though  it  remains  open  by  day,  and  is  also 
visited  by  bees.  Ludwigia  contains  a  single  species, 


iv.]  LYTHRARIE^E.  101 

L.  palustris — a  minute  marsh  plant,  hitherto  found  in 
very  few  localities  in  Britain,  though  it  ranges  over 
Central  Europe,  Asia,  and  North  America.  The 
genus  Circaea  contains  two  species,  C.  alpina  and  C. 
lutetiana,  the  Enchanter's  Nightshade.  This  species 
has  two  stamens,  and  as  the  flower  is  small,  any 
insect  of  moderate  size  would  probably  touch  both 
them  and  the  pistil ;  most  likely,  however,  coming  in 
contact  with  the  stigma  first,  as  it  projects  rather 
beyond  the  anthers.  '  \\ 


LYTHRARIE^E.      '»*'» 

This  order  contains  two  British  genera,  Ly thrum 
and  Peplis,  the  former  of  which  is  of  peculiar  interest 
and  has  been  already  alluded  to  in  the  opening 
chapter  (antt  p.  40). 

Lythrum  salicaria  (Fig.  77),  presents  us  with 
three  distinct  forms  of  flower,  which  were  already 
recorded  by  Vaucher,  while  their  function*  and 
relations  were  first  explained  by  Mr.  Darwin.  He 
distinguished  them  according  to  the  length  of  their 
styles,  as  the  Long-styled  (Fig.  78),  Mid-styled 
(Fig.  79),  and  Short -styled  (Fig.  80).  In  this 
species  it  is  remarkable  that  the  seeds  of  the  three 
forms  differ  from  one  another;  100  of  the  long- 
styled  seeds  being  equal  to  121  mid-styled,  or  142 
short-styled.  The  pollen  grains,  also,  not  only  differ 
in  size,  the  long  stamens  having  the  largest  pollen 
grains,  the  middle-sized  stamens  middle-sized  pollen 
grains,  and  the  short  stamens  small  pollen  grains ;  but 
also  in  colour,  being  green  in  the  longer  stamens,  and 


102  LY  THRUM.  [CHAP. 

yellow  in  the  shorter  ones ;  while  the  filaments  are 
pink  in  the  long  stamens,  uncoloured  in  the  shorter 
ones. 

Mr.  Darwin  has  also  proved  by  experiment  that 
this  species  does  not  set  its  seeds,  if  the  visits  of 
insects  are  prevented ;  in  a  state  of  nature,  however, 
the  plant  is  much  frequented  by  bees,  humble  bees, 


FIG.  77. — Lythrum  sahcnria. 


and  flies;  which  always  alight  on  the  upper  side  of 
the  flowers  on  the  stamens  and  pistil.  Mr.  Darwin 
has  shown  that  perfect  fertility  can  only  be  obtained 
by  fertilising  each  form  with  pollen  from  pistils  of 
the  corresponding  length. 

Thus  the  long-styled  form  is  naturally  fertilised  by 
oollen  from  the  long  stamens  of  the  two  other  forms  *, 


IV.] 


LYTHRUM. 


103 


FJG.  80. 


104  LYTHRUM,  CUCURBITACE^E.  [CHAP. 

but  it  can  be  so,  though  imperfectly,  by  its  own 
two  sets  of  stamens,  and  by  the  shorter  stamens  of 
the  two  other  forms ;  it  can,  therefore,  be  fertilised,  to 
use  Mr.  Darwin's  expression,  "legitimately"  in  two 
ways,  and  "  illegitimately  "  in  four  ways.  The  same 
is  the  case  with  the  other  two  forms,  so  that  eighteen 
modes  of  union  are  possible,  of  which  six  are  natural 
or  "legitimate,"  twelve  are  illegitimate,  and  more 
or  less  sterile.  This  case  is  therefore  indeed  most 
complex. 

Mr.  Darwin  suggests  (Jour.  Linn.  Soc.  v.  viii. 
1864,  p.  193)  that  the  trimorphous  condition  of  this 
plant  may  be  advantageous,  because  if  it  were  dimor- 
phous only  there  would  be  but  an  equal  chance  in 
favour  of  any  two  plants  being  of  different  forms,  and 
therefore  capable  of  self-fertilisation  ;  whereas,  being 
trimorphous,  the  chances  are  two  to  one.  In  the 
cowslip  and  primrose,  where  large  numbers  of  plants 
grow  together,  this,  he  thinks,  would  not  be  so 
material.  However  this  may  be,  the  stigma  and  the 
two  groups  of  stamens  appear  to  correspond  with  the 
three  divisions  of  the  body  (viz.  the  head,  thorax,  and 
abdomen)  of  the  bee,  Cilissa  melanura,  by  which  it  is 
almost  exclusively  fertilised. 

The  genus  Lythrum  is  also  remarkable  for  the 
great  differences  existing  between  different  species. 
For  instance,  L.  gr<zfferi>  like  Z-.  salicaria,  is  tri- 
morphous ;  while  L.  thymifolia  is  dimorphous,  and 
L.  hyssophifolia  is  homomorphous. 

CUCURBITACE^:. 

Of  this  order  we  have  only  a  single  species,  the  common  Bryony 
(Bryonia  dioica}.  The  flowers  are  dioecious,  the  males  in  small  clusters, 
pale  yellow,  about  half  an  inch  in  diameter ;  the  females  much  smaller. 
Both  secrete  honey. 


iv.]  CRASSULACEJE,  RIBESIACEsE.  105 


CRASSULACE^;. 

Of  this  order  there  are  four  British  genera  :  Tillaea, 
Cotyledon,  Sedum,  and  Sempervivum.  The  first  two 
contain  a  single  species  each.  Of  Sedum  we  have 
nine  species.  Though  the  flowers  are  small,  yet  from 
the  localities  they  occupy,  and  from  their  bright 
colours  they  are  somewhat  conspicuous,  and  are  visited 
by  many  insects  for  the  sake  of  their  honey,  which  is 
accessible  even  to  those  with  short  tongues.  Some 
(S.  acre,  reflexum,  and  telephium)  are  proterandrous,. 
while  ,S.  atratum,  according  to  Ricca,  is  proterogy- 
nous  ;  and  6".  rhodiola  is  dioecious. 

RIBESIACE^E. 

This  order  consists,  as  far  as  Britain  is  concerned,  of  the  genus  Ribes, 
containing  four  species,  the  Gooseberry  (R.grossulariata),  Red  Currant 
(R.  rttbrum),  Black  Currant  (R.  nigrum),  and  Mountain  Currant  (A*. 
alpinum).  They  all  supply  honey.  R.  grossulariata  is  proterandrous, 
and  is  said  to  have  lost  the  power  of  self-fertilisation.  In  R.  rubrum 
and  R.  nigrum  the  stamens  and  pistil  come  to  maturity  simultaneously. 
R.  alpinumy  on  the  contrary,  is  dioecious ;  and  it  is  interesting  that, 
according  to  Miiller,  this  species  is  more  frequented  by  insects  than  any 
of  the  others. 

SAXIFRAGACE^E. 

An  extensive  order,  ranging  nearly  over  the  whole 
world,  but  represented  in  Britain  by  only  four  genera^ 
Saxifraga,  Parnassia,  Drosera,  and  Chrysosplenium. 

The  species  of  the  genus  Saxifraga  are  melliferous^ 
and  proterandrous.  Bergenia  (Saxifraga)  crassi- 
folia,  which,  however,  is  not  British,  though  frequently 
grown  in  gardens,  is  according  to  Engler,  protero- 
gynous.  In  Chrysosplenium  the  anthers  and  stigma 
ripen  simultaneously.  Parnassia  palustris,  as  its  name 
indicates,  inhabits  wet  and  boggy  places.  It  has  ten 
stamens,  of  which  however  five  only  bear  anthers. 


106  SAXIFRAGACE^E,  PARNASSIA.  [CHAP. 

while  the  others  secrete  honey  at  the  base,  and 
terminate  in  from  eight  to  seventeen  beautiful 
yellow  globular  glands.  These  glands  so  closely  re- 
semble drops  of  honey  that  it  is  difficult  to  believe 
they  are  perfectly  dry.  They  probably  serve  as  sham 
drops  of  honey  to  attract  flies.  The  five  polliniferous 
anthers  ripen,  not  simultaneously,  but  successively, 
and  "as  each  ripens  it  places  itself  right  on  the 


FIG.  81. — Drosera  rotundifolia. 

top  of  the  stigma,  with  its  back  to  it,  and  the  pollen 
is  then  discharged  from  the  anther  on  the  side  away 
from  the  stigma,  so  that  it  is  scarcely  possible  for  any 
to  fall  on  it ;  and  this  is  done  by  each  of  the  five 
stamens  in  succession  "  (Bennett,  "  How  Flowers  are 
Fertilised,"  1873,  p.  19).  The  flowers  are  much  visited 
by  insects,  especially  by  flies. 

In    the   cases    we    have    hitherto   considered,   the 
relation    between    the    flowers  and  insects  is  one  of 


iv.]  DION^A.  107 

mutual  advantage.  The  honey  of  the  flowers  affords 
to  the  insects  a  rich  and  nutritious  food  ;  and  if  the 
latter  rob  the  flowers  of  some  of  their  pollen,  they 
make  ample  amends  by  carrying  a  portion  of  the 
remainder  from  one  flower  to  another,  and  thus  con- 
ferring on  the  plant  the  great  advantage  of  cross- 
fertilisation.  In  Drosera  (Fig.  81),  on  the  contrary, 
we  find  a  very  different  state  of  things,  for  the  plant 


FIG.  82. — Two  leaves  of  Dionsea  :  one  open,  one  closed  upon  a  fly. 

catches  and  devours  insects.  This  genus,  and  the 
other  plants  which  have  this  remarkable  habit,  have 
recently  been  the  subject  of  an  admirable  memoir, 
by  Dr.  Hooker,  read  before  the  British  Associa- 
tion (Nature,  Sep.  3,  1874).  The  first  observation 
on  insect-eating  flowers  was  made,  about  the  year 
1768,  by  our  countryman  Ellis,  on  Dionaea,  a  North 
American  plant,  the  leaves  of  which  have  a  joint 


io8  DION&A,  DROSERA.  [CHAP. 

in  the  middle,  and  thus  close  over  (Fig.  82),  kill, 
and  actually  digest  any  insect  which  may  alight  on 
them.  The  plant  has  recently  been  studied  by 
an  American  botanist,  Mr.  Canby,  and,  says  Dr. 
Hooker,  "  by  feeding  the  leaves  with  small  pieces  of 
beef,  he  found,  that  these  were  completely  dissolved 
and  absorbed  ;  the  leaf  opening  again  with  a  dry 
surface,  and  ready  for  another  meal,  though  with  an 
appetite  somewhat  jaded.  He  found  that  cheese 
disagrees  horribly  with  the  leaves,  turning  them 
black,  and  finally  killing  them.  Finally,  he  details 
the  useless  struggles  of  a  curculio  (beetle)  to  escape, 
as  establishing  the  fact  that  the  fluid  is  secreted, 
and  not  the  result  of  the  decomposition  of  the 
substance  which  the  leaf  has  seized.  The  curculio 
being  of  a  resolute  nature,  attempted  to  eat  his  way 
out — 'when  discovered  he  was  still  alive,  and  had 
made  a  small  hole  through  the  side  of  the  leaf,  but 
was  evidently  becoming  very  weak.  On  opening  the 
leaf,  the  fluid  was  found  in  considerable  quantity 
around  him,  and  was  without  doubt  gradually  over- 
coming him.  The  leaf  being  again  allowed  to  close 
upon  him,  he  soon  died.'  "  Prof.  Burdon  Sanderson 
has  recently  made  some  interesting  observations  on 
the  electrical  changes  by  which  these  movements  are 
accompanied.  (Brit.  Ass.  Report,  1873.) 

In  the  genus  Drosera  (Fig.  81),  the  hairs  which 
cover  the  leaf,  fold  over  and  capture  insects.  This  was 
first  observed  almost  simultaneously  by  Mr.  Whately 
and  Mr.  Roth.  The  latter  says,  "  I  placed  an  ant  upon 
the  middle  of  the  leaf  of  D.  rotundifolia,  but  not  so  as 
to  disturb  the  plant.  The  ant  endeavoured  to  escape, 


IV.]  SARRACENIA,  UMBELLIFER&.  109 

but  was  held  fast  by  the  clammy  juice  at  the  points 
of  the  hairs,  which  was  drawn  out  by  its  feet  into  fine 
threads.  In  some  minutes  the  short  hairs  on  the  disc 
of  the  leaf  began  to  bend,  then  the  long  hairs,  and 
laid  themselves  upon  the  insect.  After  a  while  the 
leaf  began  to  bend,  and  in  some  hours  the  end  of  the 
leaf  was  so  bent  inwards  as  to  touch  the  base.  The 
ant  died  in  fifteen  minutes,  which  was  before  all  the 
hairs  had  been  bent  themselves."  Mr.  Darwin  has 
recently  shown  that  while  the  leaves  will  in  this  way 
close  over,  and  actually  digest  pieces  of  meat  or  other 
animal  matter,  they  take  little  notice  of  inorganic 
substances. 

I  cannot  pass  from  this  subject  without  mentioning 
another  insectivorous  plant,  the  genus  Sarracenia, 
though  it  is  not  British,  and  does  not  belong  to  the 
present  order.  5.  variolaris  has  some  of  the  leaves 
in  the  form  of  a  pitcher  which  secretes  a  fluid,  and  is 
lined  internally  with  hairs  pointing  downwards.  Ants, 
flies  and  other  insects  which  fall  into  this  pitcher 
cannot  get  out  again,  and  are  actually  digested  by 
the  plant.  Up  the  outside  of  the  pitcher  there  is  a 
line  of  honey  glands,  which  lure  the  insects  to  their 
destruction.  Bees,  however,  appear  to  be  scarcely 
ever  caught. 

UMBELLIFER^E. 

This  is  a  very  extensive  order,  containing  no  less 
than  thirty-seven  British  genera  (Carrot,  Chervil, 
Parsley,  Parsnip,  &c.)  and  a  very  large  number  of 
species.  The  plants  belonging  to  this  group  possess 
two  great  advantages — namely,  firstly,  the  association 


I  io  UMBELLIFERjE.  [CHAP. 

of  the  numerous  small  flowers  into  comparatively 
large  flat  heads,  by  which  they  are  made  much  more 
conspicuous  :  and,  secondly,  they  all  secrete  honey 
in  the  centre  of  the  flower  on  a  flat  disk  (Fig. 
84,  85)  which  is  thus  accessible  to  all  insects,  even 
those  with  the  shortest  lips.  This  is  an  advantage, 
as  it  effects  a  considerable  saving  of  time,  enabling 
the  insects  to  visit  a  given  number  of  flowers 


KlG.  83.— Wild  Chervil  (Cheerophyllum  sylvestre). 

more  rapidly,  and  consequently  rendering  their  fert- 
ilisation more  certain  than  if  they  had  stood 
singly.  But  though  the  order  is  so  rich  in  genera 
and  species,  it  is  comparatively  uniform,  and  the 
divisions  are  for  the  most  part  characterised  by  the 
form  and  structure  of  the  fruit.  The  flowers  are 
generally  small ;  the  petals  five,  inserted  round  a  little 


IV.]  CHJEROPHYLLUM,  MYRRHIS.  ill 

fleshy  disk ;  the  stamens,  also  five,  alternating  with 
the  petals. 

The  self-fertilisation  which,  in  small  flowers  such 
as  these,  would  otherwise  naturally  occur,  is  provided 
against  by  the  fact  that  the  flowers  are  generally  pro- 
terandrous,  the  stamens  ripening  before  the  pistil, 
and  the  latter  not  being  mature  until  the  former  have 
shed  their  pollen ;  as,  for  instance,  is  shown  in  the 
following  enlarged  figures  of  the  Wild  Chervil  (Chcrro- 
phyllum  sylvestre).  Fig.  84  represents  a  floret  in  the 
earlier  (male)  condition,  showing  three  ripe  (cf]  and 


FIG.  84.— Flcwer  of  the  Wild  Chervil  in         FIG.  85.— Ditto,  in  the  second  (female) 
the  first  (male)  state.  state. 

two  still  immature  (a),  while  the  stigmas  have  not  yet 
made  their  appearance  :  in  Fig.  85  is  represented 
the  same  flower  in  a  more  advanced  condition,  the 
stamens  having  fallen  off,  and  the  stigmas  (sf)  being 
now  mature.  In  some  cases,  flowers  in  both  condi- 
tions may  be  found  in  the  same  head  or  umbel ;  in 
others,  as,  for  instance,  in  Myrrhis,  the  flowers  of  one 
head  are  all  firstly  in  the  male  condition,  and  subse- 
quently in  that  with  mature  stigmas,  none  of  them 
arriving  at  the  second  stage  until  they  have  all  passed 
through  the  first. 

It  will  be  seen  that  in  these  florets  the  petals  are 


112  INSECTS  AND  UMBELLIFERjE.         [CHAP 

not  symmetrical,  the  outer  ones  being  considerably 
larger  than  the  others,  and  in  many  Umbellifers  the 
florets  themselves,  on  the  outer  edge  of  the  umbel, 
are  considerably  larger  than  the  inner  ones.  This 
distinction  is  carried  still  further  in  the  Com- 
positae,  where  also  the  florets  are  so  closely  packed 
together  that  the  whole  flowerhead  is  commonly, 
though  of  course  incorrectly,  spoken  of  as  a  flower. 

H.  Miiller  has  recorded  73  species  of  insects 
as  frequenting  the  Wild  Chervil.  In  some  cases 
the  number  was  even  greater,  as  for  instance  in 
Heracleum,  on  which  he  has  observed  no  less 
than  1 1 8.  That  the  number  depends  on  the  con- 
spicuousness  of  the  umbel  he  illustrates  by  the 
following  series,  arranged  in  the  order  of  the  con- 
spicuousness  of  the  flowers, — viz.,  I.  Heracleum,  2. 
^Egopodium,  3.  Anthriscus  (Chaerophyllum)  sylvestris, 
4.  Daucus,  5.  Carum,  6.  Chaerophyllum  temulum,  7. 
Torilis.  On  these  he  found  the  following  number  of 
species  of  insects  : 

Heracleum  118 

^Egopodium  104 

Anthriscus  sylvestns  73 

Daucus  6 1 

Carum  55 
Chaerophyllum  temulum  23 

Torilis  9 

The  position  of  the  honey  on  a  flat  disk,  which 
tenders  it  accessible  to  most  insects,  has  the  opposite 
result  as  regards  the  Lepidoptera,  which  therefore,  as 
might  naturally  be  expected,  are  but  rare  visitors  of 


IV.] 


COMPOSITE  AND  UMBELLIFERAE. 


1*3 


the  Umbelliferae.  I  have  sometimes  wondered  whether 
the  neutral  tints  of  these  flowers  have  any  connection 
with  the  number  of  species  by  which  they  are  fre- 
quented. 

TABULAR  VIEW  OF  THE  INSECTS  VISITING  SOME  OF  THE  COM- 
MONEST  SPECIES  OF  COMPOSITES  AND  UMBELLIFERS. 


1 

i 

2 

3 

4 

5 

6 

7 

8 

9 

i 

1 

3 

bfl 

Percentage  of  species 
belonging  to 

V    O 

3 

.5 

w  « 

'o'S 

2 

1 

E 

'bo 

J 

J8 

terflies 

§*•£ 

K 

a  . 

3 

J>°5> 

J"F 

"S-S 

I 

I 

g£ 

S"$ 

f- 

'at 

JJ 

I2 

3-e 

•a 

Q. 

5 

S   O 

1-1  So 

|| 

E 

I 

P 

11 

0 

o 

0 

"o  S3 
x 
dS 

P 

1 

o. 

V 

« 

a 

< 

Q 

o 

COMPOSITE. 

Taraxacum  officinale 

93 

7 

58 

21 

7 

7-5 

62.5 

22.6 

7-4 

Cirsium  arvense  .     . 

88 

7 

32 

24 

25 

7-9 

36.4 

27  3 

28.4 

Achillea  millifolium  . 

8? 

5 

6 
5 
13 

3° 

12 
28 

21 
28 

6 

3° 

27 

i 

}9 

6.9 

27 

34-5 
16.6 
58.7 

24.1 

389 
125 

34-5 
37-5 

2 

CRrysanthem.  leucanth 
Centaurea  jacea  .     . 

Carduus  acanthoides 

44 

4 

32 

3 

5 

9.1 

72.7 

6.8 

H-3 

Senecio  jacobsea  .     . 
Picris  hieracioides    . 

40 
29 

3 
3 

16 
16 

18 
9 

3 

i 

7-5 
10.3 

40 
55  2 

45 
31 

75 
3-4 

Tanacetura  vulgare  . 
Eupatorium  cannabinum 

27 

18 

5 
9 

7 

2 

I 

8 

i 

18.5 
50 

25.9 
n.  i 

25.9 
33-3 

296 
5-5 

UMBELLIFERAE. 

