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February,  1836. 

ADVERTISEMENTS. 


NEW  NOVELS, 

PUBLISHED     BY 

LONGMAN,    REES,    ORME,    BROWN,    GREEN,    AND 
LONGMAN. 


ONE  IN  A  THOUSAND ; 

OR,  THE  DAYS  OP  HENRI  QUATRE. 

By  the  Author  of  "  The  Gipsy,"  "  Mary  of  Burgundy."   3  Vols.  ll.  Us.  6d. 

"  Mr.  James  in  undeniably  the  head  of  living  historical  romance  writers. 
•  *     His  most  successful  production." — Literary  Gazette. 

MARGARET   RAVENSCROFT. 

By  J.  A.  ST.  JOHN, 

Author  of  "  Tales  of  the  Ramad'han,"  &c.  &c.    3  Vols.  11.  11».  6d. 
"Mr.  St.  John  is  unquestionably  a  clever  man:  his  mind  is  cultivated   by 
reading  and  travelling,  and  he  thinks  over  what  lie  reads  and  sees.    The  present 
uork  contains  some  fine  conceptions  of  character." — Literary  Gazette. 

THE    DOCTOR,    &c. 

Vols.  I    II.  and  III.     M.  Us.  6d. 

"  Rich  beyond  almost  any  other  of  the  time,  in  the  best  knowledge  and  the 
most  beautiful  literature." — Quarterly  Review. 

THE        GIPSY. 

By  the  Aulhor  of  "Darnley,"  "  Life  and  Adventures  of  John   Marston   Hall," 
&c.    3  Vols.  post  8vo.      ll.  11s.  (id. 

5. 

ROSABEL. 

By  the  Authoress  of  "  Constance."     3  VoU.  ll.  Us.  6d. 

6. 

ENGLISH     IN     INDIA. 
2  Vols.     ll.  Is. 

"  Display?  no  common  latent.  *  *  *  •  *  The  girl  who  is  sent  out  on  specu- 
lation, and  who  is  resolved  to  marry  for  ambition,  and  tier  companion,  lively, 
unaffected,  and  true-hearted,  are  admirably  painted." — Atlas. 

WARLEIGH  ;  OR,  THE  FATAL  OAK. 

By  the  Authoress  of  "  The  White  Hoods,"  &c. 

3  Vols.    If.  11«.  6d. 

•'  Mrs.  Bray  has  with  great  skill  woven  into  the  annals  of  Cromwell's  iron 
timt  a  fearful  and  appropriate  legend." — Metropolitan  May. 

8. 

D  A  C  R  E. 

Edited  by  the  Countess  of  Morley.    3  Vols.     ll.  lit.  6d. 


ADYumssmm. 

Albermarle  Street,  Feb.  1836. 

WORKS    ON    NATURAL    HISTORY. 


i. 

THE  JOURNAL  OF  A  NATURALIST. 
Third  edition,  crown  8vo.  plates  and  wood-cuts,  lit. 

«. 
GLEANINGS  IN  NATURAL  HISTORY. 

Br    EDWARD  JESSE,   EMI  >  Surveyor   of   his    Majesty's   Park*  and    Palace? 

Including    Maxims   »nd   Hints  for   Anglers;   extract!    from    the    nnpublithe  I 

Joimiil-   "I    \\liit--   ot    Seltioinr;  notices  of  the  Royal  Parks  anil   Krtidrm -i-« ; 

S  air!  Remarks  on  the  Condition  of  the  Agricultural  Peasantry 

•  le  in  3  Tols.  post,  price  10*.  6d.  each. 

A  Third  /.'JilioK  ha*  b.-i-n  published  of  the  First  Series,  and  a  Second  Edi- 
tion of   tin-   Si  i  mill    Seriei  ;    so   that    purchasers  have  now  an  opportunity  of 
I,     Erfch  volume  may  also  be  purchased  separately. 

3. 

Sill  III  Ml'HKY    DAVY'S  SALMONIA. 

OR     DAYS     OP     FLY-FISHING. 

Third  edition,  small  8vo.  \-2i. 
4. 

CONSOLATIONS  IN  TRAVEL. 
By  SIR  HUMPHRY  DAVY.    Third  edition,  tmall  8vo.  6t. 

S. 
PRINCIPLES  OF  GEOLOGY. 

With  a   GLOSSARY,  containing  an   Explanation  of  Scientific  Term*,  ami  ; 
copious  INDEX.     By  CHARLES   L.YKLL,  F.R.S.    President  of  the   Cn|.,_i, 
Society.    A  Fourth  edition,  revised  and   enlarged,  illustrated  vtiih    Hit  U  HIM) 
cnts,  and  16  Plates  and  Maps.    4  Vols.  12mo.  price  only  'I4i. 

6. 
HOOKER'S  BOTANICAL  MISCELLANY. 

Complete  in  3  vols.Svo.  112  plates,  41. 11*.  Gd.     Single  Numbers  lOi.  6d.  each 

7. 

ILLUSTRATIONS  OF  THE  GEOLOGY  OF  YORKSIUKI, 

H>  JOHN  PHILLIPS,  F.R.S.,  F.C.S.,  Professor  of  Geology  in  King's  College 
London.     Vol.  II.    4to.    in  the  press. 

8. 

THE  "SILURIAN  SYSTEM  OF  ROCKS." 

As  developed  in  the  Counties  of  Salop,  Hereford,  Montgomrry,  Stafford 
Worcester,  (lloiicesti-r,  Monnmuih,  Radnor,  Brecon,  Caermarthen,  and  1'em 
broke;  with  Sketches  of  all  the  a<  company ini;  formation-. 

By  RODERICK   IMPKY  Mi  KL-M  I>ON,  F.li.S.,  Vice-President  of  the  Geolo- 
gical and  Royal  Geographical  Societies,  F.L.S..&C.  &c.    Royal  4to.  in  the  pre«s 

JOHN  MURRAY,  Albermarle  Street. 


ADVERTISEMENTS. 


NATURAL  EVIDENCE  OF 
A  FUTURE  LIFE,  derived  from  the 
Properties  and  Actions  of  animate  and 
inanimate  Matter.  By  FKEUERICK 
C.  BAKSWELL.  1  vol.  8vo.  price  12s. 

By  the  same  Author,  in  1  vol.  12mo. 
5s.  6d. 

PHILOSOPHICAL  CON- 
VERSATIONS ;  In  which  the  Causes 
of  daily-occurring  Phenomena  are  fami- 
liarly Explained. 

LONGMAN,  REES,  ORME  and  Co. 


This  day  is  published,  in  18mo.,  price 
28.  Gil.  in  fancy  cloth. 

HINTS  ON  ETIQUETTE, 
AND  THE  USAGES  OF  SOCIETY; 
With  a  Glance  at  Bad  Habits.  By 

Shewing  how 

To  make  a  silk  purse  out  of  a  sow's 
ear." — Old  Saying. 

"  Manners  make  the  man,  and  want 
of  them  the  fellow." — Old  Proverb. 
LONGMAN,  REES,  ORME,  and  Co. 


This  day  is  published, 

THE       EDINBURGH 
REVIEW,  No.  126. 

CONTENTS. 

1.  LIFE   and  WORKS     of    BARON 
CUVIER. 

2.  ALFORD'S  ScHOOLof  the  HEART, 
and  other  POEMS. 

3.  PROGRESS  and  PRESENT  STATE 
of  AGRICULTURE— THE  AGRICULTU- 
RAL ASSOCIATIONS. 

4.  WILLIS'S   PENCILLINGS   by  the 
WAY. 

5.  LIFE    and    OBSERVATIONS    of 
FLAMSTBED — NEWTON,     HALLEY, 

andFLAMSTEED. 

6.  LEWIS  on  the  ORIGIN  and  FOR- 
MATION of  the  ROMANCE  LANGUAGES. 

7.  WHEWELL    on   the    STUDY    of  \ 
MATHEMATICS — UNIVERSITY  of  CAM- 
BRIDGE. 

8.  THE  CAPE  of  GOOD  HOPE,  and 
the  late  CAFFRE  WAR. 

9.  ORIGIN,  NATURE,  and  TENDEN- 
CIES of  ORANGE  ASSOCIATIONS. 

London  :     LONGMAN,    and  Co.; 
Edinburgh  :  A.  and  C.  BLACK. 


TO    PEDESTRIANS.    SPORTS- 
MEN, ETC. 

PATENT  PEDOMETERS, 
for  the  Waistcoat  Pocket,  at  PAYNE'S 
163,  New  Bond  Street,  opposite  Clifford 
Street. — Pedometers  for  Ladies. 


This  day  is  published,  in  2  vols.  12mo. 
price  12*.  bound  in  cloth, 

THE    SCHOOLMASTER: 

Essays  on  Practical  Education,  select- 
ed from  the  Works  of  ASCHAM,  MIL- 
TON, LOCKE,  and  BUTLER;  from  the 
'  Quarterly  Journal  of  Education;'  and 
from  lectures  delivered  before  the 
American  Institute  of  Instruction. 

London:   CHARLES    KNIGHT, 
22,  Ludgate  Street. 


BURNETT'S  BOTANY, 
In  1  thick  volume  8vo.,  is  reduced  in 
price,    from   34s.   to  21s.   in   cloth 
bds.  lettered. 

OUTLINES  or  BOTANY. 
Including  a  General  History  of  the 
Vegetable  Kingdom,  in  which  Plants 
are  arranged  according  to  the  System 
of  Natural  Affinities.  By  GILBERT  T. 
BURNETT,  F.L.S.,  Professor  of  Botany 
iu  King's  College,  London. 

The  Work  consists  of  nearly  Twelve 
Hundred  pages  of  closely  printed  text, 
and  contains  upwards  of  Two  Hundred 
and  Fifty  Wood  Engravings. 

London:  HENRY   RENSBAW, 
356,  Strand. 

*«*  For  favourable  notices  of  this 
Work,  see  Loudon's  Magazine  of  Bo- 
tany, and  all  the  Medical  Periodicals. 


RHEUMATISM. 

If  you  suffer  from  Rheumatism  or  Rup- 
ture, read  INDEX  to  Advertisements  in 
Boyle's  Court  Guide,  Royal  Blue  Book, 
Pigot's,  Post  Office,  the  Dublin  or 
Robson's  Directories  for  1836 — the  two 
latter  contain  "  Coles  on  Rheumatism," 
wherein  you  will  perceive  at  once  to 
what  extent  the  Public  estimate  his 
services. 

"  Coles  on  Rheumatism,"  and  "Coles 
on  Ruptures,"  are  single  letters,  pub- 
lished by  Sherwood  and  Co.,  and  Wm. 
Strange,  price  one  penny :  published 
also  iu  French  by  Galignani,  a  Paris : 
and  Mons.  De  la  Porte,  Burlington 
Arcade  ;  and  at  3,  Charing  Cross. 


ADVERTISEMENTS. 


DEEDS,    NOT    WORDS,    ARE    THE    MAXIMS    OF 

THE    DAY, 

AND   TO   OBTAIN    PUBLIC    FAVOUR    IT   IS    ALONE    NECESSARY   TO    DESERVE  IT. 

THE  principles  of  honest  dealing  require  that  the  Tradesman  should  get  a 

profit,    though   a 

moderate    one,    the    ARTISAN    remunerating   wages,   and 

Families  be  supplied  at   the    owest  rate  which  tliex:   combined   objects  can 

effect;  on  this  has 

is,  HENRY   L.  COOPER  otters  the  character  and  credit  of 

an  establishment 

of  upwards  of  half  a  century  in  existence,  as  a  pledge  for 

the  fulfilment  of 

his  engagements  with   his   best  triends  and   patrons  —  the 

PUBLIC. 

To  realize  the  professions  of  this  brief  address,  H.  L.  C.  solicits  a  view  of 
his  STOCK  of  PLATE  GLASS,  CABINET  and  CHAIR  WORK,  UPHOL- 

STERY, &c.,  at  the  prices  required  for  them,  and  fearlessly  challenges  com- 
petition in   the  united  qualities  of  FASHION,   MATERIAL,  MANUFAC- 

TURE, and  COST.  No.  03,  Bishopsgate-street  Wit  lin,  and  at  hi*  WESTERN 

branch,  57,  Condu 

it-street,  Nine  Doors  from  Regent-street,  left-bund  side. 

Among  the  variety  of  articles  above  referred  to,  will  be  found  LOOKING- 

GLASSES  of  eve 

iy  denomination  and  size,  varying  from  one  foot  to  eighty 

feet  and  upwards 

PLATE  GLASS  for  windows,  carriages,  &c.,  which  pos- 

sesses  great  adva 

ittages  over  Crown,  and   when   required  for  exportation,  a 

considerable  draw 

back  obtained. 

Annexed  are  the  prices  of  current  s  zes  of  Plate  Glass,  for  sashes,  &c. 

Inches 

15  in. 

18  in. 

20  in. 

22  in. 

25  in. 

28  in. 

30  in. 

£.  *.  d. 

£.  «.  d. 

£.  «.  d. 

£.  «.  d. 

£.  *.  d. 

£.  I.  d. 

£.  s.  d. 

10 

075 

093 

0  10    6 

0  11     9 

0  13     8 

0  15     6 

0  16  11 

11 

084 

0  10     5 

0  11  10 

0   13     2 

0  15     3 

•  17     6 

0  19    2 

12 

093 

0  11     6 

0  13     0 

0  14     6 

0  16  11 

0  19     8 

1     6 

13 

0  10    2 

0  12     7 

0   14    4 

0  15  11 

0  18  10 

I  10 

3    9 

14 

on    2 

0  13     9 

0  15     6 

0  17     6 

0     9 

3  11 

6     1 

15 

0  12     1 

0     4  11 

0  16  11 

0  19     2 

2     8 

6     1 

8     2 

16 

0  13     0 

0  16     0 

0  18     6 

0  10 

4     7 

8    0 

10     0 

17 

0  13  11 

0  17     4 

0    0 

2     7 

6    6 

9    9 

11   10 

18 

0  14  11 

0  18     9 

1     0 

4     3 

S     2 

11     6 

13     0 

19 

0  15  10 

0     2 

3     'i 

5  11 

9    8 

13    2 

15     7 

20 

0  16  11 

1     6 

4    6 

7     0 

11     3 

15    0 

17     6 

22 

0  19     2 

4     3 

7     6 

1   10     3 

14     5 

18    6 

2     1     3 

25 

2    8 

8    2 

11     3 

1   14     5 

19     1 

239 

2     6  11 

28 

6     1 

11     6 

15     (j 

1  18     6 

239 

200 

2  12    6 

30 

8     2 

13     9 

17     6 

2     1     3 

2     C  11 

2  12     6 

2  16     3 

32 

10     0 

1  16     0 

200 

240 

2  10     0 

2  16     0 

300 

34 

11   10 

1   18     3 

226 

269 

2  13     2 

2  19     6 

339 

36 

13     9 

206 

250 

296 

2  16     3 

330 

376 

38 

15     7 

229 

276 

2  12     3 

2   19     4 

366 

3  11     J 

40 

17     6 

250 

2     9  11 

2  15     0 

326      3  10     0 

3  16     5 

Or  any  sizes  containing  from  three  feet  to  eight  feet,  at  9«.  per  foot  ;  thus  a 

plate  being  thirty 

inches  by  eighteen  inches,  contains  three  feet  nine  inches 

superficial  measure,  and  costs  I/.  13*.  Od.,  as  per  above  tariff.    All  under  three 

feet  superficial  at 

i  reduction. 

SECOND-HAND  LOOKING  GLASSES.   Several  superb  Glasses,  varying 

in  size,  eight  feet 

nine  feet,  ten  feet,  and  upwards  in  length,  by  five  feet  and 

five  feet  six  jnche 

s  in  width,  at  a  considerable  reduction  from  the  present  tariff 

prices.    Or  LENT  ON   HIRE  by  the  month  or  season. 

CARVING  AN 

D   GILDING,   in  all  its  branches,  with   an  assortment  of 

SPLENDID  FRAMES    for  CHIMNEY,  PIER,   CHEVAL,   and  TOILET 

GLASSES.     1'Al 

NT1NGS  and  PRINTS  mounted,  framed,  and  re-gilt. 

PAPER-HAM 

neatness  and  cleg< 

rING  In  every  decorative  department,  and  in  the  first  style  of 
nee,  with  a  rich  variety  of  new  patterns. 

ADVERTISEMENTS. 


Henry  L.  Cooper's  Advertisement — Continued. 


CABINET  AND  CHAIR  WORK,  manufactured  of  the  most  seasoned 
materials,  and  for  exportation,  of  a  solidity  to  suit  the  warmest  climate,  and 
comprises  in  this  general  stock  every  novelty  lately  introduced.  STEAM  and 
SAILING  VESSELS  promptly  fitted  up  with  CABIN  FURNITURE  and 
PASSENGERS'  Requisites. 

IN  THE  UPHOLSTERY  ARRANGEMENTS  the  greatest  attention  is 
paid  to  unite  elegance  with  economy  in  character  for  the  DRAWING-ROOM, 
BOUDOIR,  DINING-ROOM,  LIBRARY,  and  BED-CHAMBERS,  from 
the  most  quiet  to  the  most  costly  styles,  with  a  handsome  assortment  of  silks, 
tabarets,  figured  damasks,  chintz,  &c.  always  on  show. 

CARPETING,  of  the  fabric  especially  made  for  the  first  upholstery  houses, 

viz.;  Brussels,  Kidderminster,  and  Venetian;  also  a  few  of  the  much- 
admired  Velvet  Pile  Carpets,  Hearth-rugs,  Druggets,  Baize,  Floor-cloth,  &c. 

BEDDING,  BLANKETS,  &c.,  well-seasoned,  real  Dantzic  Feathers,  also 
equally  prepared  light  downy  Feathers  for  second  and  third  rate  Beds,  Elastic 
Spring  Hair  and  Wool  Mattresses;  real  Witney,  fine  Bath  and  York  Blankets, 
Marseilles  Quilts  and  Counterpanes.  In  the  articles  of  Bedding,  Blankets, 
&c.,  so  essentially  important  to  all,  H.  L.  C.  is  determined  that  no  trader  shall 
supply  them  on  better  terms. 

HOUSE  AGENCY.  A  register  kept  at  both  establishments  for  the  disposal 
or  procuring  of  every  description  of  HOUSES,  FURNISHED  or  UNFUR- 
NISHED, ESTATES,  4c.  Properties  surveyed,  and  fixtures  appraised. 

FUNERALS  furnished  and  conducted  with  the  greatest  propriety,  and  with 
every  consistent  regard  to  economy. 

With  this  short  enumeration  of  the  leading  articles  of  his  trade,  and  the  very 
favourable  terms  on  which  he  undertakes  to  supply  them,  HENRY  L.  COOPER 
APPEALS  TO  ALL  CLASSES  for  a  continuation  of  that  flattering  preference 
hitherto  afforded  his  house,  93,  B1SHOPSGATE-STREET  WITHIN;— 
WESTERN  BRANCH,  57,  CONDUIT-STREET,  Nine  Doors  from  Regent 
street. — Please  to  observe  the  NAME  and  NUMBER. 


THE  LADY'S  MAGAZINE 
AND  MUSEUM, 

Under  the  distinguished  patronage 
of  Her  Royal  Highness  the  Duchess  of 
Kent,  for  February  1st,  will,  we  trust, 
merit  public  favour,  and  without  any 
reduction  in  price  secure,  by  the  supe- 
riority of  artistical  embellishments  and 
literary  talent,  a  rival  success  with 
Drury  Lane  Theatre.  The  authentic 
full-length  portrait,  No.  36  of  the  series, 
will,  we  are  assured,  be  far  more 
splendid  in  Jewellery  and  ornament 
,  than  has  yet  been  produced-  The 
i  twelve  original  articles  are — Memoir 
of  Marie  Touchet;  St.  Valentine,  by 
Miss  Agnes  Strickland  ;  the  New  Year's 
Gift,  by  Edward  Lancaster,  Esq.,  au- 
thor of  "  The  Last  of  the  Burnings," 
which  is  dramatized,  and  will  be  im- 
mediately represented  with  a  success, 
we  augur,  equal  to  that  of  "  The 
Jewess;"  My  Ward  Jemima,  by  J. 
Carpenter,  Esq.;  Edith,  by  the  Hon. 
Miss  H.  M.  Beauclerk  ;  Sons  of  Judah, 
by  Pclikar;  Recollections  of  a  Rev. 
Bachelor,  by  Mrs.  Holland  ;  Selda,  the 


Ice  Nymph,  a  seasonable  tale,  by  Mrs 
Kinlock,  illustrated  by  a  coloured  en- 
graving, in  which  are  two  large  figures 
in  fancy  costume,  and  in  the  back 
ground,  on  the  stage,  and  in  the  boxes 
an  innumerable  group  in  fancy  charac 
ters ;  the  Dream  and  the  Midnight 
Blush,  by  H.;  Another  Tale  of  the 
English  Chronicles;  Sir  Lucas  Stan- 
more  and  the  Lord  High  Admiral,  bj 
Miss  Agnes  Strickland;  Sonnet  to  the 
Memory  of  the  late  James  White,  Esq. 
by  Mrs.  Holland;  and  a  letter  "  News 
and  Fashion,"  by  our  own  Corres- 
pondent at  Paris  ;  Reviews  of  Books. 
New  Music,  &c.,  sent  to  the  Editor  by 
authors  and  publishers;  Drama,  Mis- 
cellany, &c. 

Published  monthly,  price  2s.  6d.,  by 
Dobbs,  Page,  and  Street,  112,  Fetter 
lane,  and  15,  Carey-street,  Lincoln's 
inn,  by  whom  advertisements  of  schools 
teachers,  books,  music,  and  genera 
advertisements,  at  a  moderate  price, 
are  received.  To  be  had  of  booksellers 
in  every  part  of  the  kingdom.  The 
January  number  and  former  number 
are  still  on  sale. 


.*rVFRTI«KMFM  « 


J.  C.  &  C.  PENN, 

BOOT  AND   SHOE    MANUFACTURERS,    THE   CORDWAINER'S 
ARMS,  143,  HOLBORN  BARS,  (Corner  of  Brooke  Street.) 

Beg  to  announce  (o  the  Public,  that  they  hive  on  Sale  a  most  extensive  and 
fashionable  a-sorlnient  of  Ladie*',  Gentlemen*!,  and  Children's  Boots  and  Shoes  ; 
ron»isting  of  every  possible  variety,  which  for  quality  of  material  and  work- 
in.insliip,  cannot  be  surpassed  hy  any  House  in  the  Trade — added  to  which  the 
prices  are  such  as  cannot  fail  to  give  entire  satisfaction  even  to  the  most 

••ni-al. 

Orders  for  Exportation,  Charitable  Institutions,  and  Country  Dealers,  supplied 
011  the  shortest  notice,  and  lowest  possible  terms. 


T.  COX  SAVORY, 


47, 
C  0  R  N  H  I  L  L, 

LONDON, 

WATCHMAKER, 
GOLDSMITH, 

AND 

SILVERSMITH. 


IN  ELEGANT  CASES, 
With  finely   and  accurately-finished   Move 
ments,  to  strike  the  hours  and  half-nours,  re- 
quire winding  only  once  in  Eight  Days. 
Warranted— Five  Guineas  each. 


WITH  GLASS  SHADES, 

Shewing  the  whole  Mechanism  of  the  Clock- 

Going  for  Eight  Days, 

Not  to  Strike. 
Warranted — Four  Guineas  each. 


PATENT  LEVER  WATCH  KS. 


SILVER  CASES. 

With  Double  Bottom  Cases £6    6 

With  Hunting  Cases  6  16    6 


GOLD  r-\Sl.< 

Ladies',  with  elegant  Gold  Di;d    ____  £1616 
Gentlemen's,  with  Enamel  Dial  ____     1818    0( 


This  celebrated  construction  (the  most  accurate  on  which  a  Watch  can  be  made)  is  now  ' 
'  offered  atthe  above  price,  with  the  latest  improvements,  i.e.  the  Detached  Escapement,  Jewel-  ( 
>  led  in  Four  Holes,  Capped,  Hand  to  mark  the  Seconds,  and  maintaining  power  to  continue  ' 
while  winding  up. 

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DESCRIPTIVE  AND  PHYSIOLOGICAL 

BOTANY. 

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1836. 


•   PHYR  I  f'AL 

(,\    •,\\>  ""JSP*         \ 
(        ii(j  '  &  a  -c ' V  -L  I    a  •     i    )         \ 

THE    REV. ./.  A*.  HENSLOW,  M.A.  F.L.S.  &-c.  &< 


209105^ 


CONTENTS. 


INTRODUCTION. 

Objects  of  Botanical  Investigation  (2.).  —  Descriptive  and  Physiological 
Botany  —  Sub-divisions  (3.).  —  Advantages  of  our  Pursuit  (4.)- — Un- 
organized and  organized  Bodies  (5.).— Distinction  between  Animals  and 
Vegetables  (7.)  -  -  -  -  Page  1 


PART  I. 

DESCRIPTIVE    BOTANY; 
SECTION  I. 

ORGANOGRAPHY    AND    GLOSSOLOGY. 

CHAPTER  I. 

ELEMENTARY    ORGANS    AND    TISSUES.  ! 

External  Organs — Conservative  and  reproductive  (9.)-  —  Internal  Struc- 
ture; Elementary  Texture ;  Chemical  Composition  (12.) — Elementary 
Organs;  Cellular  and  Vascular  Tissues  (13.).  —  Compound  Organs  — 
Investing  and  complex  (28.) Primary  Groups  or  Classes  (33.)  -  9 

CHAP.  II. 
NUTRITIVE    ORGANS. 

Fundamental  Organs  (38.).  —Root  and  Appendages  (39.).  — Stems  (Aerial) 
(43.).  —  Internal  Structure  (45.).  — Forms  and  Directions  (53.).  —  Bud* 
(56.).  —  Branches  (58.).  — And  their  Modifications  (61.).  — Subterr.mean 
Stems  and  Branches  (62.).— Tubers  and  Bulbs;  their  Affinity  (63.).— 
Appendages  to  the  Stems  (67.)  -  -  -  37 


Yl  CONTENTS. 

CHAP.   III. 
NUTRITIVE  ORGANS  —  continued. 

Leave*,  simple  and  compound  (69.).  —  Vernation  (71.).  —  Formi  of  Leave* 
(7*.).  —  Phyllodia  (75.).—  Transformation  of  Leaves  (78.).  —  Venation 
(81.).  —  Disposition  and  Adhesion  (82.).  —Nutritive  Organs  of  Crypto- 
gamic  Plant*  (84.)  .  .  -  Page  59 

CHAP.  IV. 

REPRODUCTIVE    ORGANS. 

FJower  Bud*  (85.) — Inflore»cence—  Mode*  of  (86.).  —Floral  Whorls- 
Perianth  (92.).  —  Glumaceous  Flower*  (96.).  — Stamens  and  Pistils  (97.). 
—  Disk  (10L).—  Floral  Modification*  (102.).  —  Activation  (104.)  -  79 

CHAP.  V. 

REPRODUCTIVE  ORGANS  —  continued. 

Fruit  —  Pericarp  (105.).  —  Forms  of  Fruit  (If  8.).  —  Seed*  (109.).  —  Embryo 
(lit).  —  Reproduction  of  Cryptogamous  Plant*  (114.)  •  -  102 

CHAP.  VL 
MORPHOLOGY. 

Abortion  (115 ).  — Degeneration  (116.).  —  Adhesion  (11&).  —  Supernu- 
merary Whorl*  (119.). — .  Normal  Characters  (ISO.). —  Spiral  Arrangement 
of  foliaceous  Appendage*  (121.).  — Tabular  View  of  Vegetable  Organ  ii- 
(129.)  -  -  -  -  -  116 


SECTION  II. 

TAXONOMY  AND  PHYTOGRAPHY. 

CHAP.  VII. 

Natural  Groups  (131.).  — Values  of  Characters  (132.).  —  Subordination  of 
Characters  (133.}.  —  Natural  Orders  (135.).  — Artificial  Arrangements 
(136.).  — Linnaean  System  (137.).  — Application  of  it  (140.)  -  .135 


CONTENTS.  Vll 

PART  II. 

PHYSIOLOGICAL    BOTANY. 
CHAPTER  I. 

VITAL    PROPERTIES    AND    STIMULANTS. 

Vegetable  Life  (139.).  —  Properties  of  Tissues  (141.).  —  Endosmose  (144.). 

—  Vital  Properties  (145.).  —  Stimulants  to  Vegetation  (152.)    -  Page  155 

CHAP.  II. 

FUNCTION  OF  NUTRITION  —  Periods  I,  2,  3,  4. 

Absorption  (160.).  —  Ascent  of  Sap  (163.).  —  Causes  of  Progression  (165.). 

—  Exhalation  (169.).  —  Retention  of  Sap  (172.). —  Respiration  (!?&). — 
Fixation  of  Carbon   (176.). —  Organizable  Products  —  Gum   (177.).  — 
Etiolation   (179.).  — Colours  and   Chromatometer   (182.).  —  Results  of 
Respiration  (189.)  -  -  -  -  -  175 

CHAP.  III. 
FUNCTION  or  NUTRITION — continued — Periods  5,  6. 


CHAP.  IV. 
FUNCTION  OF  NUTRITION  —  continued  —  Period  7. 

Assimilation  (223.).  —  Pruning  (225.).  —  Grafting  (227.). —Development 
(230.).  — Nutrition  of  Cryptogamic  Plants  (233.).  — Parasitic  Plants  (234.). 
—  Duration  of  Life  (235.).  — Vegetable  Individuals  (236.).  —  Longevity 
of  Trees  (239.)  -  227 

CHAP.  V. 

FUNCTION  OF  REPRODUCTION — Periods  1,  2,  3. 

Propagation  (243.).  —  Origin  of  Flower-buds  (245.).  — Flowering  (246.).— 
Functions  of  the  Perianth  (252.).  —  Development  of  Caloric  (254.).  — 


Vlll  CONTENTS. 

Fertilisation  (255.).  —  Formation  of  Pollen  (261.).  —  Maturation  (265.). 
—  flavour  and  Colour  of  Fruit  (273.)  -          Page  248 

CHAP.  VL 
roHCTioii  or  REPRODUCTION  —  continued — Periodi  4,  5. 

Dissemination  (275.).  — Modes  of  Dissemination  (279.).  —  Preservation  of 
Seed  (281.).  —  Germination  (28i).  —  Vitality  of  the  [Embryo  (290.).— 
Relation  of  Bud  and  Embryo  (291.).  —  Proliferous  Flowers  (292.).  —  Hy. 
brids  (296.)  ...  .275 

CHAP.  VII. 
FPIHRHEOLOGY,    BOTANICAL    GEOGRAPHY,    FOSSIL    BOTANY. 

Epirrheology  '(298.) — Direction  of  Roots  and  Steins  (299.).  —  Botanical 
Geography  (902.).  —  Fossil  Botany  (31&)  -  .  290 


THE  PRINCIPLES 

OF 

DESCRIPTIVE  AND  PHYSIOLOGICAL 

BOTANY. 


INTRODUCTION. 

OBJECTS  OF  BOTANICAL  INVESTIGATION  (2.).  DESCRIPTIVE  AND 

PHYSIOLOGICAL  BOTANY SUB-DIVISIONS  (3.). ADVANTAGES 

OF       OUR      PURSUIT    (4.)'  UNORGANISED      AND      ORGANISED 

BODIES    (/>.).  DISTINCTION    BETWEEN    ANIMALS     AND    VEGE- 
TABLES (7.). 

(1.)  OF  the  advantages  which  accrue  from  the  culti- 
vation of  the  natural  sciences,  sufficient  has  been  said  in 
the  treatise  of  Sir  J.  Herschel,  forming  our  fourteenth 
volume ;  and  Mr.  Swainson,  in  his  discourse,  which 
forms  our  fifty-ninth  volume,  has  further  exposed  the 
importance  of  the  study  of  Natural  History  in  general, 
and  more  particularly  of  that  department  which  he  so 
successfully  cultivates.  In  introducing  the  science  of  Bo- 
tany to  the  general  reader,  for  whom  more  especially  this 
volume  is  designed,  rather  than  for  the  scientific  adept, 
it  will  be  right  that  we  should  follow  the  example  which 
has  thus  been  set  us,  and  say  a  few  words  by  way  of 
introduction  to  our  present  subject.  Whenever  we  are 
about  to  enter  upon  any  science  which  is  new  to  us,  it 

r 


2  PRINCIPLES    OF    BOTANY. 

is  always  advantageous  to  take  a  general  survey  of  the 
limits  within  which  it  is  restricted,  and  to  obtain  some 
notions  of  the  objects  of  which  it  professes  to  treat. 
We  shall,  therefore,  offer  a  few  remarks  upon  the 
position  which  Botany  holds  with  respect  to  other 
kindred  branches  of  Natural  History  ;  and  point  out 
the  separate  and  subordinate  departments  into  which  it 
may  be  advantageously  divided. 

(2.)  Botany.  —  In  the  most  extended  sense  of  the 
term,  Botany  may  be  considered  as  embracing  every 
inquiry  which  can  be  made  into  the  various  phenomena 
connected  with  one  of  the  three  great  departments  into 
which  the  study  of  nature  is  divided,  and  which  is 
familiarly  styled  the  Vegetable  Kingdom.  And  this 
inquiry  should  extend  as  well  to  the  investigation  of 
the  outward  forms  and  conditions  in  which  plants, 
whether  recent  or  fossil,  are  met  with,  as  to  the  exa- 
mination of  the  various  functions  which  they  perform 
whilst  in  the  living  state,  and  to  the  laws  by  which 
their  distribution  on  the  earth's  surface  is  regulated. 
We  may  conveniently  arrange  these  several  phenomena 
under  two  heads.  The  one  may  be  called  the 
"  Descriptive"  department  of  the  science,  being  de- 
voted to  the  examination,-  description,  and  classification 
of  all  the  circumstances  connected  with  the  external 
configuration  and  internal  structure  of  plants,  which 
we  here  consider  in  much  the  same  light  as  so  many 
pieces  of  machinery,  more  or  less  complicated  in  their 
structure;  but  of  whose  several  parts  we  must  first 
obtain  some  general  knowledge,  before  we  can  expect 
to  understand  their  mode  of  operation,  or  to  appreciate 
the  ends  which  each  was  intended  to  effect.  In  the 
"  Physiological,"  which  is  the  other  department,  we 
consider  these  machines  as  it  were  in  action  ;  and  we 
are  here  to  investigate  the  phenomena  which  result 
from  the  presence  of  the  living  principle,  operating  in 
conjunction  with  the  two  forces  of  attraction  and 
affinity,  to  which  all  natural  bodies  are  subject. 

(3.)  Subordinate  departments.  —  Each  of  the  two 


INTRODUCTION.  6 

departments  mentioned  in  the  last  article  admits  of 
subdivision  ;  and  the  several  subordinate  departments 
thus  formed  become  a  register  of  special  observations. 
Thus,  the  descriptive  department  will  include  a  "Glosso- 
logy," or  mere  register  of  technical  terms  —  composing  a 
conventional  language,  by  which  the  description  of 
plants  is  facilitated,  and  a  comparison  of  their  forms 
and  peculiarities  rendered  clear  and  precise,  without 
any  periphrasis  or  unnecessary  prolixity.  It  will  also 
include  an  "  Organography,"  containing  a  particular 
account  of  the  several  parts  or  organs  of  which  plants 
are  composed.  A  third  subordinate  department  is 
styled  "  Phytography,"  in  which  a  full  description  of 
plants  themselves  is  given :  and  lastly,  we  have  the 
"Taxonomy"  of  this  science,  in  which  plants  are 
classified  in  a  methodical  manner,  according  to  some 
one  or  other  of  those  various  methods  or  systems, 
which  serve  to  facilitate  our  knowledge  of  the  forms 
and  relations  of  the  numerous  species  already  discovered. 
We  do  not,  however,  propose  to  treat  our  subject  with 
so  much  technicality.  In  descriptive  botany  we  shall 
chiefly  restrict  ourselves  to  the  more  general  details  of 
Organography,  and  include  in  this  department  what- 
ever we  may  find  it  necessary  to  say  on  Glossology. 
The  reader  may  then  consult  the  general  index  at  the 
end  of  the  volume,  whenever  he  meets  with  a  word 
which  requires  explanation,  and  he  will  be  referred  to 
the  page  and  article  in  which  such  explanation  is 
given.  Phytography  is  entirely  subordinate  to  Taxo- 
nomy, or  Systematic  Botany,  which  forms  no  part 
of  our  scheme,  beyond  what  is  necessary  to  give  the 
reader  some  general  notions  of  the  manner  in  which 
plants  are  described  and  classified  in  the  most  cele- 
brated systems  of  systematic  authors.  We  shall  enter 
somewhat  more  fully  into  the  details  of  Physiological 
Botany,  as  this  subject  possesses  a  more  general  inter, 
est,  owing  to  the  numerous  and  striking  phenomena, 
of  practical  and  economical  importance,  which  it  ena» 
bles  us  to  explain. 

B  2 


PRINCIPLES    OF    BOTANY. 

It  is  more  usual,  indeed,  to  restrict  the  term  Botany 
entirely  to  the  descriptive  departments,  in  which, 
as  might  have  been  expected,  and  as  the  nature  of  the 
case  requires,  much  greater  progress  has  been  made 
than  in  the  physiological.  It  is,  in  fact,  only  very 
lately  that  any  successful  attempt  has  been  made  to- 
connect  the  numerous  facts  which  have  been  long 
accumulating  relative  to  the  various  phenomena  which 
attend,  and  the  laws  which  regulate,  the  functions 
performed  by  the  living  vegetable. 