Heracleum  sphondylium 
jEgopodium  podograria 
Anthriscus  sylvestris 

118 
104 
73 

o 

o 

0 

13 
15 

5 

49 
34 
26 

56 
55 
42 

0 

o 

0 

ii 

14.4 
6.8 

41-5 
32.6 
35-6 

47-4 
52.9 
57-5 

Daucus  carota      .     . 

61 

2 

8 

jq 

32 

3-3 

I^.  I 

OI.I 

Carum  carvi    .    .     . 

55 

I 

9 

21 

24 

1.8 

164 

38  2 

43^6 

Anethum  graveolens 

46 

0 

6 

15 

25 

0 

32.6 

54-3 

Slum  latifolium    .     . 

S2 

0 

0 

20 

12 

0 

0 

62.5 

37-5 

Angelica  sylvestris  . 
Chaerophyllum  temulum 

23 

I 
o 

2 

I 

II 
10 

16 
la 

3-3 

0 

6.6 
4-3 

36.6 
43-5 

53-3 
52.2 

Pimpinella  saxifraga     . 

23 

0 

3 

8 

12 

0 

13 

34.8 

52.2 

No  order  of  plants  are  more  visited  by  insects  than 
the  Compositae  and  the  Umbelliferae;  but  from  the 
difference  in  the  form  of  the  flowers  the  species  are 

I 


ii4  ARALIACE&,  CORNACE^.  [CH.  iv. 

very  different.  In  the  Umbellifers  the  honey,  being 
secreted  on  an  open  disk,  is  therefore  open  to 
all  insects.  Though  the  tubes  of  the  florets  of  the 
Compositae  are  short,  still  the  honey  is  not  quite  so 
accessible  as  in  the  Umbellifers.  H.  Muller  gives  the 
preceding  table,  which  brings  this  out  very  clearly, 
and  which  also  shows  the  care  and  perseverance  with 
which  he  carried  on  his  observations. 

Thus,  then,  while  in  Centaurea,  out  of  every  100 
insects  by  which  the  flower  is  visited,  no  less  than  58 
are  bees,  27  are  butterflies  or  moths,  12  are  flies,  and 
only  2  belong  to  other  groups ;  in  the  common 
Carrot  on  the  contrary,  where  the  honey  is  quite 
exposed,  13  in  a  hundred  only  are  bees,  3  are  butter- 
flies or  moths,  31  are  flies,  and  52  belong  to  other 
orders.  If  a  flower  with  a  longer  tube  than  that 
of  Centaurea  had  been  selected  for  comparison,  the 
difference  would  have  been  even  more  striking. 

ARALIACE.E. 

The  only  European  species  belonging  to  this  order  is  the  Common 
Ivy  (Ifedera  helix).  It  is  proterandrous,  and  is  much  visited  by  flies  and 
wasps. 

CORNACE^E. 

This  order  contains  one  British  genus,  Cornus,  with  two  species,  C. 
suecica  the  Dwarf  Cornel,  and  C.  sanguined  the  Common  Cornel.  The 
two  species  are  very  unlike ;  C.  suecica  being  a  low  herb  with  minute 
flowers,  which,  however,  are  surrounded  by  four  large,  white  bracts, 
which  look  like  petals,  and  thus  give  the  whole  umbel  the  appearance 
of  a  single  flower.  C.  sanguinea  is  a  shrub  which  attains  a  height  of 
five  or  six  feet.  The  honey  is  secreted  from  •>  fleshy  ring  at  the  base 
of  the  pistil ;  it  is  accessible  to  all  insects,  and  is  much  more  visited 
by  flies  than  by  bees.  The  anthers  and  stigma  mature  simultaneously. 


LAMIUM   ALBUM. 


CHAPTER   V. 


COROLLIFLORJE. 

This  subclass  contains  those  dicotyledons   in  which  the  petals  are 
united  together,  at  least  at  the  base. 


CAPRIFOLIACE^i. 

THIS  order,  which  contains  five  British  genera,  Adoxa, 
Sambucus,  Viburnum,  Lonicera,  and  Linnaea,  offers 
remarkable  differences,  especially  in  relation  to  the 
honey  glands.  Adoxa  is  a  low,  glabrous,  light  green 
herb  :  the  flowers,  which  are  coloured  like  the  rest 
of  the  plant,  secrete  honey,  which  is  exposed,  and 
accessible  to  all  insects.  Sambucus  nigra  (The  Com- 
mon Elder),  on  the  contrary,  secretes  no  honey.  It 
is  nevertheless  sweet-scented,  and  is  visited  by  several 


ii6  CORGLLIFLO&tE,  LONICERA.  [CHAP. 

insects,  but  often  fertilises  itself,  as  the  stamens 
and  pistil  ripen  simultaneously.  Viburnum  (the 
Guelder  Rose)  secretes  honey,  and  the  flowers  are 
collected  into  a  head  as  in  the  Elder,  but  the  outer 
florets  have  the  corolla  considerably  enlarged  at  the 
expense  of  the  stamens  and  pistil.  Although,  there- 
fore, they  produce  neither  pollen  nor  seeds,  they  are 
useful  to  the  plant,  by  rendering  the  other  flowers 
more  conspicuous,  and  thus  attracting  insects.  In 
remarkable  contrast  to  these  species,  with  their  ex- 
posed honey,  is  the  genus  Lonicera  (the  honeysuckle). 
Lonicera  caprifolium  has  a  honey  tube  no  less  than 
30  mm.  long,  for  the  most  part  not  above  I — 2  mm. 
wide,  and  moreover  a  great  part  occupied  by  the  style. 
It  is  often,  however,  half  full  of  honey.  As  in  the 
longest  tongued  bees  (Bombus  hortorum  and  Antho- 
phora  pilipes),  the  proboscis  only  attains  a  length  of 
21  mm.,  those  of  Flies  (Rhingia,  Bombylius  discolor} 
not  more  than  II — 12  mm..,  they  are  none  of  them 
in  a  position  to  extract  all  the  honey ;  and  in  fact 
M tiller  never  found  them  attempting  to  do  so,  though 
they  visit  the  flowers  for  the  pollen.  The  honey 
of  Lonicera  caprifolium  is  therefore  especially  adapted 
for  the  larger  moths.  The  flowers  open  in  the  even- 
ing, and  are  then  specially  fragrant.  M tiller  found 
the  following  moths  on  this  species :  Sphinx  convol- 
vuli;  S.  ligustri ;  S.pinastri;  Deilephila  elpenor ;  D. 
porcellus ;  Smerinthus  tilice;  Dianthcecia  capsincola, 
Cucullia  umbratica,  Plusia  gamma,  Dasyclura  pudi- 
bunda. 

L.     periclymenum     (the     Common    Honeysuckle) 
agrees  in  most  respects  with  the  preceding  species, 


v.]  STELLATE,   VALERIANE&.  11; 

but  the  tube  is  rather  shorter,  and  the  honey  in  con- 
sequence more  accessible  to  bees.  In  our  third  species 
again,  L.  xylosteum,  the  tube  is  still  shorter,  and  the 
flowers  are  regularly  visited  by  flies  and  humble-bees. 

STELLATE. 

We  have  four  British  genera  of  this  order,  Rubia  (the  Madder), 
Galium,  Sherardia  (Woodruff),  and  Asperula. 

The  flowers  are  small,  but  in  many  cases  rendered  conspicuous  by 
association.  Several  of  the  species  are  sweet-scented,  and  attract 
insects  by  means  of  honey,  which  is  either  exposed  on  a  flat  dish  (Rubia 
and  Galium),  or  contained  at  the  base  of  a  short  tube  (Sherardia  and 
Asperula).  The  stamens  and  pistil  ripen  simultaneously,  and  if  not 
visited  by  insects,  the  flowers  fertilise  themselves.  The  florets  of  Rubia 
peregrina  are  greenish  ;  those  of  Sherardia  arvensis  blue  or  pink  ;  the 
others  either  white  or  yellow.  Miiller  calls  attention  to  the  influence  of 
colour  in  the  case  of  Galium  mollugo  and  G.  verum,  which  agree  closely 
in  most  points,  but  the  former  of  which  is  white,  while  the  latter  is 
yellow,  which  he  says  renders  it  much  more  attractive  to  small  beetles. 

Fritz  Miiller  has  described  (Bot.  Zeit.  1866,  p.  129)  a  very  interesting 
South  American  species  of  this  group,  Martha  (Prosoquerid)  fragans, 
in  which  the  stamens  are  irritable,  and  when  touched  by  the  proboscis 
of  an  insect,  immediately  explode,  and  throw  the  pollen  on  to  the 
insect,  at  the  same  time  closing  the  entrance  to  the  tube  of  the  flower, 
in  which  the  pistil  is  situated,  and  thus  preventing  the  possibility  oi 
self-fertilisation. 


VALERIANE^E. 

Of  this  family  we  have  only  one  truly  British  genus,  Valeriana, 
though  Centranthus  ruber,  having  been  long  cultivated  in  gardens,  has 
become  naturalised  in  some  parts  of  England. 

The  flowers  of  the  Allheal  ( Valeriana  ojfficinalis},  though  small,  are 
rendered  conspicuous  by  association.  They  are  melliferous,  and  the 
honey  is  accessible  even  to  short-tongued  insects,  by  which  they  are 
much  frequented.  They  are  proterandrous. 

Valei'iana  dioica,  while  agreeing  with  the  preceding  as  regards  the 
honey,  is,  on  the  contrary,  generally  dioecious,  the  male  flowers  being, 
as  usual,  larger  than  the  female,  and,  consequently,  in  most  cases 
visited  first. 

COMPOSITE. 

This  great  group  contains  no  less  than  forty  British 
genera,  and  a  very  large  number  of  species.  It 


u8  COMPOSITE.  [CHAP. 

comprises  the  Daisy  (Bellis),  Dandelion  (Taraxacum), 
Groundsel  (Senecio),  Chrysanthemum,  Thistle 
(Carduus),  Lettuce  (Lactuca),  Hawkweed  (Hieracium), 
&c.  Though  there  are  many  differences  in  the 
structure  of  the  flowers,  as  might  naturally  be 
expected  in  so  large  a  group,  still  in  many  respects, 
they  are  very  uniform.  The  florets  are  so  closely  united 
on  a  common  head,  that  each  group  is  commonly, 
though  of  course  incorrectly,  spoken  of  as  a  single 
flower.  The  so-called  flower  of  the  Daisy,  for  instance, 
is  in  reality  a  group  of  flowers ;  the  outer  row  of 
which,  or  ray  florets  as  they  are  termed,  are  unlike 
the  rest  and  terminate  on  the  outer  side  in  a  white 
leaf  or  "  ray." 

The  advantages  of  this  arrangement  are : — 

1.  That  the  flowers  become  much  more  conspicu- 
ous than  would  be  the  case  if  they  were   arranged 
singly. 

2.  That  the  facility  with  which  the  honey  is  obtained 
renders  them  more  attractive  to  insects. 

3.  That  the  visits  of  the  insects  are  more  likely  to 
be  effectual,  since  the  chances  are  that  an  insect  which 
once  alights,  touches  several,  if  not  many,  florets. 

No  wonder,  therefore,  that  the  Compositae  are  the 
most  extensive  family  among  flowering  plants,  are 
represented  in  every  quarter  of  the  globe  and  in 
every  description  of  station  (Bentham,  "  Handbook 
of  the  British  Flora,"  vol.  i.  p.  408 ;  Jour.  Linn. 
Soc.  1873,  p.  335,)  and  contain  nearly  ten  thousand 
species. 

The  principal  differences  among  the  Compositae, 
regarded  from  the  point  of  view  of  the  present  work, 


COMPOSITE.  119 


consist  in  the  different  length  of  the  florets,  rendering 
the  honey  more  or  less  accessible  to  insects  ;  in  the 
arrangement  of  the  stamens  and  pistil ;  and  in  the 
character  of  the  outer,  or  "  ray  "  florets. 

In  some  of  the  Compositae  the  florets  all  contain 
both  anthers  and  stigma.  Generally,  however,  the  ray 
florets  develope  no  anthers,  but  a  pistil  only  ;  while  in 
some  species  of  Centatirea  they  are  barren,  and  merely 
serve  as  flags.  It  is  remarkable  that  in  C.  nigra, 
while  the  outer  row  of  florets  generally  resemble  the 
rest,  they  are  sometimes  enlarged  and  neuter,  as  in  C. 
cyanus,  &c.  As  regards  the  relation  to  insects,  we 
find  every  gradation,  between  Taraxacum,  Cirsium 
arvense,  and  Achillea,  on  the  one  hand  which  are 
conspicuous,  rich  in  honey  and  much  visited  by 
insects ;  and  on  the  other,  Senecio  vulgaris,  which  is 
rarely  visited  by  insects,  and  the  species  of  Artemisia, 
which  are  said  to  be  wind  fertilised. 

In  Tussilago  farfara  the  disk  florets  give  honey 
and  pollen  ;  the  ray  florets  contain  neither,  but  render 
the  flower-head  conspicuous,  and  produce  seed. 

In  the  common  Feverfew,  or  large  white  Daisy 
(Fig.  86),  (Chrysanthemum  parthenium),  which  has 
been  well  described  by  Dr.  Ogle,  "  Popular  Science 
Review,"  April  1870,  the  flower-heads  consist  of 
an  outer  row  of  female  florets,  in  which  the  tubular 
corolla  terminates  on  the  outer  side  in  a  white  leaf  or 
ray,  which  doubtless  is  useful  in  making  the  flower 
conspicuous.  The  inner  florets  are  also  tubular, 
but  are  small,  yellow,  ^.nd  without  a  ray.  Each  of 
these  florets  is  furnished  with  stamens  as  well  as  a 
pistil.  The  anthers  are  united  at  their  sides  so 


120  FEVERFEW.  [CHAP. 

as  to  form  a  closed  tube,  within  which  the  pistil 
lies.  They  ripen  before  the  pistil,  and  open  on  their 
inner  sides,  so  that  the  pollen  is  discharged  into  the 
upper  end  of  the  tube  above  the  head  of  the  pistil. 
When  the  flower  opens,  the  pollen  is  already  ripe,  and 
fills  the  upper  part  of  the  stamen  tube.  A  floret  in 
this  condition  is  represented  in  (Fig.  87).  The  pistil, 
however,  continues  to  elongate,  and  at  length  pushes 


KlG.  86. — Chrysanthemum  partkcntum. 

the  pollen  against  the  upper  end  of  the  tube,  which 
gives  way,  and  thus  the  pollen  is  forced  out  of 
the  tube,  as  shown  in  (Fig  88).  The  pistil  itself 
terminates  in  two  branches,  which  at  first  are  pressed 
closely  to  one  another,  and  each  of  which  terminates 
in  a  brush  of  hairs  (Fig.  89).  As  the  style  elongates 
this  brush  of  hairs  sweeps  the  pollen  cleanly  out  of 
the  tube,  and  it  is  then  removed  by  insects.  When 


CHRYSANTHEMUM  PARTHENIUM. 


121 


the  pistil  has  attained  its  full  length,  the  two  branches 
open  and  curve  downwards,  so  as  to  expose  the 
stigmatic  surfaces  (Fig.  89  st)  which  had  previously 
been  pressed  closely  to  one  another,  and  thus 
protected  from  the  action  of  the  pollen.  From  this 
arrangement  it  is  obvious  that  any  insect  alighting  on 


FIG.  87. 


FIG.  88. 


FIG.  89 


FIG.  87. — Floret  of  Chrysanthem MM*  parthemnm,  just  opened. 
FIG.  88.— Ditto,  somewhat  more  advanced. 
FIG.  89. — Ditto,  with  the  stigmas  expanded. 

the  flower-head  of  the  Chrysanthemum  would  dust  its 
under-side  with  the  pollen  of  the  younger  flowers, 
which  then  could  not  fail  to  be  brought  into  contact 
with  the  stigmatic  surfaces  of  the  older  ones.  As  the 
expansion  of  the  flowers  begins  at  the  outside  and 
thence  extends  to  the  centre,  it  is  plain  that  the  pollen 


122  MARIGOLD,  MATRICARIA.  [CHAP. 

of  any  given,  floret  cannot  be  used  to  fertilise  one 
situated  on  its  inner  side.  Consequently,  if  the  outer 
row  of  florets  produced  pollen,  it  would,  in  the  great 
majority  of  cases,  be  wasted.  I  have,  however, 
already  mentioned  that  these  florets  do  not  produce 
pollen,  while  the  saving  thus  effected  enables  them 
to  produce  a  larger  corolla.  It  is  also  interesting 
to  observe  that  in  these  outer  flowers  the  branches 
of  the  pistil  do  not  possess  the  terminal  brush  of 
hairs  which,  in  the  absence  of  pollen,  would  be 
useless. 

In  other  Compositae,  as  in  the  Marigold,  while  the 
ray  flowers  produce  no  pollen,  the  disk  flowers  develop 
no  stigmas.  In  this  case,  as  in  the  Feverfew,  the  pistil 
of  the  ray  flowers  does  not  require  or  possess  the 
terrrfinal  brushes  of  hairs,  there  being  no  pollen  to  be 
swept  out.  The  central  flowers,  on  the  other  hand, 
though  they  develop  no  stigmas,  require  a  pistil  in 
order  to  force  the  pollen  out  of  the  anther  tube. 
Hence  the  pistil  is  present  as  usual,  but  the  head  is 
simple  and  not  bifid.  This  complete  alteration  of 
the  function  of  the  pistil  is  extremely  curious. 

In  Chrysanthemum  leucanthemum  according  to 
Miiller,  the  pistil  of  the  ray  florets  possesses  a  ter- 
minal brush,  which,  however,  is  much  less  developed 
than  in  the  disk  florets.  Matricaria  camomilla  agrees 
in  most  respects  with  Chrysanthemum.  The  strong 
smell  of  this  flower,  however,  seems  to  be  distasteful 
to  bees,  though  Miiller  has  observed  it  to  be  visited 
by  Prosopis  signata  and  Sphecodes  gibbus.  It  is  said 
to  be  generally  fertilised  by  flies.  Anthemis  re- 
sembles the  two  preceding  genera  in  many  respects, 


v.]  DAISY,  INULA,  TUSSILAGO.  123 

but  differs  in  possessing  scales  between  all,  or  at  least 
the  central,  florets  of  the  receptacle. 

The  Common  Daisy  (Bellis  perennis]  has  ray  florets 
I — 2  mm.  in  length,  united  into  a  yellow  disk  6  mm. 
in  diameter,  and  surrounded  by  a  row  of  florets,  each 
terminating  in  a  white  "  flag  "  5  mm.  in  length.  These 
ray  florets  are  exclusively  female,  and  the  pistil  has 
lost  the  terminal  brush  of  hairs.  The  two  branches  are 
long  and  clothed  on  their  whole  upper  surfaces  with 
rows  of  stigmatic  papillae.  The  pistil  of  the  ray 
flowers,  on  the  contrary,  has  short  branches,  terminat- 
ing in  a  tuft  of  hairs,  and  only  provided  with  a  small 
number  of  stigmatic  papillae.  When  fertilised,  the 
pistil  retires  again  into  the  tube  of  the  floret. 

In  Inula  dysenterica  (the  Fleabane)  the  disk  florets 
contain  both  stamens  and  pistil;  the  ray  florets  a 
pistil  only,  which,  however,  agrees  exactly  with  that  of 
the  disk  florets,  even  in  the  position  of  the  terminal 
hairs,  which  in  the  absence  of  pollen,  must  apparently 
be  useless. 

In  Tussilago  farfara  the  disk  florets  are  male,  the 
ray  florets  female.  In  the  disk  florets  the  ovary  is 
rudimentary ;  they  contain  honey  at  the  base  of  the 
tube,  which  has  a  length  of  4  mm.  The  pistil 
terminates  in  the  usual  tuft  of  hairs.  The  ray 
florets,  on  the  contrary,  produce  no  pollen ;  they  open, 
and  as  the  stigmas  are  mature,  before  the  anther 
tubes  of  the  disk  flowers  have  opened,  they  are  in  fine 
weather  almost  always  fertilised  by  the  pollen  from 
other  flowers. 

In  the  Common  Groundsel  (Senecio  vulgaris}y  60  to 
80  florets  are  united  on  one  receptacle.  The  lower, 


124  THISTLE,  CENTAUREA.  [CHAP. 

tubular,  portion  of  the  floret  has  a  length  of  3^  to  4 
mm. ;  the  bellshaped  portion,  only  of  I — I J  mm.  The 
flower  heads  have  no  ray  flowers,  and  being  therefore 
much  less  conspicuous  than  the  allied  species,  are 
rarely  visited  by  insects. 