(4.)  Attrnnttuji-s  nf  unr  jntrsitit. — The  old  and  by- 
gone sneer  of  "  mi  honu,"  by  which  the  naturalist  was 
formerly  taunted,  now  offers  no  serious  impediment  in 
the  way  of  those  who  are  willing  to  inquire  for  them- 
selves. Even  the  few  who  still  think  that  no  advan- 
tage would  result  from  the  encouragement  of  natural 
history  as  a  branch  of  general  education,  no  longer  at- 
tempt any  very  decided  opposition  wherever  they  meet 
with  others  prepared  to  uphold  it.  Our  pursuit  has 
been  so  often  and  so  satisfactorily  shown  to  be  produc- 
tive of  direct  practical  benefit  to  the  general  interests 
of  society,  that  nothing  further  need  here  be  said  on  that 
topic.  But  we  would  more  especially  recommend  it  as 
a  resource  which  is  capable  of  affording  the  highest  in- 
tellectual enjoyment ;  and  as  much  worthy  of  general 
notice  for  mental  recreation,  as  air  and  exercise  are  for 
our  bodily  health.  All  who  feel  an  unaccountable 
delight  in  contemplating  the  works  of  nature  ;  who 
admire  the  exquisite  symmetry  of  crystals,  plants,  and 
animals ;  and  who  love  to  meditate  upon  the  wonderful 
order  and  regularity  with  which  they  are  distributed ; 
possess  a  source  of  continued  enjoyment  within  them- 
selves, which  is  capable  of  producing  a  most  beneficial 
effect  upon  their  temper  and  disposition,  provided  they 
do  not  abuse  these  advantages  by  making  such  studies 
too  exclusively  the  objects  of  their  thoughts  and  care. 
Above  all,  they  must  beware  of  pampering  the  ridiculous 
ambition  of  surpassing  others  in  the  extent  of  their  col- 
lections, or  of  fostering  an  absurd  and  captious  jealousy 


INTRODUCTION.  5 

about  maintaining  the  priority  of  their  claim  to  this  or 
that  particular  observation  or  discovery.  We  do  not  go 
so  far  as  some  persons,  who  seem  inclined  to  believe 
that  these  pursuits  are  of  themselves  capable  of  produ- 
cing a  decided  improvement  in  our  moral  sensibilities ; 
but  we  hail  that  joy  which  is  felt  in  the  pursuit  of  such 
occupations,  as  a  sacred  gift,  which  may  be  compared 
to  the  rain  from  heaven,  sent  for  the  benefit  of  all: 
for  increasing  the  temporal  welfare  both  of  the  just, 
and  of  the  unjust :  for  procuring  blessings  equally  to 
the  good  and  to  the  evil ;  but  which  the  former  only 
know  how  thoroughly  to  appreciate,  and  to  apply  to  the 
highest  and  best  advantage. 

Botany  has  its  peculiar  interest,  from  embracing  the 
study  of  natural  bodies  which  form  the  connecting  link 
between  the  animal  and  mineral  kingdoms.  If  plants 
ceased  to  grow,  animals  would  cease  to  exist.  No 
animal  derives  its  food  immediately  from  unorganised 
matter ;  and  though  there  are  many  which  prey  upon 
other  animals,  yet  the  victims  have  always  been  them- 
selves nourished  by  some  plant.  Nothing  can  exceed 
the  wonderful  manner  in  which  provision  is  made 
for  the  constant  supply  of  those  myriads  of  animated 
beings  which  people  the  earth,  ocean,  and  atmosphere. 
Most  of  them  are  not  content  with  every  chance  vege- 
table that  may  be  growing  in  their  path  ;  and  many  are 
to  be  fed,  and  can  only  be  fed,  upon  some  one  or  two 
kinds  of  vegetable,  and  would  inevitably  starve  upon 
every  other  besides  !  When,  then,  we  seek  to  investi- 
gate the  laws  by  which  the  distribution  and  the  very 
existence  of  animals  is  regulated,  it  is  of  consequence 
that  we  should  not  overlook  even  the  minutest  moss 
or  fungus  that  we  can  detect.  It  is  by  such  plants 
that  the  first  step  must  often  be  made  towards  rendering 
the  barren  and  desolate  rock  a  fertile  and  productive  soil, 
and  converting  a  spot  apparently  destined  to  eternal  si- 
lence into  a  scene  of  lively  bustle  and  delight. 

(5.)    Unorganised  Bodies. — The  most  prominent  dis- 
tinction that  subsists  between  the  various  natural  bodies 
B  3 


PRINCIPLES    OF    BOTANY. 

that  surround  us,  is  derived  from  their  possessing  or 
being  destitute  of  an  organised  structure.  The  want 
of  organisation  is  the  peculiar  characteristic  of  mere 
brute  matter,  and  affords  an  evidence  of  the  absence  of 
the  living  principle;  and  is  a  clear  proof  that  it  has  not 
been  present  in  those  bodies  during  their  formation  or 
increase.  On  the  other  hand,  the  slightest  trace  of  or- 
ganisation discoverable  in  any  natural  body  is  a  com- 
plete proof  that  life  is,  or  at  least  was  once,  present  in 
that  body.  The  separate  particles  of  which  unorgan- 
ised bodies  are  composed,  are  either  elementary  atoms, 
or  compound  molecules,  in  which  certain  elementary 
atoms  are  united  together  by  the  force  of  affinity 
in  a  definite  proportion.  When  these  separate  parti- 
cles, or  "  integrant  molecules"  as  they  are  termed  in 
mineralogy,  are  allowed  gradually  to  coalesce  from  a 
state  of  solution  or  of  fusion,  they  then  arrange  them- 
selves into  various  regular  geometric  forms,  called  crys- 
tals. These  crystals  can  increase  in  size  only  by  a 
further  juxtaposition  of  similar  molecules  added  to 
them  externally.  When  the  peculiar  circumstances 
under  which  they  may  be  placed  do  not  allow  these  in- 
tegrant molecules  to  arrange  themselves  into  crystal- 
line forms,  they  may  still  be  able  to  combine  together 
into  shapeless  masses,  which  possess  the  same  homo- 
geneity of  character  as  though  they  had  been  regularly 
crystallised.  All  such  combinations  of  unorganised 
matter  are  termed  "  simple  minerals."  Compound 
minerals,  such  as  rocks  and  stones,  the  ocean,  the  atmo- 
sphere, are  merely  heterogeneous  admixtures  of  simple 
minerals,  which  naturally  exist  under  a  solid,  liquid, 
or  gaseous  form.  When  aggregated  into  large  masses, 
these  "  compound  minerals"  constitute  our  earth,  and 
probably  also  all  the  various  heavenly  bodies. 

(6.)  Organised  Bodies.  —  Although  organised  bodies 
are  made  up  of  the  same  elementary  atoms  as  those 
which  compose  unorganised  bodies,  yet  are  they  dis- 
tinguishable from  these  latter,  not  merely  by  the  pre- 
sence of  the  living  principle,  but  completely  and  satis- 


INTRODUCTION.  7 

factorily  by  the  manner  in  which  they  increase.  The 
various  parts  or  organs  of  which  such  bodies  are  composed 
are  not  homogeneous  in  their  structure,  like  those  of  sim- 
ple minerals ;  and  their  increase  is  effected  by  an  assimi- 
lation of  certain  particles  adapted  to  its  growth,  which 
are  received  into  the  system  through  certain  cavities,  or 
vessels,  from  whence  they  are  elaborated,  by  a  peculiar 
process,  into  specific  compounds,  adapted  to  the  nutri- 
tion and  development  of  the  individual.  These  effects 
depend  upon  the  presence  and  activity  of  a  distinct 
force,  peculiar  to  the  condition  under  which  organised 
matter  exists,  viz.  that  mysterious  principle  which  we 
call  "  life,"  —  a  something  totally  different  in  its  mode 
of  action  from  any  of  the  forces  to  which  unorganised 
bodies  are  subjected ;  and  capable  of  controlling,  and,  to 
a  certain  extent,  of  counteracting,  the  effects  of  those 
forces.  One  striking  peculiarity  in  the  vital  force  is  its 
variable  condition,  and  ultimate  secession  from  all  or- 
ganised bodies  whatever.  However  effectual,  for  a 
time,  in  counteracting  the  influences  of  the  two  other 
great  forces  of  nature,  attraction  and  affinity,  a  period, 
sooner  or  later,  does  always  arrive,  in  which  it  ceases 
to  operate,  and  abandons  to  silence  and  inactivity  the 
dust  and  ashes  which  it  had  for  a  little  while  collected, 
and  employed  in  forwarding  the  high  interests  of  ani- 
mated nature. 

(7-)  Animals  and  Vegetables.  —  We  may  distinguish 
organised  bodies  into  animals  and  vegetables ;  and  our 
daily  experience  is  sufficient  to  satisfy  us  of  the  pro- 
priety of  such  a  division.  Yet  is  it  extremely  difficult, 
and  has  hitherto  baffled  the  attempts  of  naturalists, 
to  point  out  the  precise  limits  which  separate  these  two 
kingdoms  of  organised  nature ;  and  no  definitions  of 
what  is  a  plant,  and  what  is  an  animal,  have  yet  been 
framed  sufficiently  guarded  and  precise  to  satisfy  all  the 
conditions  under  which  different  organised  bodies  are 
found ;  but,  to  this  day,  there  are  some  objects  which 
it  is  very  doubtful  under  which  class  they  ought  to  be 
arranged.  Among  the  higher  tribes  of  organised  bodies, 
B  4 


8  PRINCIPLES    OF    BOTANY. 

indeed,  there  is  no  difficulty  in  pointing  out  numerous 
lines  of  demarcation  between  the  two  kingdoms;  but,  as 
we  descend  in  the  scale  of  each,  we  find  an  increasing 
similarity  in  external  characters,  and  a  closer  approxi- 
mation between  the  analogies  existing  in  many  of 
those  functions  which  mark  the  presence  of  the  living 
principle,  both  in  the  animal  and  in  the  vegetable  king- 
doms. Perhaps,  until  the  contrary  shall  be  distinctly 
proved,  we  may  consider  the  superaddition  of  "  sen- 
sibility" to  the  living  principle  as  the  characteristic 
property  of  animals ;  a  quality  by  which  the  individual 
is  rendered  conscious  of  its  existence  or  of  its  wants, 
and  by  which  it  is  induced  to  seek  to  satisfy  those  wants 
by  some  act  of  volition.  It  has  been  supposed  —  and 
both  analogy  and  experiment  appear  most  fully  to  con- 
firm the  supposition  —  that  a  sense  of  pain  is  very  nearly, 
if  not  entirely,  absent  in  the  inferior  tribes  of  animals. 
Even  in  the  higher  tribes,  certain  parts  of  the  body  are 
incapable  of  receiving  pain  ;  and  there  seems  to  be  no 
absurdity  in  considering  that  an  animal  may  be  endowed 
with  just  so  much  sensibility  as  may  be  sufficient  to 
prompt  it  to  select  its  food,  though  at  the  same  time  its 
body  may  be  so  organised  as  to  be  incapable  of  transmitting 
painful  sensations.  But  the  most  constant,  if  not  uni- 
versal .distinction, —  and  one  which  we  can  readily  appre- 
ciate, between  animals  and  vegetables, —  consists  in  the 
presence  or  absence  of  those  internal  sacs  or  stomachs, 
with  which  the  former  alone  are  provided,  for  receiving 
their  food  in  its  crude  state,  previously  to  its  being 
elaborated  by  the  organs  of  nutrition. 


PART  I. 

DESCRIPTIVE    BOTANY. 


SECTION  I. 

ORGANOGRAPHY    AND    GLOSSOLOGY. 


CHAPTER  I. 

ELEMENTARY    ORGANS    AND    TISSUES. 

EXTERNAL  ORGANS CONSERVATIVE    AND    REPRODUCTIVE   (9.). 

INTERNAL  STRUCTURE  ;  ELEMENTARY  TEXTURE  ;  CHEMICAL 

COMPOSITION  (12.).  ELEMENTARY  ORGANS  ;  CELLULAR  AND 

VASCULAR  TISSUES  (13.). — COMPOUND  ORGANS  —  INVESTING 
AND  COMPLEX  (28.).  PRIMARY  GROUPS  OR  CLASSES  (S3.). 

(8.)  Organs.  —  THE  various  parts  of  which  a  plant  is 
composed  have  been  called  its  "  organs  ;"  and  this  term 
is  equally  applied  to  those  external  portions,  which  may 
readily  be  recognised  as  being  subordinate  to  the  whole, 
such  as  its  leaves,  roots,  flowers,  &c.,  as  to  certain  mi- 
nute cells  and  vessels,  of  which  its  internal  structure 
consists.  De  Candolle  has  included  every  inquiry,  both 
into  the  external  and  internal  organisation  of  plants, 
under  the  title  of  "  Organography  ; "  although  such 
details  as  belong  to  their  external  characters  have  a  more 
exclusive  reference  to  our  descriptive  department,  whilst 
those  which  relate  to  their  internal  organisation  are  more 
especially  introductory  to  our  physiological. 

(9.)  External  Organs. —  The  principal  external  or- 


10  DESCRIPTIVE    BOTANY.  PART  I. 

gans  of  which  a  plant  is  composed  are  familiar  to  every 
one.  They  are,  the  root,  stem,  branches,  leaves,  flowers, 
&c.  These  organs  may  be  conveniently  grouped  under 
two  heads,  characterised  by  the  nature  of  the  functions 
which  they  are  severally  destined  to  perform.  The 
root,  stem,  branches,  leaves,  and  some  other  appendages 
to  each  of  these,  are  concerned  in  carrying  on  the  func- 
tion of  nutrition,  or  that  act  by  which  the  life  of  every 
separate  individual  is  maintained ;  and  these  are,  in 
consequence,  styled  the  "  Conservative"  organs.  The 
flower  and  fruit,  with  their  various  appendages,  are 
connected  with  the  function  of  reproduction,  by  which 
the  continuance  of  the  species  is  provided  for  ;  and 
these  are,  therefore,  named  the  "  Reproductive"  organs. 

(10.)  Con/ii-rriitin-  Organs. —  The  conservative  or- 
gans, again,  may  be  separated  into  two  series.  Every 
one  is  acquainted  with  the  fact,  that  the  stems  of  most 
plants  are  above  ground,  and  that  they  affect  a  more  or 
less  erect  position,  and  are  constantly  being  developed 
upwards,  whilst  the  roots  of  most  plants  penetrate  the 
soil  with  an  evident  tendency  downwards.  An  imagin- 
ary plane,  intersecting  the  plant  at  the  point  whence 
these  opposite  tendencies  originate,  is  called  the  neck  : 
the  stem,  and  the  various  organs  which  accompany  it, 
are  styled  the  "  ascendirtg,"  and  the  root  and  its  ap- 
pendages the  te  descending"  series.  But  these  defin- 
itions do  not  exactly  represent  the  truth,  since  there  are 
certain  stems  which  are  strictly  subterranean,  and  have 
a  tendency  to  creep  below  the  surface  of  the  soil ;  whilst 
there  are  also  certain  roots  which  are  aerial,  and  some 
of  these  scarcely  indicate  any  downward  tendency.  The 
terms  employed  in  defining  the  two  series  must,  there- 
fore, be  considered  as  indicating  certain  facts,  which  are 
very  generally,  though  not  universally,  applicable  to  the 
several  organs  included  under  each. 

(11.)  2{<-/ir»fi active  Organs. —  The  reproductive  or- 
gans may  also  be  classed  under  two  series.  The  first 
is  the  "  Inflorescence,"  which  includes  the  flower  and 
the  various  appendages  to  that  part  of  the  stem  on 


SECT.  I.          ORGANOGRAPHY    AND    GLOSSOLOGY.  1 1 

which  it  is  seated  ;  and  the  second  is  the  "  Fructifi- 
cation/" which  embraces  the  seed,  and  the  different  en- 
velopes by  which  it  is  surrounded,  and  which  collectively 
are  termed  the  fruit.  This  latter  series,  indeed,  consists 
of  organs  which  had  previously  belonged  to  the  former 
series  during  the  early  stages  of  their  development ;  but, 
as  a  very  material  alteration  takes  place  in  their  con- 
dition after  the  flower  has  expanded  and  faded,  they 
are  considered  as  having  so  far  changed  their  character 
as  to  merit  a  different  name  from  that  which  they  before 
possessed.  But  here,  again,  our  definitions  do  not  apply 
to  the  whole  mass  of  vegetation,  since  no  flowers 
or  seeds  are  ever  produced  by  the  lowest  tribes  of 
plants ;  but  they  are  propagated  by  little  bodies 
termed  "  sporules,"  which  do  not  require  any  previous 
process  for  securing  their  fertility,  similar  to  that  which 
we  shall  hereafter  show  to  be  essential  to  the  perfection 
of  true  seeds. 

(12.)  Internal  Structure. —  Before  we  enter  more 
fully  into  further  details  respecting  these  and  the  other 
external  organs,  we  propose  to  examine  the  internal 
structure  of  plants ;  especially  as  there  are  certain  in- 
vesting or  cuticular  organs,  which  cannot  well  be  de- 
scribed without  referring  to  the  elementary  organs,  of 
which  the  whole  structure  of  the  vegetable  is  composed. 

The  great  simplicity  of  the  vegetable  structure,  when 
contrasted  with  the  complexity  of  that  of  animals,  is  very 
remarkable;  and  whilst  every  separate  function  performed 
by  the  latter,  seems  to  require  an  organ  of  a  peculiar  con- 
struction, the  functions  of  vegetation  are  all  carried  on  by 
the  intervention  of  a  few  simple  tissues  of  the  same  kind. 
Probably,  however,  this  extreme  simplicity  is  much 
overrated ;  for  as  yet  we  know  very  little  of  the  nume- 
rous slight  modifications  which  different  plants  exhibit 
in  the  arrangement  of  the  several  parts  of  their  tis- 
sue, and  it  may  be  reasonably  conjectured,  that  every 
modification  of  this  sort,  however  slight,  implies  some 
corresponding  alteration  in  the  mode  of  performing  the 
function.  If  we  cut  or  fracture  any  portion  of  a  living 


12 


DESCRIPTIVE    BOTANV. 


plant,  we  find  it  to  be  made  up  of  solid  and  fluid  parts, 
and  with  the  aid  of  the  microscope  we  may  observe  the 
manner  in  which  these  parts  are  disposed.  The  solid 
portions  appear  somewhat  like  a  spongeous  body,  pene- 
trated by  minute  cavities,  through  which  the  fluids  are 
dispersed.  If  we  now  take  a  very  thin  transrerse  slice 
of  some  succulent  stem,  as  of  a  cucumber  (Jig,  1.),  and 


examine  a  portion  of  it  under  lenses  of  high  powers,  it 
will  present  the  form  of  a  distinct  network,  the  meshes 
of  which  consist  of  angular  figures,  differing  in  the 
number  of  their  sides,  and  in  the  degrees  of  regularity 
with  which  they  are  disposed.  In  some  cases  the  regu- 
larity of  their  form  and  disposition  is  very  remarkable  ; 
and  they  are  frequently  hexagonal.  The  meshes  in 
some  parts  of  the  slice  are  much  smaller  than  in  others, 
especially  where  they  are  observed  to  surround  certain 
circular  openings  of  a  different  appearance  from  the  rest 
of  the  cavities.  If  another  slice  be  taken  toafitvdlnatty 
through  the  stem  (fig.  2.),  and  a  portion  of  this  be 

2 
•fl 


examined  in  a  similar  manner,  the  netlike  tissue  pre- 
sents a  somewhat  different  appearance.  The  meshes 
are  for  the  most  part  quadrilateral,  or  nearly  so,  and  ge- 
nerally elongated  in  the  direction  of  the  axis  of  the  stem. 
The  circular  openings  observed  in  the  former  fig.  (1.) 


SECT.  I.          ORGANOGRAPHY    AND    GLOSSOLOGY.  13 

are  found  to  be  the  sections  of  tubes,  which  are  often 
variously  marked  by  dots,  lines,  and,  in  some  instances, 
are  composed  of  a  spirally  twisted  filament.  These 
appearances  evidently  show  us  that  the  vegetable  struc- 
ture is  composed  of  polygonal  cells  and  cylindrical 
tubes,  so  arranged  that  they  lie  with  their  greatest 
lengths  parallel  to  the  axis  of  the  part  in  which  they 
are  found.  Among  the  lowest  tribes  of  flowerless  plants, 
which  form  an  extensive  class,  no  tubes  are  observable, 
and  their  whole  mass  is  composed  of  cells  alone. 

(13.)  Elementary  Textures. — If  we  now  examine  the 
materials  of  which  these  cells  and  tubes  are  constructed, 
we  find  them  to  consist  of  a  delicate,  homogeneous 
membrane,  of  extreme  tenuity,  generally  colourless,  and 
without  any  distinct  traces  of  organisation.  Besides 
this,  there  is  a  fine  cylindrical  fibre,  which  might  be  com- 
pared to  transparent  catgut ;  and  this  is  often  spirally 
twisted  and  variously  ramified  upon  the  surfaces  of  the 
cells  and  tubes,  in  a  manner  which  we  shall  presently 
describe.  It  is  supposed  that  all  the  modifications  ob- 
servable in  the  internal  organisation  of  plants  result 
from  the  various  combinations  which  take  place  be- 
tween these  two  elementary  textures,  "  Membrane  "  and 
"  Fibre." 

(14-.)  Chemical  Composition. — It  has  not  been  ascer- 
tained whether  these  two  organic  elements  of  the  vege- 
table structure  are  identical  in  chemical  composition,  or 
whether,  indeed,  the  membrane  and  fibre  which  com- 
pose the  cells  and  tubes  in  different  parts  of  plants  are 
always  of  the  same  kind.  The  inquiry  would  be  one 
of  extreme  difficulty,  if  not  of  absolute  impossibility, 
with  the  present  resources  of  chemistry.  All  that  is 
known  of  the  composition  of  these  textures  has  been 
derived  from  experiments  made  upon  the  gross  mate- 
rial, imperfectly  separated  from  the  various  matters 
which  the  cells  and  tubes  contain.  In  this  state  it  is 
found  to  be  composed  of  the  three  elements,  oxygen, 
hydrogen,  and  carbon  ;  but  the  exact  proportion  in 
which  these  are  united  is  uncertain,  if,  indeed,  it  be 


14  DESCRIPTIVE    BOTANY.  PAHT  I. 

always  the  same.  In  the  several  products  of  vegetation — 
woods,  gums,  resins,  &c. — the  proportions  between 
those  three  elements  vary  considerably;  and  even  a 
fourth  element,  azote,  enters  as  a  fundamental  ingre- 
dient into  some  of  them.  It  should  seem  that  the 
atoms  which  compose  the  organic  molecules  in  the 
elementary  textures  of  vegetables,  are  held  together  by 
some  vital  property,  rather  than  by  the  laws  of  chemi- 
cal affinity  ;  for  although  these  substances  may,  with 
certain  precautions,  be  long  preserve"?!  in  much  the  same 
state  as  that  in  which  they  were  left  when  the  vital 
principle  was  first  abstracted  from  them,  yet  there  ap- 
pears to  have  been  no  very  definite  chemical  union 
between  their  atoms,  which  are  no  sooner  abandoned  to 
the  influence  of  surrounding  media,  than  they  enter  into 
new  combinations  distinct  from  that  under  which  they 
existed  in  the  living  plant. 

(15.)  J-'/cnii'ii (art/  Tixxnrx. —  There  are  two  element- 
ary tissues,  which  are  respectively  composed  of  the  two 
kinds  of  elementary  organs,  the  cells  and  tubes  already 
noticed.  The  one  is  c.ilkd  the  "  cellular"  tissue,  and 
consists  entirely  of  cells,  and  constitutes  the  chief  bulk 
of  every  vegetable:  the  other  is  the  "vascular"  tis- 
sue, and  is  made  up  of  tubes  ;  but  this  latter  tissue  is 
found  only  in  certain  families  of  plants.  The  vascular 
penetrates  the  cellular  tissue  in  thin  cords,  which  are 
composed  either  of  single  tubes,  or  more  frequently  of 
bundles  of  tubes,  running  continuously  throughout  the 
plant,  and  passing  into  the  leaves,  where  the  tubes 
separate,  and  diverge  in  various  directions,  and  form 
the  veined-like  appearance  which  these  organs  generally 
present. 

(16.)  O'ffntitr  Tissue.  —  If  a  fragment  of  any  plant 
be  allowed  to  macerate  for  some  days  in  water,  or  if 
it  be  subjected  to  the  action  of  nitric  acid,  the  several 
elementary  organs  of  which  it  is  composed  will  sepa- 
rate from  each  other,  and  may  then  be  examined  in  an 
isolated  state.  When  thus  detached,  the  cellular  parts 
are  found  to  have  been  made  up  of  minute  vesicles,  or 


SECT.  I.          OROANOGRAPHY    AND    GLOSSOLOGY. 


15 


bladders  (fig.  3.).  In  some 
cases  these  vesicles  are  nearly 
spherical  (a) ;  and,  in  others, 
they  approach  the  form  of  short 
cylinders  (6);  andin  others,again, 
they  are  lengthened  out,  and, 
tapering  at  each  extremity,  pre- 
sent a  fusiform  or  spindle-shaped  appearance  (c). 
The  shortest  diameters  of  those  cells  which  are  more  or 
less  spheroidal, vary  from  the  -j-^n'o  to  l^e  ~s$  °^  an  ^nc^  > 
but  are  more  frequently  found  between  the  -j^  and  -j^  Q. 
The  fusiform  cells,  sometimes  termed  "  closters,"  which 
abound  in  the  woody  fibre  of  trees,  vary  in  breadth,  at 
their  thickest  part,  from  the  -g-Q1^  to  the  -^-fa  of  an  inch. 
It  is,  therefore,  entirely  owing  to  the  close  packing  and 
mutual  compression  of  these  vesicles,  that  they  assume 
a  polygonal  form  in  the  integral  state  of  the  tissue. 
We  may  compare  the  general  appearance  of  this  tissue 
to  a  mass  of  froth,  obtained  by  blowing  bubbles  in 
soap  suds  or  gum  water.  The  bubbles,  by  mutual 
pressure,  assume  a  polygonal  structure  towards  the 
centre  of  the  mass,  but  have  spherical  surfaces  towards 
the  outside.  In  the  cells  which  are  thus  formed, 
however,  each  cavity  is  separated  from  its  neighbour  by 
only  a  single  partition;  whilst,  in  the  vegetable  tissue, 
each  partition  is  of  course  double.  As  the  cellular 
tissue  alone,  without  tubes,  exists  in  a  large  class  of 
plants,  it  is  evident  that  the  most  general  functions  of 
vegetation  must  be  carried  on  by  it :  but,  as  such  an 
inquiry  belongs  to  the  physiological  department,  we 
need  not  say  any  thing  concerning  it  at  present. 

(17.)  Polygonal  Structure. —  If 
we  place  a  number  of  equal  circles 
in  contact,  on  a  plane  surface, 
each  circle  may  be  touched  by 
six  others ;  and  if  we  suppose 
them  to  be  so  pressed  together, 
that  the  curvature  of  each  circle 
at  the  points  of  contact  may  pass 


1 6  DESCRIPTIVE    BOTANY.  PART   I. 

into  straight  lines,  the  circles  will  become  hexagons 
(fig.  4.).  If  a  number  of  spheres,  of  equal  size,  be  in 
contact,  each  may  be  touched  by  twelve  others 
(fig.  5.  a )  ;  and  if 
the  whole  be  subjected 
to  pressure,  so  that 
their  surfaces  may  be- 
come flattened  at  these 
twelve  points,  the 
spheres  will  become 
rhomboidal-dodecahedrons  (fig.  5.  ft).  But,  as  the  vesi- 
cles which  compose  the  cellular  tissue  are  never  exactly  of 
the  same  dimensions,  the  polygonal  forms  which  they 
assume  will  not  be  so  strictly  regular  as  the  geometric 
figure  we  have  just  mentioned.  Still,  there  is  often  a 
very  marked  approximation  towards  such  a  regularity  ; 
more  especially  in  those  parts  of  the  plant  which  are  the 
best  developed,  or  have  been  most  securely  defended, 
as  in  the  case  of  the  pith,  from  the  influence  of  disturb- 
ing causes.  Where  the  vesicles  are  elongated,  the  dode- 
cahedrons assume  the  character  of  rectangular  prisms, 
terminated  by  four-sided  pyramids,  whose  faces  replace 
the  angles  of  the  pyramids  at  various  degrees  of  inclin- 
ation to  the  axis  (fig.  6'.).  If  sections  be  made  through 
these,  by  planes  paral- 
lel and  perpendicular  to  //^ 
the  faces  of  the  prisms, 
they  will  exhibit  either 
hexagonal  or  quadran- 
gular surfaces,  accord- 
ing to  circumstances,  as 
a  simple  inspection  of  the  diagrams  will  be  sufficient  to 
show.  Cells  of  these  forms  may  be  so  aggregated 
(fig.  7.)  as  to  fill  space  as  completely  as  the  hexagonal 
prisms  of  the  honeycomb;  but  as  the  extreme  regularity 
here  delineated  is  never  actually  attained  in  nature,  the 
cellular  tissue  becomes  every  where  penetrated  by  small 
cavities,  by  which  an  intercellular  communication  is 
maintained  throughout  the  mass.  These  channels  are 


SECT.  I.         ORGANOGRAPHY    AND    GLOSSOLOGY.  17 

termed  "  intercellular  passages,"  and  are  very  evident 
in  some  portions  of  the  tissue,  7 

but  are  not  to  be  detected  in 
others.  The  forms  under 
which  the  vesicles  appear,  up- 
on making  a  section  through 
the  cellular  tissue,  are  much 
influenced  by  local  pressure, 
distension,  and  the  more 
obscure  causes  which  depend 
upon  the  specific  qualities  of 
each  plant ;  and  these  forms 
are  detailed  with  greater  minuteness,  in  works  which 
professedly  treat  of  this  part  of  our  subject,  in  a  more 
elaborate  manner  than  our  limits  will  afford. 

(18.)  Striated  and  dotted  Cells. —  The  separate  vesi- 
cles which  compose  the  cells,  frequently  exhibit  mark- 
ings upon  their  surface,  whose  origin  it  is  not  always 
easy  to  account  for.  Many  of  these  appearances  were 
formerly  mistaken  for  open  pores  through  the  mem- 
brane, by  which  a  communication  was  supposed  to 
subsist  between  two  contiguous  cells.  Some  observers 
have  considered  them  to  be  glands ;  and  others  have 
described  them  as  nascent  vesicles,  generated  within 
the  surface  of  the  old  cells,  and  which  are  afterwards 
developed,  and  thus  are  formed  into  new  tissue.  The 
best  representations  of  these  various  appearances,  is  given 
by  Mr.  Slack,  in  the  forty-ninth  volume  of  the  "  Trans- 
actions of  the  Society  of  Arts ; "  and  he  is  inclined 
to  refer  the  greater  part  of  them  to  one  common  origin, 
viz.  the  modification  of  the  conditions  under  which 
the  elementary  fibre  is  developed  on  the  inner  surface 
of  the  vesicles.  In  some  vesicles,  this  fibre  is  spirally 
coiled  over  the  whole  surface,  and  the  contiguous  coils 
are  blended  together,  so  as  to  render  it  very  difficult  to 
distinguish  them  :  in  others,  the  coils  are  wide  apart, 
and  distinctly  visible  (fig.  8.  a).  In  some  cases  the 
fibre  is  branched  (6) ;  and  in  others,  the  branches 
graft  together,  and  the  surface  of  the  vesicle  then  appears 


18 


DESCRIPTIVE    BOTANY. 


PART  I. 


reticulated  ;  whilst  it  sometimes  happens,  that  the  coils 
of  a  closely  developed 
spiral  become  sepa- 
rated at  intervals, 
and  then  close  to- 
gether again,  so  as  to 
leave  openings  which 
look  like  slashes  and 
dots  in  the  vesicle  itself  (c).  There  are  some  cases,  how" 
ever,  in  which  the  dots  on  the  vesicles  appear  to  be 
thickened  spots ;  and  especially  those  which  abound 
on  the  elongated  cells,  forming  the  woody  fibre  of 
Coniferous,  and  some  few  other  trees.  These  are  very 
peculiarly  marked  by  large  dots  of  a  glandular  aspect, 
with  a  dark  spot  in  the  centre  (fiy.  {).)  ;  which  latter 
circumstance,  however,  may  probably  be  owing  to  the 
manner  in  which  the  light  is  refracted 
through  them.  It  is  a  remarkable  fact, 
that  these  appearances  are  strictly  imitated 
in  many  fossil  woods ;  and  botanists  are 
thus  enabled,  by  the  inspection  of  a  small 
fragment  of  such  plants,  to  pronounce  with 
certainty,  upon  the!Class  and  Order  to  which 
they  have  belonged.  In  some  cases  it  hap- 
pens, that  the  elementary  fibre  alone  remains 
entire,  like  a  skeleton  to  the  tissue,  whilst 
the  membrane  which  originally  formed  the  walls  of  the 
cells  has  been  obliterated.  It  is  unnecessary  to  dwell 
further  upon  the  various  appearances  which  the  cellular 
tissue  presents,  especially  as  nothing  whatever  is  known 
of  the  way  in  which  a  dissimilarity  of  structure,  is  con- 
nected with  any  modification  in  the  functions  performed 
by  it. 

(19-)  Contents  of  the  Cells.  —  The  cellular  tissue  is 
every  where  replete  with  juices,  containing  minute  gra- 
nules of  amylaceous,  resinous,  and  other  qualities, 
which  appear  to  be  the  result  of  peculiar  secretions, 
formed  by  the  vesicles  themselves.  Those  which  com- 
pose the  woody  fibre,  secrete  an  abundance  of  a  car. 


SECT.  I.          OBGANOGBAPHY    AND    GLOSSOLOGY.  19 

bonaceous  material,  which  ultimately  fills  them,  and 
gives  consistency  to  the  stem.  The  juicy  contents  of 
some  cells  are  highly  coloured ;  and  even  contiguous 
cells  often  contain  liquids  of  different  tints,  although 
there  is  no  apparent  difference  in  their  structure, 
which  might  indicate  some  cause  for  such  diversity. 
Indeed,  the  brilliant  hues  of  flowers,  and  the  various 
tints  of  the  foliage,  all  depend  upon  the  coloured  juices, 
or  the  globules  floating  in  them,  which  are  contained  in 
the  vesicles  of  the  cellular  tissue,  and  have  been  elabo- 
rated by  them  ;  but  they  never  depend  upon  the  or- 
ganic membrane  itself,  of  which  they  are  composed, 
and  which  is  always  colourless,  or,  at  best,  only  slightly 
tinged  with  green. 

(20.)  Raphides.  —  But,  besides  the  strictly  organic 
compounds,  there  are  also  certain  chemical  combinations 
whose  results  appear  in  the  form  of  minute  crystalline 
spiculce,  which  have  been  deposited  from  the  heteroge- 
neous admixture  contained  in  the  cells.  These  have 
been  termed  "  raphides,"  and  were  originally  considered 
to  be  organised  bodies.  One  of  most  common  occur- 
rence, is  the  oxalate  of  lime,  the  crystals  of  which  are 
sometimes  of  such  magnitude,  and  their  forms  so  com- 
plete, that  the  law  of  their  crystallographic  structure 
may  be  readily  recognised. 

(21.)  Cavities  in  the  Tissue. —  Besides  the  intercel- 
lular passages  mentioned  above  (art.  17-);  there  are 
other  well-defined  cavities  in  the  cellular  tissue,  which 
serve  either  for  the  reception  of  various  secreted  matters, 
as  resins,  oils,  &c.,  or  else  contain  air.  The  former  are 
termed  "  receptacles,"  or  "vasa  propria,"  and  are  com- 
monly of  a  spheroidal,  cylindrical,  or  oblong  form,  the 
result  of  an  enlargement  of  the  intercellular  passages, 
or  of  a  rupture  in  the  tissue  itself.  The  latter  are 
termed  "air-cells,"  or  "lacuna?;"  and,  although  these 
are  most  frequently  very  irregular  in  their  form,  they 
are  often  constructed  in  a  more  definite  manner  than 
the  receptacles,  and  then  consist  of  extremely  regular 
c  2 


20 


DESCRIPTIVE    BOTANY. 


PART  I. 


and  well-defined  spaces,  of  hexagonal  and  other  geo- 
metric forms.  In  these  cases  the  cellular  tissue  is  so 
arranged  as  to  separate  the  lacunae  from  each  other, 
both  by  vertical  and  transverse  di-  ,  ^  A  10 
visions  (fig-  10.)  ;  and  the  whole  is 
placed  round  the  axis  of  the  stem 
in  a  beautiful  and  symmetrical  man- 
ner. The  stems  and  leaf- stalks  of 
aquatics  are  every  where  filled  with 
lacunc,  and  the  air  contained  in 
them  serves  the  purpose  of  elevating 
these  parts  towards  the  surface  of  the  water. 