Carduus  arvensis  (Cirsium  of  some  authors)  is  the 
commonest  of  our  thistles.  Each  head  contains 
about  100  florets.  The  tube  of  the  florets  is  8 — 12 
mm.  in  length,  the  upper  part  forming  a  bell-shaped 
reservoir  I — ij  mm.  in  depth,  with  five  diverging 
linear  lobes.  As  the  lateral  florets  turn  outwards,  the 
whole  form  a  flower  head,  as  much  as  20  mm.  in 
diameter.  Being  therefore  very  conspicuous,  and  as 
the  honey  in  this  species  and  most  of  its  allies  rises 
into  the  cup  of  the  flower,  so  as  to  be  accessible  even 
to  insects  with  very  short  tongues,  it  is  visited  by  a 
large  number  of  species.  Miiller  records  no  less  than 
88.  In  C.  lanceolatum,  on  the  contrary,  though  it  is 
also  a  very  common  species,  still  in  consequence  of 
the  cup  being  somewhat  deeper  (4 — 6  mm.  against 
I — ij  in  C.  arvensis),  and  the  honey  therefore  rather 
less  accessible,  he  only  records  twelve.  In  C.  palustris 
the  depth  of  the  cup  is  intermediate  between  those 
of  the  two  preceding  species,  and  also  the  number  of 
insect  visitors,  namely  22. 

Onopordon  differs  from  Carduus  only  in  the 
character  of  the  receptacle,  which  does  not  bear 
chaffy  bristles,  as  in  that  genus. 

The  genus  Centaurea  offers  several  interesting 
points.  In  C.jacea,  which  is  sometimes,  for  instance 
by  Bentham,  regarded  as  a  variety  of  C.  nigra  (the 
Knapweed),  60 — 100  florets  are  united  into  a  head  ; 


V.]  CENTAUREA.  125 

the  tubes  of  the  florets  are  7 — 10  mm.,  the  cups  3 — 4^ 
in  length,  each  with  five  long,  linear,  lobes.  The  di- 
vergence of  the  outer  florets  gives  the  whole  head  a 
diameter  of  20 — 30  mm.  The  hairs  constituting  the 
pollen  brush  are  not  situated  at  the  extremity  of  the 
stigmas  as  in  the  preceding  species,  but  form  a  ring 
round  the  pistil  at  the  spot  where  it  bifurcates.  When 
the  flower  opens  the  pollen  has  been  already  shed  into 
the  anther  tube  in  the  upper  end  of  which  it  lies, 
occupying  the  space  between  the  anthers  and  the 
pistil,  and  supported  by  the  ring  of  hairs.  If  now 
the  flower  remains  untouched,  after  a  while  the  stig- 
matic  lobes  separate,  and  some  of  the  pollen  falls 
on  them.  But  if,  as  generally  happens,  an  insect 
alights  on  the  flower,  or  if  in  any  other  way  the  tip  of 
the  anthers  is  touched,  immediately  the  stamens  con- 
tract, exposing  the  pollen,  which  is  supported  by  the 
stigmatic  lobes.  Gradually  the  pistil  elongates,  and 
the  stigmatic  lobes  separate ;  by  which  time  the 
pollen  has  generally  been  all  removed,  as  the  flowers, 
in  consequence  of  their  richness  in  honey,  are  much 
frequented  by  insects. 

In  C.  nigra  the  outer  florets  are  sometimes  of  the 
same  size  as  the  rest,  sometimes  larger,  and  without 
either  stamens  or  pistils.  In  C.  scabiosa  this  is  always 
the  case.  The  tubes  of  the  florets  also  are  longer, 
the  cups  deeper,  and  the  honey  less  accessible, 
in  consequence  of  which  it  has  fewer  insect  visitors. 
Muller  records  only  21  against  48  in  C.  nigra.  In 
C.  Cyanus  also  the  ray  florets  are  neuter.  The  con- 
tractility of  the  stamens  is  very  marked.  In  flowers 
kept  in  a  room,  Muller  observed  that  when  touched, 


126        TARAXACUM,  ARTEMISIA,  DIPSACE&.    [CH. 

they  rapidly  withdrew  themselves  2 — 3  inm.,  and  then 
more  slowly,  4 — 6  mm. 

Taraxacum  (the  Dandelion).  In  T.  officinale  the 
heads  consist  of  100 — 200  florets.  In  fine  weather 
they  stand  open,  but  at  night  and  during  rain  they 
close  completely.  The  two  lobes  of  the  stigma 
gradually  curl  over,  so  that  if  the  visits  of  insects 
are  delayed  the  flower  always  fertilises  itself.  The 
honey,  however,  is  so  abundant,  and  rises  therefore 
so  high  in  the  floret,  that  it  is  very  accessible  to 
insects,  no  less  than  93  species  of  which  have  been 
observed  by  Miiller  to  visit  this  plant.  The  bright- 
ness of  its  colour,  the  quantity  of  its  honey,  the  habit 
of  closing  in  unfavourable  weather,  and  the  power  of 
self-fertilization,  go  far  to  explain  the  great  abundance 
of  the  Dandelion. 

The  genus  Artemisia  has  minute  greenish  florets, 
and  is  said  to  be  wind-fertilised. 

This  order  is  the  subject  of  an  admirable  memoir 
by  Hildebrand  (Ueber  die  Geschlechtsverhaltnisse  bei 
den  Compositen). 

DIPSACEjE. 

There  are  two  British  genera  belonging  to  this 
order ;  Dipsacus  (the  Teasel)  and  Scabiosa.  The  so- 
called  flower  is  a  compound  flower  head,  as  in  the 
Compositae,  from  which,  however,  this  group  may  be  at 
once  distinguished  by  possessing  free  anthers.  Each 
floret,  moreover,  is  inserted  in  a  small  "  involucel." 

Dipsacus  is  a  proterandrous  genus.  The  pistil 
terminates  in  two  lobes,  the  upper  surfaces  of  which 
constitute  the  stigma.  As,  however,  in  consequence 


v.]  SCABIOSA.  127 

of  the  stiff  spines  which  radiate  on  all  sides  from 
the  flower  heads  of  this  plant,  the  humble  bees,  by 
which  it  is  principally  fertilised,  can  only  touch  the 
florets  with  their  heads,  the  two  lobes  often  get  in 
one  another's  way,  and  according  to  M  tiller  it  would 
be  a  distinct  advantage  if  one  of  them  were  absent.  He 
points  out  also  that  in  fact  one  of  them  is  sometimes 
rudimentary,  or  even  occasionally  altogether  absent. 
This  adaptation  then,  it  would  seem,  has  actually 
commenced.  The  leaves  form  a  cup  round  the  stem 
in  which  water  accumulates,  and  many  small  insects 
are  drowned.  These  it  has  been  supposed  contribute 
to  nourish  the  plant,  and  Mr.  Francis  Darwin  has 
observed  that  protoplasmic  filaments  extend  into  the 
liquid. 

Scabiosa  arvensis  is  also  proterandrous.  About  50 
florets  are  united  in  one  head ;  they  increase  in  size 
from  the  centre  towards  the  circumference,  while  in 
Sc.  columbaria  the  outer  row  is  considerably  larger 
than  the  rest,  and  in  Sc.  succisa  they  are  nearly  equal 
in  size.  The  honey  is  at  the  base  of  the  tubular 
florets,  which,  however,  are  more  or  less  funnel- 
shaped  at  the  mouth,  thus  greatly  facilitating  the 
access  of  insects.  Not  only  are  the  florets  proteran- 
drous, but  this  is  the  case  with  the  whole  head ;  for, 
though  the  anthers  come  to  maturity  slowly  and  (as 
a  general  rule)  successively  from  the  edge  to  the 
centre,  none  of  the  stigmas  emerge  until  the  anthers 
have  all  shed  their  pollen,  when  they  rapidly  come  to 
maturity.  The  male  condition  of  the  flower-head 
lasts  several  days ;  the  stigmas,  on  the  contrary,  come 
to  maturity  almost  simultaneously.  This  difference 


128  CAMPANULACE^E.  [CHAP. 

is  obviously  an  advantage.  From  the  length  of  time 
during  which  the  anthers  are  ripening,  whenever 
there  is  a  sunny  day,  and  the  insects  are  abroad,  they 
are  almost  sure  to  find  some  anthers  ready  to  dust 
them  with  pollen.  On  the  other  hand,  the  stigmas 
being  mature  at  the  same  time,  they  are  capable  of 
being  fertilized  by  a  single  visit. 

Besides  the  flower-heads  with  hermaphrodite  florets, 
there  are  others  which  contain  female  florets  only, 
the  stamens  being  more  or  less  rudimentary.  This 
is  also  an  advantage,  because  if  it  were  otherwise  the 
quantity  of  pollen  would  be  unnecessarily  large. 
Scabiosa  arvensis  is  visited  by  a  great  variety  of 
insects  belonging  to  several  orders. 

Sc.  columbaria  has  a  row  of  distinctly  larger  ray 
florets,  while  the  central  ones  are  all  of  equal  size ; 
the  florets  also  are  smaller  than  in  Sc.  arvensis ; 
and  consequently,  in  heads  of  the  same  size,  more 
numerous  ;  the  florets  appear  to  be  all  hermaphrodite  ; 
and  the  ripening  of  the  anthers  does  not  take  place, 
successively,  from  the  outside. 

CAMPANULACE/E. 

The  flowers  of  Campanula  are  much  frequented 
by  insects,  and  secrete  honey  at  the  base  of  the  bell. 
The  anthers  are  distinct,  the  filaments  of  the  stamens 
are  expanded  at  the  base  into  triangular  valves  which 
serve  to  protect  the  honey ;  the  pistil  is  cleft  at  the 
top  into  two,  three,  or  five  stigmatic  lobes.  The 
genus  is  widely  distributed  and  contains  numerous 
species. 


CAMPANULA. 


129 


The  accompanying  figures  show  a  flower  of  C. 
medium  in  three  stages.  In  the  bud  (Fig.  90)  just 
before  opening,  it  will  be  seen  that  the  large,  long 
anthers  clasp  the  pistil,  which  is  no  longer  than  they 
are  themselves.  In  the  second  stage  (Fig.  91)  the 
anthers  have  opened  on  the  inner  side,  and  shed  their 
pollen,  which  adheres  to  the  style.  The  anthers  them- 
selves then  shrivel  up,  offering  a  surprising  contrast  to 
their  former  condition.  Insects  visiting  the  flower  for 


Ca  Ca 


.  90-  FIG.  91. 

FIG.  90.— Section  of  bud  of  Campanula  medium. 
FIG.  91.— Section  of  a  flower  in  the  first  (male)  condition. 
tic.  92. — Ditto,  in  the  second  (female)  condition. 


FIG.  92. 


the  sake  of  honey,  do  not,  as  far  as  I  have  observed, 
generally  walk  on  the  petals,  being  deterred  by  the  stiff 
hairs  which  are  scattered  on  their  inner  surface.  In 
any  case,  however,  they  are  almost  sure,  sooner  or  later, 
to  clasp  the  style,  when  they  necessarily  dust  them- 
selves with  the  pollen.  In  this  stage  the  flower  is 
incapable  of  fertilization.  Gradually,  however,  the 
style  elongates,  and  the  lobes  of  the  upper  end 

K 


130  ERIC  ACE &.  [CHAP. 

separate,  so  that  by  the  time  the  pollen  is  all  removed 
the  flower  is  in  the  state  shown  in  Fig.  92,  and  it 
is  evident  that  any  bee  which  may  have  visited  a 
younger  flower,  and  dusted  its  under  side  with  pollen, 
can  hardly  fail  to  deposit  some  of  it  on  the  stigmatic 
surfaces  thus  extended  for  its  reception. 

It  had  been  supposed  that  the  hanging  position  of 
Campanula  and  other  bell-shaped  flowers  had  reference 
to  the  position  of  the  stamens  and  pistil,  so  that  the 
pollen  might  fall  from  the  former  on  to  the  latter. 
Sprengel,  however,  pointed  out  that  the  real  advan- 
tage to  the  flower  consisted  in  the  fact  that  the  honey 
is  thus  protected  against  rain.  If  the  pollen  fell  on 
to  the  stigma,  it  is  indeed  obvious  that  the  stigmatic 
surface  should  be  turned  upwards,  whereas  it  is  at  the 
end  of  the  pistil,  and  is  consequently  turned  down- 
wards, showing  that  the  pollen  comes  from  below  and 
not  from  above. 

The  other  British  genera  of  Campanulaceae  are 
Lobelia,  Jasione,  and  Phyteuma. 

ERICACEAE. 

This  order  contains  ten  British  genera. 

Erica  tetralix  (the  Cross-leaved  Heath)  has  been 
well  described  by  Dr.  Ogle  (Popular  Science  Review, 
April  1870).  The  flower  is  in  the  form  of  a  bell 
(Fig.  93),  which  hangs  with  its  mouth  downwards, 
and  is  almost  closed  by  the  pistil,  and  stigma  (st\ 
which  represents  the  clapper.  The  stamens  are  eight 
in  number,  and  each  terminates  in  two  cells,  which 
diverge  slightly,  and  have  at  their  lower  end  an  oval 


v.] 


ERICA. 


opening.  But  though  this  opening  is  at  the  lower 
end  of  the  anther  cells,  the  pollen  cannot  fall  out, 
because  each  cell,  just  where  the  opening  is  situated, 
rests  against  the  next  anther  cell,  and  the  series  of 
anthers  thus  form  a  circle  surrounding  the  pistil  and 
not  far  from  the  centre  of  the  bell.  Each  anther 


FIG.  93.— Flower  of  Erica  tetralix.  FIG  94.— Stamen  of  ditto. 

cell  also  sends  out  a  long  process  (pr,  pr\  which  thus 
form  a  series  of  spokes,  standing  out  from  the 
circle  of  anthers.  Under  these  circumstances,  a 
bee  endeavouring  to  suck  the  honey  from  the 
nectary  cannot  fail  firstly  to  bring  its  head  in  contact 
with  the  viscid  stigma  (Fig.  93,  st)  and  thus  to  deposit 
upon  it  any  pollen  derived  from  a  previous  visit  ; 
and  secondly,  in  thrusting  its  proboscis  up  the 

K    2 


132  VACCIN1UM,  PRIMULACE&.  [CHAP. 

bell,  it  inevitably  comes  in  contact  with  one  of  the 
anther  processes,  pr,  which  then  acts  like  a  lever,  and 
dislocates  the  whole  chain  of  anther  cells,  when  a 
shower  of  pollen  falls  from  the  open  anther  cells  on 
to  the  head  of  the  bee. 

Erica  cinerea  agrees  very  closely  with  E.  tetralix. 
In  Erica  (or  Callund)  vulgaris  (the  Common  Heath), 
on  the  contrary,  where  the  flowers  are,  in  their  natural 
position,  more  horizontal,  the  stamens  and  pistil 
incline  upwards,  so  that  insects  press  their  proboscis 
under  them,  and  in  this  manner  the  pollen  is  less 
likely  to  be  wasted,  than  if  they  were  central  as  in  E. 
tetralix.  In  Erica  vagans($b&  Cornish  Heath),  E.  carnea> 
and  E.  ciliata,  the  anthers  have  no  appendages. 

In  the  allied  genus  Vaccinium  there  is  an  arrange- 
ment similar  to  that  in  Erica,  but  the  anther  cells 
are  closed,  not  by  touching  one  another,  but  by 
resting  against  the  style,  so  that  the  style  itself 
closes  the  openings  until  the  anthers  are  disturbed 
by  the  proboscis  of  the  bee.  V.  uliginosum  is  much 
larger  than  V.  Myrtillus,  and  consequently  more 
conspicuous  ;  V.  Myrtillus,  on  the  other  hand,  has  the 
compensating  advantage  of  being  richer  in  honey. 

The  curious,  brown-coloured,  nearly  leafless  Mono- 
tropa  (Yellow  Birds-nest),  differs  very  much  from  the 
rest  of  the  order. 

PRIMULACE^:. 

This  order  is  represented  in  Britain  by  eight  genera : 
Primula,  Lysimachia,  Trientalis,  Glaux,  Anagallis, 
Centunculus,  Samolus,  and  Hottonia.  Cyclamen  also 
grows  wild  in  some  places,  but  is  not  a  true  native. 

I  have  already  referred  to  the  genus  Primula  in  the 


v.]       HOTTONIA,  LYSIMACHIA,  ANAGALLIS.       133 

introductory  chapter  (anti,  p.  33).  The  majority  of  the 
species  are  dimorphous,  but  not  all  (Scott, "  Proc.  Linn 
Soc.,"  vol.  viii.  1864).  In  Primula  Stricta,  according 
to  Axell  ("  Om  Anord.  for  de  Vax  Befrucktning  "), 
when  the  flowers  first  open,  the  anthers  are  already 
mature,  and  are  attached  to  the  tube  of  the 
corolla,  some  distance  above  the  as  yet  immature 
stigma.  Gradually,  however,  the  pistil  elongates, 
bringing  the  stigma  to  the  same  height  as  the 
anthers. 

Hottonia  palustris,  though  so  unlike  Primula  in 
habit  and  appearance,  is  also  dimorphous,  and  agrees 
with  the  former  genus  very  nearly  in  the  relative 
positions  of  the  stamens  and  pistil  in  the  two  forms. 
The  difference  was  noticed  by  Sprengel,  who  says 
(p.  103),  "  I  think  this  is  not  accidental,  but  a  provision 
of  nature,  though  I  am  not  in  a  position  to  point  out 
the  advantage  of  it" 

Lysimachia  vulgaris  produces  no  honey.  In  this 
species  Miiller  has  observed  the  existence  of  two  ex- 
tremes (connected,  however,  by  intermediate  forms)  ; 
one,  more  conspicuous,  which  rarely  or  never  fertil- 
ises itself;  the  other  less  conspicuous  frequenting 
shady  places,  and  habitually  self-fertile. 

Of  the  genus  Anagallis  (the  Pimpernel)  we  have, 
according  to  Bentham,  two  species  only,  A.  arvensis 
and  A.  tenella.  The  former,  however,  contains  two  well- 
marked  varieties,  one  blue  and  the  other  red,  which 
do  not  cross,  and  are  considered  by  some  botanists  as 
distinct  species,  under  the  names  of  A.  ccerulea,  and 
A.  arvensis.  Whether  it  may  be  more  convenient  to 
treat  them  as  true  species  or  as  mere  varieties,  it  must 
at  least  be  admitted  that  they  differ  considerably. 


134  LENTIBULACE&,  APOCYNACE&.      [CHAP. 

Not  only  are  they  of  different  colours,  the  one  blue, 
the  other  red,  but  A .  cczrulea  is  very  decidedly  smaller. 
The  stamens  and  pistil  ripen  simultaneously.  The 
flowers  contain  no  honey,  and  partially  close  about 
three  o'clock  in  the  afternoon. 

The  flowers  are  seldom  visited  by  insects,  and  it 
would  appear  that  they  generally  fertilise  themselves. 
This  is  said  to  be  the  case  also  with  Centunculus 
minimus. 

LENTIBULACE^E". 

This  order  contains  two  British  genera :  Utricularia 
and  Pinguicula.  Both  are  fertilised  by  insects,  and  in 
both  the  insect  first  touches  the  stigma,  and  afterwards 
comes  in  contact  with  the  stamens.  In  Utricularia 
the  stigma  is  irritable  and  retracts  at  once  on  being 
touched,  so  that  the  proboscis  after  dusting  itself  with 
the  pollen  does  not  again  come  into  contact  with  it. 

Both  genera  are  insectivorous.  Utricularia  is  aquatic, 
and  the  submerged  leaves  bear  small  bladders  or 
utricles,  at  the  entrance  of  which  are  stiff  hairs  so 
arranged  as  to  permit  the  entrance,  but  prevent  the 
exit  of  small  water  animals.  Even  fish,  of  course  only 
when  very  young,  are  sometimes  so  captured. 

In  Pinguicula  the  leaves  are  covered  with  sticky, 
glandular  hairs,  and  the  escape  of  any  small  flies  or 
other  insects  which  may  be  so  unfortunate  as  to 
alight  on  them  is  rendered  more  difficult  by  the 
fact  that  the  edges  are  curved  over. 

APOCYNACE^E. 

In  Vinca  (the  Periwinkle),  which  has  been  de- 
scribed by  Delpino  and  Hildebrand,  the  arrangement 
resembles  in  principle  that  already  described  in 


v.]  GENTIANACE^;.  135 

Polygala.  The  anthers  and  the  stigma,  which  is 
immediately  below  them,  together  nearly  close  up 
the  tube  of  the  flower.  The  upper  portion  of  the 
pistil  is  clothed  with  hairs  which  arrange  themselves 
so  as  to  form  a  sort  of  pocket  or  chamber  opposite 
each  anther,  and  when  the  pollen  is  shed  it  is  received 
into  this  pocket  or  chamber.  The  stigma  somewhat 
resembles  an  inverted  saucer,  attached  by  the  middle 
to  the  style.  The  upper  portion  of  the  stigma  is 
viscid  and  rubs  against  the  proboscis  of  the  insect  as 
it  is  withdrawn.  The  proboscis,  thus  rendered  adhesive, 
carries  off  some  of  the  pollen.  When  the  insect  visits 
the  next  flower,  the  pollen  is  scraped  off  the  proboscis 
by  the  sharp  edge  of  the  saucer,  and  is  thus  accu- 
mulated in  the  hollow  of  the  saucer,  which  is  the 
true  stigmatic  surface. 