(22.)  Vascular  Tissue.  —  This  tissue  consists  of 
tubes,  which  are  also  formed  of  membrane,  to  all  ap- 
pearance identical  with  that  which  composes  the  vesi- 
cles of  the  cellular  tissue.  Some  of  these  rubes  bear  a 
close  resemblance  to  the  elongated  cells  already  de- 
scribed, and  may  certainly  be  considered  as  mere  mo- 
difications of  that  form  of  tissue ;  and,  indeed,  all 
tubes,  whatever  be  their  length,  appear  to  taper  off 
at  each  extremity  into  conical  and  closed  terminations 
(fig.  11.  a).  A  communication  evidently  subsists  be- 
tween some  of  these  tubes,  at  the 
point  where  they  overlap  each  other 
and  are  about  to  terminate,  form- 
ing an  oval  perforation  of  large  di- 
mensions. Some  tubes  are  derived 
from  the  apposition  of  cylindrical 
cells,  base  to  base  (6),  and  the  sub- 
sequent obliteration  of  the  terminal 
portions  of  their  membrane.  In  cer- 
tain cases  this  membrane  remains 
wholly,  or  in  part,  in  the  form  of 
transverse  septa  or  diaphragms,  and 
then  these  organs  present  a  tissue  in- 
termediate between  the  cellular  and 
vascular.  The  true  vessels,  or  long  tubes,  which  more 
strictly  compose  the  vascular  tissue,  are  distinguishable 
into  two  kinds,  between  which,  however,  there  are  cer- 


SECT.  I.         ORGANOGRAPHY    AND    GLOSSOLOGY. 


21 


tain  intermediate  forms,  which  establish  the  fact  of  a 
most  intimate  connection,  and  even  appear  to  indicate 
a  common  origin.  The  two  kinds  of  vessels  alluded 
to,  are  the  spiral  vessels  and  the  ducts. 

(23.)  Spiral  Vessels.  —  These  are  generally  termed 
"  tracheae/'  from  the  resemblance  which  they  bear  to 
the  windpipe,  and  more  especially  to  the  air-cells  of 
insects,  which  are  called  by  the  same  name.  They 
consist  of  a  membranous  tube,  on  whose  inner  surface 
a  cylindrical  fibre  is  spirally  coiled  {fig.  12.  a)  ;  and 
the  whole  so  completely 
united,  that  if  the  vessel 
be  ruptured,  and  the  thread 
uncoiled,  no  trace  of  the 
membrane  is  to  be  seen, 
excepting  towards  the  co- 
nical extremity  of  the  ves- 
sel, where  the  coils  of  the 
fibre  are  wider  apart.  In 
some  tracheae,  indeed,  the 
successive  coils  are  not  in 
contact  with  each  other, 
and  then  the  investing 
membrane  is  sufficiently 
apparent.  Sometimes  the 
fibre  branches  into  two 
threads  (6),  and  each  continues  its  course  in  separate 
but  contiguous  coils;  and  instances  may  be  found, 
where  the  contiguous  coils  of  separate  threads  range  (c) 
between  this  number  and  twenty-two !  The  diameters 
of  these  vessels  vary  from  the  ^^  up  to  the  ^ 
of  an  inch.  They  may  be  detected  with  the  greatest 
facility  upon  tearing  asunder  the  leaves  of  many  plants, 
and  especially  are  very  visible  in  some  species  of  Ama- 
ryllis, when  they  form  a  set  of  parallel  fibres,  nearly  as 
conspicuous  as  the  threads  in  a  spider's  web,  and  are 
strong  enough  to  support  the  weight  of  a  considerable 
portion  of  the  leaf.  By  carefully  unravelling  them, 
they  may  sometimes  be  extended  to  eighteen  inches  in 
c  3 


22 


DKSCRIPTIVE    BOTANY. 


length.  When  the  stems  of  the  Plantain  and  Banana 
are  cut  into  slices,  the  tracheae  in  which  they  abound 
unravel  before  the  edge  of  the  knife,  and  form  floc- 
culent  masses,  which  may  be  collected,  and  wrought 
into  a  material  possessing  certain  advantages  superior  to 
those  of  cotton,  for  the  manufacturer.  The  expense, 
however,  of  collecting  this  delicate  substance  has  been 
found  too  great  to  admit  of  its  being  applied  to  any 
really  useful  purpose  ;  as  an  entire  plantain  does  not 
yield  above  a  drachm  and  a  half  of  tracheae. 

Tracheae  have  been  detected  in  a  very  few  of  the  flower- 
less  plants,  and  only  among  the  higher  tribes  of  them, 
such  as  ferns  and  club-mosses. 

(24.)  Ducts.  —  The  elementary  fibre  divides  and 
ramifies  on  the  inner  surface  of  some  tubes  which  com- 
pose the  vascular,  just  as  it  does  on  the  vesicles  which 
compose  the  cellular  tissue  (art.  18.),  and  forms  linear, 
dotted,  and  reticulated  markings  upon  them.  Some 
tubes  are  true  trachea?  in  one  part  of  their  course, 
whilst  in  another  the  fibre  becomes  ruptured  at  intervals, 
and  the  detached  portions,  uniting  at  their  extremities, 
form  rings  ;  and  where  the  ruptures  are  more  fre- 
quent, these  fragments  of  the  fibre  present  linear  and 
dotted  markings  adheriug  to  the  surface,  and  following 
a  spiral  course  (fig.  13.). 
The  name  of  ducts,  is  gene- 
rally  given  to  all  varieties  of 
tubes  composing  the  vas- 
cular tissue,  which  are  not, 
strictly  speaking,  true  trachee; 
and  they  are  separately  named 
according  to  the  appearances 
which  the  markings  on  their 
surface  assume  ;  such  as 
dotted,striped,  and  reticulated 
ducts.  Some  authors,  how- 
ever, include  all  the  marked 
tubes,  together  with  the  spi- 
ral vessels,  under  the  general 


fe 

. 


jjf, 


SECT.  I.          ORGANOGRAPHY    AND    GLOSSOLOGY. 


23 


name  of  tracheae.  The  diameters  of  most  ducts  are 
generally  larger  than  those  of  the  true  tracheae,  be- 
longing to  the  same  plant ;  and  the  dotted  ducts,  espe- 
cially, are  very  distinctly  visible  to  the  naked  eye,  and 
even  large  enough  to  admit  of  a  delicate  hair  being  thrust 
into  them,  where  they  are  divided  by  a  transverse  sec- 
tion of  the  stem. 

(25.)  Woody  Fibres  and  Layers. — When  a  piece  of 
wood  is  split  longitudinally,  or  in  the  direction  of  the 
stem,  it  cleaves  more  readily  than  when  it  is  broken 
transversely.  And  many  kinds  -of  wood  may  be  thus 
split  in  the  direction  of  the  grain,  into  very  thin 
layers,  and  these  again  be  subdivided  into  fibres  of  ex- 
treme tenuity.  The  fibres  obtained  by  macerating  flax, 
hemp,  and  other  plants  used  for  cordage,  are  of  this 
description.  If  these  fibres  are  examined  under  the 
microscope,  it  will  be  seen  that  they  do  not  consist  of 
continuous  tubes  or  filaments  alone,  but  are  composed 
of  various  combinations  of  vascular  and  cellular  tissue. 
Every  separation  in  the  direction  of  the  fibres  (fig.  14. 
a  a)  occasions  the  disunion  of  a  u  „ 

contiguous  tubes  or  vesicles,  but 
any  transverse  fracture  (6  &') 
can  be  obtained  only  by  the  ac- 
tual rupture  of  these  organs 
themselves.  It  is  upon  this  cir- 
cumstance that  the  strength  of 
woody  fibre  depends,  which  is 
very  different  in  different  plants. 
It  has  been  experimentally  ascer- 
tained, that  the  strength  of  silk, 
New- Zealand  flax  (Phormium 
tenax),  hemp,  and  flax,  are  re- 
spectively as  the  numbers  34  :  231, 

As  the  cells  and  tubes  are  of  different  lengths,  their 
extremities  overlap  each  other,  and  thus  as  it  were 
dovetail  the  mass  together.  Wherever  a  transverse 
fracture  is  most  readily  produced,  as  in  the  suture  by 
which  a  seed-vessel  opens,  or  at  the  scar  which  is 
c  4 


1H. 


24-  DESCRIPTIVE    BOTANY.  PART  I. 

left  where  the  leaf  falls,  we  may  conceive  the  vesicles 
which  are  contiguous  to  the  plane  of  separation  on 
either  side,  to  be  so  arranged,  that  all  their  ends  lie  in 
this  plane  (fig.  14.  c  c"). 

(26.)  Contents  of  the  Tubes. — A  considerable  diver- 
sity of  opinion  exists  as  to  the  probable  uses  of  the  vas- 
cular tissue  in  those  plants  in  which  it  is  found.  Some 
observers  consider  the  tracheae  destined  to  convey  air 
through  various  parts  of  the  plant;  and  support  their 
opinion  by  the  fact,  that  air  is  very  commonly  to  be 
observed  in  them,  at  least  during  certain  seasons  of  the 
year.  Others  consider  all  vessels  to  be  channels  for  the 
sap  and  nutritious  juices.  That  most  of  them  contain 
liquid  matter  is  sufficiently  evident,  but  what  may  be 
the  precise  use  of  each  in  particular  is  at  present  very 
uncertain. 

(27.)  Vital  Vessels. — Besides  the  tracheae  and  ducts, 
just  described,  there  is  found  in  certain  plants,  and 
possibly  in  all  where  the  vascular  tissue  is  most  de- 
veloped, a  sort  of  network  formed  of  anastomosing  tubes 
(Jig.  15.)  and  situate  a  little  way  beneath  the  surface  of 
the  bark,  through  which  fluids  cer- 
tainly pass,  in  a  manner  we  shall 
hereafter  describe.  These  tubes  are 
termed  "  vital  vessels,"  or  "  ducts  of 
the  latex,"  by  their  discoverer,  M. 
Schultz.  They  are  by  far  the  smallest 
of  all  the  tubes,  and  extremely  diffi- 
cult to  be  detected  in  young  shoots, 
but  may  be  seen  with  tolerable  fa- 
cility as  they  become  older.  They  are 
entirely  without  markings  of  any  kind, 
and  are  found  in  all  parts  of  the  plant,  from  the  roots 
to  the  leaves. 

(28.)  Compound  Organs. — The  organs  hitherto  de- 
scribed, may  be  considered  as  the  organic  elements  out 
of  which  plants  are  constructed,  just  as  we  say  that 
minerals  are  formed  out  of  certain  integrant  molecules. 
We  have  next  to  notice  the  various  compound  organs, 


SECT.  I.         ORGANOGRAPHY    AND    GLOSSOLOGY. 


25 


which  result  from  different  combinations  of  these  ele- 
mentary organs.  These  may  be  considered  as  of  two 
kinds.  The  first  includes  such  as  are  found  on  the 
surface  of  the  several  external  organs,  of  which  in  fact 
they  are  only  subordinate  parts,  just  as  the  skin,  hair, 
feathers,  &c.  clothe  the  body  and  particular  members  of 
animals.  We  may  call  these  superficial  organs,  the 
"  Investing  organs."  The  other  kind  may  be  styled 
the  "  Complex  organs,"  and  will  include  all  those 
which  we  have  already  classed  under  the  ascending  and 
descending  series,  alluded  to  in  art.  10.,  and  of  which  the 
investing  organs  form  only  subordinate  parts. 

(29.)  Epidermis. — The  surface  of  all  parts  of  plants 
(except  the  spongioles  and  some  stigmata  to  be  described 
hereafter)  is  covered,  at  least  when  young,  with  a  thin 
skin,  which  may  easily  be  detached,  especially  from  the 
leaves,  and  most  readily  after  these  organs  have  been 
allowed  to  macerate  for  a  few  days  in  water.  This 
skin  is  termed  the  "  epidermis,"  or  "  cuticle,"  and 
when  placed  under  the  microscope,  it  exhibits  a 
delicate  network  (fig.  16.),  whose  meshes  are  either 


either  quadrangular,  hexagonal,  or  of  other  polygonal 
forms;  or  else  they  are  irregularly  bordered  by  waved  and 
sinuous  lines,  extending  over  the  whole  surface.  Very 
frequently  also,  a  set  of  pores  may  be  observed,  hav- 
ing a  sort  of  glandular  border  (a),  which  are  scat- 
tered over  the  epidermis  at  intervals.  These  pores 
are  termed  "  stomata."  It  was  not  until  very  lately 
that  the  real  structure  of  the  epidermis  was  well  under- 
stood ;  but  M.  A.  Brongniart  has  shown,  in  the 


DESCRIPTIVE    BOTANY. 


PART  I. 


Ann.  des  Sciences  for  February,  1834,  that  a  lengthened 
maceration  causes  it  to  separate  into  three  parts  (Jig.  I?.)- 
The  outermost  of  these,  consists  of  an  extremely  de- 


licate homogeneous  pellicle  (a),  without  any  very 
decided  traces  of  organisation,  though  occasionally 
somewhat  granulated  in  its  appearance,  and  also  marked 
by  lines,  which  are  merely  the  spaces  left  between  the 
impressions  made  upon  it  by  that  portion  of  the  cellular 
tissue  with  which  it  was  in  contact.  It  is  generally 
perforated  by  small  oval  slits,  at  the  places  where 
the  stomata  exist.  A  lamina  of  flattened  vesicles  (6), 
is  closely  united  with  this  pellicle,  and  forms  the  second 
portion  of  the  epidermis ;  the  vesicles  occupy  the 
spaces  included  between  the  linear  markings  observed 
upon  the  surface.  Sometimes  this  part  contains  more 
than  one  lamina  of  flattened  vesicles.  The  vesicles  are 
in  close  contact,  excepting  immediately  under  the  spaces 
occupied  by  the  slits  in  the  pellicle.  The  third  part 
alluded  to,  consists  of  the  stomata  (c),  which  are  placed 
a  little  further  from  the  pellicle  than  the  lamina  of  cells 
last  mentioned,  and  which,  as  we  stated,  is  in  immediate 
contact  with  it. 

(30.)  Stomata. — Each  stoma  is  most  generally  com- 


SECT.  I.         OR6ANOGRAPHY    AND    GLOSSOLOGY. 


27 


posed  of  two  lunate  vesicles  (fig.  18.  a),  which  may 
be  detached  by  maceration  in  water,  but  in  the  epi- 
dermis are  in  close  contact  at  their  extremities,  and  thus 
form  a  sort  of  border  round  the  area  occupied  by  the 
slits  in  the  outer  pel- 
licle. The  space  be- 
tween these  vesicles 
may  be  contracted  or 
completely  closed,  by 
an  alteration  in  their 
position.  Some  sto- 
mata  appear  to  con- 
sist of  a  single  annular  vesicle  (6),  which  may  pos- 
sibly be  occasioned  by  the  blending  of  two ;  or  this 
may  be  owing  to  an  optical  illusion.  In  some  cases* 
the  stomata  are  square  (c) ;  in  others,  the  orifice  ap- 
pears dark,  but  whether  from  the  interposition  of  a 
peculiar  membrane,  or  merely  by  the  deposit  of  se- 
creted matters,  seems  to  be  doubtful.  As  the  vesicles 
of  the  stomata  contain  granular  matter,  they  appear  to 
be  more  nearly  related  to  those  of  the  cellular  tissue 
in  the  substance  of  the  leaf  beneath  the  epidermis, 
which  contain  a  similar  matter,  than  to  the  flattened 
cells  which  compose  this  organ  itself,  and  which  are 
generally  without  grains,  and  perfectly  transparent. 
Stomata  do  not  occur  on  flower  less  plants,  excepting 
among  their  higher  tribes,  and  which  also  possess  tra- 
cheae (art.  23.).  They  are  also  absent  on  the  sub- 
merged parts  of  aquatics,  and  are  not  to  be  found  on 
certain  parasitic  plants. 

(31.)  Pubescence.  —  There  are  great  varieties  in  the 
forms  under  which  certain  prolongations  of  the  cellular 
tissue  occur,  on  the  surface  of  different  parts  of  plants. 
To  the  naked  eye,  such  appendages  to  the  epidermis  re- 
semble hair,  silk,  bristles,  scales,  &c.,  and  have  received 
these  names  in  descriptive  botany.  Under  the  micro- 
scope, they  are  all  found  to  be  composed  of  cellular 
tissue ;  sometimes  of  a  single  vesicle,  at  others  of 


28 


DESCRIPTIVE    BOTANY. 


several  united   (fig.   19.).      In   some,  the  vesicles  are 
rigid,  elongated,  and    sharp   spicule ;  in   others  they 


constitute   a   globular  mass  of  a   glandular   structure 
(fig.  20.),  and  secrete    various    juices   of  glutinous, 


sweet,  acrid,  and  other  properties.  Stings  are  sharp, 
pointed  hollow  bristles,  perforated  at  the  extremity,  and 
seated  on  a  glandular  mass  of  cellular  tissue  which 
secretes  the  poison  (fig.  20.  a).  When  the  hand  is 
gently  pressed  against  them,  the  delicate  point  pene- 
trates some  pore  of  the  skin,  at  the  same  time  the 
bristle  is  forced  against  the  gland  at  its  base,  and  the 
poison  rises  into  the  tube  in  a  manner  strictly  analogous 
to  that  by  which  a  discharge  of  venom  is  effected  from 


SECT.  I.          ORGANOGRAPHY    AND    GLOSSOLOGY. 

the  fangs  of  a  serpent's  tooth.  The 
bristles  have  sometimes  a  stellate 
form  {fig.  21.  a)  ;  and  sometimes 
the  pubescence  is  composed  of  little 
plates  or  scales  (6). 

(32.)  Complex  Organs. — Although  the  epidermis  and 
several  of  the  other  investing  organs  are  of  a  compound 
character,  they  are  still  constructed  in  a  much  more 
simple  manner  than  the  organs  which  they  invest.  We 
have  proposed,  therefore  (art.  28.),  to  separate-  the 
latter  under  the  name  of  "  complex  organs,"  which 
will  include  all  that  have  been  already  enumerated 
under  the  name  of  external  organs  (art.  9-)'  together 
with  various  appendages  to  be  found  on  some  of  them. 
These  latter  are  not  so  generally  noticed  by  casual  ob- 
servers ;  but  it  will  be  necessary  for  us  presently  to  de- 
scribe them,  when  we  treat  of  the  forms  and  structure  of 
these  organs  themselves.  But  we  shall  here  postpone 
for  a  while  the  descriptive  details  of  these  organs,  in 
order  that  the  reader  may  first  obtain  some  general 
notions  of  the  three  great  natural  divisions  under  which 
all  plants  may  be  arranged.  Although  this  method  of 
treating  our  subject  may  seem  to  indicate  a  great  want 
of  system,  it  appears  to  us  highly  convenient  that  every 
one  should  be  acquainted  with  these  divisions  as  early  as 
possible  before  he  enters  on  certain  details  which  can- 
not be  so  well  appreciated  or  discussed  without  an 
occasional  reference  being  made  to  them.  It  must  be 
remembered  that  we  have  not  proposed  to  ourselves  any 
very  methodical  discussion  of  the  several  departments 
of  our  science,  which  would  have  required  a  series  of 
separate  treatises,  but  that  we  aim  chiefly  at  conducting 
the  general  reader,  by  such  steps  as  may  seem  suffi- 
ciently adapted  to  the  purpose,  to  the  ready  comprehen- 
sion of  some  of  the  best  established  facts  in  vegetable 
physiology,  and  to  give  him  an  idea  of  what  botany 
proposes  to  attempt. 

(33.)  Primary  Groups. — We  apply  the  term  "  spe- 
cies" to  an  assemblage  of  individuals  which  have  sprung 


SO  DESCRIPTIVE    BOTANY.  PART  I. 

from  seeds  of  the  same  common  stock.  Where  these 
individuals  differ  in  certain  respects  among  themselves, 
they  are  termed  "  varieties ; "  but  all  varieties  of  the 
same  species  may,  under  particular  circumstances,  be 
produced  from  the  seeds  of  one  plant.  When  different 
species  bear  a  striking  resemblance  to  each  other,  they 
are  classed  together  in  a  group  which  is  termed  a 
"genus;"  and  such  genera  as  agree  in  several  points, 
form  a  higher  group  called  an  "  order ; "  and  those 
orders  which  are  most  nearly  related,  constitute  our 
chief  or  primary  groups,  termed  "  classes. "  Minor 
groups  of  subordinate  value  may  be  formed  in  each  of 
these ;  but  we  do  not  consider  it  necessary  at  present 
to  enter  into  further  details  of  this  kind.  We  merely 
propose  to  explain  some  of  the  chief  characters  by 
which  all  plants  may  be  grouped  under  three  distinct 
classes.  The  considerations  upon  which  these  groups 
depend,  do  not  rest  upon  any  one  solitary  fact  relative 
to  the  structure  or  functions  of  all  the  species  they 
contain  ;  for  there  is  no  leading  characteristic  in  either 
class  which  is  not  liable  to  some  objection,  if  it  were  to 
be  considered  as  the  only  distinguishing  mark  for  de- 
ciding the  claims  of  a  species  to  be  included  in  that 
class.  But  where  one  leading  characteristic  is  deficient 
in  one  species,  and  another  in  another,  it  is  from  the 
aggregate  of  such  as  are  present  that  we  must  de- 
cide upon  the  class  to  which  each  should  be  referred. 
With  very  few  exceptions,  however,  nearly  all  plants 
may  be  referred  by  any  botanist,  at  a  single  glance,  and 
with  unerring  certainty,  to  their  proper  class ;  and  a 
mere  fragment  even  of  the  stem,  leaf,  or  some  other 
part,  is  often  quite  sufficient  to  enable  him  to  decide 
this  question.  The  names  of  these  three  classes  are 
derived  from  one  of  the  chief  characteristics  which 
prevails  through  nearly  all  the  species  included  under 
each  of  them  separately.  This  we  shall  presently  ex- 
plain ;  but  the  reader  may  understand  these  names  to 
be  Dicotyledones,  Monocotyledones,  and  Acotyledones ; 
and  that  the  two  former  of  these  classes  have  respect- 


SECT.   I.          ORGANOGRAPHY    AND    GLOSSOLOGY.  31 

ively  the  names  of  Exogenoe  and  Endogence.  The 
former  names  are  derived  from  peculiarities  connected 
with  the  structure  of  the  seed ;  the  latter,  from  a  con- 
sideration of  the  internal  organisation  of  the  plants 
themselves. 


(34.)  Dicotyledones,  or  Exogence.  — 
(1.)   Structure  of  the  Seed. 

Beans,  peas,  almonds,  the  kernels  of  our  stone  fruits, 
&c.  afford  us  familiar  examples  of  the  structure  of  the 
seeds  of  dicotyledonous  plants  (fig.  22.).  When  the 


outer  skin  is  removed,  we  find  that  they  are  composed 
of  two  large  fleshy  lobes  (a),  termed  "cotyledons," 
which  are  attached  to  a  small  rudimentary  germ  (6), 
almost  entirely  concealed  between  them.  The  entire 
mass  forms  the  "  embryo,"  and  the  skin  which  invested 
it  is  termed  the  "  seed-cover."  After  the  seed  has 
been  sown,  and  germination  has  commenced,  the  two 
cotyledons  expand  and  represent  (what  in  fact  they 
are)  a  pair  of  imperfect  leaves,  but  differ  in  many 
respects  from  the  leaves  which  are  subsequently  de- 
veloped. One  extremity  of  the  little  germ  to  which 
the  cotyledons  are  attached,  is  termed  the  "  radicle," 
and  this  descending  into  the  ground  becomes  the  root. 
The  other  extremity  is  termed  the  "plumule,"  and 
consists  of  the  rudimentary  leaves  and  stem.  In  these 
examples,  where  the  embryo  occupies  the  whole  space 
within  the  seed-cover,  the  fleshy  cotyledons  contain  the 


DESCRIPTIVE    BOTANY.  PART  I. 

nutriment  on  which  the  young  plant  subsists  until  the 
root  is  sufficiently  developed  to  support  it.  But  there 
are  other  cases,  as  in  the  seeds  of  the  castor-oil  plant 
(Rii-inus  communis),  the  marvel  of  Peru  (Miral>ilin 
Jalapa),  &c.,  where  the  cotyledons  are  thinner  and 
more  leaf-like  (fig.  23.  a),  and  the  embryo  is  wholly 

23 


or  partially  imbedded  in  a  nutritive  matter  termed  the 
"  albumen  "  (fc),  which  serves  to  develope  the  plant  in 
the  early  stages  of  its  growth.  The  few  exceptions 
which  occur  in  the  dicotyledonous  character  of  the 
embryos  of  this  class,  will  be  noticed  when  we  enter 
into  further  details  concerning  seeds  in  general. 

(2.)  Organisation  of  the  Stem. 

The  most  important  characters  in  the  organisation 
of  most  stems  of  this  class,  depend  upon  the  manner  in 
which  they  increase  in  thickness.  In  young  and  suc- 
culent stems,  we  find  a  solid  cylindric  or  prismatic 
mass  composed  of  celhJar  tissue,  and  termed  the 
"  pith :"  this  is  surrounded  by  a  ring  of  vessels,  consisting 
of  trachea?  and  ducts,  and  named  the  "medullary  sheath." 
The  whole  is  coated  by  the  epidermis.  Afterwards, 
a  further  development  both  of  cellular  and  vascular 
tissues  takes  place  between  the  medullary  sheath  and 
epidermis,  and  these  form  one  layer  of  wood,  and  also 
one  layer  of  bark,  by  the  time  that  a  stem  of  one  year's 
growth  is  completed.  During  the  second  year,  a  fresh 
development  takes  place  between  the  wood  and  bark 
previously  formed.  This  fresh  matter  appears  at  first 
as  a  semifluid  or  viscous  mass,  termed  "cambium," 


SECT.  I.          ORGANOGRAPHY    AND    GLOSSOLOGY.  S3 

which  is  gradually  organised,  and  ultimately  separates 
into  two  layers — one  making  an  addition  to  the  wood,  and 
the  other  to  the  bark,  which  had  been  previously  formed. 
Hence  a  layer  of  new  wood  forms  a  ring  round  the  old 
wood,  and  a  layer  of  new  bark  round  the  new  wood ; 
whilst  the  old  layer  of  bark,  being  necessarily  thrust  out- 
wards, is  ruptured  and  withers,  though  it  still  continues 
to  form  an  outer  coat  over  the  whole  stem.  A  layer  of 
fresh  wood  and  another  of  fresh  bark  are  in  this  way  de- 
posited every  year ;  and  in  many  cases,  we  may  ascertain 
the  exact  age  of  a  tree  by  the  number  of  the  concentric 
zones  observable  upon  making  a  transverse  section  of  its 
stem.  Thus,  in  fig.  24.,  a  is  the  pith,  b  represents  three 
layers  of  wood,  and  c  an  2*  r.'^^-TrT—-"^-^ 

equal  number  of  layers  ^ 

of  bark.  Besides  these  /£|g| 
concentric  zoned  appear- 
ances on  the  surface  of  «•*•£ 
the  section,  there  are  also 
other  traces  running  in  fc 
straight  lines,  radiating  | 
from  the  centre  to  the 
circumference,  which  are  formed  of  cellular  tissue, 
and  termed  "  medullary  rays."  Either  of  these  three  cir- 
cumstances, then —  the  existence  of  a  pith,  the  appearance 
of  concentric  zones,  or  the  presence  of  medullary  rays  — 
affords  a  sufficient  characteristic  by  which  we  recognise 
the  structure  of  dicotyledonous  plants.  The  plants  of 
this  class  are  further  named  "Exogense,"  from  the  cir- 
cumstance of  their  stems  increasing  in  thickness  by  fresh 
materials,  which  are  arranged  "externally"  with  respect 
to  the  old  layers.  The  oldest  and  hardest  parts  of  such 
stems  lie  towards  the  centre,  as  may  be  readily  seen  in 
any  tree  growing  in  our  temperate  zone. 

(35.)  Monocotyledones,  or  Endogence.  — 

(1.)   Structure  of  the  Seed. 

The  general  structure  of  the  seeds  of  this  class  may 
be  exemplified  by  an  examination  of  a  grain  of  Indian 


DESCRIPTIVE    BOTANY.  PAIIT   J. 

com,  wheat,  &c. ;  or  of  a  seed  of  an  onion,  lily,  &c. 
(fig.  25.).     An  albuminous  mass  («)  forms  the  main 


bulk  of  most  of  these  seeds,  and  the  embryo  (/y)  is 
placed  within  it  towards  the  centre,  or  on  one  side. 
The  embryo  is  not  so  distinctly  developed  in  the  seeds 
of  this  class  as  in  those  of  the  last,  and  its  several 
parts  cannot  always  be  readily  recognised  before 
germination  has  commenced.  Its  general  character  is 
that  of  a  cylindrical  body,  tapering  more  or  less  at  the 
extremities,  from  one  of  which  protrudes  the  radicle,  and 
from  the  other  arises  a  single,  conical,  and  almost  solid 
cotyledon.  This  elongates,  and  is  ultimately  pierced 
by  a  leaf,  rolled  into  a  conical  form,  and  which  was  at 
first  completely  invested  by  the  cotyledon. 

('_'.)   Organisation  of  the  Stem. 

In  Monocotyledones,  there  is  no  distinction  between 
pith,  wood,  and  bark  ;  but  their  stems  consist  of  a  cy- 
lindrical mass  of  cellular  tissue,  through  which  bundles 
of  vascular  tissue  are  distributed  in  a  scattered  manner 
( fig.  26.).  Every  fresh 
development  of  new  mat- 
ter is  carried  towards  the 
centre  of  the  stem,  and,  as 
the  stem  elongates,  the 
outer  parts  become  more 
and  more  solidified,  whilst 
the  inner  remain  soft. 
These  stems  possess  no  traces  of  medullary  rays.  The 


SECT.   I.  ORGANOGRAPHY    AND    GLOSSOIjOOY.  35 

plants  of  this  class  are  termed  "  Endogense,"  from  the 
circumstance  of  the  newly  formed  materials  being  always 
developed  towards  the  innermost  part  of  their  stems.  A 
piece  of  cane  is  a  familiar  example  for  illustrating  this 
structure  ;  but  we  have  no  woody  plants  in  our  climate 
belonging  to  this  class,  and  very  few  even  which  possess 
herbaceous  stems,  if  we  except  the  hollow  culms  of  the 
grasses,  where  the  development  of  the  materials  towards 
the  centre  is  not  sufficiently  rapid  to  keep  pace  with  the 
elongation  of  the  stem,  and  the  tissue  is  in  consequence 
ruptured. 

(36'.)  Acotyledones.  — 

(1.)   Structure  of  the  Sporules. 

The  class  to  which  we  now  refer,  includes  an  ex- 
tensive series  of  plants,  grouped  under  several  orders, 
which  differ  considerably  in  many  particulars.  The 
whole  agree,  however,  in  the  important  circumstance  of 
never  bearing  flowers,  like  those  of  the  two  former 
classes  :  hence  they  are  termed  "  cryptogamic,"  in  con- 
tradistinction to  "  phanerogamic/'  which  is  applied  to 
all  flowering  species.  Having  no  flowers,  they  produce 
no  true  seeds  ;  but,  in  lieu  of  them,  are  furnished  with 
what  certainly  bear  a  considerable  resemblance  to  seed, 
viz.  small  minute  granular  bodies  capable  of  becoming 
distinct  plants.  The  manner  in  which  these  "  sporules," 
as  they  are  termed,  are  produced,  is  very  various  in  the 
different  orders  of  this  class,  but  forms  no  part  of  our 
present  inquiry.  They  are  also  variously  shaped,  but 
generally  spherical  or  spheroidal,  and  are  not  separable 
into  distinct  parts,  with  radicle  and  cotyledon,  like  the 
seeds  of  phanerogamous  plants.  In  germinating,  the 
sporules  are  developed  by  an  increase  27 
of  cellular  tissue,  which  appears  in  the 
form  of  rounded  masses  and  filament- 
ous chords  (jig.  27-)-  Among  the 
higher  tribes,  roots  are  afterwards 
produced  ;  and  a  part  which  is  more 
or  less  elevated  above  the  soil,  is  the  representative 


36  DESCRIPTIVE    BOTANY.  I'XHTI. 

both  of  the  stem  and  leaves  of  phanerogamous  plants 
combined.  In  the  lower  tribes,  however,  there  is  sel- 
dom any  separation  of  parts  into  distinct  organs,  but 
the  functions  of  nutrition  are  carried  on  in  an  obscure 
manner  by  the  general  mass. 

(•_'.)    Internal  Organisation. 

The  internal  organisation  of  acotyledonous  plants,  is 
not  sufficiently  uniform  in  the  different  orders,  to  allow 
of  their  being  characterised  by  any  appellation  derived 
from  their  mode  of  development,  as  in  the  case  of  the 
Exogenie  and  Endogense.  But  acotyledonous  plants 
may  be  separated  into  two  groups  :  the  one,  termed 
"  Ductulosffi,"  characterised  by  the  existence  of  a  vas- 
cular tissue,  and  by  a  mode  of  development  much  re- 
sembling that  of  the  Endogena; ;  the  other,  termed 
"  Eductulosje,"  or  "  Cellulares,"  is  entirely  composed 
of  cellular  tissue.  De  Candolle  even  considers  the  for- 
mer group,  in  spite  of  their  cryptogamic  character,  to 
possess  a  monocotyledonous  mode  of  development  in 
the  germination  of  their  sporules,  and  keeps  them  se- 
parate from  the  others,  as  a  distinct  class.  The  latter 
group  may  be  strictly  termed  "  Cellulares,"  from  their 
being  composed  of  cellular  tissue  alone,  and  thus  sepa- 
rated from  the  "  Vasculares,"  which  will  include  the 
rest  of  vegetation  (as  well  cryptogamic  as  phanero- 
gamic), possessing  a  vascular  structure.  The  class  Aco- 
tyledones  is,  however,  very  readily  recognisable  by  its 
external  appearance  alone;  and  the  general  characters  of 
the  several  orders  which  it  embraces  —  ferns,  mosses, 
lichens,  seaweeds,  fungi,  &c.  —  are  pretty  familiarly 
known  as  examples. 

(37-)  Tabular  J'inc. — In  the  very  slight  sketch  here 
given  of  the  primary  groups  under  which  all  plants  may 
be  arranged,  we  have  not  pretended  to  notice  many 
terms  which  different  botanists  have  applied  to  them  ; 
but  we  shall  now  collect  the  substance  of  what  we 
have  said  in  the  form  of  a  table,  which  may  serve 
to  assist  the  memory  of  the  reader  in  fixing  any  of 


SECT.   I.  ORGANOGRAPHY    AND    GLOSSOLOGY.  37 

the  terms  here  employed,  which  may  chance  to  be  new 
to  him. 

Primary  Groups,  characterised  by  certain  Considerations 

taken  from  particular  Parts. 
Embryo.  Structure.          Fructification. 

1.  Dicotvledones.  Exogena?.      1  „, 

»»  i  j  TI    j'  <-  Phanerogams. 

2.  Monocotyledom's.       .Lndogenre.    J 

3  ")    .  f  Ductulosa?.    1  „ 

•  Acotvledones.         •[  „  ..   .  J-  Cryptogama?. 

4.  J  L  Cellulares.      J       J  r 


CHAP.  II. 
NITTRITIVE  ORGANS. 

FUNDAMENTAL  ORGANS  (38.).  ROOT  AND  APPENDAGES  (39.). 

—  STEMS    (AERIAL)  (43.). — INTERNAL    STRUCTURE    (45.). 

FORMS  AND  DIRECTIONS  (53.  ).  — BUDS  (56.). BRANCHES 

(58.) AND  THEIR  MODIFICATIONS  (6  1 .). SUBTERRANEAN 

STEMS  AND    BRANCHES  (62.).  TUBERS  AND  BULBS;  THEIR 

AFFINITY  (63.).  APPENDAGES  TO  THE  STEMS  (67.). 

(38.)  Fundamental  Organs.  —  WE  may  refer  back  to 
articles  8,  9>  &c-  f°r  a  general  notice  of  the  complex 
organs,  which  we  are  now  about  to  describe  more  in 
detail,  though  we  do  not  propose  to  enumerate  all  the 
varieties  of  form  which  these  organs  assume.  There 
are  certain  appendages  both  to  the  stem  and  root, 
(or  ascending  and  descending  "  axes"  of  vegetation), 
which  are  of  very  little  importance  in  carrying  on 
the  function  of  nutrition.  These  appendages,  as  the 
thorns,  scales,  tendrils,  &c.  found  on  some  stems, 
have  without  doubt  their  respective  uses  ;  but  as  the 
plant  may  be  deprived  of  them,  and  still  continue  to 
vegetate  as  freely  as  when  they  were  present,  they  are 
evidently  not  to  be  considered  as  fundamentally  essential 
to  the  support  of  life.  Moreover,  they  may  in  all  cases 
be  referred  to  certain  modifications  and  metamorphoses, 
which  have  taken  place  in  one  or  other  of  the  three 


S8  !'I:SCIIIPTIVB  BOTANY.  PART  ?. 

organs  —  the  root,  stem,  and  leaf, — which  are  more  es- 
pecially considered  to  be  the  "  fundamental  organs"  of 
nutrition.  The  presence  of  neither  of  these  can  be 
dispensed  with  without  injuring  vegetation,  and  ulti- 
mately involving  the  destruction  of  the  individual ;  unless 
where  some  means  have  been  provided  (as  we  shall  see. 
in  the  case  of  parasitic  plants)  to  supply  their  deficiency, 
or  where  (as  in  the  lowest  tribes  of  cryptogamic  plants) 
they  are  probably  so  blended  and  confounded  together 
that  we  are  not  able  to  distinguish  them. 

(3<).)  Root.  —  The  most  common  position  for  the 
roots  of  plants,  is  at  the  base  of  the  stern,  from  whence 
they  descend  into  the  ground,  gradually  tapering  to  a 
point,  and  giving  off  filamentous  branches  on  all  sides, 
in  an  irregular  and  indeterminate  manner.  Thrsi 
branches  of  the  roots  are  termed  "  fibrils,"  and  are 
composed  of  ducts  and  cellular  tissue,  and  covered  by  an 
epidermis,  except  at  their  extremities  where  the  cellular 
tissue  is  exposed.  It  is  here  that  the  true  absorbents  of 
the  root  exist,  termed  its  "  spongioles."  The  structure  of 
the  main  trunk,  "  caudex,"  or  "  tap"  of  the  root  (when 
well  developed)  is  strikingly  analogous  to  that  of  the 
stem,  except  that  in  dicotyledonous  plants  there  is  no 
pith,  and  in  all  cases  the  epidermis  is  without  stomata. 
The  medullary  rays,  however,  are  present ;  and  the 
bark  generally  bears  a  much  larger  proportion  to  the 
whole  mass,  than  in  the  stem.  This  latter  circumstance 
is  owing  to  its  being  kept  moist  by  its  underground 
position,  which  renders  it  more  capable  of  disten- 
tion.  In  the  carrot,  this  is  well  exhibited  by  a  differ- 
ence in  the  colours  of  these  parts.  The  concentric  woody 
layers  are  not  distinguishable,  and  it  very  seldom  hap- 
pens that  tracheae  are  found  in  roots.  They  are  very 
rarely  of  a  green  colour,  excepting  some  of  those  which 
are  developed  above  ground ;  and  even  then  it  is  seldom 
more  than  the  spongioles  which  are  thus  partially 
tinted.  Where  the  root  has  no  descending  caudex, 
which  in  some  plants  soon  dies  away,  the  fibrils  are 
given  off  from  below  the  neck,  or  from  a  flattened  disc 


SECT.   I.  ORGANOGIIAPHY    AND    GLOSSOLOGY.  39 

which  represents  the  caudex,  as,  for  instance,  in  the 
bulbs  of  hyacinths.  Roots,  however,  may  be  developed 
from  any  part  of  the  stem  and  branches,  if  these  are 
duly  subjected  to  the  influence  of  moisture  and  shade  ; 
and  some  plants  of  tropical  climates  constantly  produce 
roots  from  their  stems  and  branches,  which  descending 
into  the  ground  become  fixed,  and  serve  to  support  the 
superincumbent  vegetation,  and  thus  enable  it  to  ex- 
tend over  a  large  tract  of  ground.  The  most  celebrated 
example  of  the  kind  is  the  banyan-tree  of  the  East 
Indies  (fig.  28.).  In  this  case,  it  appears  that  when 


the  roots  have  reached  the  ground,  the  exposed  portion 
assumes  the  character  of  a  stem.  It  has,  indeed,  been 
asserted  that  the  stem  and  root  are  so  entirely  distinct, 
that  the  latter  is  never  capable  of  assuming  the  cha- 
racter of  the  former.  But  it  is  not  uncommon  to  find 
ash-trees  which  have  grown  on  the  stumps  of  pollard 
willows  and  have  sent  their  roots  through  the  decayed 
wood  into  the  ground  ;  the  exposed  roots  of  the  ash,  when 
the  willows  have  fallen  to  pieces,  become  coated  with 
a  green  bark,  and  do  not  appear  to  differ  in  any  respect 
from  the  trunk  itself.  At  all  events,  many  roots  are  as 
capable  of  producing  stems  or  branches,  as  these  are  of 
o  4, 


40  DKSCUIPTIVK    UOTANY.  PART   I. 

forming  roots :  this  is  often  the  case  with  the  white 
poplar,  and  certain  elms  which  throw  up  their  nu- 
merous suckers,  to  the  great  detriment  of  the  pasturage 
when  planted  in  meadow  land. 

Besides  the  important  purpose  which  the  root  is  more 
especially  destined  to  serve,  of  absorhing  nutriment,  it 
is  generally  so  placed  as  to  take  firm  hold  in  the  ground, 
and  thus  enables  the  plant  to  maintain  its  position  in 
one  and  the  same  spot  during  its  lifetime.  There 
are,  however,  certain  plants,  as  the  common  duck- 
wi-i'ds  (Lemrun,  fig.'l\.  b),  which  float  on  the  surface 
of  ponds,  whose  roots  are  suspended  in  the  water 
without  ever  reaching  the  bottom.  There  are  others 
termed  "  air-plants"  (some  of  the  Orchidece),  whose 
roots  cling  closely  to  the  branches  of  trees,  and  derive 
their  nutriment  from  the  moist  atmosphere  perpetually 
hanging  over  a  tropical  forest ;  and  these  plants  could 
not  live  long  if  they  were  planted  in  the  ground. 

(40.)  Forms  of  Roots.  —  The  various  forms  which 
roots  assume  need  not  be  dwelt  upon  here ;  they  are 
such  as  may  be  readily  learnt  in  any  elementary  work, 
but  their  description  would  involve  us  in  details  for 
which  we  have  not  space. 

(41.)  Appendages  to  ttie  Root. —  There  are  not  many 
distinct  appendages  to  be  found  on  roots.  In  some 
fibrils,  there  are  swollen  nodosities  (fig.  29-)>  and  on 


others  there  are  little  tuberous  excrescences.  In 
some,  the  fibrils  become  very  fleshy,  and  are  swollen 
into  masses  ( fi<j.  30.),  having  an  ovate  («),  palmate 


ORGANOGRAPHY    AND    GLOSSOLOGY. 


41 


(6),  or  fasciculate  (c)  appearance,  as  in  many  of  the 
Orchidese.     All  these  swollen  portions  serve  as  reser- 


voirs of  nutriment  for  the  future  use  of  the  plant,  but 
they  should  not  be  confounded  with  certain  analogous 
modifications  of  the  underground  portions  of  stems, 
which  we  shall  describe  when  we  speak  of  the  real 
"  tuber." 

The  extremities  of  some  aerial  roots,  as  in  the  Panda- 
nus,  are  coated  by  exfoliations  of  the  epidermis  ;  and 
the  same  may  be  observed  on  those  of  the  hyacinth. 
The  little  Lemnce,  or  duckweeds  (fig.  31.  6),  whose  roots 
hang  suspended  in  the 
water,  have  a  distinct 
cup-like  appendage  at- 
tached  to  their  extremi- 
ties. In  the  early  state 
of  their  development  this 
formed  a  membranous 
sheath  (a),  which  com- 
pletely enveloped  them, 
but  which  became  rup- 
tured at  the  base  as  they  elongated,  and  was  then  carried 
downwards  as  they  continued  to  grow. 

(42.)  Bladders.  —  The  roots  of  certains  aquatics  be- 
longing to  the  genus  Utricularia,  are  furnished  with  ap- 
pendages, in  the  form  of  little  membranous  bladders 


HI X  IUPTIVE     BOTANY. 


PART   I. 


(fig. 32.}  which  are  partially  filled  with  air,  and  serve  to 
float  the  plant,  in  order   that 
it    may  be  enabled    to  flower 
above  the  surface  of  the  water. 

(43.)  Lfntirr//{t:  —  On  the 
stem  and  branches  of  trees, 
and  very  conspicuously  in  those 
of  the  alder,  birch,  and  willow, 
there  occur  certain  roughish 
prominent  traces,  of  a  lenticular  shape  (fig.  33.),  which 
look  as  if  they  were  fissures  in  the  bark,  having  their 
edges  turned  outwards.  These 
are  termed  "  lenticells  ;"  and 
it  is  at  these  places  that  roots 
are  protruded  whenever  the 
stem  is  placed  under  circum- 
stances calculated  to  give  rise 
to  them. 

(44.)  Stems.  —  As  the  cau- 
dex,  or  main  trunk  of  the 
root,  is  not  much  extended 
downwards  in  many  plants,  so 
there  are  many  stems  which 
are  never  much  developed  up- 
wards; but  the  flower-stalk 
and  leaves  appear  to  rise  immediately  from  the  crown  of 
the  root.  Plants  possessing  this  character  are  called 
"stemless."  Strictly  speaking,  however,  there  are  no 
phanerogamous  plants  which  are  entirely  without  this 
fundamental  organ,  although  it  is  often  reduced  to  a 
mere  flattened  disc.  Occasionally  it  assumes  a  bulb- 
like  form,  as  in  the  Cyclamens  (fig.  34.),  where 
the  large  woody  mass  from  whence  the  flowers  and 
leaves  arise,  is  a  true  stem.  In  some  plants,  the  stem 
is  wholly  beneath  the  surface  of  the  ground,  forming 
the  "  subterraneous  stem,"  or  "  rhizoma  ;  "  but  most 
frequently  it  rises  above  it,  and  composes  "  the  aerial 
stem,"  which  is  called  a  "  trunk,"  "  culm,"  £c.  ac- 
cording to  its  structure. 


SECT.  I. 


ORGANOGRAPHY    AND    GLOSSOLOGY. 


(45.)  Aerial  Stems. —  The  stem  is  said  to  be  "herb- 
aceous," when  it  continues  soft,  and  lasts  only  for 
a  short  time ;  dying  soon  after  the  flower  has  ex- 
panded, and  the  seeds  ri- 
pened. It  is  called  "woody," 
when  it  continues  to  increase 
for  several  years.  Herba- 
ceous stems  belong  to  "  an- 
nuals/' "  biennials,"  and 
"  perennials,"  which  are 
thus  named,  according  to 
the  several  periods  which 
their  roots  continue  to  live. 
Woody  stems  are  confined  to 
shrubs  and  trees;  the  former 
having  many  stems  rising 
from  the  surface  of  the 

ground,  and  the  latter  possessing  one  main  trunk,  which 
branches  or  not,  according  to  the  nature  of  the  species 
to  which  it  belongs.  An  ''  undershrub,"  is  where  the 
branches  are  partly  woody  and  partly  herbaceous,  so 
that  a  portion  only  dies  back  every  year.  Besides  these, 
there  are  the  "  succulent"  stems,  so  called  from  the 
highly  developed  state  of  their  cellular  tissue,  which 
often  remains  replete  with  juices  for  many  years,  without 
hardening  into  wood. 

(46.)  Internal  Structure  of  Stems  and  Roots.  —  In 
arts.  34,  35.  we  have  given  an  account  of  the  leading 
differences,  observable  in  the  internal  composition  of  the 
stems  of  dicotyledonous  and  monocotyledonous  plants  ; 
and  we  have  now  to  explain  a  few  more  particulars 
respecting  them. 

(47.)  Dicotyledonous  Stems.  —  In  some  stems  of 
dicotyledonous  trees  it  is  difficult,  and  in  others  im- 
possible, to  distinguish  any  separation  of  the  wood  into 
concentric  layers.  This  is  especially  the  case  with 
trees  of  tropical  climates,  where  vegetation  is  not  liable 
to  the  periodic  checks  which  it  receives  in  colder  regions. 
In  a  few  examples,  also,  the  medullary  rays  are  not 


44  DESCRIPTIVE    BOTANY.  PART  I. 

clearly  distinguishable,  but  the  pith  and  bark  are  never 
wanting. 

(48.)  Pith.  —  The  vesicles  of  the  pith  are  larger 
and  more  regularly  arranged  than  those  of  other  parts. 
It  continues  to  increase  in  diameter  as  long  as  it  re- 
mains succulent,  and  in  some  trees,  as  the  elder,  it  be- 
conlPs  more  than  half  an  inch  thick  ;  but  generally  it 
is  much  smaller.  After  it  has  lost  its  succulency  and  be- 
come a  dry  spongy  mass,  it  scarcely  diminishes  in  size ; 
but  where  the  branch  is  much  distended,  the  pith  is 
ruptured,  and  in  some  cases  appears  to  be  nearly  ob- 
literated. The  stems  then  become  hollow,  as  in  many 
umbelliferous  plants.  It  always  forms  a  continuous 
mass  through  the  whole  stem  ;  but  in  some  cases  it  is 
-o  much  condensed  and  hardened  as  to  resemble  wood 
at  the  places  where  the  leaves  are  attached,  as  in  the 
horse-chestnut. 

Although  it  is  generally  without  any  fibres  of  vascular 
tissue,  such  are  found  in  some  plants,  as  in  the  elder, 
where  they  may  be  seen,  in  a  transverse  section,  forming 
a  circle  of  red  dots,  a  short  dis- 
tance within  the  medullary  sheath. 
In  ferula  communis  there  are  so 
many  of  these  dispersed  through 
it,  that  the  stem  has  the  appear- 
ance of  belonging  to  a  monocotyle- 
donous  plant  (./?</•  35.). 

(49.)  Mediilinry  Slieath.—The 
fibres  which  compose  the  medul- 
lary sheath,  appear  to  retain  their 
vitality  for  a  long  time  after  the  pith  has  been  exhausted 
and  become  dead ;  and  the  trachea?  which  abound  in  it 
may  even  be  unrolled  in  old  and  dry  wood. 

(50.)  Wood. — The  woody  layers  seldom,  if  ever,  con- 
tain perfect  tracheae  ;  but  they  are  composed  principally 
of  elongated  cellular  tissue,  traversed  by  ducts  of  various 
kinds.  As  the  tree  becomes  aged,  the  innermost  layers 
grow  darker  and  more  solid,  and  are  then  termed  the 
''  Heart-wood/'  or  "  Duramen."  The  outer  layers, 


SECT.   I.          ORGANOGRAFHY    AND    GLOSSOLOGY.  45 

which  are  called  the  "Alburnum,"  remain  soft  and 
pale,  and  are  rejected  by  workmen  as  being  unsuited  to 
economic  purposes.  The  variously  coloured  fancy  woods 
employed  by  the  turner  consist  of  the  heart  only,  the 
alburnum  in  the  ebony,  even,  being  quite  white. 

Each  zone  is  principally  composed  of  cellular  tissue 
towards  its  inner,  and  of  vascular  tissue  towards  its 
outer  parts  :  and  each  is  supposed  to  be  as  a  repetition 
of  the  parts  formed  during  the  first  year's  growth.  In 
the  common  sumach  (Rhus  typhinum),  especially,  the 
cellular  or  inner  part  of  each  zone  has  precisely  the 
same  appearance  as  the  pith,  which  is  here  of  a  pecu- 
liar brown  colour  and  easily  recognised.  But  as  there 
are  no  tracheae  among  the  vessels  in  the  outer  part  of 
the  zones,  whilst  these  are  abundant  in  the  medullary 
sheath,  the  analogy  alluded  to  is  not  perfect. 

Some  woods  contain  scarcely  any  ducts,  as  many  Coni- 
ferae ;  and  the  delicate  material  of  which  rice-paper  (as 
it  is  called)  is  composed,  consists  entirely  of  cellular 
tissue.  This  curious  substance  is  procured  from  the 
herbaceous  stems  of  a  species  of  ./Eschynomene,  growing 
in  China.  The  whole  stem  is  about  an  inch  thick,  and 
resembles  a  mass  of  pith  covered  by  a  very  thin  epi- 
dermis. There  is,  however,  a 
central  column  of  real  pith  run- 
ning through  it.  By  means  of 
some  sharp  instrument,  the  stem 
is  cut  spirally  round  the  axis  into 
a  thin  lamina  (fg.  36.),  which  is 
then  unrolled,  and  may  be  made 
up  into  sheets  containing  about  a 
foot  square  of  surface. 

(51.)  Medullary  Rays  (see  fig.  24.).— These  form 
what  carpenters  term  the  "  silver  grain  "  in  wood,  and 
are  generally  distinctly  traceable  in  dicotyledonous  trees. 
They  may  be  seen  passing  in  straight  lines  from  the  centre 
to  the  circumference,  but  cannot  be  traced  continuously 
to  any  great  extent  in  a  vertical  direction.  They  ap- 


46  DESCRIPTIVE    BOTANY. 

pear  rather  as  isolated  patches  of  cellu-  37 
lar  tissue,  arranged  in  lamina?  of  one 
or  more  cells  in  thickness,  placed 
at  right  angles  to  the  concentric  woody 
layers  (fy.  37.).  The  cells  are  elong- 
ated in  the  direction  of  the  rays. 
In  some  climbers,  where  the  stem  is 
twisted,  the  rays  are  curved  from  the 
centre  to  the  circumference. 

(.62.)  Bark. — The  layers  which  compose  the  bark, 
are  formed  on  a  reverse  plan  to  that  of  the  woody 
layers,  their  outer  portion  being  chiefly  cellular,  and 
their  inner  more  vascular.  The  last  formed  or  inner- 
most, is  termed  the  "  Liber,"  the  rest  bear  the  general 
name  of  "  Cortical  layers."  These  layers  are  capable  of 
greater  or  less  distension,  according  to  the  nature  of  the 
tree ;  and  in  some  cases  the  fibres  are  so  far  separated  as 
to  represent  a  sort  of  lace-work,  as  in  the  J)n/>lim'  Inyetto. 
In  the  lime  tree,  the  inner  layers,  when  separated  by 
maceration,  form  the  common  bass,  or  matting,  used 
by  gardeners.  The  outer  layers  of  the  birch,  beech, 
and  other  trees,  are  thrown  off  in  thin  membranous 
lamina?.  In  oaks,  elms,  and  a  multitude  of  others, 
the  old  bark  remains  in  a  rugged  cracked  state.  The 
absence  of  trachea;  is  a  nearly  universal  characteristic 
of  the  bark  ;  but  Dr.  Lindley  has  detected  them  in  great 
abundance  in  that  of  the  pitcher-plant  (Nepenthes  dis. 
fU/ntoriu). 

(53.)  Monocotyledonoua  Stems. — The  complete  want 
of  monocotyledonous  trees  in  our  climate,  has  debarred 
botanists  the  opportunity  of  examining  their  structure 
so  particularly  as  they  have  that  of  Dicotyledons ; 
and,  perhaps,  even  yet,  the  exact  course  of  the  woody 
fibres  distributed  through  the  trunk,  is  not  accu- 
rately understood.  It  was  supposed  until  lately,  that 
the  newest  fibres  were  placed  nearer  the  centre  than 
the  old  ones,  throughout  the  whole  of  their  length 
(fy.  38.  «)  ;  but  M.  Mohl  has  recently  shown  that  this 
cannot  be  the  case.  He  observes  that  the  fibres  cross 


ORGANOGRAPHY    AND    GLOSSOLOGY. 


47 


each  other  before  they  pass  into  the  leaves ;  and  there- 
fore supposes  that  the  newest  fibres  are  always  nearer 


to  the  circumference  than  the  old  ones,  at  the  bottom  of 
the  trunk,  but  that  they  cross  them  as  they  ascend,  and 
then  curve  outwards  and  pass  into  the  leaf  (6). 

Those  monocotyledonous  stems  which  have  no 
branches,  and  are  supplied  with  nutriment  entirely  from 
the  leaves  at  the  summit,  continue  of  nearly  equal  thick- 
ness throughout  their  whole  length,  as  in  the  lofty  palms 
{fig-  39-)'  whose  trunks  are  a  long  cylinder,  crowned  by 
a  splendid  mass  of  foliage.  But  those  which  are 
branched,  become  thicker  below  than  above,  as  in  dico- 
tyledonous trees.  The  same  may  be  said  of  such  Mo- 
nocotyledons as  the  grasses,  whose  stems  are  clothed 
with  leaves  throughout  their  whole  length.  It  has, 
indeed,  been  generally  asserted  that  the  trunks  of  many 
monocotyledonous  trees  do  not  increase  in  thickness 
after  they  have  risen  above  the  surface  of  the  soil ;  but 
such  an  assertion  does  not  appear  to  have  received  a 
satisfactory  confirmation.  It  is  easier  to  believe  that 
their  increase  is  very  slow,  and  that  the  fresh  materials 
are  always  equally  distributed  from  the  top  to  the 
bottom — the  diameter  of  the  terminal  bud  increasing  as 


the  trunk  lengthens.     We  find  that  even  the  trunks  of 
old  dicotyledonous  trees,  below  the  part  where  the  boughs 


Lodotcea  lecktUarum. 

set  on,  are  nearly  cylindrical,  or  frustra  of  very  elongated 
cones,  when  compared  with  the  portions  above  them. 
Mirbel  has  figured  the  trunk  of  a  monocotyledonous 
tree  which  has  become  completely  invested  by  a  climber 
whose  branches  have  grafted  together  into  a  reticu- 
lated cylindrical  mass.  This  specimen  has  been  consi- 
dered to  illustrate  the  fact,  that  the  stem  could  not  have 
increased  at  all  in  thickness  after  it  had  become  so 
closely  embraced.  But  something  of  the  same  sort  may 
occasionally  be  observed  even  in  dicotyledonous  trunks, 
where  they  have  become  completely  invested  by  ivy, 
whose  branches  intertwine  and  graft  together,  though 


SECT.  I.         ORGANOGBAPHY    AND    GLOSSOLOGY.  49 

perhaps  not  so  completely  as  in  the  case  of  the  creeper 
alluded  to.  That  Monocotyledons  increase  very  slowly 
in  thickness  may  readily  be  conceived,  but  so  do  the 
trunks  of  dicotyledonous  trees,  after  they  have  acquired 
a  great  age. 

(54.)  Forms  of  Stems.  —  The  more  usual  character 
of  dicotyledonous  stems,,  is  to  taper  off  gradually  from 
the  base  towards  the  summit,  and  they  thus  approxi- 
mate to  the  form  of  a  very  lengthened  cone.  On  the 
other  hand,  the  stems  of  woody  Monocotyledons,  with 
few  exceptions,  approximate  to  the  form  of  a  cylinder. 
Some  stems,  however,  in  the  early  stages  of  their 
growth,  and  many  herbaceous  stems  during  the  whole 
period  of  their  duration,  are  variously  angulated,  and 


channelled  (fig.  40.).  This  is  frequently  owing  to 
some  peculiarity  in  the  development  of  the  cellular 
tissue  of  which  the  bark  is  composed. 

(55.)  Directions  of  Stems.  —  The  original  tendency 
of  aerial  stems,  is  vertically  upwards;  but  many  are 
too  weak  to  support  themselves  in  that  position,  and, 
in    consequence,    either    trail  upon  the 
ground,    or    cling    to    the    surrounding 
herbage,  by  means  of   tendrils,  hooks, 
and  various  other  appendages;   which 
are  frequently  modifications  of  the  leaf. 
There  are   certain   stems,  also,  which, 
by  continually  twisting  in  a  spiral  man- 
ner, twine  themselves  round  the  trunks 
and  branches  of  neighbouring  trees  and 
shrubs,  and  are  thus  supported  to  a  great      « 
height.     The  spiral  which  these  stems  describe,  is  termed 


DESCRIPTIVE    BOTANY. 


PART  I. 


50 

"right-handed"  (fig.  41. 6),  or  "left-handed"  (a), 
according  as  its  coils  appear  to  rise  from  left  to 
right,  or  from  right  to  left,  to  a  person  supposed 
to  be  placed  in  its  axis ;  or,  if  we  were  to  hold  the 
spiral  in  an  upright  position  before  us,  then  the  coils  of 
a  right-handed  spiral  will  seem  to  descend  from  the. 
left  towards  the  right,  and  those  of  a  left-handed  spiral 
to  descend  from  the  right  towards  the  left. 

(56'.)  Knots,  Internodia,  and  Joints. —  Many  stems 
are  swollen  at  intervals,  where  the  leaves  are  at- 
tached, and  such  swellings  are  termed  "  knots."  The 
space  which  intervenes  between  two  knots,  is  an  "  in- 
ternodium."  "  Joints"  are  also  swollen  parts,  where 
the  tissue  is  less  firm  than  elsewhere  (see  art.  25.),  and 
may  easily  be  fractured.  They  often  occur  immedi- 
ately below  the  knots. 

(57.)  Buds.  —  As  branches  always  originate  in  the 
development  of  "  buds,"  we  shall  here  describe  these 
bodies,  before  we  proceed  with  further  details  concerning 
stems,  of  which  the  branches  appear  to  form,  as  it  were, 
mere  subdivisions.  Buds  usually  consist 
of  several  scales,  or  rudimentary  leaves, 
closely  wrapped  round  an  axis  ;  and 
within  these  are  other  leaves,  in  a 
still  more  rudimentary  state,  which 
are  destined  to  assume  a  more  highly 
developed  condition  than  the  outer 
scales  of  the  bud.  It  is  the  outermost 
scales  which  thus  serve  to  protect  the 
innermost  and  more  delicate  parts,  from 
the  inclemencies  of  the  weather.  Some 
are  covered  with  down,  which  may, 
as  some  suppose,  be  effective  in  pre- 
serving them  from  the  intensity  of 
cold  ;  others,  as  the  horse-chestnut, 
are  coated  over  with  gluten,  which  is 
certainly  a  more  effectual  protection 
against  moisture ;  and  perhaps  this  is  the  end  which 
these  scales  best  fulfil  in  most  cases,  as  their  closely  im- 


SECT.   I.          ORGANOGRAPHY    AND    GLOSSOLOGY.  51 

bricated  condition,  would  seem  to  indicate.     Buds  are 
sort  of  nascent  germ,  originating  within  the  stem,  from 
the  surface  of  which  they  ultimately  protrude,  and  are 
developed  (fig.  42.). 

In  ordinary  cases,  buds  are  formed  about  the  places 
where  the  leaves  unite  with  the  stem  ;  and  they  are 
most  frequently  situate  immediately  above  the  "  axil" 
of  the  leaf — or  place  where  this  union  occurs  (fig.  42.  a). 
In  some  plants,  however,  the  buds  are  produced  on  the 
sides  of  the  axils;  and,  in  some,  even  within  the  space 
covered  by  the  leaf- stalk,  where,  conse-  ^  4, 
quently,  they  lie  concealed  until  the  leaf  falls. 
Buds  may,  however,  be  developed,  under  pe- 
culiar circumstances,  from  any  part  of  the 
stem  ;  and  such  are  called  "  adventitious  " 
buds,  to  distinguish  them  from  those  which 
are  formed  in  the  ordinary  way. 

(58.)  Shoots.  —  In  the  early  stages  of 
their  development,  branches  are  termed 
"  shoots  ;'"  and,  when  they  rise  from  under- 
ground stems,  and  their  leaves  assume  the 
form  of  scales,  as  in  the  common  asparagus 
(fig.  43.),  the  shoot  is  termed  a  "  turio." 
In  this  plant,  the  leaves  are  never  fur- 
ther developed  ;  but  buds  are  formed  and 
branches  proceed  from  the  axils  of  the 
scales. 

(59-)  Branches.  —  In  very  many  plants,  but  more 
especially  in  dicotyledonous  species,  we  find  the  stem 
furnished  with  "branches."  But  monocotyledonous 
plants  do  not  so  generally  put  forth  branches,  if  we 
except  certain  species  in  which  they  are  always  pro- 
duced (as  in  the  asparagus),  as  readily  as  in  Dicoty- 
ledons. But  most  monocotyledonous  trees,  especially 
among  the  palms,  are  without  them ;  and  the  same  is 
true  of  others,  as  with  the  dragon-tree  Dracaena  draco] 
in  a  young  state;  though  they  are  developed  after- 
wards, at  an  advanced  age.  Branches  have  precisely 
the  same  organisation  as  the  stem  ;  and  they  may, 
E  2 


•52 


DKSCRIPT1VE    BOTANY. 


PART  I. 


in  fact,  be  considered  as  so  many  partial  stems  en- 
grafted into  the  main  trunk.  Originating,  as  we  have 
stated,  from  buds,  their  disposition  round  the  stem 
must  depend  upon  the  arrangement  of  the  leaves,  to 
which  we  shall  allude  when  we  treat  of  those  organs. 
We  may,  however,  remark,  that  branches  are  never 
so  symmetrically  arranged  as  leaves ;  because  a  great 
many  buds  are  never  developed  at  all.  This  arises 
from  the  unfavourable  circumstances  under  which  many 
are  placed,  for  receiving  a  sufficiency  of  air,  of  moisture, 
and  more  especially  of  light.  The  consequence  is,  that 
those  which  originate  on  the  lower  parts  of  the  stem,  are 
either  much  stunted,  or  become  abortive. 

(60.)  Development  of  Branches.  — When  a  branch 
is  not  developed,  where  a  bud  has  been  formed,  the 
latter  still  continues  to  live ;  and,  in  dicotyledonous 
trees,  is  carried  outward  with  the  increasing  bulk  of 
the  stem,  and  awaits  at  the  surface  for  a  proper  op- 
portunity, when  a  sufficient  quantity  of  light,  or  of 
some  other  requisite,  may  enable  it  to  "break"  into 
a  branch.  This  fact  is  familiar  to  every  horticul- 
turist, and  is  the  foundation  of  the  principle  upon  which 
he  regulates  the  pruning  of  his  trees.  If  a  section  of 
the  stem  be  made  at  the  point  where  an  undeveloped 
bud  is  seen  to  protrude,  it  will  show  the  course  which 
the  bud  has  followed  in  passing  from  the  centre  outwards, 
marked  by  a  line  or  wake, 
which  traverses  the  several 
layers  (fig.  44-.).  Hence, 
branches  of  the  same 
age,  may  have  origin- 
ated from  buds  which 
have  been  formed  at  very 
different  periods  of  the 
tree's  growth.  This  is 
a  further  cause,  tending 
to  destroy  the  symmetry 
which  they  might  other- 
wise have  exhibited  in  their  arrangement  round  the  axis 


SECT.   I.          ORGANOGRAPHY    AND    GLOSSOLOGY. 

of  the  stem.  In  the  annexed  diagram  (fig.  45.),  a  re- 
presents a  bud,  developed  on 
a  branch  which  is  one  year 
old  ;  and  this  branch  is  seated 
on  another  which  is  two  years 
old,  and  which  originated 
from  a  bud  of  the  same  age 
as  6,  which  has  not  yet  been 
developed. 

(6l.)  Direction  of  branches. 
—  The  general  contour  given 

to  the  whole  foliage  of  trees, — which  bears  the  name 
of  " cyma,"  depends  upon  the  angle  which  the  branches 
make  with  the  stem  at  their  point  of  union,  combined 
with  the  degree  of  rigidity  which  they  possess.  When 
they  stand  out  at  various  angles,  more  or  less  approach- 
ing to  a  right  angle,  they  are  termed  "  divergent ; " 
and,  when  such  branches  are  rigid,  a  rounded  form  is 
given  to  the  cyma,  as  in  the  oak  and  elm.  When  the 
angle  is  more  obtuse,  they  are  said  to  be  "  patent,"  or 
"  spreading."  If  they  rise  at  a  very  acute  angle,  and 
are  packed  close  together  into  the  pyramidal  forms 
assumed  by  the  cypress  and  Lombardy  poplar,  they  are 
called  "•  appressed."  When  they  are  very  long,  and  so 
flexible  as  to  bend  by  their  own  weight,  they  are 
"  pendant,"  as  in  the  weeping  willow.  But  in  that 
variety  of  the  common  ash,  which  is  also  called  "  weep- 
ing," the  branches  are  rigid,  and  possess  a  natural 
tendency  downwards,  from  their  very  origin,  and  are  in 
this  case  termed  "  depressed." 

(62.)  Modifications  of  Branches. — 

Thorns.  —  When  a  bud  is   imperfectly    developed, 

it  sometimes  becomes  a  short  branch,  very  hard    and 

sharp  at  the  extremity,  and  is  then  called  a  "  thorn." 

We    must    not,    however,    confound    the    "  prickle" 

with    the    thorn.       The    former  of  these    is    a    mere 

prolongation  of   cellular    tissue,    from    the    bark,    and 

may  be  considered  as  a  compound  kind  of  pubescence 

(art.  3L);  whilst  the  thorn,  containing  both  wood  and 

B  3 


54  DESCRIPTIVE    BOTANT.  PART  I. 

bark,  is  an  organ  of  the  same  description  as  the  branch 
itself.  "  Spines "  originate  in  the  transformation  of 
leaves,  &c.  (see  art.  78.). 

J{n/nierg.  —  These  are  branches  which  trail  along 
the  ground,  striking  root  at  intervals,  where  the  buds 
develop  and  give  rise  to  young  plants,  as  in  the  straw- 
berry. 

Suckers  are  branches  originating  below  the  surface 
of  the  soil,  and  their  base  in  consequence  soon  emits 
roots.  Any  branch  may  be  made  to  assume  this  cha- 
racter artificially,  by  confining  a  portion  of  it  below  the 
surface ;  as  the  horticulturist  is  aware  when  he  forms 
his  "  layers." 

(63.)  Subterranean  Stems  and  Branches. — There  are 
some  stems  and  branches,  which,  instead  of  rising  up- 
wards, continue  under  ground,  and  creep  horizontally 
below  the  surface  of  the  soil.  These  are  very  generally 
mistaken  for  roots,  and  are  usually  termed  "  creeping 
roots ;"  but  they  may  readily  be  distinguished  from 
roots,  if  not  by  their  internal  structure,  at  least  by  their 
external  appendages.  They  are  mostly  furnished  with 
scaly  processes,  or  other  traces  of  a  degenerated  and 
modified  form  of  the  leaves  ;  and  they  produce  buds, 
and  often  throw  up  branches  which  rise  above  ground  ; 
or  else  they  themselves  ultimately  take  a  tendency  up- 
wards, and  become  true  aerial  stems  ;  a  good  example 
of  which  occurs  in  the  common  reed  (Phragmites  cuiii- 
mnnin,  fig.  4(5.).  The  swollen  rhizomata  of  this  plant 
runs  among  the  turf  of  our  fens,  forming  large  tubes 
through  the  masses  cut  for  burning.  They  are  furnished 
at  intervals  with  pale  membranous  scales,  or  rudimentary 
leaves  ;  and  fibrous  roots  are  given  off  from  all  the  knots. 
So  soon  as  the  rhizoma  takes  an  upward  tendency,  it 
contracts  its  dimensions, and  ultimately  rises  above  ground 
as  a  slender  stem,  invested  with  long  green  leaves.  The 
term  "  rhizoma  or  root-stalk,"  is  equally  applied  to  pro- 
strate stems,  as  in  the  iris  tribe,  and  in  some  ferns,  where 
the  upper  surface  gives  rise  to  the  leaves,  and  the  lower 
to  the  roots ;  and  also  to  the  completely  subterraneous 


SECT.  I.  ORGANOGBAPHY    AND    GLOSSOLOGY.  55 

stems   which   throw  up  stalks  and  leaves  at  intervals 


(fig.  47.),  as  in  the  Carex  arenaria,  Elymus  arenarius, 
Sac.,  —  plants  of  inestimable  utility  in  certain  regions, 


where  they  serve  to  bind  the  shifting  sands  of  the  sea 
shore,  which  would  otherwise  drift  before  the  wind, 
and  form  irruptions  over  the  neighbouring  land.  The 
common  but  noxious  couch-grass  is  another  familiar  ex- 

E  4 


56 


DESCRIPTIVE    BOTANY. 


ample  of  the  kind,  equally  interesting  to  the  botanist, 
though  not  treated  with  a  like  consideration  by  the  agri- 
culturist 

(64.)  Tubers. — Some  subterranean  stems  or  branches 
terminate  in  swollen  nodosities,  analogous  to  those  which 
we  have  described  as  formed  on  the  roots  of  some 
plants  (art.  40.).  The  common  potato  (fig.  48.)  is  a 


familiar  example  of  this  kind.  These  are  called  "  tubers," 
and  form  magazines  of  nutriment  which  serve  for  the 
development  of  the  buds  or  "  eyes,"  seated  upon  their 
surface.  In  general,  the  distortions  produced  by  the 
formation  of  the  tuber,  destroy  the  symmetry  which  the 
buds  on  the  surf  ace  of  this  portion  of  the  stem  would  other- 
wise exhibit,  in  their  mode  of  arrangement ;  but  still  they 
may,  in  many  cases,  be  observed  to  follow  a  spiral 
course,  characteristic,  as  we  shall  hereafter  see,  of  the  dis- 
position of  the  leaves.  In  one  peculiar  variety  of  this 
tuber,  termed  the  "  pine-apple  potato,"  this  disposition 
of  the  buds  is  very  striking ;  each  is  subtended  by  a 
swollen  projection  which  represents  the  base  of  the 
leaf-stalk,  in  whose  axil  we  may  consider  it  to  have 
been  formed.  In  turnips,  radishes,  &c.,  this  tuberous 
development  originates  in  the  lowest  portions  of  their 
stems,  which  are  placed  either  wholly  or  partially 
below  ground ;  whilst  in  the  Kohl-rabbi  (a  variety  of 


SECT.   I.          OKGANOGRAPHY    AND    GLOSSOLOGY. 


57 


cabbage),  the  effect  is  produced  on  a  part  of  the  stem 
which  is  entirely  above  ground. 