GENTIANACEiE. 

In  this  order  we  have  six  British  genera  :  Cicendia, 
Erythraea,  Gentiana,  Chlora,  Menyanthes,  and  Lim- 
nanthemum. 

Gentiana  Pneumonanthe  is  proterandrous.  It 
secretes  honey  at  the  base  of  a  tube  25 — 30  mm.  long  ; 
Bees,  however,  can  creep  half  way  down,  in  doing 
which  they  come  in  contact  with  the  anthers  in 
younger  flowers,  and  in  older  ones  with  the  stigma, 
which  lies  somewhat  higher  in  the  tube.  The  power 
of  self-fertilisation  appears  to  be  lost.  Gentiana  ama- 
rella,  on  the  contrary,  is  homogamous,  the  anthers  and 
stigma  coming  to  maturity  together,  though  as  the 
style  of  pistil  is  somewhat  longer  than  the  stamens,  an 
insect  touches  the  stigma  before  reaching  the  anthers. 

The   beautiful   Erythraa  centaurium  is  frequently 


136  POLEMONIACEJE)  BORAGINACE&.     [CHAP. 

visited  by  butterflies,  though  it  contains  no  honey, 
at  least  neither  Sprengel  nor  M tiller  could  find  any. 
Menyanthes  and  Limnanthemum  (Kuhn, "  Bot.  Zeit," 
1867)  are  said  to  be  dimorphous. 

POLEMONIACE^E. 

This  family  is  represented  in  England  by  one  species, 
Polemonium  cceruleum^  and  even  this  is  a  doubtful  native. 
It  has  been  shown  by  Axell  to  be  proterandrous. 

BORAGINACE^:. 

This  order  is  easily  distinguished  from  all  others, 
except  the  Labiatae,  by  the  four  seed-like  nuts ; 
from  the  Labiatae  by  the  form  of  the  flowers,  and 
by  the  leaves  being  alternate.  It  contains  eleven 
British  genera,  viz., — Echium,  Pulmonaria  (Fig.  96), 
Mertensia,  Lithospermum,  Myosotis,  Anchusa,  Ly- 
copsis,  Symphytum,  Borago  (Fig.  95),  Asperugo,  and 
Cynoglossum. 

In  consequence  of  its  conspicuousness,  and  the 
easy  accessibility  of  its  honey,  Echium  vulgare  is 
visited  by  a  great  variety  of  insects.  The  flower  is 
tubular,  contracting  towards  the  base,  so  that  insects 
are  naturally  conducted  to  the  honey.  The  stamens 
are  five  in  number  ;  one  remains  in  the  tube  of  the 
flower,  while  the  other  four  project,  and  form  a  con- 
venient alighting  stage  for  insects,  which  can  thus 
hardly  fail  to  dust  their  undersides  with  pollen. 

Echium  is  proterandrous  ;  when  the  flower  opens 
the  anthers  are  already  ripe  ;  the  pistil,  on  the  other 
hand,  is  still  quite  short  and  immature,  scarcely 
reaching  to  the  mouth  of  the  tube.  Gradually,  how- 
ever, it  extends  until  it  reaches  10  mm.  beyond 


v.] 


BORAGE. 


137 


the  tube,  and  divides  at  the  end  into  two  short 
branches,  with  terminal  stigmas.  In  this  species, 
therefore,  cross-fertilisation  is  favoured ;  firstly,  by 
the  fact  that  the  stamens  ripen  before  the  stigmas ; 
and,  secondly,  by  the  relative  position  of  the  two,  the 
stigmas,  as  we  have  seen  in  so  many  other  cases, 
projecting  somewhat  beyond  the  stamens.  Under 
these  circumstances  cross-fertilisation  is  so  thoroughly 


FIG.  g^.—Borago  officinalis. 

secured,  that  the  plant  is  said  to  have  lost  the 
power  of  fertilising  itself.  Miiller  observed  no  less 
than  67  species  of  insects  on  the  flowers  of  this 
plant :  some  of  which  (Osmia  adunca  and  O.  camen- 
tarid]  seem  to  confine  themselves  to  it 

In  the  Borage  (Borago  officinalis,  Fig.  95)  we  find 
an   arrangement  of    the   stamens  and    pistils   very 


138  PULMONARIA.  [CHAP. 

different  to  that  in  Echium,  but,  as  Sprengel  has 
pointed  out,  somewhat  resembling  that  already  de- 
scribed in  the  Violet.  The  flowers  are  drooping,  of 
a  beautiful  blue,  with  a  white  central  circle ;  dark 
stamens,  combined  into  a  tube,  and  a  pink  pistil.  The 
pale  yellow,  fleshy  ovary  secretes  honey,  which  lies 
in  a  short  tube  formed  of  the  basis  of  the  stamens. 
The  anthers  are  long,  and  open  gradually  from  the 
apex  to  the  base,  so  that  the  pollen  falls  into  the 
closed  space  between  them  and  the  pistil.  This 
arrangement  effectually  protects  both  the  pollen  and 
the  honey  from  all  insects,  excepting  bees.  The 
latter,  however,  force  their  proboscis  down  to  the 
honey,  between  the  anthers,  which,  however,  return 
to  their  former  position  again,  as  soon  as  the  pro- 
boscis is  withdrawn.  As  soon  as  the  anthers  are 
separated,  the  pollen  drops  down  on  to  the  head  of 
the  bee,  and  is  thus  carried  from  one  flower  to 
another.  Cross-fertilisation  is  also  favoured  by  the 
flower  being  proterandrous,  the  stigma  not  becoming 
mature  until  the  anthers  have  shed  all  their  pollen. 
The  Borage  is  much  visited  by  bees,  especially  by 
the  common  hive  bee. 

Pulmonaria  officinalis  (Fig.  96)  is  a  dimorphous 
species  ;  being  rich  in  honey  and  much  visited  by  in- 
sects, it  has  not  only  lost  the  power  of  self-fertilisation, 
but  is  said  by  Hildebrand  (Bot.  Zeit.,  1865)  to  be 
sterile  to  pollen  from  the  same  form  of  flower ;  that 
is  to  say,  long-styled  flowers  require  to  be  fertilised 
by  pollen  from  short-styled  flowers,  and  vice  versa. 
Darwin,  however,  succeeded  in  obtaining  seeds  and 
raising  seedlings  from  some  long-styled  plants  which 


V.]  BORAGINJE  139 

were  fertilised  with  pollen  of  the  same  form.  (Jour. 
Linn.  Soc.,  v.  x.  p.  430.)  We  have  already  seen  that 
this  is  partially  the  case  with  other  dimorphous  species. 
The  genus  Myosotis  (the  Forget-me-not)  has 
already  been  alluded  to  in  the  introductory  chapter 
(anti,  p.  35).  The  species,  however,  appear  to  differ 
among  themselves  in  the  relative  positions  of  the 
stamens  and  pistil. 


FIG.  96. — Pulmonaria  ojficinalis. 

In  this  beautiful  and  interesting  family,  though  we 
have  not  above  twenty  British  species,  we  find,  as 
Miiller  has  well  pointed  out,  the  widest  differences  in 
the  conditions  of  fertilisation.  Pulmonaria  officinalis 
is  dimorphous,  and  sterile — not  only  with  its  own 
pollen,  but  even  in  some  cases  with  that  of  a  different 
flower,  unless  it  belongs  to  the  different  form.  Echium 
vuigare  has  lost  the  power  of  self-fertilisation,  but,  so 


140  CONVOLVULACE&.  [CHAP. 

far  at  least  as  we  know,  is  fertile  with  the  pollen  of 
any  other  flower  belonging  to  the  species.  Other 
species  are  generally  fertilised  by  insects,  but  in  their 
absence  perform  this  office  for  themselves ;  while 
lastly,  some  species,  such  as  Lithospermum  arvense, 
and  Myosotis  intermedia,  habitually  fertilise  them- 
selves. Again  cross-fertilisation  is  secured  in  Pulmo- 
naria  by  dimorphism ;  in  Echium  and  Borago  by 
proterandrousness  (if  I  may  be  permitted  to  coin  the 
word)  :  in  Symphytum  and  Anchusa,  by  the  projec- 
tion of  the  stigma  beyond  the  stamens ;  in  Lithos- 
permum and  Myosotis,  by  the  narrowness  of  the 
flower  tube. 

CONVOLVULACE.E. 

The  well-known  Convolvulus  and  the  singular  little 
Dodder  (Cuscuta)  are  the  only  British  genera  belong- 
ing to  this  family. 

Cuscuta  is  a  leafless,  annual,  parasitic  plant,  with 
thread-like  stems.  The  flowers  are  small,  nearly 
globular,  and  grow  in  lateral  heads  or  clusters.  One 
species  attacks  the  clover,  and  is  sometimes  sufficiently 
abundant  to  do  much  mischief. 

We  have  in  England  three  species  of  Convolvulus 
— C.  arvensis,  C.  sepiumy  and  C.  soldamlla. 

C.  arvensis  being  melliferous  and  slightly  sweet- 
scented,  is  much  visited  by  insects.  The  honey  is 
situated  below  the  bases  of  the  stamens,  which  are 
somewhat  flattened  and  bent  inwards,  so  that  the 
insect  can  only  reach  the  honey  by  pressing  its  pro- 
boscis down  between  them.  The  stigmas  and  anthers 


v.]  SOLANACE^E,  OROBANCHACE^E.  141 

mature  at  the  same  time ;  but  as  the  former  project 
above  the  latter,  they  are  necessarily  touched  first. 
If  the  visits  of  insects  be  too  long  deferred,  the 
flower  fertilises  itself.  C.  arvensis  closes  in  wet 
weather  and  at  night. 

C.  sepium,  on  the  contrary,  remains  open  during 
rain,  but  closes  at  night,  unless  there  be  a  moon, 
when  it  remains  expanded.  It  has  no  smell,  and  is 
perhaps,  on  that  account,  in  spite  of  its  large  size, 
comparatively  little  visited  by  insects. 

SOLANACE^:. 

The  British  genera  are  the  following  :  Hyoscyamus  (the  Henbane), 
Solanum  (the  Nightshade),  and  Atropa.  Datura  is  sometimes  found 
growing  wild,  but  it  is  not  a  true  native. 

Solanum  secretes  no  honey,  and  is  little  visited  by  insects.  Hyos- 
cyamus, on  the  contrary,  is  melliferous,  and  cross -fertilisation  is  favoured 
by  the  projection  of  the  stigma  beyond  the  anthers. 

OROBANCHACE^E. 

A  curious  family,  with  simple  or  rarely- branched  stems,  and  scales 
instead  of  leaves.  The  species  are  either  brown  or  purplish,  but  never 
green,  and  are  parasitical  on  the  roots  of  other  plants.  There  are  two 
British  genera  :  Orobanche  (Broomrape)  and  Lathraea  ;  both  are  para- 
sitic. In  Lathraea  the  scale-like  leaves  are  hollowed  out,  the  inner 
surfaces  being  provided  with  peculiar  structures  of  two  kinds ;  both 
consist  of  three  cells,  two  of  which  are  spherical,  and  situated  on  the 
third,  which  in  the  one  sort  is  cylindrical,  so  that  they  resemble  gland- 
ular hairs  ;  in  the  second  sort  the  basal  cell  is  flattened.  These  organs 
have  been  described  as  possessing  the  power  of  throwing  out  proto- 
plasmic extensions,  which  have  been  supposed  to  extract  nourishment 
from  small  insects  which  are  captured  in  the  hollows,  but  this  has  not 
yet  been  confirmed. 

SCROPHULARIACE^E. 

This  is  a  large  family,  consisting  of  fourteen  genera, 
and  contains  :  Veronica  (Fig.  97),  Verbascum  (Mullein), 
(Fig.  98),  Linaria,  Antirrhinum  (Snapdragon),  Scro- 
phularia  (Fig.  99),  Digitalis  (Foxglove),  (Fig.  100), 
Euphrasia  (Eyebright),  (Fig.  106),  Rhinanthus 
(Rattle),  &c. 


142  VERONICA.  [CHAP. 

The  first  two  genera  have  more  or  less  open 
flowers ;  while  the  others  are  more  distinctly  tubular, 
and  have  much  the  appearance  of  Labiatae,  but  differ 
from  that  group  in  having  the  ovary  two-celled,  with 
several  ovules  in  each  cell. 

Veronica.  The  flowers  are  rendered  conspicuous 
by  their  colour  and  the  association  in  racemes.  In 
V.  Chamcedrys  (Fig.  97),  the  anthers  and  stigmas 
ripen  simultaneously,  but  while  the  latter  project 


FIG.  97.—  Veronica  -Chamcedrys. 

straight  forwards,  the  two  stamens  turn  outwards,  so 
that  fertilisation  can  hardly  take  place. 

V.  Beccabunga  in  many  respects  resembles  V.  Cha- 
mcedrys \  but  is  proterogynous.  In  V.  spicata  some 
flowers  are  proterogynous,  others  proterandrous,  and 
being,  in  consequence  of  their  conspicuousness,  much 
visited  by  insects,  they  appear  to  have  lost  the  power 
of  self-fertilisation.  In  V.  hederafolia,  on  the  con- 


VERBASCUM. 


trary,  the  flowers  are  minute,  and  habitually  fertilise 
themselves. 

The  species  of  Verbascum  (Mullein)  are  showy 
plants,  with  either  white  or  yellow  flowers,  forming  a 
tall  spike,  which  in  V.  Thapsus  reaches  a  height  of 
four  feet.  V.  nigrum,  L.  (Fig.  98)  has  yellow  flowers ; 
the  stamens  clothed  with  beautiful  violet  hairs.  They 
secrete  very  little  honey,  but  are  visited  by  various 


FIG.  98. —  Verbascum  Thapsus. 


insects  for  the  sake  of  the  pollen,  and  perhaps  also 
on  account  of  the  glandular  terminations  of  the  violet 
staminal  hairs.  The  stamens  turn  somewhat  upwards, 
the  pistil,  on  the  contrary,  downwards,  so  that  an 
insect  alighting  on  the  lower  lip  of  the  corolla,  which 
is  the  most  convenient  place,  would  naturally  come 
in  contact  with  it  before  touching  the  stamens,  V. 


144  SCROPHULAR1A.  [CHAP. 

nigruniy  however,  according   to  Gaertner,  cannot   be 
fertilised  by  its  own  pollen. 

The  genus  Scrophularia,  from  which  the  family 
takes  its  name,  is  remarkable  in  many  respects. 
From  the  general  arrangement  of  the  blossom  in 
flowers  of  the  Labiate  form,  the  pistil  could  hardly 
occupy  any  other  position  than  the  central  median 


FIG.  99. — Scr?phnla.ria  nodosa. 

line,  and  a  fifth  stamen  would  accordingly  be  in  the 
way.  It  has  therefore  disappeared,  though  Miiller 
mentions  that  he  once  found  one  in  Lamium  album. 
In  Scr.  nodosa  (Fig.  99),  however,  the  four  normal 
stamens  and  the  pistil  occupy  the  lower  side  of  the 
flower,  and  the  presence  of  a  fifth  stamen,  even  if 
useless,  is  under  these  circumstances  not  injurious. 
A  rudimentary  fifth  stamen  is,  in  fact,  habitually 


v.]  LINARIA,  ANTIRRHINUM.  145 

present,  and  in  some  cases  bears  pollen.  Scr.  nodosa 
is  proterogynous,  and  is  much  frequented  and  fertil- 
ised by  wasps.  Pentstemon  also  has  a  fifth  stamen, 
which  curves  in  a  very  curious  manner  from  the 
upper  to  the  under  side  of  the  flower  so  as  to  be 
out  of  the  way  of  the  pistil.  Ogle  regards  it  as 
perfectly  useless  (Popular  Science  Review,  Jan.  1870), 
but  it  is  so  large  that  I  cannot  help  thinking  it  must 


FIG.  too.  FIG.  101.  FIG.  102. 

FIG.  100. — Section  of  Digitalis  furpurea,  showing  the  anthers  unripe  and  horizontal. 
FIG.  101. — Ditto,  more  advanced.  The  upper  anthers  ripe  and  vertical,  the  lower  ones 

as  before. 
FIG.  102. — Ditto,  still  more  advanced.    All  the  anthers  ripe  and  vertical 

have  some  function,  though  I  am  unable  to  suggest 
one. 

In  Linaria  vulgaris  the  flowers  form  a  closed  box 
terminating  behind  in  a  spur,  10 — 13  mm.  in  length, 
which  contains  the  honey,  and  the  orifice  of  which  is 
protected  by  hairs.  Under  these  circumstances,  the 
long-lipped  bees  are  the  only  insects  which  can  suck 
the  honey.  Antirrhinum  majus  (the  Snapdragon) 
differs  in  the  larger  size  of  the  flowers,  the  greater 

L 


146  DIGITALIS.  '  [CHAP. 

firmness  with  which  they  are  closed,  and  in  the  posi- 
tion of  the  honey,  which  lies  at  the  basis  of  the 
corolla,  and  does  not  penetrate  into  the  short  spur, 
which  is  hairy,  and  therefore  not  suited  for  such  a 
purpose.  They  are  almost  always  fertilised  by  humble 
bees,  though  smaller  bees  occasionally  force  their  way 
into  them. 

Digitalis  purpurea  (the  Foxglove)  is  also  exclusively 
fertilised   by  humble    bees,   which   alone    are   large 


FIG.  103 — Bartsia  odontites. 

enough  to  fill  the  bell,  and  thus  to  deposit  pollen 
on  the  stigma.  The  flower  is  proterandrous,  but 
appears  to  be  self-fertile  if  the  visits  of  humble  bees 
are  delayed  or  prevented.  The  cells  of  the  anthers, 
as  Ogle  has  pointed  out,  are  at  first  transverse  (Fig. 
100),  but  as  the  two  pairs  ripen  they  successively 
become  longitudinal  (Figs.  101  and  102). 


V.]  BARTSIA.  147 

The  other  British  genera  of  this  group  have  narrow 
tubular  flowers ;  in  which  the  upper  lip  protects  the 
anthers  and  pistil,  while  the  lower  lip  serves  as  an 
alighting  stage  for  insects.  The  stamens  are  so  ar- 
ranged that  the  insects  in  searching  for  the  honey 
dust  themselves  with  the  pollen.  For  instance,  in 
Bartsia  odontites  (Fig.  103),  the  common  red  Bartsia, 
the  flower  forms  a  tube  4 — 5  mm.  long ;  at  the  base 
of  which  is  the  honey,  while  the  entrance  is  protected 
against  rain  by  the  four  hairy  anthers.  These  lie 


FIG.   104.— Bartsia  odontites.     Flower        FIG.  105.     Ditto.      Flower  with  a  long 
with  a  short  pistil.  pistil. 

close  together ;  but  immediately  below  them,  the 
filaments  of  the  stamens  separate  so  as  to  leave  a 
space  through  which  bees  can  insert  their  proboscis, 
and  thus  reach  the  honey.  In  doing  so  they  natur- 
ally dust  themselves  with  pollen,  some  of  which 
they  transfer  to  the  stigma  (Fig.  105,  st}  of  the 
next  flower  they  may  visit.  Miiller  has  observed 
that  in  plants  of  this  species  which  live  in  shady 
places  and  are  consequently  less  visited  by  insects, 
the  pistil  is  shorter  (Fig.  104),  the  stigma  consequently 

L  2 


148 


EYEBRIGHT. 


[CHAP. 


nearer  to  the  anthers,  and  more  likely  to  be  fertilised 
directly  by  them. 

He  also  observes  that  this  flower  is  not  perfectly 
adapted  to  present  circumstances,  since  bees  are  able 
to,  and  often  do,  insert  their  proboscis  above  the 
stamens,  in  which  case  they  do  not  fertilise  the 
flower. 

Euphrasia  officinalis  (the  Eyebright)  (Fig.  106), 
agrees  in  many  respects  with  the  preceding ;  but  there 


Co 


FIG.  106.—  Euphrasia  ojfictnalis.       FIG.  1=7.— Flower  of  Euphrasia  officinalis. 

is  no  room  above  the  stamens  for  the  proboscis  of 
the  bee.  The  anthers  (Fig.  107)  also,  which  in 
Bartsia  odontites  are  merely  locked  together  by  hair, 
in  this  species  are  more  intimately  connected,  the  two 
uppermost  anthers  to  one  another,  the  lower  anther 
of  each  upper  pair  with  the  upper  anther  of  the  lower 
stamen  on  the  same  side.  The  lower  anther  of  the 
lower  stamen  is  produced  into  a  strong  point  (Fig. 


v.]  RHINANTHUS.  •    149 

107,  which  is  touched  by  the  proboscis  of  the  bee 
in  passing  down  the  tube  to  the  nectary,  and  serves 
as  a  lever,  shaking  the  whole  system  of  anthers  and 
thus  causing  the  pollen  to  fall  out  on  to  the  bee. 