(6'5.)  Bulbs.  —  The  buds  of  some  plants  are  subject 
to  a  peculiar  modification.  Instead  of  expanding  into 
branches  and  leaves,  in  the  usual  way,  the  rudimentary 
parts  of  which  they  consist,  become  depositaries  of 
nutriment,  —  swelling  preternaturally,  but  still  conti- 
nuing in  a  condensed  or  undeveloped  form.  In  this  state 
they  are  termed  "  bulbs ;"  and  are  sometimes  found 
on  the  stems,  and  in  the  axils  of  the  leaves,  as  in  the 
Orange-lily  (Lilium  bulbiferum) ;  and  even  among 
heads  of  flowers,  as  in  a  variety  of  the  common 
onion.  The  bulbs,  however,  with  which  we  are  most 
familiar,  as  of  lilies,  hyacinths,  onions,  &c.,  contain 
the  whole  of  the  ascending  organs  of  these  plants  in 
a  condensed  form,  with  their  roots  proceeding  from  a 
flat  disk  below  (fig.  49.).  The  chief  differences  among 


bulbs  depend  upon  the  rudimentary  leaves  of  which 
they  are  composed,  being  either  in  the  form  of  succulent 
or  fleshy  scales  (a),  as  in  the  lily ;  or  in  concentric 
coats  (b)  which  completely  surround  the  axis,  as  in 


58  DESCRIPT1YK    BOTANY.  PART  I. 

the  onion  ;  in  the  latter  case,  also,  some  of  the  outermost 
lamina:  are  thin  and  membranous.  The  young  bulbs, 
or  "cloves,"  as  gardeners  term  them,  are  produml.  as 
we  should  expect,  by  the  development  of  fresh  buds 
in  the  axils  of  the  scales  or  laminse  of  the  old  bulb. 

(66.)  Cormiw.  —  The  name  of 
"  cormus,"  is  given  to  the  swollen 
base  of  some  stems  of  mono- 
cot  yledonous  plants,  or  rather  to 
the  condensed  state  of  the  whole 
stem  {fig-  50.)  ;  which  is  deve- 
loped underground,  and  assumes 
the  general  appearance  of  a  coated 
bulb,  as  in  Crocus  and  Colchicum, 
where  it  is  sometimes  erroneously 
termed  a  "  solid  bulb ;"  or  else  it 
resenfbles  a  tuber,  as  in  the  common 
Arum  maculatum. 

(67.)  Affinity  of  Bulb  to  Tuber.  —  There  is  evidently 
a  great  affinity  between  the  tuber  and  the  bulb ;  each 
consisting  of  the  same  organs,  peculiarly  modified,  and 
adapted  to  analogous  purposes.  In  the  tuber,  the  de- 
position of  nutriment  has  taken  place  mainly  in  the  stem, 
whilst  the  leaves,  having  received  none,  have  disap- 
peared. But  in  the  bulb,  on  the  other  hand,  the  leaves 
have  generally  received  the  greatest  portion  of  the 
deposited  nutriment,  whilst  the  stem  is  slightly,  or  not 
all,  distended.  This  affinity  is  strikingly  exemplified 
by  the  little  tubers  which  are  sometimes  produced  on 
the  stalks  of  potatoes,  and  which  are  evidently  modi- 
fications of  the  buds  in  the  axils  of  their  leaves ;  the 
bulbs  on  the  stalks  of  the  orange-lily  alluded  to  in 
art.  64.,  are  equally  modifications  of  the  leaf-buds  of 
that  plant. 

(68.)  Appendages  to  the  Stem.  —  The  various  organs 
which  we  have  just  been  describing,  ought  rather  to  be 
considered  as  "modifications,"  of  certain  parts  of  the 
stem,  than  as  distinct  appendages  to  it :  but  we  have  now 
to  mention  a  long  list  of  organs,  situate  on  some  part  or 


SECT.   I.  ORGANOGRAPHY    AND    GLOSSOLOGY.  59 

other  of  its  surface,  which  are  properly  styled  "  ap- 
pendages" to  the  stem  or  ascending  axis.  Diversified  as 
these  organs  are  in  their  forms,  and  even  in  their  func- 
tions, they  may  all  be  considered  as  modifications  or 
transformations  of  one  fundamental  organ,  of  very  ge- 
neral, though  not  universal  occurrence,  viz.  the  leaf. 
In  order  to  obtain  a  general  notion  of  the  varied  appear- 
ances assumed  by  this  organ,  we  must  suppose  that  some 
of  the  materials  which  compose  the  stem  have  become 
detached  from  the  rest,  and  are  then  given  off  at  the 
surface,  in  the  form  of  distinct  organs. 


CHAP.  III. 

NUTRITIVE  ORGANS  —  continued. 

LEAVES,  SIMPLE  AND  COMPOUND  (69.).  —  VERNATION  (71.). 
FORMS  OF  LEAVES  (74. ).  PHYLLODIA  (75.).  TRANS- 
FORMATION OF  LEAVES  (78.).  VENATION  (81.). DIS- 
POSITION AND  ADHESION  (82.).  NUTRITIVE  ORGANS  OF 

CRYPTOGAMIC    PLANTS    (84.). 

(69.)  Leaves.  —  IN  by  far  the  greater  number  of 
plants,  these  organs  consist  of  thin  flattened  expansions, 
in  which  the  vascular  portion,  termed  "  veins/'  or 
"  nerves,''  is  arranged  in  a  kind  of  network,  having  the 
interstices  rilled  up  with  cellular  tissue  — here  termed  the 
"  parenchyma  ;"  and  the  whole  is  invested  with  the 
epidermis.  In  Dicotyledons,  the  vessels  proceed  imme- 
diately from  the  medullary  sheath.  In  a  few  rare  ex- 
amples, as  in  the  Dracontium  pertusum  (fig.  51.),  the 
parenchyma  imperfectly  fills  up  the  interstices  between 
the  veins,  and  large  holes  are  left  through  the  leaf  (a). 
In  the  most  curious  and  interesting  Hydrogeton  fenes- 
tralis  (fig.  52.),  an  aquatic  of  Madagascar,  the  paren- 


60 


DESCRIPTIVE    BOTANY. 


chyma  is  so  little  developed,  that  the  leaf  appears  to 
consist  entirely  of  the  veins,  and  resembles  those  skeletons 
of  leaves  which  are  sometimes  pre- 
pared by  maceration  in  water.  A 
large  proportion  of  trees  produce 
fresh  leaves  in  the  spring,  which 
afterwards  fall  in  the  autumn  ; 
such  are  termed  "  deciduous,"  in 
contradistinction  to  "  evergreens," 
which  are  never  entirely  divest- 
ed of  leaves.  No  plant,  how- 
ever, retains  its  leaves  for  more 
than  two  or  three  years ;  but  as 
the  leaf-fall  in  evergreens  is  par- 
tial, consisting  perhaps  of  one 
half  or  one  third  at  a  time,  there 
are  always  a  sufficient  number  left 
on  the  tree,  to  keep  it  clothed  with 
perpetual  verdure. 

In  succulent  plants,  the  ves- 
sels which  quit  the  stem  to  form  the  leaf,  diverge  in 
different  planes,  and  the  leaves  in 
consequence  consist  of  solid  fleshy 
masses  of  cylindrical  and  other  solid 
forms,  instead  of  flattened  laminae. 

The  complete  leaf  consists  of 
two  parts  :  the  leaf- stalk,  or 
"  petiole  ;"  and  the  expansion, 
or  "  limb."  There  is  often  an  ^^-t  CV 
alteration  in  the  colour  and  tex- 
ture of  the  petiole  at  the  point 
where  it  is  attached  to  the  branch, 
and  sometimes  a  slightly  swollen 
protuberance.  This  is  termed  an 
"  articulation  ; "  and  it  is  at  that 
part  that  a  disunion  takes  place  at  the  period  of 
leaf-fall,  and  a  "  scar "  is  left  upon  the  stem.  But 
where  no  articulation  exists,  the  withered  petiole  re- 


'/®$OT% 

•fffi  PrrW 

I-  rr  .1  r-^i  ri 

f-  trCCr 


SECT.  I.         ORGANOGRAPHY    AND    GLOSSOLOGY. 


61 


mains  a  long  time  attached  to  the  stem  before  it  falls  off 
and  leaves  the  scar.  Some  petioles  are  termed  "  clasp- 
ing," when  they  are  attached  for  some  extent  around  the 
stem ;  and  they  form  "  sheaths/' 
when  they  wholly  embrace  it,  as  in 
the  grasses.  In  some,  a  membranous 
limb-like  expansion  occurs  on  each 
side  of  the  petiole,  which  is  then  said 
to  be  "  winged."  The  limb  in  gene- 
ral is  similarly  constructed  on  each 
side  of  the  midrib  ;  but  to  this  there 
are  striking  exceptions,  as  in  the  leaves 
of  Begonia  (fig.  53.),  Epimedium, 
&c. 

(70.)  Simple  and  compound  Leaves. 
—  The  most  obvious  classification  of 
leaves,  is  in  to  "simple"  and  "compound."  The  limb  of  the 
former  consists  of  one  piece 
only  (fig.  54.),  which  may 
either  be  entire  at  the  mar- 
gin (a),  or  variously  indent- 
ed (6)  ;  and  attached  to  the 
stem  with  or  without  the  in- 
tervention of  a  petiole :  in 
the  latter  case  it  is  said  to 
be  "  sessile."  Compound 
leaves  (fig.  55.)  are  made  up 
of  one  or  more  pieces,  called 
"  leaflets,"  each  of  which 
is  articulated  to  the  petiole  ; 
and  the  degree  to  which  it  is 
compounded,  depends  upon 
the  number  of  times  in  which 
the  main  petiole  branches,  before  the  leaflets  are  attached 
to  its  ramifications.  Hence  we  have  the  simply  (a), 
doubly,  triply  (6),  &c.  compound  leaf. 

(71.)    Venation  or  Nervation  of  Leaves. — The  distri- 
bution of  the  vascular  tissue  through  the  limb  of  the 


62 


DESCRIPTIVE    BOTANY. 


PART  I. 


leaf  is  termed  its  "venation"  or  "nervation"  —  the 
course  of  the  vessels  bearing  some  resemblance  to  the 
distribution  of  veins  and  nerves  in  certain  parts  of  the 
animal  structure.  The  bundles  of  vessels  which  com- 
pose the  veins,  maintain  a  nearly  parallel  course  in 


their  passage  through  the  petiole,  and  are  closely  con- 
densed together ;  but  on  arriving  at  the  limb,  they 
separate,  and  are  distributed  in  various  ways  ;  all  of 
which  may,  however,  be  referred  to  one  or  other  of 
two  classes,  called  the  "  angulinerved,"  and  the  "  curvi- 
nerved,"  disposition.  The  former  of  these  is  eminently, 
though  not  exclusively,  characteristic  of  dicotyledonous 
plants  ;  and  the  latter  equally  predominant  among  such 
as  are  monocotyledonous. 

(72.)  Angulinerved  Leaves. — In  these,  the  vessels, 
after  entering  the  limb,  either  branch  off  immediately 
from  the  apex  of  the  petiole,  arid  form  several  strong 
veins ;  or  they  form  one  midrib,  from  which  secondary 
veins  are  given  off  on  either  side,  and  which  at  their 
origin,  maintain  a  straight  course  for  a  short  distance. 


SECT.  I.          ORGANOGBAPHY    AND    GLOSSOLOGY.  0.3 

however  they  may  afterwards  be  curved  (fig.  54.).  The 
angle  at  which  they  diverge  is  generally  acute,  towards 
the  apex  of  the  limb,  and  their  mode  of  ramification 
bears  a  resemblance  to  the  branching  of  trees.  This 
kind  of  nervation  may  be  subdivided  into  four  sub- 
ordinate groups,  which  are  important  in  regulating 
the  conditions  upon  which  some  of  the  principal  forms 
of  leaves  depend. 

(a.)  Penninerved. — Here  the  midrib  is  continued  to 
the  extremity  of  the  limb,  and  the  primary  nerves 
branch  off  from  it  on  either  side,  throughout  its  whole 
length  (fig.  56.).  The  breadth  of  the  leaf  is  chiefly 
regulated  by  the  size  of  the  an-  56 
gle  at  which  the  nerves  quit  the 
midrib,  being  narrower  in  pro- 
portion as  this  angle  is  more 
acute.  The  contour  of  the  limb 
is  also  defined  by  the  proportion 
which  the  different  nerves  bear 
to  each  other  on  quitting  differ- 
ent parts  of  the  midrib.  This 
form  of  nervation  is  by  far  the 
most  usual,  and  regulates  the 
structure  of  many  compound 
leaves.  In  these  the  main  petiole 
may  be  likened  to  the  midrib  of  a 
simple  leaf,  with  its  parenchyma 
only  partially  developed  round  the  secondary  nerves,  so 
that  it  becomes  split  up  into  separate  leaflets.  Compound 
leaves  are  pinnate,  bi-,  tri-,  &c.  pinnate,  according 
to  the  degree  of  subdivision  to  which  the  branching  of 
the  petiole  extends.  But  when  the  limb  of  a  leaf  is 
merely  subdivided,  without  being  completely  separated 
into  distinct  leaflets,  the  terms  applied  to  designate  the 
degree  of  subdivision  are  "  pinnatifid,"  "  bi-,  tri-,  &c. 
pinnatifid."  In  pinnate  leaves,  the  leaflets  are  fre- 
quently arranged  in  pairs,  on  opposite  sides  of  the 
petiole.,  with  or  without  a  terminal  leaflet. 


64  DESCRIPTIVE    BOTANY.  PART  1. 

The  intimate  relation  which  subsists  between  simple 
and  compound  leaves,  is  well  exemplified  in  some 
cases,  where  two  or  more  contiguous  leaflets  become 
grafted  together,  and  thus  reduce  the  usual  extent  of 
the  subdivision  to  a  lower  degree.  This  may  be  often 
seen  in  some  species  of  Gleditsia  (fig.  57-),  where  dif- 


ferent parts  of  the  same  leaf  assume  a  simply,  doubly,  or 
triply  compound  character.  It  is  difficult  in  some  cases 
to  decide  whether  a  leaf  should  be  considered  compound, 
or  simple  ;  and  it  is  usual  to  account  all  leaflets  which 
are  articulated  to  the  petiole,  as  parts  of  a  compound 
leaf,  even  though  they  may  be  reduced  to  one  in  num- 
ber, as  in  the  case  of  the  orange ;  but  those  which  are 
not  articulated,  even  though  they  may  be  otherwise  dis- 
tinctly formed,  are  considered  as  subdivisions  only  of  a 
simple  leaf.  Where  these  articulations  exist,  each 
leaflet  falls  separately  from  the  main  petiole,  when 
this  also  becomes  detached  from  the  stem  ;  but  where 
the  leaflets  are  not  articulated  to  the  petiole,  the  limb 
falls  entire,  with  the  petiole  attached. 

(b.)  Palminerved. — Instead  of  forming  a  midrib,  the 


SECT.  I.          ORGANOGRAPHY    AND    GLOSSOLOGY. 


65 


58 


vessels  here  diverge  from  the  extremity  of  the  petiole 
into  several  (usually  three  or  five)  equally  strong  nerves, 
which  are  afterwards 
subdivided  in  a  penni- 
nervedmanner(^.58.). 
The  whole  system  of 
venation  here  resembles 
that  of  a  compound 
penninerved  leaf,  whose 
leaflets  have  become 
grafted  together  into 
one  limb.  This  nerv- 
ation stamps  the  character  of  the  palmate  leaves. 

(c.)  Peltinerved. — The  vessels  in  this  case  diverge  in 
a  plane  which  is  inclined  to  the 
direction  of  the  petiole ;  and  in 
proportion  as  the  angle  of  inclin- 
ation approaches  a  right  angle,  the 
limb  of  the  leaf  is  more  symmetri- 
cally formed,  round  the  point  where 
the  petiole  is  attached  to  it  (fig.  59-). 
Where  the  angle  is  acute,  the 
nerves  which  diverge  on  the  side 
nearest  to  the  petiole  are  the  short- 
est, and  the  limb  is  proportion- 
ably  contracted.  From  this  nervation  originate  the 
peltate  leaves. 


59 


(d.)  Pedalinerved. — In  this  case  there  is  no  decided 


66 


DESCRIPTIVE    BOTANY. 


midrib,  but  the  vessels  diverge  in  two  strong  lateral 
nerves,  from  which  branches  are 
given  off,  on  that  side  only  which  is 
towards  the  apex  of  the  leaf  (fig.  60.). 
This  form  of  nervation  is  far  less  com- 
mon than  either  of  the  preceding.  The 
pedate  leaves  are  thus  nerved. 

(73.)  Curvinerved  Leaves.  —  In 
these  leaves,  the  nerves  are  more  or 
less  curved  at  their  base,  or  point 
whence  they  diverge ;  and  they  retain 
a  certain  parallelism  among  them- 
selves, as  well  as  a  simplicity  of 
structure,  which  very  readily  distin- 
guishes them  from  the  angulinerved 
leaves.  This  mode  of  nervation  may 
be  subdivided  into  two  classes. 

(a.)  Convergent.  — Where  several 
nerves,  curved    at    the   base  of    the 
limb,  run  nearly  parallel  to    its  margins,  and  proceed 
gradually  converging  towards  its  apex 
(fig- 6l.). 

(b.)  Divergent. — Where  the  ves- 
sels collectively  form  a  midrib  to 
the  limb,  and  numerous  simple  nerves 
diverge  from  it  in  a  pinnate  manner, 
but  maintain  nearly  a  parallel,  or  some- 
what curvilinear  course  (fig.  62.). 

(74.)  Forms  of  Leaves. —  It  will 
easily  be  understood,  how  very  much 
varied  the  forms  of  leaves  may  be- 
come. Their  contour  is  principally 
determined,  by  the  distance  to  which  the 
ramifications  of  the  nerves  extend ; 
and  the  shape  of  the  margin  is  modi- 
fied, by  the  degree  to  which  the  paren- 
chyma is  developed  between  them. 
Thus,  in  ovate  leaves  (fig.  63.),  the 
margin  of  a,  which  is  only  slightly  indented,  is  said  to 


SECT.   I.  ORGANOGRAPHY    AND    GLOSSOLOGY.  67 

be  "  toothed ;"  that  of  b,  which  has  the  indentations 
deeper,  is  called  "divided/'  or  "incised;"  and  c  is 
termed  "  partite."  Where  the 
limb  is  almost  severed  into  se- 
parate segments,  each  portion, 
when  tolerably  large,  is  also  termed 
a  "lobe,"  and  the  angle  at  which 
the  lobes  meet  is  the  "  sinus."  ) 
When  the  teeth  are  large  and 
regular,  they  are  termed  "  ser- 
ratures ; "  and  when  these  are 
rounded,  ."  crenations."  Thus, 
a  vast  number  of  terms,  most  of  a  b  c 

them  of  very  simple  construction,  and  easy  compre- 
hension, are  used,  for  expressing  a  variety  of  different 
modifications,  by  which  these  and  other  organs  of  planst 
may  be  accurately  defined. 

The  leaves  on  different  parts  of  the  same  plant  often 
differ  in  shape  ;  and  even  those  on  the  same  part  are 
sometimes  subject  to  great  modifications,  according  as 
they  are  influenced  by  the  peculiar  circumstances  under 
which  they  are  developed.  Thus,  we  may  occasionally 
find  three  varieties,  among  the  radical  leaves  on  the  same 
plant  of  horse-radish  (Cochlearia  armoracia),  where  the 
marginal  indentations  vary  as  much  as  in  fig.  63.  In  ge- 
neral, however,  the  leaves  of  the  same  plants,  or  at  least  on 
the  same  parts  of  a  plant,  retain  a  sufficient  constancy 
in  their  character,  to  enable  us  to  use  them  for  the  pur- 
pose of  discriminating  between  species  which  are  very 
closely  allied.  It  would  not  be  in  character  with 
our  present  undertaking,  to  enter  more  minutely  into 
any  description  of  the  forms  of  leaves ;  but  we  recom- 
mend all  who  wish  to  pursue  this  subject  further,  and 
to  become  acquainted  with  those  technicalities  of  the 
science  which  are  necessary  for  the  purposes  of  accurate 
description  and  descrimination  of  species,  to  notice  the 
dependence  which  the  forms  of  leaves  possess  upon  the 
conditions  of  their  venation.  In  the  first  place,  they 
should  remark  the  general  contour  of  the  limb,  without 
F  2 


DESCRIPTIVE    BOTANY. 


PART  I. 


reference  to  its  marginal  incisions ;  then  they  should 
consider  the  character  of  the  incisions,  and  the  relation 
they  bear  to  the  disposition  of  the  veins.  In  com- 
pound leaves,  the  degree  to  which  the  subdivisions 
of  the  petiole  take  place  must  be  considered,  and  the 
analogy  noted,  which  exists  between  the  disposition  of 
the  partial  petioles  and  the  venation  of  simple  leaves. 
Thus  the  student  will  soon  learn  to  fix  in  his  memory 
the  numerous  modifications  of  form  which  leaves  pre- 
sent. 

(75.)  Phyllodium. — There  are  some  plants,  as  many 
of  the  acacias  of  New  Holland,  in  which  the  limb  of 
the  leaf  is  not  developed,  but  the  petioles  themselves  are 
laterally  compressed,  and  so  much  flattened  out  as  to 
assume  the  appearance  of  a  limb  ;  except  that  they  affect 
a  vertical  position  instead  of  a  horizontal  one,  and  that 
there  is  no  apparent  difference  between  their  two  sur- 
faces in  colour,  or  other  characters.  In  young  plants 


of  this  description,  however,  and  occasionally  also  in  old 
ones  which  have  been  freely  pruned,  we  may  observe  all 
the  intermediate  states  or  varieties  between  a  doubly 


SECT.  I.          ORGANOGRAPHY    AND    GLOSSOLOGY.  69 

compound  leaf  (fig.  64>.  a)  and  the  simply  expanded 
petiole  just  described  (i) ;  the  latter*  being  more  dilated 
in  proportion  as  the  leaflets  of  the  limb  are  fewer  in 
number.  These  flattened  petioles  are  termed  "phyl- 
lodia,"  and  the  character  of  their  venation,  corresponds 
very  closely  with  that 
of  the  curvinerved 
leaves  of  monocoty- 
ledonous  plants.  The 
non-development  of 
the  limb  is  also  com- 
mon in  some  species 
of  Monocotyledons, 
which  are  never- 
theless, capable  of 
producing  one.  The 
Sagittaria  sagittifolia 
(fig.  65.),  an  aquatic 
of  this  class,  has  the 
limb  developed  at  the  summit  of  those  leaves  only, 
which  reach  above  the  surface  of  the  water,  all  the  rest 
consisting  merely,  of  strap-shaped  expansions  of  the  pe- 
tioles. 

De  Candolle  considers  the  greater  number  of  sheathing 
leaves,  which  are  not  furnished  with  distinct  limbs,  to 
be  only  petioles ;  and  although  such  are  found  in 
several  Dicotyledons,  as  in  Ranunculus  gramineus,  La- 
thyrus  nissolia,  the  whole  genus  Bupleurum,  and  some 
others,  yet  they  are  more  especially  characteristic  of  Mo- 
nocotyledons, where  he  supposes  the  development  of  a 
true  limb  to  the  leaf  to  be  comparatively  rare ;  though 
it  certainly  occurs  in  the  Arum  tribes,  Sagittariae,  and 
some  others.  Some  limbless  petioles  are  cylindrical  and 
pointed  like  the  leaves  of  a  rush. 

(76.)  Foliaceous  Branches. — The  phyllodium  is  not 
the  only  substitute  which  nature  provides,  to  supply  the 
absence  of  a  perfect  leaf.  In  some  plants,  the  leaf  is  com- 
pletely abortive,  and  becomes  a  small  dry  scale,  incapable 
F  3 


70 


DESCRIPTIVE    BOTANY. 


of  performing  any  of  the  proper  functions  of  this 
organ.  In  these  cases,  the  branches  themselves  be- 
come flattened,  and  assume  the  appearance  of  leaves 
(fig.  66.).  In  the  com- 
mon butchers'-broom 
(  RIIXCHS  aculeatua),  and 
others  of  this  genus, 
the  flowers  are  seated 
in  the  middle  of  the 
upper  surface  (a)  of 
these  flattened  branches. 
In  the  genus  Xylophylla 
they  are  placed  round 
the  edges  of  similar  or- 
gans (6). 

(77.)  Stipules.  — 
At  the  base  of  some 
leaves,  and  on  each  side 
of  their  axils,  there  are 
appendages  of  a  foliaceous  character,  sometimes  resem- 
bling the  leaflets  of  compound  leaves,  and  sometimes  like 
small  membranous  scales  (fg.  67.  a  «).  These  are 


termed  "  stipules,"  and  are  very  characteristic  of  certain 
groups  of  plants,  but  are  entirely  wanting  in  others. 
They  are  never  found  on  any  Monocotyledons,  or  on 


SECT.  I.         ORGANOGBAPHY    AND    GLOSSOLOGY. 


71 


any    dicotyledonous    plant    where     the    petioles    are 
"  sheathing." 

(78.)  Spines.  —  Some  leaves,  which  do  not  freely 
develop  in  the  usual  manner,  assume  a  dry  hardened 
appearance,  and  pass  into  spines,  as  in  the  common 
furze;  just  as  some  abortive  branches  have  been  stated 
to  assume  the  character  of  thorns  (art  62.).  In  the 
berberry  (fig.  68.)  all  the  intermediate  states  (#)  be- 


tween a  well-developed  leaf  and  the  hard  spine,  may 
be  distinctly  traced,  on  vigorous  suckers  of  a  year's 
growth. 

(79-)  Tendril.  —  In  some  leaves,  the  midrib  is  pro- 
truded beyond  the  apex  of  the  limb,  in  the  form  of  a 
filamentous  chord,  and,  in  many  cases,  the  limb  entirely 
disappears,  and  the  whole  petiole  is  transformed  into 
what  is  termed  a  "  tendril."  These  organs  serve  to 
support  the  weak  stems  of  certain  plants,  by  twisting 
round  the  branches  of  others,  in  their  neighbourhood. 
F  4 


72 


DESCRIPTIVE    BOTANY. 


PART  I. 


In  \hcLathyrus  aphaca  (fig.  6*9.) 
all  the  leaves  become  tendrils, 
except  the  first  pair  in  the 
young  plants,  which  are  com- 
pound, and  have  two  or  three 
pairs  of  leaflets.  Occasion- 
ally an  odd  leaflet  (6)  is  de- 
veloped on  the  tendrils,  in  a 
later  stage  of  growth,  which 
further  indicates  the  origin  of 
the  organ  on  which  it  is  seated. 
A  provision  is  made  for  sup- 
plying the  want  of  leaves  in  this 
plant,  by  an  unusual  development  of  the  stipules  (a), 
which  are  so  large  that  they  might  readily  be  mis- 
70 


taken  for  real  leaves.  All  tendrils,  however,  do  not 
originate  in  the  modification  of  the  leaf;  but  some 
are  derived  from  an  altered  condition  of  the  stipules,  as 
in  the  cucumber ;  others,  from  a  transformation  of  the 
branches  or  peduncles,  as  in  the  vine  (fig.  70.).  In 
fact,  they  may  result  from  any  of  the  caulinar  append- 
ages, which  become  lengthened  out  at  their  extremi- 


SECT.  I.          ORGANOGRAPHY    AND    GLOSSOLOGY.  TO 

ties  into  filiform  flexible  cords,  more  or  less  spirally 
twisted. 

(80.)  Pitcher.  —  Of  all  the  metamorphoses  which 
the  leaf  is  found  to  undergo,  the  singular  productions 
called  "  pitchers"  are  the  most  curious.  The  annexed 


cut  (fig.  71-)  represents  three  different  forms  of  these 
organs. 

(a.)  In  the  genus  Sarracenia,  nearly  the  whole  leaf 
resembles  a  funnel,  with  the  upper  extremity  crowned 
by  a  membranous  expansion,  tapering  to  a  point. 

(6.)  In  the  Nepenthes,  or  true  pitcher-plant,  the 
pitcher  (6)  is  placed  at  the  extremity  of  a  tendril,  ter- 
minating a  winged  petiole.  It  is  crowned  with  a  mem- 
branous lid,  which  is  closely  shut  in  the  early  stages  of 
its  growth,  but  is  afterwards  raised,  and  does  not  again 
close  the  aperture.  These  pitchers,  in  some  species, 
are  six  or  seven  inches  in  length,  and  have  the  lower 
portion  of  the  inner  surface,  of  a  glandular  structure, 
which  is  constantly  secreting  a  subacid  liquid.  In 
this  liquid  a  number  of  insects  are  continually  drowned ; 


DESCRIPTIVE    BOTANY. 


PART   1. 


and,  strange  as  the  idea  may  seem,  it  has  been  conjectured, 
that  the  providing  of  such  animal  manure  for  the  plant, 
is  one  object  which  these  singular  appendages  were  in- 
tended to  accomplish.  There  is,  certainly,  a  striking 
analogy  between  this  result,  and  the  still  less  equivocal 
object  effected  by  the  fly-traps  of  the  Dionaea,  to  which 
we  shall  have  occasion  to  allude  when  speaking  of  the 
irritability  of  plants. 

(c.)  In  the  Cephalotua  follicularis,  the  pitchers  (r) 
are  about  two  inches  long,  and  are  seated  round  die 
base  of  the  flower-stalk,  intermixed  with  the  radical 
leaves.  Though  so  much  smaller,  they  are  perhaps 
still  more  curious  and  striking  than  those  of  the  Ne- 
penthes. 

(81.)  Vernation  of  Leaves.  —  Before  the  leaves  ex- 
pand, they  are  compactly  folded  together  in  the  leaf-bud  ; 


and  the  various  modes  in  which  this  takes  place,  is  called 
their  "  vernation."  The  folds  or  plaits  either  lie  in  a 
longitudinal  direction,  parallel  to  the  midrib ;  or  they 
are  transverse,  so  as  to  bring  the  apex  and  base  towards 
each  other.  Different  terms  are  applied  to  the  various 
modes  of  vernation,  some  of  which,  however,  are  seldom 
employed  in  descriptive  botany.  The  appearances  re- 
presented in  the  annexed  cut  (fiy.  72.)  are  among  the 


SECT.  I.         OBGANOGRAPHY    AND    GLOSSOLOGY.  "5 

most  striking  and  important,  and  are  obtained  by 
making  a  trfensverse  section  through  the  leaf-buds  of 
different  plants :  a,  plicate  ;  b,  equitant  ;  c,  imbricate ; 
d,  involute  ;  e,  revolute ;  /,  obvolute ;  g,  circinate. 

(82.)  Disposition  of  Leaves.  —  Although  the  term 
"  radical  leaves,"  is  applied  to  those  which  are  seated 
close  to  the  ground,  and  appear  to  spring  from  the 
summit  of  the  root  itself,  yet  all  leaves  do,  in  fact, 
originate  upon  the  stem  or  branches.  In  a  general 
way  we  may  refer  their  disposition  to  one  or  other  of 
two  modes :  either  "  verticillate,"  when  more  than 
one  is  attached  to  the  stem  at  the  same  altitude,  or 
about  the  same  horizontal  plane  ;  or  " alternate,"  when 
they  are  so  dispersed  upon  the  stem  that  no  two  are 
seated  precisely  in  the  same  horizontal  plane.  When  the 
number  of  leaves  in  the  same  plane  does  not  exceed  two, 
and  these  lie  on  contrary  sides  of  the  stem,  they  are  said 
to  be  "  opposite."  Leaves  are  frequently  so  arranged, 
one  above  another,  as  to  form  two  or  more  ranks  down 
the  stem ;  and  sometimes  they  appear  to  follow  the 
direction  of  spiral  lines  which  coil  round  it.  These 


different  appearances  receive  appropriate  names  in  de- 
scriptive botany,  which  it  does  not  fall  in  with  our 
plan  to  dilate  upon  ;  but,  before  we  have  concluded  this 


DESCRIPTIVE    BOTANY. 


PART   I. 


part  of  our  subject,  we  shall  enter  somewhat  more  fully 
into  the  details  of  a  theory,  which  has  been  proposed 
for  reducing  under  general  laws,  all  the  modes  which  are 
observable  in  the  distribution  of  foliaceous  appendages. 

(83.)  Adhesion  of  Leaves.  —  In  some  species  where 
the  leaves  are  opposite,  we  find  them  "  connate,"  or 
grafted  together  by  their  bases  (fig.  73.  a),  so  as 
completely  to  surround  the  stem  ;  and  in  other  species, 
where  they  are  alternate,  and  without  a  petiole  (sessile), 
the  edges  at  the  base  of  the  limb  extend  round  the 
stem  (6),  and  are  united  together.  Both  these 
cases  are  termed  "  perfoliate  ; "  the  stem  seeming  as  it 
were  to  penetrate  the  leaf.  In  some  plants,  the  middle 
of  the  leaf  adheres  to  the 
stem,  through  a  greater 
or  less  extent,  whilst  its 
edges  are  free  (fig.  74.). 
The  leaf  is  here  said  to 
be  "  decurrent,"  and  the 
stem  "  winged." 

(84.)  Nutritive  Organs 
of  Cryptogamic  Plants. — 
In  art.  $6.  we  have  al- 
ready stated  nearly  all 
that  it  will  be  necessary  for 
us  to  mention  respecting 
the  organs  of  cryptogamic 
plants ;  a  more  particu- 
lar account  would  involve 
us  in  descriptive  details, 
which  belong  rather  to 
the  department  of  phytography  and  systematic  botany, 
with  which  we  do  not  profess  to  interfere.  The  higher 
tribes  of  these  plants,  contained  in  the  division  "  Duc- 
tulosae/'  have  green  expansions,  much  resembling  leaves 
in  their  general  appearance,  and  like  them  possessing 
stomata;  but  differing  from  them  very  considerably  in 
some  respects,  especially  in  bearing  the  fructification 
upon  their  surface.  These  have  therefore  received  a 


SECT.  I.          ORGANOGRAPHY    AND    GLOSSOLOGY.  77 

distinct  appellation,  and  are  called  "  Fronds ;"  and  that 
part  of  a  frond  which  is  analogous  to  the  petiole,  is 


termed  the  "  Stipes."  In  some  cases,  as  in  the  tree 
ferns  of  tropical  climates  (fig.  75.),  the  bases  of 
the  decayed  fronds  form  a  tall  trunk,  which  is  termed 
their  "  caudex ;"  but  when  this  portion  creeps  upon  the 
ground,  as  in  the  humbler  forms  of  our  own  climate,  it 
has  received  the  name  of  "  rhizoma."  In  several 
tribes  the  fronds  possess  nerves,  but  in  many  cases  they 
are  composed  entirely  of  cellular  tissue.  The  vernation 
of  the  fronds  of  most  ferns  is  peculiar,  and  termed 
"  circinate "  (fig.  72.  #).  It  consists  in  having  all 
the  extremities  of  its  different  subdivisions,  as  well  as 


•s 


DESCRIPTIVE    BOTANY. 


the  whole  frond  itself,  rolled  inwards.  The  lower 
tribes  of  cryptogamic  plants,  included  in  the  division 
"  Cellulares,"  are  very  homogeneous  in  their  struc- 
ture, and  of  different  degrees  of  consistency  —  from 
highly  gelatinous,  to  tough  and  leathery.  When  they 
consist  of  a  plane  membranous  lamina,  as  in  the  Lichens, 
this  is  termed  a  "  thallus  "  (fig.  76.)  ;  but  when  more 


or  less  branched,  the  name  of  frond  is  retained.  They 
are  either  terrestrial,  aquatic,  or  marine.  Many  of 
them  are  parasitic,  seldom  green,  and  without  stomata. 


ORGANOOEAPHY    AND    GLOSSOLOGY.  79 


CHAP.  IV. 

REPRODUCTIVE    ORGANS. 

FLOWER    BUDS    (85.).  INFLORESCENCE MODES    OF    (86.). 

FLORAL  WHORLS PERIANTH   (92.). GLUMACEOUS    FLOWERS 

(9fi.). STAMENS      AND      PISTILS      (97.).  DISK      (101.). 

FLORAL   MODIFICATIONS    (102.).  ESTIVATION    (104.). 

(85.)  Flower  Buds. — NUMEROUS  examples  are  perpetually 
occurring,  in  which  the  attentive  observer  of  nature  may 
catch  a  glimpse  of  the  mysterious  connection  which 
subsists  between  the  organs  of  nutrition  and  reproduction, 
in  plants.  Instances  continually  present  themselves,  of 
flowers  whose  separate  portions  are  singularly  charac- 
terised, by  possessing  an  intermediate  condition,  partly 
leaf- like,  and  partly  like  those  variously  coloured  append- 
ages which  constitute  the  blossom.  By  an  accurate  ex- 
amination of  these  and  other  "monstrosities,"  as  all 
deviations  from  the  ordinary  conditions  of  vegetation  are 
termed,  it  has  been  clearly  ascertained,  that  the  organs 
of  reproduction  and  nutrition  are  merely  modifications 
of  some  one  common  germ,  which  may  be  developed 
according  to  circumstances,  either  in  the  form  of  a 
flower-bud,  or  of  a  leaf-bud.  In  the  latter  case  we  have 
shown,  how  this  body  becomes  a  branch  and  leaves ;  and 
we  have  now  to  explain  the  conditions  and  characters  of 
those  several  organs  which  are  developed  from  the  flower- 
bud,  and  collectively  termed  the  "inflorescence."  It 
would  be  equally  erroneous  for  us  to  call  the  flower- 
bud  a  metamorphosed  state  of  the  leaf-bud,  as  to  say 
the  leaf-bud  was  an  altered  condition  of  the  flower-bud ; 
and  we  are  nearer  the  truth,  when  we  consider  each  of 
them  to  be  a  peculiar  modification  of  the  same  kind  of 
germ,  adapted  in  the  one  case  to  perform  the  functions 
of  nutrition,  and  in  the  other,  those  of  reproduction. 


SO  DESCRIPTIVE    BOTANY.  PART  I. 

Flower-buds  ought  consequently  to  make  their  appear- 
ance on  similar  parts  of  the  stem  and  branches  with  the 
leaf-buds,  viz.  in  the  axils  of  the  leaves ;  and  the  de- 
velopment of  each  will  present  us  with  analogous 
phenomena.  However  different  in  their  external  cha- 
racters, still  the  various  parts  of  the  inflorescence  must 
bear  a  strong  affinity  to  those  of  the  foliaceous  append- 
ages on  the  branch. 

(86.)  Inflorescence. —  In  this  term  we  include,  not 
merely  the  flower  which  proceeds  from  the  development 
of  the  flower-bud,   but  also  the  stalk  on  which  it  is 
placed,  and  any  of  those  other  various  appendages  upon 
it,  which  are  always  more  or  less  distinct  from  true  leaves. 
The  more  general  term  for  the  flower-stalk  is  "  pedun- 
cle," but  the  term    "  pedicel  "  is  also  used    in    a  re- 
stricted sense,  where  there  are  partial  flower-stalks  seated 
upon  a  common  peduncle.     The  flower-stalk  is  more 
or  less  dilated  at  the  apex,  when  there  are  several  flowers 
closely  crowded  upon  it,  and  without  distinct  pedicels, 
as  in  the  order  Composite.      Such   dilatations   of  the 
flower-stalks  receive  the  general  name  of  "  receptacles," 
but  other  terms  are  specially  applied  to  some  of  their  mo- 
difications.    The  foliaceous  appendages  on  the  peduncle, 
which  more  or  less  resemble  the  stem-leaves,  but  which 
are  also  sometimes  reduced  to  the   condition  of  mere 
scales,  are  called  "bractete."      The  flower  terminates 
the  pedicel,  and  is  composed  of  certain  foliaceous  ap- 
pendages,  which   are  still  further    removed  from  the 
character  and  condition  of  leaves,   than  the  bractete. 
The  analogy  which  exists  between  the  various  parts  of 
a  leaf-branch  and  those  organs  which  compose  the  in- 
florescence, is  very  often  exhibited  in  certain  monstrosities 
of  the  rose;  where  we  find  the  central  parts  of  the  flower, 
instead  of  assuming  their  usual  character,  become  deve- 
loped as  a  branch.      It   sometimes  happens  that  this 
monstrous  development  will  again  make  an  effort  to  pass 
to  the  state  of  a  flower,  and  then  the  central  parts  will 
a  second  time  assume  the  condition  of  a  branch.     In  the 
Water-avens  (Geum  rivale,  Jig.  77-)  this  description  of 


SECT.  I.         ORGAN06RAPHY    AND    GLOSSOLOGY. 


81 


monstrosity  is  particularly  frequent ;  and,  indeed,  it  may 
be  often  seen  in  many  other  flowers. 


77 


(87.)  Modes  of  Inflorescence. — From  what  we  have 
said,  it  will  be  evident  that  the  term  inflorescence,  is 
either  applied  to  the  appearance  presented  by  the  general 
disposition  of  all  the  flowers  on  a  plant  taken  collect- 
ively, or  it  is  confined  to  certain  groups  of  flowers 
which  are  found  on  different  branches ;  or,  lastly,  it 
is  restricted  to  solitary  flowers  produced  from  sepa- 
rate buds.  In  order  to  understand  the  general  law, 
which  regulates  the  distribution  of  flowers  under  every 
form  of  inflorescence,  according  to  the  vague  appli- 
cation of  this  term  in  descriptive  botany,  it  will  be 
well  to  consider  the  manner  in  which  we  may  conceive 
it  possible,  for  a  succession  of  buds  to  become  developed 
upon  the  main  stem,  or  any  of  the  branches.  Assuming 
any  bud  (fig.  78.)  from  which  the  stem  or  given  branch 
is  developed,  to  be  the  "primary"  bud  (No.  1.)  of 


DESCRIPTIVE    BOTANJT. 


PART  1. 


the  series  we  are  investigating,  then  "  secondary  "  buds 
(Nos.  2.)  are  developed  from  the  axils  of  the  leaves  or 
bractes;  and  when  these  become  branches,  "tertiary" 


buds  (Nos.  3.)  are  similarly  developed  from  them  ;  and  so 
on.  In  this  way  a  plant  may  be  considered  capable  of 
indefinitely  multiplying  the  number  of  its  branches,  and 
also  of  extending  them  to'  any  length,  by  the  continued 
development  of  the  terminal  bud  at  the  extremity  of 
each  of  them.  Trees  continue  to  develop  a  succession 
of  buds  in  this  manner  for  many  years  together,  without 
producing  flower-buds ;  but  some  trees,  and  all  herb- 
aceous plants,  soon  produce  flower-buds,  and  then  the 
branches  on  which  they  occur  are  abruptly  terminated. 
Now,  it  appears  to  be  a  general  rule,  that  when  the 
buds  of  one  order  cease  to  develop  as  branches,  by 
becoming  flower-buds,  then  the  buds  of  the  next  order, 
which  are  developed  round  the  axis  of  the  former,  like- 
wise terminate  in  flower-buds.  Thus,  if  No.  1.,  after 
developing  a  branch  and  leaves,  ultimately  becomes  a 
flower-bud,  then  every  bud  (Nos.  2,  3,'  4,  &c.)  which 
terminates  the  branches  developed  round  its  axis,  will 
also  ultimately  terminate  in  flowers.  Now,  in  the  com- 


SECT.  I.         ORGANOGRAPHY    AND    GLOSSOLOGY. 


83 


mon  definition  or  notion  of  Inflorescence,  we  either  in- 
clude only  a  certain  aggregation  of  branches,  all  of  which 
terminate  in  flowers,  or  else  we  include  one  or  more  of 
those  branches,  whose  terminal  buds  still  continue  to 
develop  as  leaf-buds,  without  ever  becoming  flower- 
buds.  It  has  been  supposed,  indeed,  that  there  are  two 
distinct  modes  of  inflorescence,  in  one  of  which  the 
terminal  bud  does,  and  in  the  other  it  does  not,  become 
a  flower.  But  this  depends  merely  upon  the  vague 
manner  in  which  we  include  under  our  definitions  of  in- 
florescence, a  greater  or  less  number  of  buds  of  different 
orders  of  development.  If  we  admit  a  bud  which  does 
not  terminate  in  a  flower,  to  be  the  primary  bud  in- 
cluded in  the  inflorescence,  then  we  have  what  has 
been  termed  the  "  Indefinite  inflorescence,"  because  the 
main  axis  continues  to  develop  indefinitely,  whilst  the 
lateral  buds  alone  terminate  in  flowers.  But  if  the  main 
axis,  of  what  we  choose  to  include  within  the  inflo- 
rescence, terminate  in  a  flower,  then  the  "  Terminal 
inflorescence"  is  the  result.  There  are  numerous  modi- 
fications of  both  these  kinds  of  inflorescence,  which  either 
depend  upon  the  disposition  of  the  leaves  or  bracteae,  in 
whose  axils  the  flower-buds  originate,  or  else  upon  the 
partial  abortion,  or  peculiar  de- 
velopment, of  some  or  of  all  the 
secondary,  tertiary  &c.  buds  ; 
and  also  upon  other  circum- 
stances. 

(88.)  The  Terminal  Inflores- 
cence. —  The  principal  axis  in- 
cluded in  this  inflorescence,  ter- 
minates in  a  flower-bud,  and  the 
secondary  buds  are  developed  in 
the  axil  of  each  leaf  or  brae  tea, 
situated  at  the  base  of  that 
portion  of  the  branch  which 
becomes  a  peduncle,  and  must 
therefore  be  placed  immediately  a 
between  a  leaf  and  aflower  (fig.  790- 
G  2 


second- 


8+  DESCRIPTIVE    BOTANY.  PART  I. 

ary  bud  is  not  developed,  the  inflorescence  must  consist 
of  a  solitary  flower  («).  If  the  leaves  are  placed  alter- 
nately on  the  axis,  the  peduncle  of  the  flower  will  bear 
a  single  bractea  at  its  base.  If  the  secondary  bud  is  de- 
veloped (ft  No.  2.),  it  will  terminate  in  a  flower  with  a 
bractea  at  the  bottom  of  its  peduncle,  bearing  a  ter- 
tiary bud  in  its  axil ;  and  this  (No.  3.)  may  develop 
like  the  former ;  and  so  on.  In  this  case,  all  the 
flowers  will  appear  to  stand  opposite  the  leaves  or 
bractea?,  upon  a  stem  which  seems  40  develop  inde- 
finitely ;  but  which  is,  in  reality,  composed  of  a  succes- 
sion of  branches  or  peduncles,  originating  from  different 
orders  of  buds.  Since  No.  1.  is  the  real  termination 
of  the  main  axis,  and  Nos.  2,  3,  &c.  are  further  and 
further  removed  from  it,  the  order  in  which  the 
flowers  expand  is  from  the  centre  outwards,  and  this 
has  in  consequence  been  termed  the  "Centrifugal  inflo- 
rescence." 

When  the  leaves  or  bracteae  are  opposite  or  verticillate, 
in  the  terminal  inflorescence,  this  is  called  a  "  cyme." 
When  each  secondary  bud  is  developed  from  the  axils  of 
a  pair  of  opposite  bractese,  and  the  tertiary  buds  origin- 
ate in  the  same  manner,  and  so  on,  the  cyme  is  styled 
"  dichotomous"  (fig.  80.  a).  If  there  be  a  whorl  of  three 


bractese,  the  cyme  is   "  trichotomous,"  &c.     If,  how- 
ever, one  bud  only  is  developed    in  the  dichotomous 


SECT.  I.          ORGANOGRAPHY    AND    GLOSSOLOGY. 


85 


cyme,  and  always  on  the  same  side  of  the  axis,  it  as- 
sumes a  peculiar  character,  termed  "  scorpioidal"  (6). 

(89-)  Indefinite  Inflorescence. — Here  the  terminal 
bud,  of  the  main  axis  included  in  the  inflorescence,  con- 
tinues to  develop  as  a  leaf-bud,  until  sooner  or  later  it 
is  exhausted,  and  the  branch  stops ;  but  it  does  not  pass 
to  the  condition  of  a  flower-bud.  If  we  first  consider 
the  case  where  the  leaves  are  alternate,  then  the  second- 
ary buds  in  the  axils  of  the  leaves  or  bracteae  may  either 
become  flowers  immediately  (fig. 81.  a);  or  they  may  be 


1 


partially  developed  as  branches  (ft)  which  give  rise  to 
tertiary  buds  ;  and  these  may  become  flowers,  or  branch 
in  the  same  way  as  the  secondary  buds.  When  the 
secondary  buds  become  flowers,  without  previously 
branching  (a),  the  inflorescence  is  termed  a  "  raceme," 
or  "  cluster,"  provided  each  flower  has  a  pedicel ;  but 
it  is  called  a  "  spike,"  if  the  flowers  are  sessile,  or 
without  pedicels.  Where  the  secondary  buds  become 
branches,  bearing  flowers  produced  from  tertiary  buds, 
the  raceme  is  called  "  compound"  (6).  A  few  of  the 
subordinate  varieties  of  these  forms  may  hei'e  be  noticed. 
In  such  plants  as  the  willow,  hazel  (fig.  82.),  and 
o  3 


86 


DESCRIPTIVE    BOTANY. 


PART  I. 


oak,  the  peculiar  spike  in  which  the  flowers  are 
arranged  is  termed  a  "  catkin."  In  the 
tribe  to  which  the  common  arum  belongs 
(Aroidea-^),  the  fleshy  mass  which  forms 
the  axis  round  which  the  flowers  are 
aggregated  in  a  spike,  is  termed  the  "spa- 
dix"  (fig.  88.  6).  The  small  spikes  in 
which  the  flowers  of  grasses  are  aggre- 
gated, are  termed  "spikelets"  (fig,  95. 
c) ;  and  these,  again,  are  arranged  round 
a  common  axis  into  a  compound  spike. 

In  this  kind  of  inflorescence,  those 
secondary  buds  which  are  seated  lowest 
on  the  main  axis  are  the  first  formed, 
and  their  flowers  expand  the  earliest. 
As  these  are  also  the  outermost,  with 
respect  to  the  terminal  bud,  the  order 
of  expansion  is  from  the  circumference 
inwards,  or  contrary  to  that  which  takes 
place  in  the  terminal  inflorescence ;  and  hence 
has  been  called  the  "  Centripetal  inflorescence." 

When  the  leaves  are  ver- 
ticillate,  the  secondary  buds 
may  either  become  flowers,  or 
produce  branches,  on  which 
buds  of  a  lower  order  be- 
come flower-buds.  This  kind 
of  inflorescence  is  generally 
called  "  whorled,"  and  is  either 
simpleor  compound  (fig.83.). 

(90.)  Modifications  of 
Inflorescence.  —  It  will  be 
seen  from  what  has  been 
said,  that  the  application  of 
the  term  "  inflorescence,"  is 
as  indefinite  as  the  use  of 
the  word  "  organ,"  which 
we  equally  employ,  to  signify 
the  several  parts  of  a  plant,  as  well  as  the  subordinate 


SECT.  I.          ORGANOGRAPHY    AND    GLOSSOLOGY. 


87 


portions  of  which  those  parts  themselves  are  composed. 
And  thus,  in  some  cases,  we  term  a  single  flower  the 
inflorescence ;  in  others,  an  aggregation  of  flowers ;  or 
even  include  some  buds  which  produce  no  flowers. 
Perhaps  we  might  find  terms,  which  would  express 
more  definitely  the  different  orders  of  buds,  included 
in  our  notion  of  inflorescence :  and  then,  the  flowers 
of  all  terminal  inflorescences  would  be  subordinate  to 
buds  of  the  first  order ;  whilst  the  flowers  of  those 
which  are  styled  indefinite,  would  commence  only  from 
buds  of  a  second,  third,  &c.  order.  Each  kind  of  inflo- 
rescence might  be  considered  as  simple,  or  as  doubly, 
triply,  &c.  compound,  according  as  one  or  more  orders 
of  buds  were  developed  in  the  form  of  flowers.  It 
might  happen,  that  a  terminal  inflorescence,  in  which 
several  orders  of  buds  were  developed  (as  fig.  79-)> 
would  contain  fewer  flowers  than  an  indefinite  inflo- 
rescence, in  which  one  order  only  (as  fig.  81.  a)  was 
developed.  Both  kinds  also  include  several  forms,  strik- 
ingly similar  in  their  general  appearance,  and  which, 
in  descriptive  botany,  have  received  the  same  names. 
Of  these  forms  we  may  enumerate  the  following  : 

"  Panicle."  —  When  the  se- 
condary, tertiary,  &c.  buds  are 
developed  on  long  peduncles  and 
pedicels,  so  that  the  flowers  are 
loosely  aggregated,  or,  as  it 
were,  scattered  round  the  axis 

(fig-  84.). 

"  Corymb."  — When  the  main 
axis  soon  terminates,  and  the 
secondary,  tertiary,  &c.  buds 
form  peduncles  of  such  lengths, 
that  the  flowers  which  terminate 
them  stand  at  nearly  the  same 
level.  The  peduncles  are,  of 
course,  of  different  lengths,  those  towards  the  summit 
being  the  shortest  (fig.  85.). 

"  Umbel/'  —  When  the  main  axis  is  so  contracted 
G  4 


88 


DESCRIPTIVE    BOTANY. 


between  the  bracteae,  that  all  the  secondary  buds  are 
crowded  together,  and  developed  from  one  point  at  its 


summit  (fig.  86.).  The  pedicels  are  of  the  same 
length,  so  that  all  the  flowers  stand  at  the  same  level, 
as  in  the  last  case.  When  several  small,  or  "partial" 


M 


umbels,  are  themselves  arranged  in  an  umbelliferous 
manner  round  a  common  axis,  the  inflorescence  is  called 
a  "compound  Umbel." 


SECT.  I.         OBGANOGRAPHY    AND    GLOSSOLOGY.  89 

An  umbellate  form,  may  evidently  result  also  from 
a  terminal  inflorescence,  where  the  leaves  are  whorled, 
and  the  secondary  buds  become  flowers  without  pro- 
ducing tertiary  buds.  It  often  happens  (as  in  the 
genus  Euphorbia)  that  the  main  axis  is  crowned  by  an 
umbel  of  this  description,  whilst  the  lower  part  pos- 
sesses the  character  of  a  raceme. 

"  Capitulum."  —  This 
form  bears  much  the  same 
relation  to  an  umbel,  that 
the  spike  does  to  the  ra- 
ceme ;  the  pedicels  of  the 
single  flowers  being  want- 
ing, or  scarcely  distinguish- 
able.  The  flowers  are,  in 
consequence,  crowded  into 
a  dense  head  (fig.  8?.)- 

(91.)  Bractea.  —  We 
have  said,  as  the  flower- 
bud  expands,  a  succession 
of  various  kinds  of  append- 
ages, which  depart  more  or  less  from  the  leafy  struc- 
ture, are  developed  round  the  peduncle,  and  that  all  of 
these  would  have  become  true  leaves,  if  the  bud  had 
been  impressed  with  the  character  of  the  leaf-bud. 
Of  these  appendages,  the  "bractese,"  as  we  stated 
(art.  86'.),  exhibit  the  closest  approximation  to  the 
leaf  itself,  and,  in  many  cases,  are  only  nominally  dis- 
tinguishable from  it,  by  their  position  alone.  In  general, 
however,  they  are  of  much  smaller  dimensions  than  the 
leaves,  and  are  often  reduced  to  mere  scales.  Some- 
times they  approach  the  appearances  presented  by  the 
parts  which  compose  the  flower,  and  are  brilliantly 
coloured.  In  the  "cone"  (fig.  137-)?  which  is  a 
modified  form  of  the  spike,  having  the  flowers  very 
closely  arranged  together,  the  bracteae  become  large 
scales.  These,  in  the  fir  tribe  are  coriaceous,  and  mem- 
branaceous  in  the  hop. 

When  the  bractese  are  arranged  in  a  distinct  whorl 


DKSCRIPTIVE    BOTANY. 


round  the  peduncle,  it  is  termed  an  "  involucrum ; " 
and  in  some  cases  they  cohere  by  their  edges,  and 
thus  form  a  single  piece.  Where  the  bractea,  or  rather 
involucrum,  is  very  large,  and  completely  envelopes  the 
flowers,  as  in  the  Aroideae,  it  is  called  a  "  spathe" 
(fig.  88.  a).  In  the  extensive  order 
Composite,  the  little  florets  are  crowded  on 
a  highly  dilated  receptacle,  as  in  the  com- 
mon daisy  and  dandelion ;  and  they  are 
closely  surrounded  by  an  involucrum 
(fig.  87.  «),  composed  of  many  bracteae, 
which  are  either  free,  or  adhere  together, 
and  the  whole  head  has  the  appearance  of 
a  single  flower.  The  cup  in  which  the 
acorn  is  placed,  is  an  involucrum,  com- 
posed of  several  whorls  of  bracteae,  all 
adhering,  and  blended  together  into  a  solid 
mass  (fig.  118.). 

(92.)  Floral  Whorls.  —  The  foliaceous 
appendages  which  succeed  the  bracteae  in 
the  order  of  development,  are  brought  close  together, 
by  the  non-extension  of  the  axis,  so  as  to  crown  the 
summit  of  the  flower-stalk  with  a  series  of  whorls, 
partaking  still  less  of  the  leafy  character  than  the  bractea? 
(art.  86.).  These  whorls  constitute  the  flower;  and 
the  portion  of  the  axis  on  which  they  are  seated,  is 
termed  the  torus,  which  bears  the  same  relation  to 
a  single  flower,  as  the  receptacle  does  to  a  head  of 
flowers. 

In  flowers  which  possess  the  greatest  number  of 
whorls,  such  as  those  of  the  natural  order  Ranuncu- 
laceae,  we  may  distinguish  four  different  kinds  of  organs; 
two  of  which,  composing  the  outermost  whorls,  are  col- 
lectively termed  the  "  perianth ; "  and  these  are  not 
essential  to  the  fertility  of  the  plant ;  but  the  two 
kinds  which  make  up  the  innermost  whorls,  are  abso- 
lutely requisite  to  secure  the  perfection  of  the  seed.  It  is 
not  necessary,  indeed,  that  both  the  latter  kinds  should 


SECT.  I.         ORGANOGRAPHY    AND    GLOSSOLOGY.  91 

be  found  in  the  same  flower,  or  even  in  different  flowers 
seated  on  the  same  individual  plant ;  but  unless  both 
exist,  and  can  be  subjected  to  a  mutual  influence,  the  fer- 
tility of  the  seed  is  never  secured.  A  more  accurate  notion 
of  these  several  whorls  may  be  obtained,  if  we  now  exa- 
mine the  blossoms  of  a  common  ranunculus  in  greater 
detail  (fig.  89-  a).  Here,  the  outermost  whorl  of  the 


perianth  consists  of  five  parts,  of  a  greenish  yellow 
colour,  and  is  sufficiently  distinguished  from  the  next 
whorl,  to  admit  of  its  receiving  a  specific  appellation  ; 
it  is  therefore  termed  the  "  calyx "  (5)  ;  whilst  its 
subordinate  parts  are  called  "  sepals."  The  five  parts 
which  compose  the  next  whorl  are  of  a  bright  yellow 
colour,  and  are  termed  "  petals "  (c),  or,  collectively, 
the  "  corolla."  The  calyx  rarely  consists  of  more  than 
one  whorl  of  sepals,  but  the  corolla  is  frequently  com- 
posed of  more  than  one.  Next,  within  these,  are 
several  whorls  of  "  stamens,"  one  of  which  is  repre- 
sented at  (rf).  These  are  the  fertilising  organs  of 
the  flower,  composed  of  threadlike  stems,  surmounted 
by  oval  cells,  or  pouches,  which  contain  a  fine  powder, 
named  pollen.  Lastly,  we  have  several  whorls  of 
"  carpels"  (e),  which  are  little  ovate  bodies,  containing 
the  "  ovule,"  or  young  seed.  The  carpels,  like  the 
sepals,  are  not  often  ranged  in  more  than  one  whorl, 
though  they  are  so  in  this  instance ;  but  the  stamens 
frequently  occupy  several.  When  the  carpels  adhere 


92  DESCRIPTIVE  BOTANY!  PART  i. 

together,  so  as  to  form  one  mass,  this  is  termed  a  com- 
pound "pistil;"  but  when  they  are  distinct,  as  in  the 
present  case,  each  forms  a  separate  pistil.  Having 
given  a  general  notion  of  the  various  parts  of  the 
flower,  we  must  now  enter  a  little  more  fully  into  a 
description  of  the  several  whorls,  and  mention  some 
of  the  numerous  modifications  which  they  present; 
also  premising,  that  although  it  is  not  necessary  for 
flowers  to  be  composed  of  all  the  four  kinds  of  organs 
here  enumerated,  and  that  some  contain  only  one  or 
other  of  the  two  innermost,  yet,  wherever  more  than 
one  kind  are  present,  these  always  maintain  the  pre- 
cise order  of  collocation,  which  we  have  stated  above 
—  the  calyx  outermost,  then  the  corolla,  next  the  sta- 
mens, and  the  carpels  in  the  centre. 

(93.)  Perianth.  —  In  the  bractece,  we  often  find  a 
striking  resemblance  to  the  leaf;  but  in  the  several  parts 
of  the  perianth,  this  becomes  so  much  slighter,  that  in 
most  cases  the  close  affinity  between  these  organs  would 
scarcely  be  acknowledged,  were  it  not  clearly  perceptible 
in  some  flowers ;  and  also  established  by  those  cases  of 
monstrous  development,  where  the  several  parts  of  the 
perianth  assume  a  leafy  appearance.  In  many  cases,  and 
especially  in  monocotyledonous  plants,  the  several  whorls 
of  the  perianth  so  nearly  resemble  each  other,  that  no 
distinction  can  be  drawn  between  calyx  and  corolla, 
and  the  separate  parts  are  described  as  "  segments  of 
the  perianth."  In  those  Dicotyledones  where  the  pe- 
rianth consists  of  a  single  whorl,  it  generally  assumes 
the  usual  characters  of  a  calyx ;  and  is  always  so  con- 
sidered by  most  modern  botanists,  though  Linnaeus  and 
others,  have  described  it  as  a  corolla,  in  many  species 
where  it  happens  to  be  coloured.  Stomata  exist  both 
on  the  calyx  and  corolla,  but  more  especially  on  the 
former. 

(94.)  Calyx. —  Although  the  calyx  very  frequently 
"  persists,"  —  or  remains  whilst  the  fruit  ripens,  after 
the  corolla  has  fallen,  —  it  is  in  some  instances  very 
fugacious.  The  sepals  frequently  cohere  by  their  edges 


SECT.  I.         ORGANOGRAPHY    AND    GLOSSOLOGY.  Q3 

into  a  tube,  and  the  calyx  is  then  "  monosepalous, " 
or  "  monophyllous,"  or  more  correctly  "  gamosepalous." 
In  proportion  as  this  cohesion  extends  from  the  base 
towards  the  apices  of  the  sepals,  the  several  modifi- 
cations which  it  presents  receive  different  appellations. 
It  is  termed  "  partite,"  when  the  cohesion  extends  but 
a  short  way;  "divided,"  when  it  reaches  about  half- 
way up;  "toothed,"  when  it  is  nearly  complete;  and 
"entire,"  when  the  sepals  are  completely  united  to  the 
very  summit.  In  this  last  case,  the  number  of  the 
sepals  can  only  be  ascertained  by  their  venation,  each 
separate  sepal  being  indicated  by  the  position  of  its 
midrib ;  but  in  the  other  cases,  which  are  most  usual, 
the  free  apices  of  the  sepals  readily  point  out  their 
number.  Some  sepals  are  so  firmly  united  by  their 
apex  into  one  piece,  that  no  separation 
takes  place  in  this  part,  as  the  corolla 
enlarges.  The  calyx  is  then  ruptured 
round  the  base,  or  transversely  across 
the  middle,  and  is  thrown  off  in  the 
form  of  a  little  cup,  as  in  Eucalyptus 
(fig-  90.).  When  the  cohesion  is  more 
perfect  between  some  sepals  than  others,  so  as  to  form 
two  lobes  to  the  calyx,  it  is  termed  ec  lipped."  An 
analogy  is  frequently  maintained  be- 
tween sepals  and  the  leaves,  in  such 
plants  as  bear  stipules.  This  is  indicated 
by  the  presence  of  little  scales,  re- 
sembling bracteae,  seated  on  the  outside 
of  a  monosepalous  calyx,  and  alternating 
with  the  sepals  themselves,  as  in  Poten- 
tilla  (fig.  91.). 

(95.)  Corolla.  —  The  petals  are  generally  even  less 
leaf-like  than  the  sepals,  more  highly  coloured,  and 
more  variously  modified  in  shape.  Like  the  sepals, 
they  are  either  free,  or  cohere  by  their  edges,  forming  a 
"monopetalous"  corolla.  In  many  cases,  the  petals  may 
be  divided  into  two  parts — the  "  claw,"  which  is  ana- 
logous to  the  petiole  of  the  leaf;  and  the  "limb,"  which 


9*  DESCRIPTIVE    BOTANY.  '      PART  I. 

corresponds  to  the  limb  of  that  organ.  By  the  cohesion 
of  the  claws,  a  tube  is  frequently  formed,  whilst  the 
limbs  continue  more  or  less  free,  and  appear  as  a  border 
round  the  top  of  it.  In  some  cases,  the  petals  adhere 
at  the  base  and  apex,  but  are  free  in  the  middle,  as  in 
Phyteuma.  An  irregularity  in  the  cohesion,  produces  a. 
lipped  corolla,  as  in  the  case  of  the  calyx.  We  will 
here  enumerate  a  few  of  the  most  important  forms 
which  the  corolla  assumes,  the  most  remarkable  of 
which  are  among  such  as  are  monopetalous. 

1.  Regular  monopetalous  Corolla.  —  Where  the 
several  parts  are  symmetrically  arranged  round  the 
axis,  the  forms  are  named  after  certain  appearances 
which  they  are  supposed  to  resemble ;  as  the  bell-shaped 
(fiy-  92.  u),  funnel-shaped  (6),  salver-shaped  (c), 
rotate  (d). 


2.  Irregular  monopetalous  Corollte.  —  Where  the 
petals  cohere,  but  one  part  of  the  corolla  is  differently 
modified  from  another;  as  in  the  "lipped"  or  "labiate" 
flower  (fig.  93.),  which  has  two 
lobes  forming  the  limb;  and  the  "  per- 
sonate" flower  (fig.  131.  a),  formed 
on  somewhat  the  same  plan,  but  where 
the  mouth  of  the  tube  is  closed.  In 
these,  and  in  other  cases  of  irregular 
monopetalous  corollse,  it  is  not  always 
easy  to  distinguish  the  precise  number 
of  petals  which  cohere  together,  al- 
though we  may  generally  do  so  by 
examining  the  venation,  or  by  observing  the  apices  of 


SECT.  1.         ORGANOGRAPHY    AND    GLOSSOLOGY.  95 

the   petals,   which  are  free,   and  project  beyond  the 
margin. 

3.  Irregular  polypetalous  Corollce. 
—  One  of  the  most  prominent  of 
this  class  is  the  "  papilionaceous" 
flower  (fig.  94.),  composed  of  five  pe- 
tals ;  which,  however,  are  not  always 
free  at  their  base ;  but  in  a  few  cases 
cohere  by  their  claws  into  a  tube. 
The  large  single  petal  is  termed  the 
ic  standard"  (a)  ;  the  two  lateral,  the 
"wings"  (6);  and  the  two  others, 
which  often  cohere  into  one,  form  the 
"  keel "  (c).  These  flowers  belong  ex- 
clusively to  certain  groups  of  the 
extensive  order  "  Leguminos*,"  of  which  beans  and 
peas  are  familiar  examples. 

There  is  a  vast  variety  among  the  irregular  poly- 
petalous corollae,  originating  in  peculiarity  of  shape, 
and  in  the  proportion  and  numbering  of  the  several  parts. 

(96.)  Glumaceous  Flowers. — The  grasses  ( Graminece) 
and  sedges  (Cyperaceai)  have  their  flowers  constructed 
in  so  peculiar  a  manner,  that  it  will  be  necessary  to 
describe  them  somewhat  more  particularly.  Their  peri- 
anth consists  of  membranous  scales  termed  "  glumes," 
which  are  referable  to  a  modification  of  bracteae,  rather 
than  of  those  more  or  less 
flaccid  and  foliaceous  organs, 
which  we  have  described  as 
sepals  and  petals.  In  the 
example  selected  for  fig.  95., 
there  is  a  pistil  (a),  com- 
posed of  an  ovarium  which 
contains  a  single  ovule>  and 
is  surmounted  by  two 
stigmas.  At  the  base  are  two 
scales.  There  are  three  sta- 
mens. These  parts  are  in- 
cluded between  two  glumes  (6),  one  of  which  is  towards 


96  DESCRIPTIVE    BOTANY.  PART  I. 

the  stalk,  or  "  rachis,"  on  which  the  flower  is  seated ; 
and  this  glume  appears  by  its  nervation  to  be  composed 
of  two  united  ;  this  is  further  indicated  by  a  little 
notch  at  its  apex.  The  other,  or  outermost  glume,  is 
furnished  with  a  bristle-shaped  projection  at  the  back, 
termed  an  "  awn."  Several  of  these  flowers  are  closely 
ranged  on  opposite  sides  of  a  stalk,  and  form  a  "  spike- 
let"  (c),  which  is  itself  contained  between  two  glumes 
at  the  base.  When  several  of  these  spikelets  are  ar- 
ranged alternately  on  the  main  rachis,  they  form  a  spike, 
as  in  wheat.  In  some  examples,  the  flowers  have  three 
glumes.  Some  flowers  are  solitary,  and  on  separate 
pedicels,  as  in  the  oat ;  and  the  lax  branched  inflorescence 
assumes  the  form  of  a  "panicle"  (fig.  84>.).  Some 
grasses  have  only  two  stamens,  and  some  have  only  one 
glume  at  the  base  of  each  spikelet. 

In  the  Cyperacese  (as  in  fig.  96.)  we  have  only  one 
glume  to  each  flower  (a).  The  >j  95 
pistil  (6)  is  inclosed  in  a  mem- 
branous bag  (at  a),  composed  of 
two  glumes  united.  The  stamens 
are  two  or  three,  as  also  are  the 
stigmas.  The  flowers  of  many  of 
the  Cyperacea:  are  unisexual,  and 
arranged  in  spikelets  and  spikes, 
much  in  the  same  way  as  in  the 
grasses.  These  two  orders,  although 
so  closely  allied,  are  readily  distinguishable ;  for  be- 
sides the  different  character  of  their  inflorescence,  the 
grasses  have  round,  hollow,  ar/tl  jointed  stems  (cw/m*), 
whilst  those  of  the  sedges  are  more  or  less  angular,  and 
solid. 

(97.)  Stamens. — These  organs  are  generally  com- 
posed of  two  parts :  the"  anther"  (fig.  97*  d),  which  bears 
an  analogy  to  the  limb  of  the  leaf,  and  is  a  sort  of  pouch 
containing  a  fine  powder  termed  the  "  pollen;"  and 
the  filament  (e)  or  stalk  upon  which  it  is  seated,  ana- 
logous to  the  petiole,  or  leaf-stalk.  The  latter  part, 
however,  is  sometimes  wanting,  and  then  the  anther  is 


SECT.   I.          OBOANOGRAPHY    AND    GLOSSOLOGY. 


9? 


consequently  sessile.  Sometimes  the  filaments  cohere,  and 

form  a  tube  round  the  carpels,  and  the  stamens  are  then 

termed    "  monadelphous  " 

(fig.  97.  a).      When  they 

cohere   into    two    separate 

bundles,   they   are   said  to 

be    "  diadelphous  ;"     and 

when  they  appear  in  more 

than  two,  "polyadelphous." 

In  some  orders,  but  more 

particularly  in  the  extensive  order  of  the  Composite, 

where  this  circumstance  is  universal,  the  filaments  are 

free,  whilst  the  anthers  alone  cohere,  and  form  a  ring 

round  the  pistil  (6).     This  disposition  of  the  stamens  is 

termed  "  syngenesious."     In  some  plants  the  filaments 

are  dilated  and  closely  resemble  petals  (c),  to  which 

organs  they  also  frequently  adhere  through  a  greater  or 

less  extent. 

(98.)  The  Anther  generally  consists  of  two  separate 
lobes  or  pouches,  which  contain  the  pollen  (fig.  8Q.  d); 
and  this,  when  fully  ripened,  escapes  through  a  fissure. 
When  the  fissure  is  closed,  excepting  at  one  extremity, 
the  opening  is  a  mere  pore  (fig.  98.  a).  In  a  very  few 
instances  the  pollen  escapes 
through  vales,  formed  on 
the  face  of  the  anther  (6). 
That  part  of  the  filament 
by  which  it  is  connected 
with  the  lobes  of  the  anther, 
is  termed  the  "connective;"  and  although  more  frequently 
obscure  and  of  small  dimensions,  yet  in  some  species  it 
spreads,  or  branches  laterally,  and  keeps  the  two  cells 
wide  apart  (c).  The  cells  themselves  assume  various 
appearances,  and  sometimes  only  one  is  perfected.  In 
its  earliest  state,  each  is  subdivided  by  a  partition,  which 
afterwards  disappears  ;  but  in  some  cases  it  remains,  and 
then  each  lobe  contains  two  cells. 

(99.)   Pollen.  —  The  grains  of  pollen  (fig.  99.)  are 
minute  vesicles  composed  of  one  or  two  membranous 


98  DESCRIPTIVE    BOTANY.  PAK1    I. 

coats,  and  are  generally  spherical   or  spheroidal,  and 
often  have  determinate  markings,  warty  projections,  and 


minute  bristles  upon  their  surface.  Some  of  the  larp-M 
grains  do  not  exceed  the  7|c  or  -^ 0  part  of  an  inch 
in  diameter  ;  and  in  some  species  they  are  not  so  much 
as  the  TV i,1,,,,.  In  several  species,  the  grains  approach 
a  tetrahedral  shape ;  others  are  very  singularly  modi- 
fied, of  which  the  few  examples  represented  in  the  an- 
nexed cut  may  serve  as  a  specimen.  In  some  tribes 
of  the  remarkable  order  Orchideac,  the  grains  ad- 
here together  in  waxy  "  masses,"  which  fill  the  anthers. 
Each  grain  of  pollen  contains  a  quantity  of  minute 
"  granules,"  the  largest  of  which  do  not  exceed  the 
i~To?TU  Part  °f  an  inch-  These  are  occasionally  inter- 
spersed with  oblong  particles,  two  or  three  times  larger 
than  the  granules.  We  reserve  further  details  for  the 
physiological  department,  when  we  shall  speak  of  the 
manner  in  which  the  grains  act  upon  the  stigma,  in  se- 
curing the  fertility  of  the  ovule. 