In  this  species  also  H.  Miiller  has  observed  that 
there  are  two  forms,  a  larger  one  which  is  adapted  to 
be  fertilised  by  insects,  and  a  smaller  one  which  more 
frequently  fertilises  itself. 

In  Rhinanthus  Cristagalli  (the  Common  Rattle)  the 
anthers  are  locked  together,  and  the  pollen  is  shed 
on  to  the  bee,  but  the  mode  in  which  this  is  effected 
is  not  the  same.  In  this  species,  as  in  Bartsia  odon- 
tites,  the  bee  has  to  pass  its  proboscis  between  the 
filaments  of  the  anthers  in  order  to  reach  the  honey, 
and  the  space  between  them  is  so  narrow,  that  the 
bee  in  pressing  its  proboscis  down  the  tube,  presses 
the  filaments  apart,  thus  shaking  the  anthers,  and 
freeing  the  pollen.  In  this  species  also  H.  Miiller 
has  observed  the  existence  of  two  forms. 

In  the  common  Pedicularis  (Fig.  108)  (Pedicularis 
sylvatica\  which  has  been  well  described  by  Hilde- 
brand  and  Delpino,  the  arrangement  is  somewhat  dif- 
ferent. The  anthers  open  on  their  inner  sides,  and 
the  edges  of  the  open  anther  cells  on  the  one  side  of 
the  flower  exactly  correspond  with,  and  are  applied 
to,  the  corresponding  edges  of  the  anthers  on  the 
other  side  of  the  flower ;  each  pair  of  anthers  thus 
forming  as  it  were,  a  closed  box.  The  outer  sides 
of  the  anthers  are  slightly  attached  to  the  walls  of 
the  hood.  But  the  sides  of  the  hood  are  somewhat 
too  near  together  to  admit  the  head  of  the  humble- 
bee,  and  the  insect  therefore,  in  order  to  reach  the 


150 


PEDICULARIS. 


[CHAP. 


honey,  pushes  them  a  little  apart,  thus  opening  the 
anther-box  and  letting  down  a  little  shower  of  pollen, 
which  is  prevented  from  spreading  by  the  fringe  of 


8t 


FIG.  1 08. — Pedicularis  sylvatica. 


hairs  on  the  lower  edge  of  the  anther,  and  thus  falls 
on  to  the  head  of  the  bee,  at  the  very  spot  which  a 
moment  before  had  touched  the  stigma,  and  which 
will  again  touch  that  of  the  next  flower  she  visits. 


v.]  LABIATE.  151 

In  P.  palustris  the  point  m  is  elongated,  and  the 
anthers,  in  the  specimens  which  I  have  examined,  are 
glabrous. 

The  structure  of  Melampyrum  agrees  in  essentials 
with  that  of  Pedicularis.  In  Calceolaria  pinnata, 
Hildebrand  describes  an  arrangement  somewhat 
similar  to  that  which  we  shall  meet  with  in  Salvia. 


LABIATE. 

This  large  and  interesting  order  contains  eighteen 
British  genera,  amongst  which  are  the  Salvia,  Dead 
Nettle,  Sage,  Thyme,  Mint,  Marjoram,  Bugle,  and 
Calamint.  Most  of  them,  if  not  all,  produce  honey 
at  the  base  of  the  ovary. 

In  few  flowers  is  the  adaptation  of  the  various 
parts  to  the  visits  of  insects  more  clearly  and  beauti- 
fully shown  than  in  the  common  white  Dead  Nettle 
(Lamium  album),  (Fig.  109). 

The  honey  occupies  the  lower  contracted  portion 
of  the  tube,  and  is  protected  from  the  rain  by  the 
arched  upper  lip  and  by  a  rim  of  hairs.  Above  the 
narrower  lower  portion  the  tube  expands,  and  throws 
out  a  broad  lip  (Fig.  in  m),  which  serves  as  an 
alighting  place  for  large  bees,  while  the  length  of 
the  narrow  tube  prevents  the  smaller  species  from 
obtaining  access  to  the  honey,  which  would  be  in- 
jurious to  the  flower,  as  it  would  remove  the  source 
of  attraction  for  the  bees,  without  effecting  the  object 
in  view.  At  the  base  of  the  tube,  moreover,  at  the 
point  marked  ca,  Fig.  in,  there  is  a  ring  of  hairs 


152  LAMIUM.  [CHAP. 

which  prevent  small  insects  from  creeping  down  the 
tube  and  so  getting  at  the  honey.  Lamium,  in  fact, 
like  so  many  of  our  other  wild  flowers,  is  especially 
adapted  for  humble  bees.  They  alight  on  the  lower 
lip,  which  projects  at  the  side,  so  as  to  afford  them 
a  leverage,  by  means  of  which  they  may  press  the 
proboscis  down  the  tube  to  the  honey  ;  while,  on  the 
other  hand,  the  arched  upper  lip,  in  its  size,  form,  and 


FiG.  109. — Lamium  album. 

position,  is  admirably  adapted  not  only  as  a  protec- 
tion against  rain,  but  also  to  prevent  the  anthens  (Fig. 
ay  a)  and  pistil  (Fig.  1 1 1,  st)  from  yielding  too  easily 
to  the  pressure  of  the  insect,  and  thus  to  ensure  that 
it  should  press  the  pollen  which  it  has  brought  from 
other  flowers  against  the  pistil. 

The  stamens  do  not  form  a  ring  round  the  pistil, 
as   is   so    usual.      On  the  contrary,   one  stamen   is 


v.]  THE  DEAD  NETTLE.  153 

absent  or  rudimentary,  while  the  other  four  lie  along 
the  outer  arch  of  the  flower,  on  each  side  of  the  pistil. 
They  are  not  of  equal  length,  but  one  pair  is  shorter 
than  the  other;  the  inner  pair  in  some  species,  the 
outer  pair  in  others  being  the  longest.  Now,  why 
is  this?  Probably,  as  Dr.  Ogle  has  suggested,  be- 
cause if  the  anthers  had  lain  side  by  side,  the  pollen 
would  have  adhered  to  parts  of  the  bee's  head  which 
do  not  come  in  contact  with  the  stigma,  and  would 
therefore  have  been  wasted ;  perhaps  also  partly,  as 


CO 


FIG.  no. — Flower  of  Lantium  album.  FIG.  in. — Section  of  ditto. 

he  suggests,  because  it  would  have  been  deposited 
on  the  eyes  of  the  bees,  and  might  have  so  greatly 
inconvenienced  them  as  to  deter  them  from  visiting 
the  flower.  Dr.  Ogle's  opinion  is  strengthened  by 
the  fact  that  there  are  some  species,  as  for  instance 
the  Foxglove,  in  which,  as  shown  in  Figs.  100 — 102, 
the  anthers  are  transverse  when  immature,  but  become 
longitudinal  as  they  ripen. 

But  to  return  to  the  Dead  Nettle.  From  the 
position  of  the  stigma  which  hangs  down  below  the 
anthers  (Fig.  in  st\  the  bee  comes  in  contact  with 


154  THE  DEAD  NETTLE.  [CHAP. 

the  former  before  touching  the  latter,  and  conse- 
quently generally  deposits  upon  the  stigma  pollen 
from  another  flower.  The  small  processes  (Figs. 
no,  in  m)  on  each  side  of  the  lower  lip  are  the 
rudiments  of  the  lateral  leaves  with  which  the  an- 
cestors of  the  Lamium  are  provided.  Thus,  then, 
we  see  how  every  part  of  this  flower  is  either — like 
the  size  and  shape  of  the  arched  upper  lip,  the  re- 
lative position  of  the  pistil  and  anthers,  the  length 
and  narrowness  of  the  tube,  the  size  and  position 
of  the  lower  lip,  the  ring  of  hairs,  and  the  honey 
— adapted  to  ensure  the  transference,  by  bees,  of 
pollen  from  one  flower  to  another;  or,  like  the 
minute  lateral  points  (m),  an  inheritance  from  more 
highly-developed  organs  of  ancestors.  If  we  com- 
pare Lamium  with  other  flowers  we  shall  see  how 
great  a  saving  is  effected  by  this  beautiful  adaptation. 
The  stamens  are  reduced  to  four,  the  stigma  almost 
to  a  point ;  how  great  a  contrast  to  the  pines  and 
their  clouds  of  pollen,  or  even  to  such  a  flower  as 
the  Nymphaea,  where  the  visits  of  insects  are  se- 
cured, but  the  transference  of  the  pollen  to  the 
stigma  is,  so  to  say,  accidental.  Yet  the  fertilisa- 
tion of  Lamium  is  not  less  effectually  secured  than 
in  either  of  these. 

Lamium  maculatum  has  a  somewhat  longer  tube 
(15 — 17  mm.)  than  L.  album,  and  only  bees  with  a 
long  proboscis  can  therefore  suck  it.  B.  terrestris, 
however,  obtains  access  to  it  by  force,  and  B.  rayellus, 
according  to  H.  Miiller,  uses  the  holes  made  by  B. 
terrestris.  In  L.  purpureum  the  tube  is  somewhat 
shorter. 


v.]  THE  DEAD  NETTLE.  155 

Lamium  amplexicaule,  in  addition  to  the  normal 
flowers,  also  produces  cleistogamous  ones  (Figs.  36, 
37),  which  appear  in  the  early  spring  and  again  in 
autumn. 

In  this  genus  it  would  appear,  as  already  men- 
tioned, that  the  pistil  matures  as  early  as  the  stamens, 
and  that  cross-fertilisation  is  obtained  by  the  relative 
position  of  the  stigma,  which,  as  will  be  seen  in  the 
figure,  hangs  down  slightly  below  the  stamens,  so 
that  a  bee  bearing  pollen  on  its  back  from  a  pre- 
vious visit  to  another  flower  would  touch  the  pistil 
and  transfer  to  it  some  of  this  pollen,  before  coming 
in  contact  with  the  stamens. 

In  other  species  belonging  to  the  same  great  group 
(Labiates)  cross-fertilisation  is  secured  by  the  fact 
that  the  stamens  come  to  maturity,  shed  their  pollen, 
and  are  shrivelled  up,  before  the  stigma  is  mature. 
The  genus  Sal  via  was  described  by  Sprengel,  and 
more  recently  by  Hildebrand  and  Ogle  (Pop.  Sci.  Rev. 
July,  1869).  Fig.  112  represents  a  young  flower  of 
Salvia  officinalis  in  which  the  stamens  (/)  are  mature, 
but  not  the  stigma  (/),  which,  moreover,  from  its 
position  is  untouched  by  bees  visiting  the  flower, 
as  shown  in  Fig.  113.  The  anthers,  as  they  shed 
their  pollen,  gradually  shrivel  up ;  while  on  the  other 
hand  the  pistil  increases  in  length  and  curves  down- 
wards, until  it  assumes  the  position  shown  in  Fig. 
1 14  st,  where,  as  is  evident,  it  must  come  in  contact 
with  any  bee  visiting  the  flower,  and  would  touch 
just  that  part  of  the  back  on  which  pollen  would  be 
deposited  by  a  younger  flower.  In  this  manner  self- 
fertilisation  is  effectually  provided  against.  There 


IS6 


SALVIA. 


[CHAP. 


are,  however,  several  other  points  in  which  5. 
officinalis  differs  greatly  from  the  species  last  de- 
scribed. 

The  general   form   of  the   flower    indeed  is  very 
similar.      We  find  again  that,   as   generally   in  the 


FIG. 


FIG.  114. 


FIG.  xi2.—Salvia  officinalis.     Section  of  a  young  flower. 
FIG.  113.— Ditto,  visited  by  a  Bee. 
FIG.  114.— Ditto,  older  flower. 


Labiates,  the  corolla  has  the  lower  lip  adapted  as  an 
alighting  board  for  insects,  while  the  arched  upper 
^ip  covers  and  protects  the  stamens  and  pistils. 

In   Salvia   officinalis,   however,  the  back   ot    tne 


v.]  SALVIA.  157 

upper  lip  shows  an  arch  at  the  part  x,  and  the 
front  portion  of  the  lip,  containing  the  stamens,  is 
loftier  than  in  Lamium,  and  does  not  therefore  come 
in  contact  with  the  back  of  the  bee  (Fig.  112).  In  evi- 
dent correlation  with  this  arrangement,  we  find  a  very 
remarkable  difference  in  the  stamens  (Figs.  115-16). 
Two  of  the  stamens  (Fig.  112,  /')  are  minute  and 
rudimentary.  In  the  other  -pair,  the  two  anther  cells 
(Fig.  115  a,  a'}  instead  of  being,  as  usual,  close 


FIG.  115. — Stamens  in  their  natural  FIG.  116. — Stamens  when  moved  by 

position.  a  Bee. 


together,  are  separated  by  a  long  connective  (m). 
Moreover,  the  lower  anther  cells  (a,  a)  contain  very 
little  pollen ;  sometimes  indeed  none  at  all.  This 
portion  of  the  stamen,  as  shown  in  Fig.  1 12,  hangs 
down  and  partially  stops  up  the  mouth  of  the 
corolla  tube.  When,  however,  a  bee  thrusts  its  head 
into  the  tube  in  search  of  the  honey,  this  part  of 
the  stamen  is  pushed  into  the  arch  (x),  the  con- 
nectives of  the  two  large  stamens  revolve  on  their 
axis,  and  consequently  the  fertile  anther  cells  (a'} 


158  TEUCRIUM,  A  JUG  A.  [CHAP. 

are  brought  down  on  to  the  back  of  the  bee  as 
shown  in  Fig.  113. 

In  5.  pratense  the  lower  branch  of  the  anther  is 
comparatively  short.  The  different  species  of  Salvia 
differ  indeed  considerably  from  one  another  in  this 
respect.  One  of  them,  S.  cleistogama,  produces  cleis- 
togamous  flowers,  as  its  name  denotes. 

Tencrium  Scorodonia  is  very  markedly  proteran- 
drous.  When  the  flower  first  opens  the  stigma  stands 
behind  the  stamens  (Fig.  117)  and  is  not  touched  by 


FIG.  iij.—  Teucnnm  Scorod&nta,  in  (lit         FIG.  118. — Ditto,  in  the  second  state, 
first  state. 

the  insect.  Gradually,  however,  the  stamens  turn 
backwards,  and  the  pistil  moves  forwards  (Fig.  118), 
so  that  in  older  flowers,  it  stands  where  the  stamens 
stood  before,  and  in  its  turn  comes  in  contact  with 
the  insect.  This  flower,  though  not  conspicuous,  is  a 
favourite  with  insects. 

In  Ajuga  reptans  the  upper  lip  is  very  short,  but 
the  flowers  stand  close  to  one  another,  and  the 
stamens  and  pistil  of  each  are  protected  by  the 


v.]      GALEOBDOLON,  GALEOPSIS,  STACHYS.       159 

lower  bract  of  the  flower  above.  According  to 
Delpino,  Ajuga  is  proterandrous.  The  pistil  is 
already  mature  when  the  flower  opens,  but  then  lies 
behind  and  is  protected  by  the  stamens.  After  a 
while  the  stamens  separate  a  little,  so  that  the 
stigma  is  in  its  turn  exposed.  In  Ballota  nigra 
the  arrangement  of  the  stamens  and  pistils  is 
somewhat  similar,  and  the  flower  is  also  slightly 
proterandrous. 

In  Galeobdolon  luteum,  the  flower  tube  is  eight  mm. 
(but,  as  the  upper  end  is  dilated,  practically  only 
six  mm.)  in  length.  Though  the  stigmatic  ends  of 
the  pistil  diverge  shortly  after  the  opening  of  the 
flower,  and  appear  to  be  then  already  mature,  still 
they  occupy  a  more  prominent  position  at  a  later 
period.  In  this  respect,  therefore,  it  is  intermediate 
between  Lamium  and  Ballota. 

Galeopsis  tetrahit  is  a  variable  plant,  and  the  tube 
varies  in  length  in  different  specimens  from  n  to  17 
mm. ;  of  which,  however,  the  4 — 6  upper  millimetres 
are  somewhat  expanded.  This  variability  is  an  in- 
teresting fact  in  relation  to  the  theory  of  natural  selec- 
tion. The  pistil,  when  mature,  moves  forward,  as  in  the 
preceding  species.  G.  ochroleuca  agrees  very  closely 
with  G.  Tetrahit,  but  the  tip  of  the  pistil,  instead  of 
lying  between  the  anthers  of  the  two  longer  stamens, 
projects  slightly  beyond  them.  G.  versicolor  has  a 
longer  tube,  while  G.  Ladanum  has  a  somewhat 
shorter  one ;  in  most  respects,  however,  they  agree 
with  G.  ochroleuca. 

S tacky s  sylvatica  is  distinctly  proterandrous,  but 
has  not  lost  the  power  of  self-fertilisation.  In  »S. 


160          BETONICA,  CALAMINTHA,  THYME.     [CHAP. 

palustris  the  tube  is  shorter  than  in  5.  sylvatica  ;  the 
four  stamens  are  of  equal  length ;  and  when  the  flower 
opens,  the  anthers  of  the  outer  ones  lie  in  front  of 
the  inner  ones.  When  they  have  shed  their  pollen 
they  turn  outwards,  thus  exposing  the  inner  ones, 
which  in  their  turn  shed  their  pollen,  and  then 
move  outwards  to  make  room  for  the  pistil,  which 
thus  occupies  the  place  which  they  had  previously 
rilled. 

Betonica  officinalis  is  also  proterandrous  ;  the  pistil 
being  comparatively  short  when  the  flower  first  opens, 
and  not  attaining  its  full  length  until  the  anthers 
have  shed  their  pollen. 

In  Calamintha  Clinopodium  the  upper  process  of  the 
stigma  varies  considerably  in  size.  The  stamens  are 
still  more  remarkable  in  this  respect,  presenting  vari- 
ations which,  as  mentioned  in  the  case  of  Galeopsis 
tetrahit,  are  very  interesting. 

I  have  already  in  the  introductory  chapter  referred 
to  the  Thyme  (Thymus  Serpyllum,  Figs.  32  and  33) 
as  a  type  of  a  proterandrous  flower.  It  is  extremely 
rich  in  honey,  much  frequented  by  insects,  and, 
according  to  Muller,  has  lost  the  power  of  self- 
fertilisation.  Besides  the  ordinary  flowers,  which 
contain  both  stamens  and  pistils,  there  are  other 
smaller  ones,  which  contain  a  pistil  only.  In  Italy, 
Delpirio  has  observed  not  only  these  two  kinds,  but 
also  a  third  in  which  the  pistil  is  quite  rudimentary. 
Ogle  also  in  England  has  observed  that  in  some 
flowers  the  pistil  never  becomes  fully  developed.  On 
the  contrary  in  Germany,  Hildebrand,  Ascherson,  and 
Muller,  have  sought  in  vain  for  these  male  flowers. 


v.]  MENTHA,  MARJORAM,  NEPETA.  161 

This  geographical  differentiation,  if  it  really  exist,  is 
very  interesting. 

H.  Miiller  attempts  to  explain  the  presence  of 
these  small  flowers  by  pointing  out  that  where  there 
is  any  variation  in  the  size  of  the  flowers,  the  smaller 
and  less  showy  ones  would  be  the  last  to  be  visited 
by  the  insects.  Under  these  circumstances,  as  such 
flowers  would  be  fertilised  by  the  pollen  derived 
from  previous  visits,  the  stamens  of  such  smaller 
flowers  would  be  useless,  and  would  tend  to  become 
rudimentary.  Further  observations  are,  however,  I 
think,  required  before  this  explanation  can  be  re- 
garded as  satisfactory. 

The  Mint  (Mentha  arvensis)  is  also  proteran- 
drous,  and,  like  the  Thyme,  possesses,  in  addition 
to  the  hermaphrodite  flowers,  others  which  are 
smaller  and  merely  female.  Some  species  of  the 
genus  are  dimorphous.  The  genus  Mentha  seems 
to  be  in  some  respects  a  connecting  link  between 
the  typical  Labiates,  and  the  ordinary  tubular 
form. 

Origanum  vulgar e  (the  Marjoram)  also  has  plants 
with  large,  proterandrous,  bisexual  flowers  ;  and 
others  with  smaller  female  ones.  In  the  secretion 
and  position  of  the  honey  it  agrees  with  the  Thyme ; 
but  while  on  the  one  hand  it  is  less  sweet,  it  is,  on 
the  other,  more  conspicuous.  These  two  differences 
nearly  counterbalance  one  another;  the  flowers  are 
consequently  much  visited  by  insects,  and  have  also 
lost  the  power  of  self-fertilisation. 

Nepeta  glechoma  (the  Ground  Ivy),  like  the  three 
preceding  genera,  is  proterandrous,  and  has  small 

M 


1 62     LYCOPUS,  VERBENA,  PLUMBAGINE^E.    [CHAP. 

female  flowers,  as  well  as  the  larger  hermaphrodite 
ones. 