(100.)  Pistil. — The  parts  which  compose  the  in- 
nermost whorl  or  whorls,  are  termed  carpels,  as  we  have 
already  stated  (art.  92.)  ;  and  when  they  are  not  united 
together,  each  is  also  considered  as  a  "  pistil."  This 
pistil,  whether  simple  or  compound,  consists  essentially 
of  an  "  ovarium"  or  "  germen,"  containing  the  young 
seed  or  "  ovules  ; "  and  of  a  "  stigma,"  or  glandular 
summit,  which  is  either  seated  immediately  upon  the 
ovarium,  or  on  a  sort  of  stalk,  called  the  "  style,' 


two    or 


SECT.   I.          ORGANOGRAPHY    AND    GLOSSOLOGY.  99 

interposed  between  them.  The  construction  of  the 
compound  pistil  will  be  more  readily  understood,  by 
considering  the  manner  in  which  the  carpels  themselves 
may  be  supposed  to  originate.  Each  carpel  is  an 
organ,  analogous  to  a  leaf  folded  inwards  upon  its  mid- 
rib, so  as  to  bring  the  edges  into  contact,  which  cohere 
and  form  the  "  placenta/'  and  upon  this  the  ovules  are 
produced.  In  general,  the  carpels  may  be  likened  to 
a  sessile  leaf ;  but  in  a  few  cases  they  are  fur- 
nished with  a  support  (thecaphore)  analogous 
to  the  petiole.  When  two  or  more  carpels 
are  placed  closely  in  contact,  and  adhere  to 
gether  by  their  sides,  the  compound  ovarium 
will  contain  two  or  more  "  cells"  (fig.  100.) 
And  if  the  styles  and  stigmas  also  cohere,  the 
pistil  will  assume  the  appearance  of  a  simple 
organ,  although,  in  fact,  compounded  of 
more  carpels.  Where  there 
is  more  than  one  row  of 
carpels  in  the  composition 
of  a  pistil,  this  will  con- 
tain more  than  one  tier 
of  cells  ;  as  in  the  fruit  of 
the  pomegranate  (^.  101.). 

The  stigma  is  variously 
modified  in  different  spe- 
cies. It  consists  of  vesi- 
cles of  cellular  tissue  de- 
nuded of  the  epidermis, 
excepting  in  a  few  cases, 
where  the  thin  pellicle  which  we  have  stated  to  form 
the  outer  skin  of  this  investing  organ,  appears  to  cover 
it. 

(101.)  Disk.  —  The  term  "  disk,"  is  applied  to  a 
portion  of  the  torus  between  the  calyx  and  pistil, 
when  it  assumes  a  glandular,  swollen,  or  fleshy  appear- 
ance This  is  always  supposed  to  proceed  from  the 
abortion,  or  imperfect  development  of  some  of  the  pe- 
ri 2 


101 


100  DKSCRIPTIVE    BOTANY.  PAHT    I. 

tals  and  stamens.  The  disk,  therefore,  is  not  properly 
a  distinct  organ  ;  but  merely  a  modification  of  one 
or  other  of  these.  As  connected  with  the  develop- 
ment and  modification  of  the  torus  itself,  we  may  here 
describe  three  conditions  of  the  flower,  which  are  con- 
sidered of  the  greatest  importance  in  systematic  botany, 
and  which  we  will  explain  by  referring  to  the  annexed 
diagram  (fig.  102.).  When  that  part  of  the  torus  from 


which  the  petals  and  stamens  originate,  is  limited  to  the 
space  immediately  between  the  calyx  and  pistil :  the 
corolla  and  stamens  are  necessarily  seated  below  the 
ovarium,  and  are  in  consequence  termed  "  hypogy- 
nous"  (a).  But  when  the  torus  is  so  developed,  that  it 
becomes  partially  extended  over  the  inner  surface  of  the 
calyx,  the  corolla  and  stamens  appear  to  arise  from,  and 
are  seated  upon,  this  organ,  and  they  are  then  termed 
'•  perigynous"  (6).  When  the  torus,  modified  as  in  the 
last  case,  also  extends  up  the  sides  of  the  ovarium,  the 
pistil  is  closely  united  with  the  calyx  ;  and  the  corolla 
and  stamens  are  placed  near  the  summit  of  the  ovarium, 
and  are  then  styled  "  epigynous"  (c).  In  this  case,  the 
ovarium  is  also  said  to  be  "  inferior,"  with  respect  to 
the  other  parts  of  the  flower,  and  these  again  are  called 
"  superior,"  with  respect  to  it.  In  the  perigynous  and 
hypogynous  corollae,  the  reverse  is  the  case,  the  ovarium 
being  superior  and  the  other  parts  inferior.  There  are 
a  few  other  modifications  which  cannot  exactly  be  re- 
ferred to  either  of  these  three.  In  the  white  Water-lily 
(Nymphtfa  allxi),  the  petals  and  stamens  are  attached  to 
the  sides  of  the  ovarium,  though  the  calyx  is  perfectly 


SECT.   1.          ORGANOGRAPHY    AND    GLOSSOLOGY.  101 

free.     In  the  passion  -flowers,    the   stamens  adhere   to 
the  ovarium,  and  the  petals  to  the  calyx. 

(102.)  Floral  Modifications.  —  As  an  illustration  of 
these,  we  may  state,  that  the  orders  of  the  class  Dicoty- 
ledones,  are  thrown  into  four  principal  groups,  two  of 
which  are  characterised  by  the  circumstances  alluded  to 
in  the  last  article.  The  first  of  these,  the  Thalamiflorae, 
includes  those  flowers  which  have  their  several  whorls  de- 
tached, or  not  adhering  together  —  each  whorl  occupying 
a  distinct  position  on  the  torus,  as  in  fig.  89-  The  sepa- 
rate parts  of  the  several  kinds  of  whorls,  however,  may 
or  may  not  adhere  together.  This  group  can  strictly 
include  only  hypogynous  flowers.  The  next,  or  the  Ca- 
lyciflorae,  includes  those  orders  whose  flowers  have  their 
petals  and  stamens  adhering  to  the  calyx,  whether  in 
the  perigynous  or  epigynous  form  of  the  flower.  In  both 
groups,  all  the  four  floral  whorls  are  almost  universally 
present.  Each,  however,  contains  a  few  examples  which 
cannot  be  separated  from  their  congeners,  but  in  which 
the  petals  are  wanting,  or  are  very  rarely  developed. 

Of  the  two  other  groups,  one  is  termed  Corolliflorae, 
where  the  corolla  is  monopetalous,  and  the  stamens  ad- 
here to  the  inside  of  its  tube.  This  includes  only 
hypogynous  flowers.  The  last  group  is  termed  Mono- 
chlamydese,  where  the  perianth  consists  of  only  one 
whorl,  which  is  almost  universally  recognised  as  a 
calyx. 

(103.)  Nectary. — The  word  "  nectary,"  is  of  very 
general  application,  and  is  used  to  express  some  pecu- 
liar modification  in  the  sepals  or  petals,  by  which  they 
assume  an  unusual  form;  but  more  especially,  when  there 
is  some  alteration  of  structure,  by  which  they  are  wholly 
or  partially  converted  into  secreting  organs,  and  exude 
a  saccharine,  glutinous  juice. 

(104.)  Mstivation.  —  As  the  condition  of  the  leaf 
whilst  yet  in  the  bud, is  termed  its  vernation,  so  the  man- 
ner in  which  the  several  parts  of  the  flower  lie  folded  in 
the  flower-bud,  is  termed  their  "  aestivation."     Of  this 
H  3 


102 


DESCRIPTIVE    BOTANY. 


there  are  several  kinds  ;  the  most  important  distinctions 
depending  upon  whether  the  edges  of  two  contiguous 
sepals  or  petals  meet  without 
overlapping  —  when  the  aesti- 
vation  is    called   "valvular" 
(fig.  103.  v)  ;  or  whether  the 
one  overlaps  the  other  —  when 
it    is     termed    "  imbricate " 
(fig.  103.   i).      The   various 
modifications     to   which    the 
estivation  is  subject,  is  rea- 
dily seen,  by  making  a  trans- 
verse section  through  the  flower-bud.    Thus,  the  "  con- 
duplicate"   (fig.   104.  c),   is  ,M 
where  the  edges  in  the  valvu-     / /^~~'::\\         n^^^A 
lar  aestivation,  are  rolled  in-    (((C  ^j\V\l       <  > 
wards    beyond    the    line    of     \^^//J         U_,     ^ 
contact.       The    "contorted"                                    £; 
or  "  twisted  "  aestivation  (T), 

when  the  parts  of  an  imbricate  aestivation  are  so 
curved,  that  each  is  partially  wrapped  round  one, 
and  at  the  same  time  is  partially  enveloped  within 
another.  These  examples  are  sufficient  to  afford  a  ge- 
neral notion  of  this  phenomenon. 


CHAP.  V. 

REPRODUCTIVE    ORGANS  —  Continued. 

FRUIT  PERICARP     (105.).    FORMS     OF     FRUIT      (108.).  

SEEDS        (109.).    EMBRYO      (111.).    REPRODUCTION      OF 

CRYPTOGAMOUS    fLANTS    (114.). 

105.)    Fruit. —  IMMEDIATELY   after   the  flower    has 
become'  fully  expanded,   several  of  its  parts  begin   to 


ORGANOGRAPHY    AND    GLOSSOLOGY. 


103 


decay ;  but  the  ovarium,  sometimes  the  calyx,  and 
other  parts  continue  to  grow,  and  ultimately  assume  a 
very  different  appearance  from  what  they  possessed  in 
the  flower.  This  altered  condition  of  these  parts  is 
termed  the  "  fruit."  In  many  cases,  the  fruit  is  not 
ripened  unless  the  ovula  are  subjected  to  the  fertilising 
influence  of  the  pollen  ;  but  if  this  process  be  com- 
pleted, then  these  bodies  undergo  certain  remark- 
able changes,  and  pass  to  the  condition  of  "  seeds." 
Certain  fruits,  however,  will  ripen  freely  enough,  al- 
though they  produce  no  seed,  as  some  varieties  of 
oranges,  grapes,  pineapples,  &c. 

(106.)  Pericarp. —  The  part  of  the  fruit  immedi- 
ately investing  the  seed,  and  which  originally  formed 
an  ovarium,  becomes  the  "  pericarp."  When  the 
carpels  are  separate,  the  fruit  is  termed  "  apocarpous  ;" 
but  when  composed  of  several  adhering  carpels,  it  is 
said  to  be  "  syncarpous."  The  pod  of  a  common  pea, 
is  a  familiar  example  of  a  simple  pericarp,  with  a 
structure  not  very  dissimilar  to  that  of  a  leaf  folded 
longitudinally  inwards,  with  the  seeds  attached  along 
the  margins,  united  and  forming  a  swollen  placenta. 
De  Candolle  has  given  a  figure,  in  his  "-Memoir  on 


10.5 


the  Leguminosae,"  of  a  monstrosity,  where  the  pericarps 


104 


HKSCR1PTIVE    BOTANY. 


PART   I. 


have  manifested  a  decided  tendency  to  develop  in 
the  form  of  leaves,  and  where  the  position  of  the 
ovules  is  marked  on  their  edges  by  small  projections 
(fig.  105.). 

If  we  suppose  five  carpels,  formed 
on  the  same  general  principle  as 
that  of  the  pea-pod,  to  be  ar- 
ranged round  an  axis,  and  to  be  en- 
veloped in  a  mass  of  pulpy  matter, 
contained  in  a  swollen  calyx  (as 
in  the  apple  blossom),  we  have  such 
syncarpous  fruits  as  apples,  pears,  &c.  (fig.  106.). 

A  multitude  of  examples  might  be  adduced,  where  the 
compound  structure  of  the  pericarp  is  easily  referable 
to  an  aggregation  of  several  carpels.  In  such  cases, 
each  carpel  forms  a  distinct  "  cell  ;"  and  the  wall  of  se- 
paration between  two  contiguous  cells,  is  termed  a  "  dis- 
sepiment" {fig.  107.).  There  are,  however, 
many  pericarps,  which,  in  their  nascent  state, 
possess  this  structure,  but  become  further 
modified  as  they  ripen,  by  the  rupture  and 
subsequent  obliteration  of  the  dissepiments; 
at  the  same  time  the  placentae  coalesce  round 
the  axis,  so  that  the  ripe  fruit  consists  of  a  single  cell, 
formed  by  an  outer  shell,  which  is  entirely  detached 
from  a  central  placenta  bearing  the  seed  (fig. 
This  is  the  case  in  the  seed-vessels  of  pinks, 
primroses,  &c.  In  some  cases,  the  edges 
of  the  adhering  carpels  do  not  extend  so  far 
inwards  as  to  reach  the  axis,  and  then  the 
dissepiments  are  not  complete,  as  in  the 
poppy  (fig.  lOQ.).  In  other  cases,  the  edges 
of  the  contiguous  carpels  meet  without  ex- 
tending inwards  at  all,  and  then  the  placenta? 
are  said  to  be  "  parietal,"  because  they  are 
placed  on  the  inner  surface  of  the  shell 
which  forms  the  one-celled  capsule,  as  in  the  violet 
(fig.  110.).  The  pericarp  is  essentially  composed  of 
three  parts,  analogous  to  those  in  the  leaf — two  skins,  and 


SECT.  I.         ORGANOGRAPHY    AND    GLOSSOLOGY. 


105 


the  cellular  matter  between  them.  The  outer  skin  forms 
the  "  epicarp,"  the  inner  the  "  en. 
docarp/'  and  the  intermediate  por- 
tion is  the  "  sarcocarp."  In  many 
pericarps^  these  parts  are  not  well 
defined  ;  but  in  such  as  are  fleshy, 
as  in  the  stone-fruits,  peaches, 
plums,  &c.,  it  is  the  endocarp  which 
develops  into  the  "  stone,"  the  epi- 
carp forms  the  "  skin,"  whilst  the 
sarcocarp  becomes  the  delicious  and 
edible  portion  of  the  fruit. 

(107.)  Dehiscence.  —  When  the 
ripened  pericarp  divides  spontane- 
ously, in  any  definite  manner,  it  is  said  to  be  "  dehis- 
cent/' and  the  line  of  division  is  termed 
the  "  suture,"  whilst  the  separate  parts 
are  called  "  valves"  (fig.  111.).  In  ge- 
neral, the  suture  tallies  either  with  the 
adhering  edges  of  the  carpels,  or  with 
a  line  parallel  and  midway  between  them, 
in  the  position  of  the  midrib  or  nerve  of 
each  carpel.  In  the  former  case,  the  dehiscence  is 
termed  "  septicidal "  (a),  as 
in  the  Colchicum  autumnale ; 
and  in  the  latter,  which  is  the 
most  usual,  "  loculicidal"  (6), 
as  in  the  tulip.  In  a  few 
plants,  as  in  the  common  pimpernel  (Anagallis  arven- 
st's),  the  suture  is  transverse  to  the  lines  112 
formed  by  the  edges  of  the  carpels ;  such 
a  pericarp  is  termed  a  "  pyxidium  "  (fig. 
1 12.).  In  some  cases,  the  dehiscence  is  so 
limited,  that  it  merely  forms  pores  or  small 
valves,  at  the  extremities  of  the  pericarp. 
In  many  pericarps  there  is  no  particular 
line  of  suture  :  but  they  rupture  irregu- 
larly, to  permit  the  escape  of  the  seed ;  or  else  they 
decay  and  gradually  rot  without  bursting. 


106 


DESCRIPTIVE    BOTANY. 


PART   1. 


(108.)  Form  of  Fruits.  —  It  would  be  impossible 
in  this  treatise  to  enumerate  the  vast  variety  of  forms 
and  characters  which  different  fruits  present.  Some 
are  soft  and  pulpy  ;  others  are  very  hard,  woody,  dry, 
or  membranaceous.  It  is  sometimes  one  part,  and 
sometimes  another,  of  the  inflorescence,  which  becomes 
developed  into  a  succulent  and  nutritious  form,  in  dif- 
ferent fruits ;  and  a  casual  observer  might  easily 
overlook  these  distinctions,  in  the  general  resem- 
blance which  they  bear  to  one  another  (Jig.  113.). 


The  raspberry  (a),  the  strawberry  (6),  and  perhaps 
the  mulberry  (c),  may  be  mentioned,  as  bearing  a 
considerable  general  resemblance  to  each  other.  In 
the  first,  however,  the  juicy  part  consists  of  nume- 
rous distinct  and  globular  pericarps,  each  enclosing  a 
single  seed,  which  are  seated  on  a  spongy  unpalatable 
torus.  In  the  second,  it  is  the  torus  which  becomes 
pulpy,  whilst  the  pericarps  remain  dry,  and  are  scat- 
tered over  its  surface  in  the  form  of  little  grains,  com- 
monly considered  as  naked  seeds.  In  these  two  cases, 
the  fruit  is  the  produce  of  a  single  flower  ;  but  in  the 
mulberry,  the  structure  is  altogether  different.  This 
tree  is  monoecious  ;  and  the  small  fertile  flowers  —  or 
such  as  contain  pistils,  and  no  stamens  —  are  disposed 
in  a  dense  spike.  It  is  the  calyx  of  each  flower  which 
becomes  succulent,  and  thus  the  fruit  is  made  up  of 
the  aggregate  mass  of  these  altered  calyces,  each  of 
which  invests  a  dry  pericarp,  containing  the  seed. 


SECT.   1.        ORGANOGRAPHY    AND    GLOSSOLOGY. 


107 


We  shall  very  briefly  notice  a  few  of  the  most  im- 
portant forms  which  fruits  assume,  hut  cannot  pretend 
to  enter  into  any  details  on  so  extensive  a  subject.  Dr. 
Lindley's  "  Introduction  to  Botany"  may  be  advan- 
tageously consulted  for  further  information,  and  Gaert- 
ner's  invaluable  works  for  the  fullest  details. 


SIMPLE  PERICARPS. 

1.  Follicle.  —  Where  the   pericarp    is   dry,  114 
and  dehiscent   only  along   the  suture  formed 

by  the  union  of  the  edges  of  a  foliaceous  carpel, 
it  may  be  considered  as  composed  of  a  single 
valve :  as  in  the  monkshood  (Aconitum  napel- 
lus),  and  larkspur  (Delphinium  consolida, 

2.  Legume. — This  form  is  familiarly  illus- 
trated in  the  pericarps  of  peas  and  beans.     In 

many  cases,  it  presents  a  near  approach  to  the  leafy  struc- 
ture, and  may  be  considered  as  a  modified  condition  of  the 
leaf,  folded  longitudinally  on  its  midrib,  with  the  edges 
adhering,  and  forming  a  suture  (fig.  115.  a).  Another 


suture  is  also  formed  along  the  midrib  or  dorsal  nerve, 
so  that  the  legume  separates  into  two  valves.  In 
some  species,  however,  the  sutures  are  so  firmly  closed, 
that  the  legume  becomes  indehiscent.  Its  varieties 
are  very  numerous.  In  the  genus  Astragalus,  it  is 


108  DESCRIPTIVE    BOTANY.  PART   I. 

divided  into  two  spurious  cells  (fe),  by  the  back  of  the 
legume  becoming  doubled  inwards  until  it  reaches  the 
placenta.  In  some  cases,  the  legume  is  divided  by 
transverse  partitions  (e),  formed  by  the  agglutination 
of  the  opposite  parietes,  so  that  each  seed  appears 
to  be  contained  in  a  separate  cell ;  and  in  some  cases 
the  pericarp  is  pinched  between  each  seed,  so  that 
the  sides  nearly  meet,  when  it  is  termed  "  lomen- 
taceous"  (</).  In  some  cases  it  falls  to  pieces  at  these 
transverse  contractions,  and  breaks  up  into  as  many 
detached  cells  as  there  are  seeds.  In  the  genus  Medi- 
cago,  the  legume  is  curiously  twisted  in  a  spiral  manner, 
and  somewhat  resembles  a  snail-shell  (e). 

3.  Drupe.  —  This   form  may  be  illustrated   by  the 
plum,  cherry,  and  other  stone-fruits,  where   the   peri- 
carp has  a  thickened  and  pulpy  mesocarp,  with  a  stony 
endocarp.     It   contains  two  seeds   in  the  early  state  ; 
but  one  of  them  is  most  frequently  abortive,  and  withers 
completely   before  the    fruit    is    ripe.     The  numerous 
small  drupes,  or  "  drupels,"  of  the  raspberry,  and  other 
Rubi,  are  closely  aggregated  on  a  spongy  convex  torus 
(fig.  I  IS.  a). 

4.  Nut.  —  This  is  a    bony    pericarp,    containing  a 
single   seed,  to  which  it  is   not  closely  attached  (fig. 
116.).     The  strawberry  has  a  fleshy  succulent  torus, 
covered    with    small     nuts    (fig.   113.). 

The  torus  of  the  rose,  coats  the  interior 
of  the  tube  of  the  calyx,  and  its  nuts 
are  placed  round  the  sides  and  at  the  bot- 
tom of  this  tube.  This  form  of  the  pe- 
ricarp must  not  be  confounded  with  the  fruit  usually 
called  a  nut,  and  which  belongs  to  the  "  glans,"  pre- 
sently to  be  described. 

Pericarps  simple  by  Abortion. 

5.  Cariopsis.  —  This  pericarp    is  a  thin,   dry,  ancj 
indehiscent    membrane,    closely    investing,    and    in- 


SECT.  I.         ORGANOGRAPHY    AND    GLOSSOLOGY. 


109 


deed  adhering  to,  the  seed  —  as  in  corn,  and  other  Gra- 
minese.  As  these  pericarps  bear  two  or  three  stigmas, 
the  seed  is  probably  simple  by  abortion,  and  there- 
fore the  fruit,  strictly  speaking,  is  compound. 

6.  Akenium.  —  This  may  be  con- 
sidered as  a  cariopsis,  with  the  su- 
peraddition  of  the  calyx,  adhering  to 
the  pericarp,  and  forming  a  single 
skin  round  the  seed  —  which,  in  this 
case  also,  is  simple  by  abortion.  The 
fruit  of  the  "  Composite  "  are  formed  on  this  plan 


118 


1.  Glann.  —  Acorns  (^.118.), 
hazel  nuts,  and  chestnuts,  are  exam- 
ples of  this  form.  The  base  of  the 
fruit  is  enveloped  by  an  involu- 
crum,  which  at  first  contains  several 
flowers,  but  one  of  them  alone  per- 
fects its  seed.  The  pericarp  is  tough 
or  woody,  indehiscent,  adhering  to 
the  perianth,  one-celled  by  abortion, 
and  containing  one  or  more  seeds. 

8.  Capsule,  —  This  is  a  very  general  term,  for  dry 
fruits  composed  of  two  or  more  carpels,  variously  com- 
bined and  modified. 

9-  Gourd.  —  The  carpels 
are  not  complete,  but  united 
by  their  edges  so  as  to  form 
a  single  cell  with  parietal  pla- 
centae. The  pericarp  is  thick 
and  fleshy,  with  the  outer  coat 
hard  (fig.119.). 

10.  Berry.  —  This  term 
is  applied  to  very  liquid  fruits, 
which  are  covered  with  an  in- 
dehiscent  skin,  as  the  grape, 
gooseberry,  and  others.  In 
the  gooseberry  the  carpels  are  incomplete,  and  form  one 
cell  with  parietal  placentae  (fig.  120.  a)  ;  and  the  calyx 


119 


110 


DESCRIPTIVE    BOTANY. 


adheres  to  the  pulpy  pericarp ;  but  in  the  grape 
(fig.  120.  ft),  the  calyx  is  free,  and  forms  no  part  of  the 
fruit;  the  carpels  are  complete,  and  the  placenta  central. 


11.  Pomum. — Several  membranous,  or  bony  carpels, 
are   embedded  in     a    fleshy 

mass,  which  is  the  swollen 
calyx.  Apples  (fig.  IOC.), 
medlars  (fig.  121.),  quinces, 
&c.,  are  examples. 

12.  Samara.  — The  peri- 
carp is  here  extended  into  a 
flat  wing-like  appendage,  as 
in   the  sycamore  (fig.  L22.) 
and  ash ;  the  fruit  of  which 

trees  is  commonly  termed  a  "  key." 

13.  Siliqtta. —  This  is   the  name  given  to  the  bi- 
locular  and  bivalvular  seed- 
vessels     of    the    Cruciferje. 

The  seeds  are  attached  to  ggZ  Ml^c 
lateral  placenta?;  the  dissepi- 
ment is  formed  by  a  thin 
membrane,  which  is  appa- 
rently a  prolongation  of  the 
inner  skin  (endocarjf)  of  the  two  carpels  (fig.  123.). 

(109.)  Seed.  —  It  would  be  impossible  to  obtain  a 
just  notion  of  the  seed,  without  first  tracing  the  ovule 
through  the  several  alterations  which  it  undergoes,  after 
it  has  been  subjected  to  the  fertilising  influence  of  the 
pollen  ;  but,  as  such  details  are  more  especially  con- 


SECT.   I.          ORGANOGRAPHV    AND    GLOSSOLOGY. 


Ill 


123 


nected  with  the  physiology  of  our  subject,  we  shall  for 
the  present  confine    ourselves  to  a  few 
general  observations  .on   the   ripe    seed. 
Every  seed  is  attached   to  the  placenta, 
by  what  is  termed  a  "  funicular,  or  um- 
bilical   cord;"  and  when   the  seed  has 
fallen  from  the  pericarp,  it  is  marked  by 
a  scar  or  "  hilum,"  at  the  place  where 
this  cord  was  attached  to  it.     In  very 
many    cases,    this    cord    is    small,    and 
scarcely  distinguishable,  but  in  some  it 
is  well  marked  ;  and  in  the  genus  Mag- 
nolia, when  the  pericarp  bursts,  the  seeds 
hang  out  for  some  time,  and  to  a  con- 
siderable   distance,  by    means    of   their 
umbilical  cords,  before  they  become  de- 
tached and  fall  to  the  ground  (^z#.  124.). 
In  a  few  plants,  the  funicular  cord  is 
unusually  developed  ;  and,  rising  round 
the    seed,    forms    a    distinct   skin    or    covering 
termed    an    "  arillus."      The 
nutmeg   (fig.  125.)    is    thus 
enveloped     by      an     arillus, 
which  is  the  cc  mace"  of  com- 
merce.      In   the    spindle-tree 
(Euonymus     europceus),    the 
seeds  are  invested  by  an  arillus, 
of    a  fleshy   consistency  and 
bright  scarlet  colour. 

In  its  ripe  state  every  seed 
is  essentially  composed  of  an 
outer  skin,  or  "  spermoderm," 
and  a  "  kernel"  within  it.  The 
spermoderm,  however,  is  not 
a  distinct  organ,  but  is  rather 
the  dry  and  exhausted  remains  of  two  or  more  coats, 
with  which  the  embryo  was  invested  in  its  earliest 
state,  but  which  have  ultimately  united,  and  form 
a  single  skin  on  the  ripe  seed.  The  kernel  consists 


112  DESCRIPTIVE    BOTANY.  PART   I. 

of  the  "  embryo ; "  and,  in  many  cases,  also  con- 
tains a  peculiar  substance  termed  the 
"  albumen,"  which  is  a  nutritious  mat- 
ter secreted  for  the  use  of  the  embryo, 
and  is  either  of  an  oily,  farinaceous, 
or  hard  and  horny,  consistency.  This 
substance  is  always  wholesome  ;  and  in  .  . 
many  seeds,  especially  in  corn,  forms  an  \ 
important  article  of  human  food.  In 
some  cases,  the  embryo  is  completely 
invested  by  the  albumen,  as  in  the 
cocoa-nut ;  in  others  it  is  only  partially  embedded,  as 
in  wheat  and  other  corn  (see  Jigs.  23.  and  25.).  In  a 
multitude  of  seeds,  however,  there  is  no  trace  of  this 
substance,  in  a  detached  form ;  but  then  we  often  find  the 
cotyledons  themselves  much  swollen,  and  abundantly 
supplied  with  a  similar  material.  This  is  the  case  in 
peas  and  beans,  whose  cotyledons  are  very  large,  and 
contain  a  nutritious  material,  which  serves  to  develop 
the  young  plant  in  the  early  stages  of  its  growth.  Some 
few  seeds,  as  the  orange,  contain  more  than  one  em- 
bryo ;  a  fact  which  has  been  considered  analogous  to 
the  phenomenon  of  double  fruits,  and  to  be  explained 
on  the  supposition  that  two  or  more  ovules  have  adhered 
together  in  the  earliest  state  of  their  development. 

(110.)  Forms  of  Seeds.  —  The  forms  which  seeds 
assume  are  very  various,  and  their  surface  is  either 
smooth,  rough,  or,  in  some  cases,  furnished  with  pe- 
culiar downy  or  membranous  appendages.  The  various 
appendages,  however,  which  assist  the  dissemination  of 
the  seed,  are  more  frequently  attached  to  the  pericarp  ; 
arid  afford  abundant  instances  of  an  adaptation  of  means, 
admirably  calculated  to  secure  the  end  for  which  the 
seed  is  destined  —  the  preservation  of  the  species  upon 
the  earth. 

(111.)  Embryo.  —  We  have  already  described  (arts. 
34,  35.)  the  two  principal  distinctions,  which  subsist  be- 
tween the  embryos  of  flowering  plants,  and  which  es- 
sentially separate  them  into  two  great  classes.  To  those 


SECT.  I.          ORGANOGRAPHY    AND    GLOSSOLOGY. 


113 


remarks,  we  may  add  the  following: — The  embryo 
may  be  either  straight  or  curved;  placed  in  the  centre  of 
the  albumen,  where  this  substance  exists  in  a  separate 
form,  or  else  laterally  disposed  with  respect  to  it.  The 
parts  of  which  it  is  composed  are,  1.  The  "  radicle," 
which  is  the  conical  extremity,  afterwards  developed 
into  a  root;  and,  2.  The  " plumule," — consisting  of  the 
"  cotyledon  or  cotyledons,"  and  the  "  gemmule,"  or 
first  leaf-bud,  which  is  afterwards  evolved  in  the  form 
of  stem  and  leaves. 

The  position  of  the  embryo  is  determined  by  the 
direction  of  its  radicle,  the  point  of  which  is  constantly 
turned  towards  the  "  foramen," —  a  small  hole  pierced 
through  the  outer  coat  of  the  seed,  and  of  which  we 
shall  speak  more  particularly  hereafter.  Now,  the  posi- 
tion of  the  foramen  varies  with  respect  to  the  hilum, 
and  may  be  either  on  the  opposite  side,  or  placed 
near  it,  on  the  same  side  of  the  seed.  The  radicle  will, 
consequently,  either  point  from  or  towards  the  hilum, 
and  the  embryo  become  "  inverse"  (fig.  126.  a)  or 


"  erect"  (6)  accordingly;  or  the  embryo  may  lie  "  trans- 
verse" (c),  when  the  apex  is  on  one  side  of  the  seed,  and 
the  radicle  cannot  be  said  to  point  either  towards  or 
from  the  hilum.  Some  authors,  however,  make  the 
direction  of  the  embryo  to  depend  also  on  the  position 
of  the  seed  itself,  which  may  be  either  erect  or  pendent 
within  the  pericarp  ;  but  this  is  a  circumstance  which 
can  merely  modify  the  direction  of  the  embryo  with 
respect  to  the  pericarp,  and  not  with  respect  to  its  po- 
sition in  the  seed. 

(112.)   Cotyledons.  —  In  many  plants,  the  cotyledons 
have  comparatively  little  resemblance  to  leaves,  but  in 


114 


DESCRIPTIVE    BOTANY. 


PART  I. 


others  they  alter  their  character  very  considerably  after 
germination  has  commenced  ;  they  then  become  green, 
and  expand  in  a  form  which  closely  resembles  the  or- 
dinary leafy  structure.  Some  cotyledons,  however,  whilst 
still  in  the  seed,  have  the  appearance  of  miniature  leaves, 
are  extremely  thin,  and  delicately  veined  (fig.  23.  a)  ; 
and  no  one  could  for  a  moment  consider  them  in  any 
other  light,  than  as  these  organs  in  a  young  and  un- 
developed state.  In  ma/iy  Dicotyledons,  the  embryo  is 
a  cylindrical  body,  with  nothing  more  than  a  notch  at 
one  end,  indicating  the  position  of  the  cotyledons  ;  but, 
in  a  few  species,  there  is  no  appearance  of  any  division, 
and  then  it  is  presumed  that  the  cotyledons  adhere 
together ;  or  rather,  if  we  judge  from  analogy,  that 
they  are  entirely  abortive.  Their  stem  consists  merely 
of  a  slender  filament  which  twines  itself  round  other 
plants,  from  which  it  extracts  its  nutriment  by  means 
of  suckers  provided  for  this  purpose. 

Here  and  there,  we  often  find  a  young  plant  of  several 
dicotyledonous  species,  which  have  three,  or  even  more 
cotyledons,  instead  of  two.  The  common  sycamore 
(Acer  pseudoplatanus}  affords  frequent  examples,  where 
this  unusual  number  appears  to  have  originated  in  some 
process  of  subdivision,  rather  than  by  any  supernumerary 
development  of  these  organs  (fig.  127.).  These  devi- 


ations  from  the  usual  character,  in  species  where  the 
cotyledons  are  most  frequently  two  in  number,  may 
as  a  connecting  link  between  them  and  plants 


SECT.   I.          ORGANOGRAPHY    AND    GLOSSOLOGY. 


115 


of  the  coniferous  tribes  (the  fir  trees),  which  possess 
several  cotyledons. 

An  attempt  has  been  made,  to  establish  an  affinity 
between  the  embryonic  structure  of  dicotyledons  and 
monocotyledons,  by  supposing  the  single  cotyledon  in 
the  latter  class,  which  completely  envelopes  the 
rest  of  the  embryo,  to  be  in  reality  compounded 
of  two  cotyledons,  united  by  their  edges  into  one 
mass.  In  some  cases  this  occurs  in  dicotyle- 
dons; and  the  annexed  figure  (128.)  represents 
a  monstrosity,  observed  in  a  young  plant  of 
the  sycamore,  which  exhibits  an  approximation 
to  the  condition  of  a  monocotyledon,  at  the 
commencement  of  its  germination :  the  two 
cotyledons  having  adhered  by  one  of  their 
edges  nearly  throughout  their  whole  lengths. 

In  all  monocotyledons,  it  is  more  difficult  to  determine 
the  several  parts  of  which  the  embryo  is  composed,  than 
in  dicotyledons.  It  generally  consists  of  a  nearly  cylin- 
drical fleshy  mass,  without  any  external  traces  of  organis- 
ation ;  but  if  it  be  cut  longitudinally,  the  position  of  the 
radicle  and  the  gemmule  may  then  be  seen,  traced  by  a 
faint  outline,  indicative  of  a  separation  in  the  substance 
of  the  embryo  (fig.  25.). 

(113.)  Reproductive  Organs 
of  Cryptogamic  Plants.  —  The 
sporules  mentioned  in  art.  36. 
are  contained  in  pecu  liar  cells 
placed  on  the  surface,  or  em- 
bedded   in   the  substance    of 
the  plant,  among  the  crypto- 
gamic  tribes.     Among  the  higher  families  Ot  tais  class, 
the  cells  assume  a  distinct  capsular  form, 
termed   "theca"  (fig.  12y.),  which  has 
various  characters,  in  the  ferns  (a),  Equi- 
seta  (6),   mosses    (c),  &c.       The    cells, 
or  cases  which  contain  the  sporules,  among 
the  inferior  families  of  this  class,  are  more 
simple  in  their  structure,    and  often    re- 
i  2 


1  16  DESCRIPTIVE    BOTANY.  PART  I. 

soluble  short  closed  filamentous  tubes,  or  sacks  (fig.  130.), 
which  ultimately  discharge  their  contents  by  the  rupture 
of  one  of  their  extremities. 


CHAP.  VI. 

MORPHOLOGY. 

A  BORT10N  (115.).  —  DEGENERATION  (116.).  —  ADHESION  (118.). 
SUPERNUMERARY  WHORLS  (119.).  NORMAL  CHARAC- 
TERS (120.).  SPIRAL  ARRANGEMENT  OF  FOLIACEOU8 

APPENDAGES    (121.).  TABULAR     VIEW     OF    VEGETABLE    OR- 
GANISATION   (123.). 