Prunella  vulgaris  also  has  the  two  kinds  of  indi- 
viduals, but  the  female  plants  are  comparatively  rare. 
Axell  says  that,  in  the  absence  of  insects,  the  larger 
flowers  fertilise  themselves,  but  this  was  not  the 
case  with  those  observed  by  Miiller.  If  Prunella  be 
really  self-fertile  this  would  constitute  an  argument 
against  Miiller's  view  of  the  origin  of  the  small  female 
flowers. 

Lycopus  Europceus  is  distinctly  proterandrous.  In 
this  species,  as  in  Salvia,  two  of  the  stamens  are  rudi- 
mentary. This  is  an  advantage  in  Salvia,  on  account 
of  the  curious  mechanical  structure  of  the  stamens. 
In  Lycopus,  the  diminution  is  perhaps  connected  with 
the  smallness  of  the  size  of  the  flower.  Veronica, 
which  has  the  smallest  flowers  of  all  the  Scrophu- 
lariaceae,  has  also  only  two  stamens  instead  of  four, 
or  more. 

VERBENACE.E. 

The  common  Verbena  officinalis  is  the  only  British  species  of  this 
order.  The  calyx  is  five-toothed,  the  corolla  distinctly  tubular,  and 
with  five  somewhat  unequal  lobes.  The  stamens  are  sometimes  two, 
sometimes  four,  in  number.  It  secretes  honey  at  the  base  of  the  tube. 


PLUMBAGINE^:. 

There  are  two  British  genera  of  this  order,  viz.  Statice  and  Armeria. 
The  genus  Plumbago  has  already  been  referred  to  in  the  introductory 
chapter  (ante,  p.  10)  as  an  illustration  of  an  insect-fertilised  flower,  in 
contrast  with  Plantago  major,  which  is  wind-fertilised. 


v.]  PLANTAGINE&.  163 


PLANTAGINE^:. 

This  order  contains  two  British  genera  ;  Plantago 
and  Littorella. 

Plantago,  the  common  Plantain,  has  small,  herma- 
phrodite flowers  in  heads  or  spikes  on  a  leafless 
peduncle.  The  sepals  are  four ;  the  corolla  has  four 
lobes ;  the  stamens  are  four,  alternating  with  the 
petals,  and  very  long ;  the  style  is  long,  simple,  and 
hairy.  This  genus  offers  several  interesting  pecu- 
liarities. 

Plantago  major  is  proterogynous,  and  according 
to  Axell,  as  I  have  already  mentioned  (anti,  p.  10), 
is  wind-fertilised,  which,  however,  is  not  invariably 
the  case  in  other  species. 

In  PL  lanceolata,  Delpino  has  observed  three  dif- 
ferent forms  : — 

Firstly,  a  form  with  a  strong  and  high  stalk ;  white 
and  broad  anthers.  This  he  says  is  entirely  wind- 
fertilised. 

Secondly,  one  with  a  less  elevated  stalk,  and  less 
exclusively  anemophilous.  On  it  he  observed  a 
species  of  Halictus,  which  endeavoured  to  collect 
pollen.  The  plant  is,  however,  so  little  suited  to  this, 
that  most  of  the  pollen  fell  to  the  ground. 

Thirdly,  a  dwarf  variety,  with  shorter  stamens. 
This  form  was  visited  by  several  species  of  bees 
and  is  intermediate  between  wind- fertilisation  and 
insect-fertilisation.  Miiller  also  has  observed  two 
varieties  of  this  species ;  one  tall  and  long-eared,  the 
other  shorter  and  smaller  ;  both  of  them  were  visited 
by  insects.  P.  lanceolata  is  proterogynous. 

M    2 


164  PLANTAGO.  [CHAP.  v. 

Plantago  media  is  also  proterogynous,  though  less 
so  than  P.  lanceolata.  It  is  more  frequently  visited 
by  insects,  having  a  slight  scent,  and  stamens  with 
pink  filaments.  Nevertheless,  it  appears  to  be  gene- 
rally fertilised  by  wind. 

According  to  Darwin,  several  North  American 
species  are  dimorphous  (Proc.  Linn.  Soc.  v.  vi.,  1862, 
p.  95),  and  Kuhn  states  that  some  have  also  cleisto- 
gamous  flowers. 


FlG.   Iig.  — CHENOPOPIUM    BONUS-HENRICUS. 

CHAPTER  VI. 

INCOMPLETE. 

OF  this  sub-class  we  have  in  Britain  representa- 
tives of  fifteen  orders,  some  of  them  very  numerous 
and  important  To  it,  for  instance,  belong  many  of 
our  forest  trees,  such  as  the  elm,  oak,  beech,  birch, 
poplar,  willow,  pine,  fir,  &c.  ;  and  a  large  number 
of  the  common  herbs,  such  as  the  nettles,  cheno- 
podiums,  euphorbias  (spurges),  &c.  The  flowers, 
however,  are  generally  less  conspicuous  (see  Fig.  119) 
than  those  we  have  hitherto  been  considering,  and 
offer  fewer  adaptations  in  relation  to  insects ;  being 
in  many  cases  wind-fertilised:  thus  in  H.  Miiller's 
work,  less  than  ten  pages  are  occupied  by  this  whole 
sub-class,  of  which  more  than  half  are  devoted  to  the 
Polygonaceae,  and  a  greater  part  of  the  remainder  to 


166  CHENOPODIUM,  POLYGONUM.          [CHAP. 

the  Aristolochiaceae ;  two  orders  which  in  many  re- 
spects form  a  marked  contrast  to  the  remainder,  and 
have,  at  least  in  some  species,  conspicuous  flowers. 
In  the  other  orders,  on  the  contrary,  the  flowers  are 
generally  minute.  Thus  in  the  Paronychiaceae, 
Bentham  says,  "  Petals  usually  none,  or  represented 
by  five  small  filaments ; "  in  Santalaceae,  "  flowers 
small;"  in  Empetraceae,  flowers  "  minute,  axillary;" 
in  Callitrichineae,  flowers  "  minute ; "  in  Urticaceae, 
flowers  "  small  ; "  in  Ulmaceae,  flowers  "  small  ;  " 
while  in  the  Amentaceae  (beech,  oak,  birch,  &c.),  and 
Coniferae,  the  flowers  rarely  are  coloured,  or  contain 
honey.  Indeed,  it  is,  I  think,  a  strong  argument  in 
favour  of  Sprengel's  views,  that  while  large  flowers 
are  almost  always  coloured,  small  ones  are  usually 
greenish ;  thus  out  of  thirty-nine  British  genera  of 
Incompletae,  by  far  the  greater  number  of  which  have 
small  flowers,  in  no  less  than  thirty-seven  genera  they 
are  also  more  or  less  greenish.  In  the  Nettle,  which 
is  wind-fertilised,  the  anthers  are  provided  with  a 
spring  which,  suddenly  opening,  scatter  the  pollen. 

In  the  Polygonaceae,  the  species  of  the  genus 
Rumex  are  wind-fertilised ;  occasionally,  however, 
visited  by  insects. 

The  species  of  Polygonum  differ  considerably  from 
one  another  in  the  mode  of  their  fertilisation.  Some, 
as,  for  instance,  P.  aviculare  (Knotweed),  have  small 
inconspicuous  flowers,  and  very  little,  if  any,  honey. 
They  are  consequently  but  seldom  visited  by  insects. 
Other  species,  on  the  contrary,  such  as  P.  Fagopyrum 
(the  Buckwheat),  and  P.  Bistorta,  are  much  more  con- 
spicuous, contain  honey,  and  are  fertilised  by  insects. 


VI.]  POLYGONUM,  AMENTACE^E.  167 

These  species,  however,  also  differ  considerably ;  P. 
Bistorta  is  proterandrous.  When  the  flower  opens 
the  stamens  are  ripe,  while  the  stigmas  do  not  mature 
till  the  anthers  have  shed  their  pollen,  and  shrivelled 
up.  P.  Fagopyrum,  on  the  contrary,  is  dimorphous ; 
some  plants  having  short  stigmas  and  long  stamens  : 
others,  on  the  contrary,  long  stigmas  and  short 
stamens.  In  Polygonum  amphibium  the  stems,  if  grow- 
ing in  water,  are  smooth  :  while  if  on  dry  land  they 
are  provided  with  a  certain  number  of  glandular  hairs. 

The  curious  arrangement  by  which  cross-fertilisa 
tion  is  secured  in  Aristolochia,  has  been  already  de- 
scribed in  the  introductory  chapter  (ante,  p.  31). 
Asarum,  according  to  Delpino,  is  also  proterogynous. 
Ruppia  is  an  aquatic  genus.  At  the  time  when 
the  pollen  is  shed,  the  female  flowers  are  immature, 
and  the  flower-stalk  is  short  and  submerged ;  when, 
however,  the  pollen  has  all  escaped,  the  female 
flowers  mature,  the  flower-stalk  elongates  and  as- 
sumes a  spiral  form,  so  that  notwithstanding  any 
slight  change  of  level,  the  flower  rests  on  the  sur- 
face of  the  water.  A  similar  arrangement  occurs 
in  Valisneria. 

Potamogeton  is  proterogynous  (Delpino — Ult.  Os- 
serv.  Part  ii.  p.  22). 

In  the  Amentaceae  (oak,  beech,  willow,  poplar, 
hazel,  hornbeam,  birch,  alder,  &c.)  the  flowers  are 
unisexual,  and  generally  monoecious ;  the  males  are, 
in  some  species — as,  for  instance,  in  the  hazel — visited 
by  insects  for  the  sake  of  the  pollen.  As,  however, 
they  scarcely  ever  produce  honey,  the  female  flowers 
offer  no  attraction  to  insects,  which  consequently  take 
no  part  in  the  fertilisation. 


OPHKYS    AiMFERA. 


CHAPTER  VII. 
MONOCOTYLEDONS. 

IN  this  class  the  plumule,  or  bud,  is  in  germination 
developed  from  a  sheath-like  cavity  on  one  side  of 
the  embryo. 

Although  among  the  Monocotyledonous  orders  we 
do  not  meet  with  so  many  instances  of  adaptation 
to  insects  as  is  the  case  in  the  Dicotyledons  ;  none 
are  more  curious  or  interesting  than  those  afforded 
by  the  Orchidacese. 

ALISMACE.E. 

Alisma  Plantago  has  rather  small,  pale,  rose- 
coloured  flowers,  forming  a  loose  pyramidal  panicle 


CH.  VIL]  HYDROCHARIDE^E.  169 

one  to  three  feet  high.  The  flowers  secrete  honey 
from  twelve  glands,  situated  on  each  side  of  the 
projecting  bases  of  the  stamens.  These  are  six  in 
number,  and  the  pollen-covered  side  of  the  anthers 
is,  according  to  H.  Miiller,  turned  outwards.  Under 
these  circumstances,  insects  are  more  likely  to  fertilise 
the  flower  with  pollen  obtained  from  another  blossom 
than  with  its  own. 

In  Butomus,  on  the  contrary,  the  flowers  are  on 
stalks,  and  form  a  large  flat  umbel.  They  are 
proterandrous ;  while  Triglochin,  according  to  Axell, 
is  proterogynous. 


HYDROCHARIDE^. 

This  order  contains  three  British  genera ;  Elodea, 
Hydrocharis,  and  Stratiotes. 

Elodea  canadensis  (Anacharis  Alsinastrum]  is  a 
common  American  weed,  which  first  appeared  in  our 
country  in  1 847,  and  has  since  spread  with  great 
rapidity.  It  is  dioecious,  and  it  is  remarkable  that  it 
has  not  as  yet  been  known  to  produce  male  flowers 
in  this  country  ;  they  are,  moreover,  rare  in  America. 
The  female  flowers  are  small,  with  a  long,  threadlike, 
perianth-tube,  containing  a  style  which  terminates  in 
three  stigmas. 

Stratiotes  aloides  is  also  dioecious.  The  male 
flowers  are  contained  several  together  in  a  spathe, 
stalked,  and  have  twelve  or  more  stamens.  The 
female  flowers  are  solitary  and  sessile.  Both  sexes 
secrete  honey. 


1 70  ORCHIDACE&.  [CHAP. 


ORCHIDACE^E. 

This  order  is  the  subject  of  Mr.  Darwin's  admirable 
work,  "  On  the  Various  Contrivances  by  which  British 
and  Foreign  Orchids  are  fertilised  by  Insects,"  from 
which  the  following  facts  are  taken.  The  order  con- 
tains sixteen  British  genera,  several  of  them  extremely 
curious  and  pretty.  The  species  with  long  nectaries 
are  fertilised  by  Lepidoptera,  those  with  shorter  ones, 
as  a  general  rule,  by  bees  and  flies ;  Epipactis  latifolia, 
it  is  said,  exclusively  by  wasps,  so  that,  according  to 
Darwin,  "if  wasps  were  to  become  extinct  in  any 
district,  so  would  the  Epipactis  latifolia"  Other 
species  on  the  contrary  such  as  Epipactis  viridifolia, 
and  Ophrys  apifera  (the  Bee  Orchis)  habitually 
fertilise  themselves.  It  is  remarkable  that  in  some 
Orchids  the  ovules  are  not  developed  until  several 
weeks,  or  even  months,  after  the  pollen  tubes  hare 
penetrated  the  stigma.  (Hildebrand,  Bot.  Zeit.,  1863 
and  1865.  Fritz  Muller,  Bot.  Zeit.,  1868.) 

The  flower  in  this  order  is  very  abnormal.  There 
is,  except  in  Cypripedium,  only  one  anther,  which 
is  confluent  with  the  style,  forming  the  so-called 
"column."  The  anther  is  divided  into  two  cells, 
which  are  often  so  distinct  as  to  appear  like  two 
separate  anthers.  The  pollen  in  most  Orchids  co- 
heres in  masses,  which  are  supported  by  a  stalk 
or  "  caudicle  ; "  the  pollen  masses  with  their  stalks 
are  called  "pollinia."  The  styles  are  theoretically 
three  in  number ;  but  the  stigma  of  the  upper  one 
is  modified  into  a  remarkable  organ  called  the 


VII.] 


ORCHIS. 


171 


"  rostellum,"  and  those  of  the  two  lower  ones  are 
often  confluent,  so  that  they  appear  like  one. 

Orchis  mascula  (Fig.  120)  is  perhaps  our  commonest 
species. 

Fig.  121  represents  the  side  view  of  a  flower  from 
which  all  the  petals  and  sepals  have  been  removed, 
except  the  lip  (/)  half  of  which  has  been  cut  away, 
as  well  as  the  upper  portion  of  the  near  side  of 


FIG.  120. — Orchis  mascula. 

the  nectary  (ri).  The  pollen  forms  two  masses 
(Figs.  121,  I22#,  and  123),  each  attached  to  a  taper- 
ing stalk,  which  gives  the  whole  an  elongated  pear- 
like  form,  and  is  attached  to  a  round  sticky  disk  (Fig. 
123^),  which  lies  loosely  in  a  cup-shaped  envelope  or 
rostellum  (r).  This  envelope  is  at  first  continuous, 
but  the  slightest  touch  causes  it  to  rupture  transversely, 


172 


ORCHIS. 


[CHAP. 


and  thus  to  expose  the  two  viscid  balls  (dd).     Now 
suppose  an  insect  visiting  this  flower:  it  alights  on 


FIG.  laa.  FIG.  123. 

Fie.  i2i.— Side  view  of  flower,  with  all  the  petals  and  sepals  cut  off  except  the 

hp,  of  which  the  near  half  is  cut  away,  as  well  as  the  upper  portion  of  the  near 

side  of  the  nectary  . 

FIG.  122.— Front  view  of  flower,  with  all  sepals  and  petals  removed  except  the  lip. 
FIG.  123. — The  two  pollinia. 

the  lip  (/),  and  pushing  its  proboscis  down  the  nec- 
tary to  the  honey,  it  can  hardly  fail  to  bring  the 


VII.] 


ORCHIS. 


173 


base  of  the  proboscis  into  contact  with  the  two 
viscid  disks,  which  at  once  adhere  to  it,  so  that  when 
the  insect  draws  back  its  proboscis,  it  carries  away 
the  two  pollen  masses.  It  is  easy  to  imitate  this  with 
a  piece  of  grass,  and  to  carry  away  on  it  the  two 
pollen  masses  and  their  stalks.  If,  however,  the 
pollinium  retained  this  erect  position  when  the  insect 
came  to  the  next  flower,  it  would  simply  be  pushed 
into  or  against  its  old  position.  Instead,  however,  of 
remaining  upright,  the  pollinia,  by  the  contraction  of 
the  minute  disk  of  membrane  to  which  they  are 
attached,  gradually  turn  downwards  and  forwards, 
and  thus  when  the  insect  sucks  the  next  flower,  the 
thick  end  of  the  club  exactly  strikes  the  stigmatic 
surfaces  (st  st).  The  pollinium  or  pollen-mass  consists 
of  packets  of  pollen  grains,  fastened  together  by 
elastic  threads.  The  stigma,  however,  is  so  viscid, 
that  it  pulls  off  some  of  these  packets,  and  ruptures 
the  threads,  without  removing  the  whole  pollinium, 
so  that  one  pollinium  can  fertilise  several  flowers. 

This  description  applies  in  essentials  not  only  to 
Orchis  mascula,  but  also  to  O.  Morio,  O.  fusca,  O. 
maculata,  and  O.  latifolia,  as  well  as  to  Aceras 
anthropophora  (the  Man  orchis),  in  all  of  which 
the  pollinia  undergo,  after  removal  from  the  anther 
cells,  the  curious  movement  of  depression,  which  is 
necessary  in  order  to  place  them  in  the  right  position 
to  strike  the  stigmatic  surface. 

0.  pyramidalis  differs  from  the  above  group  in 
several  important  points.  The  two  stigmatic  surfaces 
are  quite  distinct,  and  the  rostellum  is  brought  down, 
so  as  to  overhang  and  partly  close  the  entrance  to  the 
nectary.  The  viscid  disks  which  support  the  pollen 


I74  OPHRYS.  [CHAP. 

masses,  are  united  into  a  single  saddle-shaped  body. 
The  lower  lip  is  furnished  with  two  prominent  ridges, 
which  serve  to  guide  the  proboscis  of  the  insect  into 
the  orifice  of  the  nectary.  It  is  of  course  important 
that  the  proboscis  should  not  enter  obliquely,  for  in 
that  case  the  pollen  masses  would  not  occupy  exactly 
the  right  position. 

Following  Darwin  and  other  botanists,  I  have 
applied  to  the  spur  of  Orchis  the  term  "  nectary." 
As  a  matter  of  fact,  however,  the  flowers  of  this 
genus  produce  no  honey ;  whence  Sprengel  applied 
to  them  the  term  "  Scheinsaftblumen "  or  "  Sham- 
honey-flowers."  Darwin  does  not,  however,  think  that 
moths  (by  which  the  flowers  of  this  group  are  prin- 
cipally fertilised)  could  be  so  deceived  for  generation 
after  generation ;  and  as  he  has  observed  that  the 
membrane  of  the  interior  of  the  spur  is  very  delicate, 
and  the  cellular  tissue  extremely  juicy,  he  suspected 
that  insects  possibly  pierce  the  membrane,  and  suck 
the  juicy  sap  lying  beneath.  His  suggestion  has 
been  confirmed  by  H.  Miiller,  and  he  himself  in  a 
subsequent  memoir  ("  Ann.  and  Mag.  of  Nat.  His.,** 
1869,  p.  143)  speaks  confidently  on  the  point.  Del- 
pino,  on  the  contrary,  is  confident  that  the  species 
examined  by  him  (O.  sambucina,  O.  morio,  O.  mascula, 
and  O.  maculata)  do  not  secrete  honey  either  on  or 
under  the  epidermis. 

The  flowers  belonging  to  the  genus  Ophrys  are 
formed  somewhat  on  the  same  plan  as  those  of  Orchis, 
but  they  have  no  spur,  and  the  rostellum  is  double. 
The  Bee  orchis  (0.  apifera),  Fig.  124,  however,  differs 
widely  from  the  other  allied  British  species.  The 
two  pouch-formed  rostellums,  the  viscid  disk,  and 


VIL]  BEE  OPHRYS.  175 

the  position  of  the  stigma,  are  nearly  the  same,  but 
the  stalks  of  the  pollen  masses  are  long,  thin,  flexible, 
and  too  weak  to  stand  upright.  The  distance  of  the 
pollen  masses  from  one  another,  and  the  shape  of 
the  pollen  grains  is  moreover  variable.  The  anther 
cells  open  soon  after  the  flower  expands,  and  the 
pear-shaped  pollen  masses  drop  out,  so  as  to  hang 
directly  over  the  stigma,  with  which  a  breath  of  air 
is  sufficient  to  bring  them  in  contact.  While  there- 
fore in  most  species  of  Orchis  and  Ophrys,  self-fertilis- 


FIG.  124.— Ophrys  apifera. 


ation  appears  to  be  impossible,  in  the  Bee  Ophrys, 
as  R.  Brown  long  ago  pointed  out  (Trans.  Linn.  Soc., 
v.  xvi.)  it  is  carefully  provided  for.  Darwin  has 
examined  hundreds  of  flowers,  and  has  never  seen 
reason  in  a  single  instance  to  believe  that  pollen  had 
been  brought  from  one  flower  to- another;  and  he 


I ;6     SPIDER,  MUSK,  BUTTERFLY  ORCHIS.    [CHAP. 

has  met  with  very  few  cases  in  which  the  pollen  mass 
failed  to  reach  its  own  stigma.  He  has  never  seen 
an  insect  visit  the  flowers  of  this  species,  and  R. 
Brown  suggested  that  the  resemblance  of  the  flower 
to  bees  was  to  deter  insects  from  visiting  them. 
Darwin  does  not  think  this  probable.  He  believes 
also  that,  though  this  species  habitually  fertilises 
itself,  the  curious  arrangements  which  it  possesses 
in  common  with  other  allied  species,  are  of  use  in 
securing  an  occasional  cross,  even  if  only  at  very 
long  intervals. 

Ophrys  arachnites  is  by  some  botanists  (for  instance 
by  Bentham)  regarded  as  a  mere  variety  of  O. 
apifera,  but  the  stalks  of  the  pollen  masses  are  not 
much  more  than  half  as  long,  without  any  diminution 
of  thickness.  In  proportion,  therefore,  and  in  their 
stiffness,  they  more  nearly  resemble  the  other  section 
of  the  group.  Mr.  Moggridge,  however,  has  found 
at  Mentone  intermediate  forms,  'not  only  between 
O.  arachnites  and  O.  apifera,  but  also  between 
these,  O.  aranifera  and  O.  Scolopax.  O.  arachnites 
and  O.  apifem  do  not  in  England  appear  liable  to 
pass  into  one  another. 

In  the  Musk  orchis  (Herminium  monorchis],  the 
stalks  of  the  pollen  masses  are  short,  and  the  disks 
large.  This  species  does  not  produce  honey,  but  has 
a  strong  odour,  especially  at  night. 

Habenaria  chlorantha  (the  Large  Butterfly  orchis) 
has  both  a  sweet  scent  and  honey.  It  is  much  fre- 
quented by  insects.  The  anther  cells  are  widely 
separated ;  the  pollinia  slope  backwards,  and  are 
much  elongated  ;  the  viscid  disk  is  circular,  prolonged 
on  its  imbedded  side  into  a  short,  drum-like  pedicel 


VII.]  CEPHALANTHERA.  177 

When  exposed  to  the  air  this  drum  contracts  on  one 
side,  and  alters  the  direction  of  the  pollen  mass,  thus 
bringing  it  (as  in  Orchis  mascula]  into  such  a  position 
that  it  comes  in  contact  with  the  stigmatic  surface  of 
the  flower  to  which  it  is  carried. 

Habenaria  bifolia  (the  Lesser  Butterfly  Orchis)  is 
by  Bentham  and  other  high  authorities,  considered  as 
a  mere  variety.  Yet,  as  Darwin  points  out,  it  differs 


FlG.  125. — Cephalanthera  grand  (flora, 

in  many  important  particulars.  The  viscid  disks  are 
oval ;  the  viscid  matter  itself  is  of  somewhat  different 
character ;  the  drum-like  pedicel  is  rudimentary  ;  the 
stalk  of  the  pollen  mass  is  much  shorter ;  the  packets 
of  pollen  shorter  and  whiter;  and  the  stigmatic 
surface  more  distinctly  tripartite. 

The  genus  Cephalanthera  (Fig.  125,  Cephalanthera 

N 


178 


CEPHALANTHERA. 


[CHAP. 


grandiflora)  differs  from  those  hitherto  described  in 
not  possessing  a  rostellum,  and  in  having  the  pollen 
grains  single.  The  flower  stands  upright,  and  the 
labellum  is  formed  of  two  portions;  a  base,  and  a 
small  triangular  flap,  which  at  first  closes  the  tube ; 
then  turns  back,  thus  forming  a  small  landing  place 
in  front  of  a  triangular  door,  situated  half  way  up 
the  tube ;  and  lastly  rises  up  again  and  closes  the 


FIG.  126. — Listera  ovata. 

entrance.  The  pollen  mass  is  situated  just  above  the 
stigma;  and  while  the  flower  is  in  bud,  or  at  any 
rate  before  it  becomes  quite  open,  the  pollen  grains 
which  rest  on  the  sharp  edge  of  the  stigma,  emit  a 
number  of  tubes  which  deeply  penetrate  the  stigmatic 
tissue.  These  serve  partially,  but,  as  Darwin  has 
shown,  only  partially,  to  fertilise  the  flower;  he 
suggests  that  the  principal  use  of  this  closing  of  the 


VIL]  TWAYBLADE.  179 

flower  and  emission  of  the  pollen  tubes  is  probably 
to  retain  the  pollen,  which  would  otherwise  fall  out 
of  the  flower.  In  this  curious  manner,  however,  they 
are  retained  in  a  proper  position  until  the  flower  is 
visited  by  insects,  to  which  they  readily  adhere ;  and 
which  are  necessary  to  ensure  the  perfect  fertility  of 
the  plant. 

Listera  ovata  (the  Twayblade,  Fig.  126)  has  been 
carefully  described  by  Sprengel,  by  whom  the  struc- 
ture and  action  of  the  rostellum  was,  however,  mis- 
understood, and  by  Dr.  Hooker  (Philosophical  Trans- 
actions, 1854),  who  described  the  flower  with  accuracy 
and  minuteness ;   but  the  relations  of  the  flower  to 
insects,  and  consequently  the  true  functions  of  the 
various  parts,  were  first  perceived  by  Waechter.     The 
pollen  masses  lie  immediately  above  the  rostellum ; 
the  pollen  is  friable  and  would  not  of  itself  adhere 
to  insects,  but  this  is  effected  by  a  very  remarkable 
contrivance  (see  Hildebrand,  p.  53).      The  moment 
the  summit  of  the  rostellum  is  touched  it  expels  a 
large  drop  of  viscid  fluid,  which  glues  the  pollen  to 
the  insect  or  other  body.     A  very  slight  touch,  even 
for  instance  with  a  human  hair,  is  sufficient  to  pro- 
duce this  remarkable  phenomenon.     This   species  is 
exclusively  visited  by  ichneumons. 

Neottia  nidus  avis  (the  Bird's  Nest  Orchis)  agrees 
in  the  essential  points  with  Listera,  though  in  the 
position  of  the  honey,  &c.,  it  offers  minor  differences. 

Cypripedium  (the  Ladies'  Slipper,  Figs.  127  and 
128,  C.  longifolium),  the  lower  lip  has  the  form  of  a 
slipper,  whence  the  name.  This  genus  has  two  fertile 
anthers,  which  are  rudimentary  in  other  Orchids, 
while  the  one  which  is  present  in  them  is  represented 

N  9 


i8o 


LADIES'  SLIPPER. 


[CHAP. 


by  a  singular  shield-like  body.  The  opening  into 
the  slipper  is  small,  and  partly  closed  by  the  stigma 
and  this  shield-like  body,  which  lies  between  the 
other  two  anthers.  The  result  is  that  the  open- 
ing into  the  slipper  has  a  horseshoe-like  form,  and 
that  bees  or  other  insects  which  have  once  en- 
tered the  slipper  (Figs.  127-8)  have  some  difficulty 
in  getting  out  again.  While  endeavouring  to  do 
so  they  can  hardly  fail  to  come  in  contact  with  the 


VIG.  127.— Flower  of  Cvprtpedium  Ion-        FIG.  128.— Ditto.     Seen  from  the  side. 
gifoliunt.     Front  view. 

stigma,  which  lies  under  the  shield-like  representa- 
tive of  the  middle  anther.  As  the  margins  of  the 
lip  are  inflected  (Figs.  127-8^),  the  easiest  exit  is 
at  the  two  ends  of  the  horseshoe,  and  by  one 
or  other  of  these  (Fig.  127  e)  the  insect  generally 
escapes,  in  doing  which,  however,  it  almost  inevitably 
comes  in  contact  with,  and  carries  off  some  of  the 
pollen,  from  the  corresponding  anther.  The  pollen 


VII.]  CATASETUM.  181 

of  this  genus  is  immersed  in  a  viscid  fluid,  by  means 
of  which  it  adheres  firstly  to  the  insect,  and  secondly 
to  the  stigma,  while  in  most  Orchids  it  is  the  stigma 
which  is  viscid.  In  a  Trinidad  species,  Coryanthes 
macrantha,  according  to  Dr.  Cruger,  the  basal  part 
of  the  lip  forms  a  bucket,  which  secretes  a  copious 
fluid  which  wets  the  wings  of  the  bees,  and  by 
rendering  them  temporarily  incapable  of  flight,  com- 
pels them  to  creep  out  through  the  small  pas- 
sages close  to  the  anther  and  stigma  ;  thus  securing, 
though  by  different  means,  the  object  which  in  Cypri- 
pedium  is  effected  by  the  inflected  margins  of  the 
labellum.  (Jour.  Linn.  Soc.,  1864.) 

Such  are  a  few  of  the  remarkable  contrivances  ex- 
isting among  British  Orchids.  I  must  refer  those  who 
wish  for  more  detailed  information  to  Mr.  Darwin's 
charming  work. 

Although  I  have  thought  it  well  to  confine  myself 
for  the  most  part  to  illustrations  taken  from  our 
common  wild  flowers,  I  cannot  resist  mentioning 
the  case  of  Catasetum,  one  of  the  Vandeae,  which  as 
Mr.  Darwin  says,  are  "the  most  remarkable  of  all 
Orchids."  In  Catasetum,  the  pollinia  and  the  stig- 
matic  surfaces  are  in  different  flowers,  hence  it  is 
certain  that  the  former  must  be  carried  to  the  latter 
by  the  agency  of  insects.  The  pollinia  moreover  are 
furnished  with  a  viscid  disk,  as  in  Orchis,  but  the 
insect  has  no  inducement  to  approach,  and  in  fact 
does  not  touch,  the  viscid  disk.  The  flower,  however, 
is  endowed  with  a  peculiar  sensitiveness,  and  actually 
throws  the  pollinium  at  the  insect.  Mr.  Darwin  has 
been  so  good  as  to  irritate  one  of  these  flowers  in  my 


182  CATASETUM.  [CHAP. 


presence :  the  pollinium  was  thrown  nearly  three  feet, 


FIG.  129. — Side  view  of  Catasetutn  saccatum,  with  all  the  sepals  and  petals  removed 
except  the  labellum. 

\vhen  it  struck  and  adhered  to  the  pane  of  a  window. 


VII.] 


CATASETUM. 


183 


This  irritability,  however,  is  confined  to  certain  parts 
of  the  flower.  Fig.  129  represents  a  male  flower  of 
Catasetum  saccatum,  which  is  also  shown  in  section 
in  Fig.  130.  In  this  figure  it  will  be  seen  that 
the  pollinium  (ped]  is  curved  and  in  a  state  of  con- 
siderable tension,  but  retained  in  that  position  by 


FIG.  130. — Section  of  ditto,  with  all  the  parts  a  little  expanded. 

a  delicate  membrane.  Now  insects  alight  as  usual 
on  the  lip  of  the  flower  (/),  and  it  will  be  seen  that  in 
front  of  it  are  two  long  processes  called  antennae  (an). 
In  some  species  of  Catasetum  both  these  antennae  are 


1 84  AMARYLLIDE^E,  IRIDEJE.  [CHAP. 

highly  irritable  ;  in  the  present  species  the  right-hand 
one  is  apparently  functionless  ;  but  the  moment  the 
insect  touches  the  left-hand  one,  the  excitement  is 
conveyed  along  it,  the  membrane  retaining  the  polli- 
nium  is  ruptured,  and  the  latter  is  immediately  jerked 
out  of  the  flower,  by  its  own  elasticity,  with  consider- 
able force,  with  the  viscid  disk  (d)  foremost,  and  in  such 
a  direction  as  to  come  in  contact  with  the  head  of  the 
insect  which  had  touched  the  antenna.  On  subse- 
quently visiting  a  female  flower  the  insect  brings  the 
pollen  into  contact  with  the  stigma. 


AMARYLLIDE^E. 

This  beautiful  order  contains  three  British  genera  ;  Narcissus,  Galan- 
thus  (the  Snowdrop),  and  Leucoium. 

The  Snowdrop  is  probably  not  a  true  native  of  this  country,  but  has 
long  been  naturalised  in  many  parts.  It  is  sweet  scented,  and  melliferous ; 
as  the  flower  hangs  down,  the  honey  is  perfectly  protected  from  rain  by 
the  leaves  of  the  perianth.  The  flower  remains  open  from  about  ten  in 
the  morning  till  four  in  the  afternoon,  when  it  closes  for  the  night. 
The  pistil  is  white,  except  at  one  part  a  little  above  the  middle  where 
it  is  tinged  green,  a  character  more  marked  in  the  next  genus, 
Leucoium. 


We  have  five  British  genera  of  this  group ;  Iris,  Gladiolus,  Sisyrin- 
chium,  Trichonema,  and  Crocus. 

Iris  pseudacorus  L.  secretes  honey.  It  is  fertilised  by  humble  bees, 
and  according  to  Muller,  still  more  frequently  by  Rhingia.  The  flowers 
are  large  and  showy,  the  three  outer  perianth-segments  large,  spreading 
and  reflexed,  the  three  inner  ones  much  smaller  and  erect.  The  stigmas 
are  three  in  number,  enlarged,  and  each  with  an  appendage  resembling  a 
petal,  which  arches  over  the  corresponding  stamen  and  outer  segment  of 
the  perianth.  In  order  to  reach  the  honey,  insects  have  to  force  their 
wav  between  this  segment  and  the  over-arching  srigmatic  leaf. 


vii.]    DIOSCORIDE&,  LILIACE^:,  JUNCACE^E.      185 


DIOSCORTDE^. 

The  Yam  family  contains  but  one  British  genus,  Tamus  ;  with  one 
species,  Tamus  communis  (Black  Bryony).  A  pretty,  straggling  creeper, 
dioecious,  with  small,  yellowish  green  flowers;  the  male  in  laxer, 
the  female  in  closer,  racemes. 


LILIACE.E. 

This  order  contains  seventeen  British  genera,  including  the  Lily, 
Onion,  Tulip,  Colchicum,  Asparagus,  Solomon's  Seal,  Fritillaria,  Lily 
of  the  Valley,  Butcher's  Broom  (Ruscus),  &c. 

Paris  quadrifolia  is  proterogynous.  The  perianth  is  yellowish  green, 
and  produces  no  honey.  The  structure  of  this  curious  flower  has  not  I 
think  been  satisfactorily  explained.  It  appears  to  be  one  of  the  species 
which  deludes  flies.  The  dark  purple  ovary  glitters  as  if  it  were  covered 
by  honey. 

The  Lily  of  the  Valley  (Convallaria  majalis}  is  likewise  honeyless 
but  is  much  visited  by  Hive  bees  for  the  pollen. 

A  Ilium  tirsinum  is  melliferous,  and  imperfectly  proterandrous  ;  LlovdtA 
scrotina,  on  the  contrary,  is  said  by  Ricca  to  be  very  decidedly  so. 

Hyacinthus  orientalis  produces  no  honey,  but  the  fleshy  base  of  the 
flower  is  pierced  by  some  insects  for  the  sake  of  the  sap. 

The  Common  Asparagus  is  a  cultivated  variety  of  A.  officinalis, 
which  grows  on  maritime  sands,  or  sandy  plains,  in  central  and  western 
Asia,  and  on  the  south  European  coasts  up  to  the  English  Channel. 
The  flowers  are  melliferous,  small,  greenish  white,  on  slender  stalks 
two  or  three  together  in  the  axils  of  the  branches.  The  species  is  par- 
ticularly interesting,  as  an  instance  of  an  unisexual  flower,  which  is 
evidently  descended  from  bisexual  ancestors ;  since  the  male  flowers 
contain  a  rudimentary  style,  the  female  flowers  rudimentary  stamens. 
In  accordance  with  Sprengel's  rule,  the  male  flowers  are  distinctly  larger 
than  the  female,  being  about  six  mm.  long,  while  the  female  are  only 
three  mm.  long. 

Colchicum  autumnale  is  proterogynous,  though  the  stigma  is  still 
capable  of  fertilisation  when  the  anthers  ripen.  Honey  is  secreted  by 
the  base  of  the  stamens. 


JUNCACE^:. 

We  have  two  genera  belonging  to  the  Juncaceas  (Rushes).  Jancus 
(the  Rush),  with  fourteen  species  ;  and  Luzula  (the  Woodrush)  with 
five.  They  are  wind-fertilised,  and,  at  least  as  regards  some  species, 
are  proterogynous. 


1 86  CONCLUSION.  [CHAP. 


CYPERACE^:. 

The  Cyperacese  (Sedges)  are  a  veiy  numerous  group  containing  eight 
British  genera.  The  flowers  are  minute,  greenish  or  brownish,  and 
wind-fertilised,  but  are  sometimes  visited  by  insects  for  the  sake  of 
the  pollen. 


GRAMINE.E. 

The  order  Graminese  (Grasses)  is  very  extensive,  containing  more  than 
forty  British  genera.    They  are,  however,  wind-fertilised. 


This  is  the  last  order  which  I  have  to  mention. 
Those  who  have  done  me  the  honour  to  read  so  far, 
will  not  need  to  be  told  that  this  little  book  is  frag- 
mentary and  incomplete.  For  my  own  part,  I  am 
only  too  sensible  of  it.  Nevertheless,  the  fault  is  not 
altogether  mine.  Our  knowledge  of  the  subject  is  as 
yet  in  its  infancy  ;  and  indeed,  my  great  object  has 
been  to  bring  prominently  before  my  readers  how 
rich  a  field  for  -  observation  and  experiment  is  still 
open  to  us.  Most  elementary  treatises  unfortunately, 
though  perhaps  unavoidably,  give  the  impression  that 
our  knowledge  is  far  more  complete  and  exact  than 
really  is  the  case.  This  naturally  tends  to  discourage, 
rather  than  to  promote,  original  observations.  Few, 
I  believe,  of  those  who  are  not  specially  devoted  to 
zoology  and  botany  have  any  idea  how  much  still 
remains  to  be  ascertained  with  reference  to  even  the 
commonest  and  most  abundant  species.  In  the  pre- 
sent case,  I  have  confined  myself  to  the  consideration 
of  Flowers  in  relation  to  Insects.  The  interesting 
adaptations  presented  by  such  forms  as  the  grasses, 


VIL]  CONCLUSION.  187 

conifers,  &c.,  which  are  fertilised  by  the  action  of  the 
wind,  did  not  therefore  come  within  my  subject. 

The  causes  which  have  led  to  the  different  forms 
of  leaves  have  been,  so  far  as  I  know,  explained  in 
very  few  cases  :  those  of  the  shapes  and  structure  of 
seeds  are  tolerably  obvious  in  some  species,  but  in 
the  majority  they  are  still  entirely  unexplained  ;  and 
even  as  regards  the  blossoms  themselves,  in  spite  of 
the  numerous  and  conscientious  labours  of  so  many 
eminent  naturalists,  there  is  no  single  species  as  yet 
thoroughly  known  to  us. 


INDEX. 


ACACIA,  6 
Achillea,  119 
Adoxa,  115 
^Egopodium,  1 12 
^nothera,  100 
Agrimonia,  97,  99 
Ajuga,  158 
Alchemilla,  97,  99 
Alder,  86 
Alisma,  1 68 
Alismacese,  168 
Allheal,  117 
Alliurn,  185 
Althaea,  78 
Amaryllidese,  184 
Amentacese,  166 
Anacharis,  169 
Anagallis,  25,  132,  133 
Anchusa,  136,  140 
Anemony,  54,  58 
Anemophilous  plants,  9 
Anthemis,  122 
Anther,  27 
Anthriscus,  1 12 
Anthyllis  91,  97 
Antirrhinum,  141,  145 
Aquilegia,  23,  44 
Araliacese,  114 
Arenaria,  25 
Aristolochia,  31,  167 
Aristolochiaceoe,  167 
Armeria,  71,  162 
Artemisia,  119,  126 
Arum,  15,  28,  32 


Asarum,  167 
Asparagus,  185 
Asperugo,  136 
Asperula,  117 
Atropa,  141 
Auricula,  38 

BALLOTA,  159 
Bartsia,  147 
Beech,  165 
'  Bellis,  118,  123 
Berberis,  59 
Berginia,  105 
Betonica,  160 
Birch,  8,  157 
Birdcherry,  97 
Bird's-nest  orchis,  171 
Blackberry,  97 
Blackthorn,  97 
Borage,  137 
Borago,  137,  140 
Broom,  86,  94 
Broomrape,  141 
Bryonia,  24,  017 
Bryony  (Black),  185 
Buckthorn,  86 
Bugle,  151 

Butcher's  Broom,  185 
Butomus,  169 
Buttercups,  12,  55 

CABBAGE,  62 
Calamintha,  151,  160 
Calceolaria,  151 


190 


INDEX. 


Caliciflorse,  54,  85 

Callitrichinese,  166 

Calluna,  132 

Caltha,  12,  56 

Calyx,  27 

Campanula,  24,  128 

Campanulaceae,  34,  128 

Campion,  73 

Caprifoliacese,  115 

Carduus,  118,  124 

Carrot,  109,  114 

Carum,  112 

Caryophyllaceae,  71 

Catasetum,  181,  182 

Celandine,  60 

Celastracese,  85 

Centaurea,  53,  114,  119 

Centranthus,  117 

Centunculus,  133,  134 

Cephalanthera,  177 

Cerastium,  71,  72 

Chaerophyllum,  in,  112 

Chelostoma,  19 

Chenopodium,  166 

Cherleria,  71 

Cherry,  97 

Chervil,  109,  112 

Chickweed,  72 

Chinchona,  40 

Chlora,  134 

Chrysanthemum,  114,  118,  121 

Chrysosplenium,  105 

Cicendia,  134 

Circsea,  100,  101 

Cirsium,  119,  124 

Cistinere,  64 

deist ogamous  flowers,  36, 83,91,155 

Clematis,  54,  58 

Clover,  86 

Colchicum,  185 

Colors  of  flowers,  12 

Columbine,  54 

Cornpositae,  34,  54,  112,  117,  126 

Coniferae,  8,  166 

Convallaria,  185 

Convolvuiaceae,  140 

Convolvulus,  140 

Cornaceas,  114 

Cornel,  114 

Corolla,  27 

Corolliflorse,  115 

Corrigiola,  54 


Coryanthes,  181 
Corydalis,  30,  6l 
Cotyledon,  105 
Cowslip,  103 
Crassulaceae,  104 
Crataegus,  97,  100 
Crocus,  183 
Cross-fertilisation,  6 
Cruciferae,  29,  62 
Cryptogams,  53 
Cucullia,  116 
Cucurbitaceae,  103 
Currant,  104 
Cuscuta,  140 
Cyclamen,  133 
Cynoglossum,  136 
Cyperaceas,  186 
Cypripedium,  170,  179 

DAISY,  118,  119,  12? 
Dandelion,  8,  25,  118,  126 
Dasyclura,  ill 
Datura,  141 
Daucus,   112 

Dead  Nettle,  60,  151,  153 
Deilephila,  116 
Delphinium,  44,  56 
Dianthsecia,  116 
Dianthus,  71,  75 
Diclinous  plants,  28 
Dicotyledons,  52,  168 
Dichogamous  plants,  28 
Digitalis,  42,  141,  146 
Dimorphism,  29 
Dioecia,  31 
Dionaea,  107 
Dipsacus,  126 
Discorideas,  183 
Dodder,  140 
Drosera,  105,  107 
Drymospermum,  40 

ECHIUM,  24,  136 
Elder,  115 
Elm,  165 
Elodea,  169 
Empetracese,  165 
Enchanter's  nightshade,  IOI 
Endogens,  53 
Entomophilous  plants,  9 
Epilobium,  31,  34,  46,  loo 
Epimediuni,  58 


INDEX. 


191 


Enipactis,  170 
Erica,  130 
Erodium,  72,  8l 
Erythrsea,  135 
Euphorbia,  165 
Euphrasia,  45,  141,  148 
Evening  Primrose,  100 
Exogens,  53 
Eyebright,  45,  141,  148 

FARAMEA,  43 

Feverfew,  119,  122 

Filament,  27 

Fir,  8,  164 

Flax,  9,  76 

Fleabane,  123 

Flower  (structure  of),  27 

Forget-me-not,  35,  139 

Foxglove,  43,  141,  146,  153 

Fragaria,  97,  99 

French  Bean,  24 

Fritilaria,  185 

Fumaria,  6 1 

Furze,  86,  93 

GALANTHUS,  185 

Galeobdolon,  159 

Galeopsis,  159,  160 

Galium,  117 

Genista,  24,  92,  94,  97 

Gentiana,  34,  135 

Gentianacese,  135 

Geranium,  2,  34,  42,  48,  79,  8l 

Geum,  97 

Gladiolus,  184 

Glaux,  133 

Gooseberry,  105 

Graminese,  186 

Grasses,  8,  186 

Ground  Ivy,  161 

Groundsel,  118,  123 

Guelder  Rose,  116 

HABENARIA,  176,  177 
Hawkweed,  25,  118 
Heath,  132 
Helianthemum,  64 
Hellebore,  12,  54,  56 
Henbane,  141 
Heracleum,  112 
Herb  Paris,  185 
Hesperis,  26,  63 


Heteromorphism,  29,  38 
Hieracium,  14,  26,  118 
Hippuris,  100 
Holosteum,  71 
Homomorphism,  38 
Honey,  12 
Honeysuckle,  n6 
Hottonia,  134 
Hyacinthus,  185 
Hydrocharis,  169 
Hyoscyamus,  141 
Hypericum,  75 

IMPATIENS,  34,  79,  84 
Incomplete,  54,  165,  166 
Inula,  123 
Ipomsea,  7 
Iris,  184 
Ivy,  114 

JASIONE,  130 
Juncus,  185 

KNAPWEED,  124 
Knotweed,  166 

LABIATVE,  34,  60,  136, 151, 156, 161 

Laburnum,  94 

Lactuca,  118 

Lady's-mantle,  97,  99 

Lady's-slipper,  179 

Lamium,  36,  144,  151,  154,  157 

Larkspur,  54 

Lathrsea,  141 

Lathyrus,  95,  97 

Lavatera,  78 

Leguminosse,  86,  95 

Leontodon,  '25 

Lettuce,  118 

Leucoium,  184 

Leucosmia,  40 

Liliacese,  185 

Lily,  185 

Lily  of  the  Valley,  185 

Lime,  78 

Limnanthemum,  135 

Linacese,  76 

Linaria,  44,  141,  145 

Linnsea,  115 

Linum,  39,  76 

Listera,  178 

Lithospermum,  136, 


192 


INDEX. 


Littorella,  163 

Lloydia,  185 

Lobeliaceae,  34,  130 

Lonicera,  44,  115 

Lotus,  88,  89,  92,  97 

Ludwigia,  100 

Lupins,  92,  97 

Luzula,  185 

Lychnis,  26,  49,  71,  72,  75 

Lycopsis,  136 

Lycopus,  162 

Lysimachia,  24,  44,  132,  133 

Lythrariese,  101 

Lythrum,  24,  38,  40,  101,  104 

MADDER,  117 
Msehringia,  75 
Maenchia,  71 
Mallow,  34,  44,  78 
Malva,  34,  46,  78 
Malvaceae,  34,  44,  78 
Marigold,  122 
Marjoram,  151,  161 
Martha,  117 
Matricaria,  122 
Medicago,  94,  95,  97 
Melampyrum,  151 
Melilotus,  97 
Mentha,  161 
Menyanthes,  40,  135 
Mertensia,  40,  136 
Mignonette,  63 
Milkwort,  69 
Mint,  151,  161 
Mitchella,  40 
Monsecious  plants,  28 
Monochlamydeae,  54 
Monocotyledons,  168 
Monopetalse,  54 
Mouth  parts  of  Bees,  17 
Mouth  parts  of  Wasps,  16 
Mullein,  141 
Myosotis,  36,  136,  139 
Myriophyllum,  100 
Myrrhis,  III 

NARCISSUS,  184 
Nasturtium,  82 
Nectary,  1 1 
Neottia,  179 
Nepeta.  161 
Nettle,  165 


Nigella,  36 
Night-flower,  50 
Nightshade,  141 
Nuphar,  60 
Nymphrea,  25,  60,  154 

OAK,  164,  165 
CEnothera,  100 
Onagraceae,  100 
Oncidium,  30 
Onion,  185 
Onobrychis,  92,  97 
Ononis,  91,  97 
Onopordon,  124 
Ophrys,  1 68,  176 
Orchidese,  168 
Orchis,  25,  171,  181 
Origanum,  161 
Orobanchacese,  141 
Orobanche,  141 
Ovary,  27 

Oxalis,  36,  38,  79,  83 
Oxyria,  13 

P^EONIA,  12,  55 
Panurgus,  19 
Papaveraceae,  60 
Paris,  185 
Parnassia,  105 
Paronychiaceae,  166 
Parsley,   109 
Parsnip,  109 
Pea,  86,  90,  95 
Pedicularis,  149,  151 
Pentstemon,  145 
Peplis,  I oi 
Petals,  27 
Phaseolus,  95,  97 
Phyteuma,  130 
Pimpernel,  25,  133 
Pine,  165 
Pinguicula,  134 
Pink,  34,  35 
Pistil,  2,  3,  24 
Plantagineae,  162 
Plantago,  10,  41,  163 
Plantain,  163 
Plumbagineae,  162 
Plumbago,  10,  162 
Polemoniacese,  136 
Polistes,  17 
Pollen,  2,  7,  11,  27 


INDEX. 


193 


Polyanthus,  38 

Polycarp,  71 

Polygala,  69 

Polygamia,  31 

Polygonacese,  13,  166 

Polyg  >num,  23,  40,  44,  165,  166 

Poplar,  8,  165 

Poppy,  60 

Potamogeton,  167 

Potentil,  97,  99 

Poterium,  10,  97,  99 

Primrose,  104 

Primula,  23,  30,  37,  39,  100,  133 

Prosoqueria,  117 

Proterandrous  plants,  28,"  33 

Proterogynous  plants,  28,  31 

Prunella,  162 

Prunus,  97 

Pseudomyrma,  6 

Pulmonaria,  23,  40,  136,  138 

Pulsatilla,  15,  58 

Pyrus,  97,  loo 

RADIOLA,  76 

Ranunculacese,  n,  12,  30,  55 

Raspberry,  98 

Rattle,  141,  149 

Red  Rattle,  105 

Reseda,  63 

Rhamnacese,  85 

Rhamnus,  40,  86 

Rhinanthus,  44,  141,  149 

Ribes,  103 

Ribesiaceae,  105 

Rosa,  97,  99 

Rosacese,  13,  97,  99 

Rubia,  117 

Rubus,  97,  98 

Ruellia,  37 

Rumex,  13,  166 

Ruppia,  167 

Ruscus,  185 

Rushes,  185 

Ruta,  41 

SAGE,  151 

Sagina,  71,  75 

Sal  via,  151,  156,  162 

Sambucus,  115 

Samolus,  133 

Sanguisorba,  10,  97,  99 

Santalacese,  106 


Saponaria,  71,  75 
Sarapoda,  22 
Sarothamnus,  94,  97 
Sarracenia,  109 
Saxifragacese,  105 
Saxifrage,  105 
Scabiosa,  24,  126,  128 
Scarlet  Runner,  23,  95 
Scent,  II 

Scrophularia,  33,  141 
Scrophularineze,  141,  162 
Sedge,  186 
Sedum,  105 
Sempervivum,  105 
Senecio,  118,  119,  123 
Shepherd's  Purse,  62 
Sherardia,   117 
Silene,  49,  71,  72 
Sisyrinchium,  184 
Sleep  of  flowers,  24 
Snapdragon,  141 
Snowdrop,  184 
Solanaceae,  141 
Solanum,  141 
Solomon's-seal,  185 
Spergularia,  71 
Spiraea,  97 
Stachys,  159 
Stamens,  27 

Standard  of  Leguminosse,  87 
Statice.  162 
Stellaria,  71,  72,  73 
Stellatse,  117 
Stigma,  26 
Stock,  62 
Stratiotes,  169 
Strawberry,  97,  99 
Style,  26 
Syrnphytum,  136,  140 

TAMUS,  185 
Taraxacum,  118,  126 
Tarsus  of  Bees,  21 
Teasel,  126 
Teucrium,  158 
Thalamifiorse,  52 
Thalictrum,  56 
Thistle,  118 

Thyme,  34,  35,  151,  161 
Tibia  of  Bees,  21 
Tilia,  78 
Tiliacese,  78 


194 


INDEX. 


Torilis,  1 12 
Tragopogon,  25 
Trefoil,  91 
Trichonema,  184 
Trientalis,  132 
Trifolium,  30,  36,  91,  92,  97 
Triglochin,  169 
Trimorphous,  29,  38 
Tropseolum,  82 
Tulip,  185 
Tussilago,  119,  123 
Twayblade,  179 

ULEX,  93 
Ulmacese,  166 

Umbelliferse,  34,  44,  109,  113 
Urticacese,  166 
Utricularia,  134 

VACCINIUM,  132 
Valerianese,  117 
Valisneria,  42 


Vandese,  181 
Verbascum,  30,  141 
Verbena,  162 
Verbenacese,  162 
Veronica,  44,  142,  162 
Vetch,  86 
Viburnum,  115 
Vicia,  23,  96,  97 
Vinca,  134 
Vine,  85 

Violet,  36,  43,  65,  66,  138 
Virginian  Creeper,  85 

WALLFLOWER,  62 
Watercress,  62 
Waterlily,  60 
Wheat,  9 
Willow,  165 
Woodruff,  117 
Woodrush,  185 

YAM,  185 


THE   END. 


R     CLAY  AND  SONS,    LTD.,    BREAD   ST.   HILL,    E.G.,    AND   BUNGAV,    SUFFOLK. 


Macmillan's  Nature  Series. 

Crown  8vo,  cloth. 

THE   ORIGIN   AND   METAMORPHOSES   OF 

INSECTS.     By  LORD  AVEBURY.     With  Illustrations.     3*.  6d. 

ON  BRITISH  WILD  FLOWERS  CONSIDERED 

IN  RELATION  TO  INSECTS.     By  LORD  AVEBURY.     Illus- 
trated.    4s.  6d. 

FLOWERS,  FRUITS,  AND  LEAVES.     By  LORD 

AVEBURY.     Illustrated.     4*.  6d. 

SOUND :  A  Series  of  Simple,  Entertaining,  and 
Inexpensive  Experiments.  By  A.  M.  MAYER.  3^.  6d. 

ON  LIGHT.  The  Burnett  Lectures.  By  Sir 
GEORGE  GABRIEL  STOKES,  F.R.S.  Three  Courses:  I.  On  the 
Nature  of  Light.  II.  On  Light  as  a  Means  of  Investigation. 
III.  On  Beneficial  Effects  of  Light.  1*.  6d. 

A   CENTURY   OF    ELECTRICITY.       By  T.  C. 

MENDENHALL.    4^.  6d. 

POPULAR    LECTURES    AND     ADDRESSES. 

By  LORD  KELVIN.     Vol.  I.  Constitution  of  Matter.     Illustrated. 
7-y.  6d.     Vol.    II.     Geology  and   General   Physics,     yj.  6d. 

THE  CHEMISTRY  OF   PHOTOGRAPHY.     By 

Prof.  R.  MELDOLA,  F.R.S.     Illustrated.     6s. 

TIMBER    AND    SOME    OF    ITS    DISEASES. 

By  Prof.  H.  M.  WARD,  M.A.     Illustrated.     6s. 

DISEASE  IN  PLANTS.     By  Prof.  H.  M.  WARD 

is.  6d. 

ARE  THE  EFFECTS  OF  USE  AND    DISUSE 

INHERITED?    An  Examination  of  the  View  held  by  Spencer 
and  Darwin.     By  W.  PLATT  BALL.     3^.  6d. 

MACMILLAN  AND  CO,  LTD,  LONDON. 


THE  CAMBRIDGE  NATURAL  HISTORY. 

Edited  by 
S.  F.  HARMER,  Sc.D.,  F.R.S.,  and  A.  E.  SHIPLEY,  M.A.,  F.R.S. 

In  Ten  Volumes.     Fully  Illustrated.    Medium  8vo,  i-js.  net  each. 
Vol.  I.     PROTOZOA,  by  MARCUS  HARTOG,  M.A.,  D.Sc. ; 

PORIFERA  (SPONGES),  by  IGERNA  B.  J.  SOLLAS,  B.Sc. :  COELENTERATA 
AND  CTENOPHORA,  by  S.  J.  HICKSON,  M.A.,  F.R.S. ;  ECHINO- 
DERMATA,  by  E.  W.  MACBRIDE,  M.A.,  F.R.S. 

Vol.  II.     FLATWORMS   AND   MESOZOA,   by   F.    W. 

GAMBLE,  D.Sc.;  NEMERTINES,  by  Miss  L.  SHELDON;  THREAD- 
WORMS AND  SAGITTA,  by  A.  E.  SHIPLEY,  M.A.,  F.R.S.;  ROTIFERS, 
by  MARCUS  HARTOG.  M.A.,  D.Sc.;  POLYrHAET  WORMS,  by  W.  BLAX- 
LAND  BENHAM,  D.Sc.,  M.A.  ;  EARTHWORMS  AND  LEECHES,  by  F.  E. 
BEDDARD,  M.A.,  F.R.S.  ;  GEPHYREA  AND  PHORON1S,  by  A.  E. 
SHIPLEY,  M.A.,  F.R.S. ;  POLYZOA,  by  S.  F.  HARMER,  Sc.D.,  F.R.S. 

Vol.  III.     MOLLUSCS,  by  the  Rev.  A.  H.  COOKE,  M.A.  ; 

BRACHTOPODS  (Recent),  by  A.  E.  SHIPLEY,  M.A.,  F.R.S.;  BRACHIO- 
PODS  (Fossil),  by  F.  R.  C.  REED,  M.A. 

Vol.  IV.     CRUSTACEA,    by    GEOFFREY   SMITH,    M.A. ; 

TRILOBITES,  &c.,  by  H.  WOODS,  M.A. ;  LIMULUS,  LINGUATULIDA, 
AND  TARDIGRADA,  by  A,  E.  SHIPLEY,  M.A..  F.R.S.  ;  SPIDERS, 
MITES,  SCORPIONS,  &c.,  by  C.  WARBURTON,  M.A. ;  PYCNOGONIDS, 
by  D'ARCY  W.  THOMPSON,  C.B.,  M.A. 

Vol.  V.     PERIPATUS,  by  ADAM  SEDGWICK,  M.A.,  F.R.S.  \ 

MYRIAPODS,  by  F.  G.  SINCLAIR,  M.A.  ;  INSECTS,  Part  L,  Introduction, 
Aptera,  Orth./ptera,  Neuroptera,  and  a  portion  of  Hymenoptera  (Sessili  venires 
and  Parasitica),  by  DAVID  SHARP,  M.A.,  M.B.,  F.R.S. 

Vol.  VI.     HYMENOPTERA,   continued  (Tubulifera  and 

Aculeata),  Coleoptera,  Strepsiptera,  Lepidoptera,  Diptera,  Aphaniptera,  Thy- 
sanoptera,  Hemiptera,  Anoplura,  by  DAVID  SHARP,  M.A.,  M.B.,  F.R.S. 

Vol.  VII.     HEMICHORDATA,  by  S.  F.  HARMER,  Sc.D., 

F.R.S.  ;  ASCIDIANS  AND  AMPBIOXUS,  by  W.  A.  HERDMAN,  D.Sc., 
F.R.S. ;  FISHES  (Exclusive  of  the  Systematic  Account  of  Teleostei),  by  T.  W. 
BRIDGE,  Sc.D.,  F.R.S.  ;  FISHES  (Systematic  Account  of  Teleostei),  by 
G.  A  BOULENGER,  F.R.S. 

Vol.  VIII.     AMPHIBIA    AND   REPTILES,    by   HANS 

GADOW,  M.A.,  F.R.S. 

Vol.  IX.     BIRDS,  by  A.  H.  EVANS,  M.A. 

Vol.  X.     MAMMALIA,    by    FRANK     EVERS     BEDDARD, 

M.A.,  F.R.S. 

MACMILLAN  AND  CO.,  LTD.,  LONDON. 


RETURN     BIOLOGY  LIBRARY 

TO—*     3503  Life  Sciences  Bldg.     642-2531 


ALL  BOOKS  MAY  BE  RECALLED  AFTER  7  DAYS 
Renewed  books  are  subject  to  immediate  recall 

DUE  AS  STAMPED  BELOW 


Bit  F 

llf&W^B 

u  t 

SuDjeet  to  Heca« 

Subioct  to  R?c3'i 

BluL^1" 

immediately 

APR  0  3  13 

- 

BIQL3CY  LIBRA 

? 

DUE 

$$f/yWyB° 

£k  f  s  **    "^  '  *4"  *f  •  j     H* 

/  •  'C7UW 

:-\-  r  ;nr>/,nv 

Wcitn  UnKAKr 

UNIVERSITY  OF  CALIFORNIA,  BERKELEY 
FORM  NO.  DD4  BERKELEY,  CA  94720 

I 


®s 


U.C.  BERKELEY  LIBRARIES 


717093 


LIBRARY 

/  G 

UNIVERSITY  OF  CALIFORNIA  LIBRARY