(114.)  Morphology. —  IT  is  an  observed  fact,  that  the 
subordinate  parts  which  make  up  the  floral  whorls  of 
very  many  plants,  are  symmetrically  arranged  round  the 
axis,  and  that  the  parts  of  each  separate  whorl  are  placed 
alternately  with  those  of  the  contiguous  whorls.  Con. 
nected  with  these  facts,  it  has  been  remarked,  that  the 
flowers  of  certain  species,  whose  parts  are  not  symmetri- 
cally arranged,  and  which  do  not  alternate  in  the  manner 
described,  do  nevertheless  occasionally  assume  a  per- 
fectly regular  structure,  by  the  development  of  super- 
numerary parts.  As  an  illustration  of  our  meaning,  we 
may  select  the  common  snapdragon  (Linaria  vnlyaris)  ; 
in  which,  as  well  as  in  some  other  species  of  this  and  of 
the  allied  genus  Antirrhinum,  the  phenomenon  we  are 
about  to  describe  may  occasionally  be  observed.  The 
common  form  of  the  flowers  of  this  plant  is  termed 
"personate"  (fig.  131.  a);  the  corolla  is  monopetal- 
ous,  and  divided  into  two  large  lobes,  closed  in  front, 
and  presenting  somewhat  the  appearance  of  an  animal's 
face.  The  upper  portion  of  the  corolla  is  prolonged 
backwards,  into  a  tubular  "  spur ;"  it  contains  four 
stamens,  arranged  in  pairs  of  unequal  length  (didy- 


SECT.  I.         OBGANOGBAPHY    AND    GLOSSOLOGY.  117 

namous)  :  the  calyx  is  subdivided  into  five  segments, 
indicating  the  adhesion  of  as  many  sepals ;  the  pisti 


13! 


is  a  two-celled  capsule,  with  the  seeds  arranged  on 
a  central  placenta.  In  short,  the  flower  is  highly  un- 
symmetrical  and  irregular,  in  all  its  parts.  Now,  there 
is  an  interesting  variety  of  this  plant,  termed  "  Peloria," 
in  which  the  corolla  is  strictly  symmetrical,  consisting 
of  a  conical  tube,  narrowed  in  front,  and  elongated 
behind  into  five  spurs  (6).  It  contains  five  stamens  of 
equal  length.  In  this  state,  therefore,  we  have  a  flower 
composed  of  five  sepals,  adhering  through  a  considerable 
portion  of  their  length,  constituting  a  five-toothed  mo- 
nosepalous  calyx  ;  five  petals,  adhering  into  a  monope- 
talous  corolla ;  five  stamens  ;  but  a  pistil  which  is  com- 
posed of  only  two  carpels,  as  in  the  irregular  flowers. 
The  three  first  whorls  are  therefore  strictly  symmetrical, 
and  the  parts  are  also  arranged  in  an  alternating  order 
round  the  axis.  It  should  seem,  that  the  ordinary 
irregularity  of  this  flower  is  somehow  connected  with 
the  disappearance  of  the  fifth  stamen,  involving  a 
partial  suppression,  as  well  as  modification,  of  four 
of  the  petals.  Other  specimens  may  be  seen  in  every 
intermediate  condition,  between  the  regular  and  irre- 
gular forms  here  described ;  some  having  two,  others 
three  or  four  spurs,  to  the  corolla  (c).  If  we  connect 
these  and  similar  facts,  with  the  observations  already 
detailed,  viz.  that  the  subordinate  parts  of  the  flower- 
bud  are  analogous  to  those  which  compose  the  leaf-bud, 
i  3 


118  DESCRIPTIVE    BOTANY.  PARTI. 

and  consequently  that  all  these  parts  are  only  analogous 
to  so  many  leaves,  which  under  other  circumstances 
would  have  developed  regularly  round  the  branch  on 
which  they  grew — then  may  every  deviation  from  the 
symmetrical  arrangement  in  the  parts  of  the  flower,  be 
ascribed  to  the  operation  of  certain  modifying  causes, 
connected  with  some  peculiarity,  inherent  in  the  several 
species  themselves.  These  causes  may  be  arranged  under 
the  heads  of  "Abortion,"  "Degeneration,"  and  "Ad- 
hesion." 

(115.)  Abortion. —  This  term  is  used,  wherever  some 
organ  is  wanting,  to  complete  the  symmetry  of  the 
flower ;  in  which  case,  such  organ  is  supposed  to  lie 
dormant  under  ordinary  circumstances,  though  capa- 
ble of  development  under  other  and  peculiar  condi- 
tions. As  the  latter  are  of  accidental  occurrence, 
they  only  give  rise  to  those  various  monstrosities,  or 
deviations  from  the  ordinary  form,  which  are  frequently 
(as  in  the  case  of  the  Linaria  above  mentioned  (art. 
I  1  k)  so  valuable),  in  determining  what  is  considered 
to  be  the  "  normal "  structure,  or  regular  condition,  to 
which  various  unsymmetrical  flowers  may  be  referred. 
Portions  of  the  inner  whorls  are  more  often  abortive 
than  those  of  the  outer  ;-and  thus  the  number  of  carpels 
is  far  less  frequently  in  accordance  with  the  normal 
structure,  than  the  number  of  the  stamens.  All  uni- 
sexual flowers,  may  be  considered  as  resulting  from  the 
complete  abortion  of  one  or  other  of  the  two  innermost 
whorls. 

(116.)  Degeneration,  is  where  the  abortion  of  an 
organ  is  not  fully  completed,  but  where  it  has  become 
imperfectly  developed,  or  very  differently  modified  from 
its  usual  state.  In  many  instances,  we  find  certain 
anomalous  appendages,  which  occupy  the  place  of  some  of 
the  subordinate  parts  belonging  to  one  or  other  of  the 
floral  whorls,  and  which  are  consequently  considered  as  a 
monstrous  or  incomplete  state  of  those  parts.  Perhaps 
the  stamens  are  more  especially  subject  to  this  condition 
of  degeneracy  than  any  other  organs.  They  frequently 


SECT.  I.         ORGANOGRAPHY    AND    GLOSSOLOGY. 


119 


assume  the  form  and  structure  of  secretory  glands,  and 
of  various  processes  and  appendages,  of  an  anomalous 
character.  In  many  cases,  the  parts  which  have 
degenerated  from  their  usual  condition,  assume  a 
highly  developed  structure,  and  become  more  leaf- 
like.  Thus,  we  find  double  flowers  are  often  formed 
by  the  stamens  having  put  on  the  appearance,  and 
all  the  characters  of  petals,  —  organs  which  are  usually 
of  larger  dimensions,  though  of  inferior  importance 
in  the  floral  economy.  In  some  plants,  as  the  com- 
mon white  Water-lily  (Nymphaea  alba),  the  transition 
from  the  character  of  a  petal  to  that  of  a  stamen,  is  so 
very  gradual  (fig.  132.),  through  successive  whorls  of 


these  organs,  that  it  is  hardly  possible  to  determine  where 
one  set  begins  and  the  other  terminates. 

(117-)  Causes  of  Abortion  and  Degeneration. —  An 
inquiry  into  the  causes  of  abortion  and  degeneration, 
more  properly  belongs  to  our  physiological  department, 
but  may  as  well  be  alluded  to  in  this  place.  The  par- 
tial or  total  abortion  of  certain  organs,  is  very  frequently 
occasioned  by  accidental  circumstances  —  from  some 
impediment  thrown  in  their  way,  from  a  deficiency  of 
light  in  a  particular  direction,  and  many  other  external 
causes.  In  these  cases,  when  the  influence  is  removed, 
the  suppressed  organ  will  sometimes  appear,  and  assume 
its  proper  character.  Thus,  in  trees,  it  seldom  happens 
that  all  the  buds  generated  in  the  axills  of  the  leaves, 
are  developed  into  branches ;  but  many  of  them  remain 
dormant,  especially  about  the  lower  parts  of  the  stem  ; 
and  it  is  not  until  a  better  supply  of  light  and  air  is 
i  4 


120  DESCRIPTIVE    BOTANY.  PART  I. 

afforded  them  by  the  pruning  knife,  that  they  are 
enabled  to  grow.  Sometimes  the  development  of  an 
organ  is  impeded  or  prevented,  by  the  want  of  a  suffi- 
cient supply  of  nutriment ;  and  this  often  arises  from 
the  abstraction  of  what  was  naturally  destined  for  it, 
by  the  more  vigorous  growth  of  some  neighbouring 
portion.  Hence  the  different  characters  which  dis- 
tinct individuals  of  the  same  species  assume,  depend 
upon  the  various  degrees  of  influence  which  those  and 
many  other  external  circumstances  have  upon  them. 
From  such  causes  as  these,  we  find  the  leaves  of  a 
tree  gradually  dwindling  into  membranous  scales ;  the 
calyx  of  the  florets  in  the  Composite  becoming  a 
downy  pappus  (fig.  11?.).  The  thorny  prickles  of 
the  wild  plum  are  merely  stunted  branches,  and  by 
culture  readily  disappear,  —  an  effect  which  Linnieus 
fancifully  termed,  the  taming  of  wild  fruits.  But 
besides  these  merely  external  influences,  which  may  all 
be  considered  as  accidental  causes,  tending  to  produce 
the  abortion  of  particular  parts,  there  are  others  of  a 
more  subtle  and  incomprehensible  description,  which 
are  in  constant  operation  within  the  plant ;  and  which, 
acting  from  the  very  earliest  periods  in  which  certain 
organs  begin  to  develop,  tend  to  suppress  or  modify 
them;  and  thus  produce  that  infinite  diversity  of 
forms  and  characters,  which  we  find  even  among  those 
which  are  destined  to  perform  the  very  same  function. 
And  sometimes  the  altered  organs  are  so  far  changed 
from  their  original  character,  as  to  become  adapted  only 
to  serve  some  new  secondary  purpose,  distinct  from 
that  for  which  they  were  primarily  intended.  Thus, 
the  spines  of  the  common  furze  (Ulex  europceus),  are 
merely  modified  leaves.  In  the  common  berberry 
(Herheris  vulgaris},  the  transition  may  be  readily  traced 
(see  fig.  68.). 

(118.)  Adhesion. — If  to  the  operation  of  the  two 
causes  already  noticed,  we  add  the  "  adhesions,"  which 
take  place  between  the  contiguous  parts  of  similar  or 
different  organs,  we  introduce  a  third  cause,  in  very 


SECT.   I.          ORGANOGRAPHY    AND    GLOSSOLOGY. 


121 


general  operation,  which  serves  to  modify  the  normal 
condition  of  the  several  parts  of  the  separate  whorls. 
For  example/ the  Phlox  amaena  has  a  monopetalous 
tubular  corolla  (fig.  133.  a),  expanding  into  a  flattened 


border  at  the  summit,  and  forming  what  is  called  a 
"  salver-shaped "  flower.  But  a  monstrosity  of  this 
plant  has  been  observed,  where  the  corolla  is  split  up 
into  five  distinct  petals,  resembling  those  of  a  pink 
(Dianthus}.  This  shows  us,  that  the  ordinary  mono- 
petalous condition  of  the  corolla  in  this  flower,  has 
resulted  from  an  adhesion  of  the  five  subordinate  parts 
of  which  it  is  composed ;  and  some  blossoms  have 
been  found,  in  which  this  adhesion  has  only  taken  place 
partially,  some  of  the  petals  being  cemented  half-way 
up  the  tube,  whilst  others  adhere  nearly  throughout  its 
whole  length  (6). 

Not  only  may  the  several  parts  of  the  separate 
whorls  contract  adhesions  of  these  kinds,  but  two  or 
more  of  the  whorls  may  be  grafted  together,  throughout 
a  greater  or  less  extent. 

The  causes  here  enumerated,  as  modifying  or  dis- 
guising the  several  parts  of  which  flowers  are  composed, 
are  brought  into  operation  at  such  early  stages  of  their 
development,  that  it  is  very  seldom  we  can  trace  the 
successive  steps  by  which  the  metamorphosis  has  been 
effected.  In  many  cases,  however,  we  find  the  number 
of  ovules  in  the  ovarium,  far  exceeding  the  number  of 
ripened  seeds  in  the  pericarp;  and  the  obliteration  of 


122  DESCRIPTIVE    BOTANY.  PART  I. 

those  which  have  become  abortive,  may  be  some- 
times traced  to  the  circumstance  of  there  having  been 
more  ovules  originally  formed  than  could  possibly  be 
contained,  as  ripened  seeds,  in  the  pericarp,  which  would 
be  too  small  to  hold  them  all.  It  is  easy,  therefore,  to. 
conceive,  that  those  parts  of  a  flower  which  are  only 
exhibited  in  cases  of  monstrous  development,  may  in 
like  manner  have  been  choked  by  the  compression  of 
some  contiguous  parts,  which  got  the  start  of  them  in 
the  progress  of  their  growth.  It  is  equally  easy  to 
comprehend,  that  two  contiguous  parts  may  be  con- 
stantly predisposed  to  graft  together,  long  before  we 
can  trace  them  in  a  detached  state.  We  perpetually 
see  apples,  peaches,  and  a  variety  of  other  fruits, 
become  double,  owing  to  the  great  facility  with  which 
their  tissues  graft  together,  when  brought  into  close 
contact;  and  we  can  readily  imagine  that  the  tissues 
of  two  contiguous  organs,  whilst  they  are  yet  in  their 
nascent  state,  must  be  in  a  condition  even  still  better 
adapted  for  receiving  this  impression,  than  they  would 
be  at  a  later  period  of  their  growth. 

In  those  cases  of  adhesion  where  the  union  is  most 
perfect,  it  generally  happens  that  some  portions  have 
necessarily  become  suppressed,  and  thus  a  monstrous 
form  is  produced,  in  which  the  number  of  its  parts  will 
lie  between  the  regular  number  in  a  single  flower,  and 
some  multiple  of  that  number.  Now,  that  which  is  so 
evidently  the  result  of  a  natural  grafting  of  contiguous 
parts,  in  these  monstrous  cases,  may  be  conceived  also  to 
exist  in  other  instances,  where  the  same  cause  may  have 
been  in  operation,  previous  to  the  very  earliest  stage  of 
development  to  which  the  existence  of  the  flower  can 
be  traced. 

(119.)  Supernumerary  \Vhorla. — It  sometimes  hap- 
pens, that  a  supernumerary  development  takes  place, 
of  one  or  more  entire  whorls,  or  of  the  parts  of  a 
whorl.  In  this  way,  certain  flowers  become  double  ;  but 
such  are  not  necessarily  barren, as  is  the  case  where  double 
flowers  have  resulted  from  the  transformation  of  the 


SECT.   I.         ORGANOGRAPHY    AND    GLOSSOLOGY.  123 

stamens  and  pistils  into  petals.  The  various  parts  of 
these  supernumerary  whorls  alternate  with  those  which 
precede  them  in  the  series. 

(120.)  Normal  Characters. — It  will  readily  he  un- 
derstood, how  numerous  may  be  the  modifications 
which  can  be  referred  to  the  same  normal  condition 
of  the  parts  of  a  flower,  —  if  we  suppose  the  three 
causes  which  we  have  enumerated,  capable  of  acting 
separately,  or  together.  If,  for  instance,  the  normal 
character  of  a  flower  consisted  of  five  sepals,  five 
petals,  five  stamens,  and  five  carpels;  and  these  several 
parts  were  so  arranged,  that  all  those  which  were 
in  any  one  whorl,  alternated  in  position  with  those  in 
the  contiguous  whorls — this  arrangement  would  consti- 
tute a  highly  regular  flower,  such  as  we  meet  with  in 
the  genus  Crassula  (fig.  134.).  By  simultaneously  sup- 
pressing one,  two,  three,  or  four 
parts  of  each  whorl,  we  may  con- 
ceive four  other  flowers  to  be 
formed,  equally  symmetrical  with 
the  original,  but  disagreeing  with 
this  normal  type,  in  not  possessing 
a  quinary  arrangement  of  their 
parts.  Irregularity  might  now  be 
introduced,  by  suppressing  certain 
parts  of  some  whorls  and  not  of  others,  or  by  form- 
ing adhesions  between  two  or  more  parts  of  one  whorl, 
whilst  the  other  parts  remained  free  ;  or  by  supposing 
some  of  the  parts  of  one  whorl  to  degenerate,  and 
assume  a  variety  of  distorted  shapes.  In  this  way,  an 
infinite  variety  of  forms  may  be  supposed  to  result 
from  a  few  normal  types ;  and  it  is  by  detecting  these, 
that  the  systematic  botanist  is  enabled  to  ascertain  the 
affinities  of  certain  species,  which  at  first  sight  appear 
widely  separated. 

Whenever  the  parts  of  one  whorl  are  placed  opposite, 
instead  of  alternate  with,  the  parts  of  the  contiguous 
whorls,  this  circumstance  is  considered  to  indicate  a 
want  of  regularity  in  the  flower,  although  there  may  be 


124 


DESCRIPTIVE    BOTANY. 


PART  I. 


no  real  want  of  symmetry  in  the  arrangement ;  and 
such  a  state  of  things  is  always  supposed  to  have 
originated  in  the  abortion  of  one  or  more  of  the  whorls. 
These  whorls  may  possibly  be  still  developed  under 
certain  conditions,  and  then  the  regularity  of  the 
flower  would  be  restored,  and  the  normal  condition  ex- 
hibited. In  the  annexed  figure  (135.)  there  are  five 
whorls  ascribed  to  the  normal 
condition  of  certain  organs, 
which  "  alternate  "  with  each 
other  in  some  flower;  and  by 
suppressing  the  parts  in  the 
second  and  fourth  whorl,  those 
in  the  first,  third,  and  fifth 
are  brought  "  opposite "  to 
each  other.  Where  two  con- 
tiguous whorls  are  abortive, 
no  irregularity  would  be  ap- 
parent, and  the  existence  of  the  suppressed  parts  might 
not  be  suspected,  unless  it  were  indicated  by  some  ana- 
logy in  other  allied  species. 

It  is  a  remarkable  circumstance  connected  with  these 
inquiries,  that  the  normal  condition  of  dicotyledonous 
plants,  appears  most  frequently  to  involve  a  quinary 
arrangement,  in  the  disposition  of  the  subordinate 
parts  of  the  several  whorls  j  whilst  that  of  Monocoty- 
ledons, equally  affects  a  ternary.  In  a  multitude  of 
examples,  where  the  parts  or  organs  of  the  class  exceed 
these  numbers  respectively,  they  are  still  observed  to  be 
some  multiples  of  them —  10,  15,  20,  &c.,  or  6,  9,  &c.; 
and  many  deviations  from  this  rule,  are  clearly  referable 
to  the  abortions  of  some  of  the  parts,  and  the  adhesions 
of  others ;  so  that  a  considerable  approximation  has 
apparently  been  made,  towards  the  discovery  of  some 
general  laws  on  this  subject. 

(121.)  Spiral  Arrangement  of  foliaceous  Append- 
ages.— The  variety  exhibited  in  the  disposition  of  leaves, 
and  other  foliaceous  appendages  to  the  stem,  or  other 


SECT.  1.         ORGANOGRAPHY    AND    GLOSSOLOGY. 


125 


axes,  may  be  reduced  to  a  general  mode  of  expres- 
sion, by  a  method  proposed  by  M.  Schimper,  and 
subsequently  elucidated  by  M.  Braun.  Even  in  those 
cases  where  their  distribution  does  not  seem  to  be 
regulated  by  any  law  of  symmetry,  this  may  be  con- 
sidered to  be  owing  to  the  various  disturbing  causes 
which  are  perpetually  modifying  the  conditions  under 
which  their  arrangement  would  otherwise  have  taken 
place.  As  the  mineralogist  refers  the  crystalline 
forms  of  his  minerals,  to  certain  geometric  solids, 
whose  angles  at  least  are  the  same  as  those  on  the 
crystal;  so  we  must  here  neglect  the  accidental  displace- 
ments, produced  by  the  unequal  development  of  those 
parts  to  which  the  foliaceous  appendages  are  at- 
tached, or  some  other  circumstances,  and  look  only  to 
the  primary  conditions  upon  which  their  distribution 
depends.  If  in  those  cases,  even,  where  the  leaves  are 
most  scattered  on  the  plant,  we  were  to  draw  a  line 
from  any  one  which  is  seated  lower  down  the  stem 
or  branches,  to  another  next  above  it,  and  so  on, 
this  line  will  be  found  to  follow  a  spiral  direction ;  and 
thus  we  ultimately  arrive  at  a  leaf,  which  is  seated  ver- 


tically above  that  from  which  we  started.     The  usual 
mode  of  expressing  this,  is  to  name  the  number  of  the 


126  DESCRIPTIVE    BOTANY.  PART  I. 

leaf  which  ranges  vertically  over  the  first  on  this  spiral, 
but  without  any  reference  to  the  number  of  coils  which 
the  spiral  makes  before  this  happens.  Thus,  in  each  of  the 
annexed  figures  (fig.  136.),  No.  8.  ranges  vertically  over 
No.  1 .  ;  but,  in  A,  this  happens  after  one  coil ;  and  in 
B,  not  until  after  three  coils  of  the  spiral.  The 
numbers  are  ranged  at  equal  intervals,  indicated  by 
the  eight  vertical  lines  drawn  on  the  surface  of  the 
cylinder. 

( 1 22.)  Divergence  of  general  in  <j  Spirulx.  —  M.  Braun 
proposes  to  note  the  nature  of  this  arrangement,  by 
giving  it  a  numerical  value,  which  shall  be  expressive  of 
the  angular  distance  between  two  successive  leaves  on 
the  spiral,  when  they  are  projected  on  a  plane  perpen- 
dicular to  the  axis.  The  expression  obtained,  is  termed 
the  "  divergence  "  of  the  generating  spiral.  Thus,  the 
divergence  in  A,  is  the  angular  distance  between  1  and 
2  (viz.  |  of  the  circle)  ;  but  the  divergence  in  B, 
is  f ,  as  may  be  seen  by  inspecting  the  summits  of  the 
two  figures.  The  numerators  of  these  fractions  also 
express  the  number  of  coils  which  the  generating  spirals 
make,  before  one  leaf  ranges  vertically  over  another ; 
and  their  denominators,  are  the  number  of  leaves  distri- 
buted upon  this  interval  —  which  is  called  the  "  length" 
of  the  spiral.  It  is  further  evident,  that  the  leaves 
arrange  themselves  along  as  many  lines  drawn  parallel  to 
the  axis,  as  there  are  leaves  on  one  length  of  the  spiral, 
viz.  seven  in  each  of  these  figures. 

Where  the  coils  of  the  spiral  are  not  very  close,  and 
the  numbers  succeed  each  other  at  short  intervals,  it  is 
easy  to  trace  its  course  round  the  axis  ;  but,  in  many 
cases,  the  coils  are  so  close  together,  and  the  leaves,  or 
other  appendages,  so  disposed  upon  them,  that  all  traces 
of  its  course  are  either  obliterated,  or  much  confused. 

(123.)  Secondary  Sjiiralx.  —  But  still,  the  symmetry 
with  which  the  leaves  are  really  disposed,  is  now  ma- 
nifested by  the  appearance  of  several  "  secondary" 
spirals,  which  may  be  traced  in  various  directions. 
This  is  well  exhibited  in  the  arrangement  of  the  scales 


SECT.   I.          ORGANOGRAPHY    AND    GLOSSOLOGY. 


127 


of  a  fir-cone  (fig.  137.)  ;  and  we  shall  endeavour  to 
show,   how  the  real  dispos-  137 

ition  of  the  scales  on  the 
"  generating"  spiral  may  be 
readily  ascertained,  from 
merely  inspecting  the  ap- 
pearances presented  by  these 
secondary  spirals.  Thus,  in 
the  spruce  fir  (Pinus  abies*), 
it  is  easy  to  trace  several  sets 
of  spirals,  running  parallel  to 
1,  9,  17,  25,  &c.;  and  other 
sets  parallel  to  1,  6,  11, 
16,  &c. ;  and  others  to  1,  4, 
7,  &c.,  and  so  on.  In  the 
present  example,  there  are  twenty-one  lines  which  may 
be  drawn  through  those  scales  which  are  ranged  ver- 
tically over  the  others,  as  1,  22,  43,  &c.,  14,  35,  56', 
&c.  and  so  on.  This  number,  as  was  before  shown  of 
the  seven  verticals,  inland  B  (fig.  136'.),  indicates  the 
number  of  scales  that  are  ranged  upon  one  length  of  the 
spiral.  But  the  course  of  the  generating  spiral  is  not 
apparent,  and,  consequently,  the  numerator  of  the  frac- 
tion which  expresses  the  divergence  is  unknown. 

(124.)  To  fix  Numbers  to  the  Scales.  —  We  may 
easily  observe,  that  the  numbers  on  the  scales  which 
form  the  different  secondary  spirals,  are  in  arithmetical 
progression  ;  and  we  shall  presently  show,  in  the  next 
article,  that  the  common  differences  in  these  progressions, 
also  indicate  the  number  of  similar  secondary  spirals 
which  range  parallel  to  each  other.  Thus,  there  are 
eight  parallel  spirals,  1,  9,  17,  &c.,  6,  14,  22,  &c., 
where  the  arithmetical  progressions  have  all  the  same 
common  difference  — eight.  Hence  we  see  a  ready  means 
of  numbering  the  scales  on  the  cone,  without  the  necessity 
of  previously  ascertaining  the  course  of  the  generating 
spiral.  Fixing  on  scale  (l)  for  a  beginning,  and  count- 
ing the  number  of  parallel  spirals  (viz.  eight)  which 
run  in  one  direction,  as  above,  we  can  fix  the  numbers 


128  DESCRIPTIVE    BOTANY.  PART   I. 

1>  9>  17,  &c.  on  one  of  these  spirals;  then  counting 
the  number  (viz.  five)  which  lie  parallel  with  I,  6,  11, 
&c.,  and  which  run  in  a  contrary  direction,  we  can 
also  fix  those  numbers,  upon  that  spiral  :  and  it  is  easy 
to  see  that,  as  these  two  sets  of  spirals  intersect  one 
another,  we  may  fix  numbers  to  every  other  spiral 
parallel  to  each  of  them,  that  is,  to  every  scale ;  and 
thus  the  position  of  the  generating  spiral  becomes  ap- 
parent, by  observing  the  scales  on  which  the  numbers 
1,  2,  3,  &c.  occur,  in  succession.  We  may  easily  count 
the  number  of  parallel  spirals  of  the  same  class,  even  in 
a  mere  segment  of  a  cone,  by  observing  the  intersections 
which  they  make  with  a  circle  drawn  round  it ;  and,  where 
the  cone  is  complete,  they  may  be  counted,  by  observing 
how  many  lie  between  the  coil  which  completes  a  length, 
in  one  of  them.  Thus  the  spiral  1,  6,  11,  16  .  .  .  38, 
46,  51,  56,  has  four  others  lying  parallel  to  it,  and 
between  two  of  its  successive  coils ;  there  are,  therefore, 
five  such  spirals  in  all,  and,  consequently,  the  common 
differences  on  them  are  five.  Looking  to  the  truncated 
edge,  we  might  ascertain  the  same  fact,  by  observing 
that  five  such  spirals  meet  it  in  the  scales  59,  6l,  58, 
&c.  Also  eight  parallel  spirals  meet  it  in  the  scales 
54,  59,  56,  6l,  58,  &c.  '  But  even  without  numbering 
many  of  the  scales,  we  may  ascertain,  first  the  deno- 
minator, and  then  the  numerator,  of  the  fraction  which 
expresses  the  divergence.  We  need  only  place  the  num- 
bers 1,  Q,  17  in  one  direction,  and  then  pass  from  17  to 
22  in  another  direction,  and  we  arrive  at  the  scale 
placed  vertically  over  number  1  ;  and  thus  we  know  that 
21  is  the  denominator  of  the  fraction.  To  find  the  nu- 
merator, we  must  fix  the  scales  2  and  23  —  the  latter 
ranging  vertically  over  the  former  ;  and  then  fixing  all 
the  scales  that  lie  between  the  verticals  (1,  22,)  and  (2, 
23),  which  we  shall  find  to  be  9,  17,  4,  12,  20,  7, 
15  —  through  each  of  which  other  verticals  may  be 
drawn  —  we  obtain  the  angular  distance  between 
any  two  vertical  lines,  viz.  $  of  a  circle :  and  this 
gives  the  number  8,  for  the  required  numerator.  This 


SECT.   I.          ORGANOGRAPHY    AND    GLOSSOLOGY.  129 

may  perhaps  be  rendered  more  evident  by  an  inspection 

of    the    annexed    figure        ]<5S 

(138.),  which  shows  the 

relative    position  of   the 

scales  on   one  length  of 

the    spiral,  seen    in    the 

direction  of  the  axis. 

(125.)  Number  ofse. 
condary  Spirals.  —  Al- 
though the  number  of 
secondary  spirals  which 
are  readily  distinguish- 
able, is  limited,  yet  it  is 
evident  that  we  may  really 

establish  the  existence  of  any  number,  however  great, 
by  merely  passing  a  line  successively,  from  No.  1  to 
any  other  scale,  and  so  on  to  that  scale  next  beyond 
it,  which  has  the  same  relative  position  towards  it,  as 
it  has  to  No.  1.  In  other  words,  we  may  have  arith- 
metical progressions  with  all  possible  common  differ- 
ences, which  shall  represent  different  secondary  spirals  ; 
and  these  spirals  may  be  coiled,  some  to  the  right,  and 
others  to  the  left.  We  proposed  to  show  (what  we 
took  for  granted  in  the  last  article)  that  the  number 
of  parallel  spirals  of  the  same  class,  was  always  equal 
to  the  common  differences,  of  the  progressions  on  these 
spirals.  It  is  clear  that  the  generating  spiral,  passing 
successively  through  1,2,  3,  &c.,  must  be  unique : 
but  the  secondary  spiral,  which  passes  through  the 
odd  numbers,  1,  3,  5,  &c.,  leaves  the  even  numbers,  2, 
4,  6',  &c.,  which  form  a  second  spiral,  of  the  same 
class  ;  that  is  to  say,  there  are  two  secondary  spirals, 
where  the  common  difference  is  2.  There  are  three 
spirals,  in  the  same  manner,  which  pass  through  1,  4, 
7,  &c.,  2,  5,  8,  &c.,  3,  6,  9>  &c->  where  the  common 
difference  is  3  ;  and  so  on  of  all  the  rest.  Several 
other  properties,  of  a  mathematical  /nature  might  be 
mentioned;  but  sufficient  has  been  said,  to  show  the 
simplicity  of  the  investigations  necessary  for  obtaining 


ISO  DESCRIPTIVE    BOTANY.  PART  I. 

an  expression  for  the  divergence,  which  is  all  that  the 
botanist  requires. 

(126.)  Irregularity  of  Divergence.  —  Although  the 
appendages  on  one  part  of  a  plant,  may  be  arranged 
according  to  one  law  of  divergence,  it  does  not  follow 
that  those  of  another  kind,  and  on  another  part,  possess 
the  same  law  ;  and  even  the  same  kind  of  appendages 
are  not  all  subject  to  the  same  law :  thus,  a  few  cones 
on  the  same  fir  tree  often  possess  a  different  diverg- 
ence from  the  rest,  and  even  different  parts  of  the 
same  cone  are  sometimes  differently  disposed.  Many 
of  these  anomalies  originate  in  disturbing  causes,  which 
it  is  not  difficult  to  appreciate;  such,  for  instance,  as 
some  slight  torsion  of  the  axis,  or  the  abortion  of  some  of 
the  parts,  &c.  It  is  also  common  to  find  the  generating 
spiral  turning  to  the  right  in  some  cones,  and  to  the 
left  in  others,  upon  the  same  tree. 

(127.)  Examples  of  Divergences. —  From  what  has 
been  said,  it  will  readily  be  seen,  that  the  disposition  of 
foliaceous  appendages  may  be  conveniently  and  accu- 
rately expressed,  in  terms  of  the  divergence  of  the 
scales  on  the  generating  spiral,  unless  they  happen  to 
be  so  irregularly  disposed  as  to  lose  all  traces  of  a  sym- 
metrical arrangement.  '  Thus,  where  the  appendages 
range  in  a  line  along  one  side  of  the  axis,  the  divergence 
is  =  ^ ;  where  they  are  ranged  in  two  rows,  on  opposite 
sides  of  the  axis  (distichous,  fig.  139-),  the 
divergence  =  ^ ;  when  in  three  rows 
(trifarious'),  the  divergence  may  be  -^  or 
-*  :  the  latter,  however,  may  be  considered 
the  same  as  ±,  turning  round  the  axis  in 
an  opposite  direction.  One  of  the  most 
common,  the  "  quincunxial"  arrangement, 
where  the  appendages  range  in  five  ranks, 
may  be  produced  by  four  different  diverg- 
ences, represented  on  the  circles  in  the  an- 
nexed figure  (fig.  140.);  but  here  also  it  will 
be  seen,  that  two  of  them  are  the  same  as 
other  two,  only  that  the  spirals  turn 


SECT.   I.          OKGANOGRAPHY    AND    GLOSSOLOGY. 


131 


directions.  And  always,  where  the  denominator  of  the 
fraction  is  a  prime  number, 
there  will  exist  one  number 
less  than  that  of  the  divergences, 
according  to  which  the  gener- 
ating spiral  may  be  construct- 
ed —  and  a  similar  number  of 
vertical  ranges  will  still  be  the 
result.  But  where  -the  deno- 
minator is  not  a  prime  number, 
then  some  of  the  fractions  which 
express  these  different  diver- 
gences, are  not  in  their  lowest 
terms ;  and  these  divergences 
represent  the  very  same  spirals 
as  when  such  fractions  are  so 
reduced.  Thus,  when  there  are 
six  vertical  ranges  (fig.  141.), 
the  divergences  may  be  taken  as 


•'•*// 

.'  '','l 


represent  the  trifarious  arrange- 
ment ;  also  jj-  —  i,  which  is  the 
distichous.     Hence  ^  and  -j?  are  •>/' 
the    only    divergences     which  fj 
represent    the  hexafarious   ar-  |  | 
rangement,  and  even  these  may  '   ' 
be   reduced    to  one  kind,  only  ^  \ 
the  spiral  would  be  turned  in  *  \ 
opposite  directions  in  the  two 
cases. 


=  f,  both  of  which 


*\ 
i 

=>/ 


I      I 


132 


DESCRIPTIVE    BOTANY. 


Examples  of  various  Forms  of  Divergence  among  cer 
tain  Species  of  the  following  Genera,  selected  from   n 
long  List  given  by  M.  Braun. 


JEM*. 

Dicutyledonft. 

Monocotyledonet. 

Acotyledonet. 

i 

Alarum  ;  Tilia  ; 
Vicia;  Orobus. 

Spike*  of  all  Gramineae  ; 
Cyperus;  Acoruscalamus. 

Fissidens  ;      Didymodon 
capillaceus. 

4 

Cactus    triangu- 
lar is. 

Carcx  ;    Colcnicum   au. 
tumnale. 

Gymnostomum  sstivum; 
jBBMnMnnla  tricho- 

phylla. 

1 

Common  in  this 
class. 

Scirpus  aciculari*; 
SchcenuR  I'uscus. 

Common. 

2 

Laurui    nobili*  ;  Lilium  camlidum  ;   Scir- 
Ilex  aquifolium.      pus  lacustri*. 

Commonot    in   mosses  , 
Lycopodium  Selago. 

r, 

Euphorbia  sege- 
talis  ;   Convol- 
vulus tricolor. 

Agave  Americana  ; 
many  Orchis. 

Urthotrichum  afflne  ; 
Aspidium  rilix  mas. 

A 

Isatis   tinctoria  ; 
I'lantago    Ian- 
ceolata. 

Orchis  ronoptea;  many 
YUCOE. 

Hypnum     alopecurum  ; 
folytricum  pilirerum. 

* 

Euphorbia    rs»»- 
pitosa  ;     Plan- 
tago  media. 

Yucca   aloefolia  ;    Orni. 
thogalum  pyrenaicum. 

Sphagnum  ;  Politrichu'.m 
formosum. 

£ 

Cactus     corona- 
rius. 

(128.)  Mode  of  examining  the  Divergence.  —  To  the 
above  list  we  will  add  a  complicated  example,  in  the 
spinous  bractese  which  compose  the 
involucrum  of  Carduus  Eriophorus,  D 
and  explain  the  manner  in  which 
the  divergence  may  be  ascertained. 
It  is  easy  to  observe  two  sets  of 
spirals  respectively  parallel  to  A  B 
and  CD  (fig.  142.),  of  which  there 
are  34  of  the  former,  and  21  of 
the  latter.  Fixing  the  Nos.  1,  35, 
(J9,  in  one  direction,  and  90  in 
the  other,  as  in  art.  124.,  we  ar- 
rive at  the  bractea  which  ranges  vertically  over  No.  1. 


SECT.    I.          ORGANOGRAPHY    AND    GLOSSOLOGY. 


133 


Also  No.  35,  is  evidently  nearer  than  any  other  bractea 
to  the  vertical  line  through  1  and  90-  To  con- 
struct the  figure  which  represents  the  projection  of  one 
length  of  the  generating  spiral,  we  may  thus  proceed. 
Place  No.  1  in  the  circumference 
of  the  circle  (fig.  143.),  and  di- 
vide it  into  89  equal  parts;  place 
No.  35  on  the  part  nearest  to  35I 
No.  1  :  and  34  is  the  com-  69\ 
mon  difference  on  that  secondary 
spiral,  which  is  more  nearly 
perpendicular  than  any  of  the 
others.  The  series  on  this 
spiral  is,  therefore,  1,  35,  6'9, 
103,  &c.,  of  which  we  may 
place  69  on  the  next  division 
to  35  ;  but  as  103  belongs  to  a 
second  length  of  the  generating 
spiral,  we  must  subtract  89  from  it,  and  thus  we  shall 
obtain  No.  14,  which  ranges  vertically  below  it,  and 
is,  consequently,  within  the  first  coil  of  the  generating 
spiral  itself,  and  therefore  succeeds  No.  69,  on  the  circle. 
From  No.  1 4  then,  we  may  begin  with  another  secondary 
spiral,  whose  common  difference  is  the  same  as  the  last ; 
and,  consequently,  we  place  the  Nos.  48,  82,  next  in 
succession  to  14;  but  106  rises  into  the  second  length 
of  the  generating  spiral,  and  we  must  subtract  89  as 
before,  which  gives  us  No.  17,  for  the  next  number  in  the 
circumference  of  the  circle  which  represents  only  the  first 
length.  And  so  on  until  we  arrive  at  No.  2.  We  shall 
thus  ascertain  that  No.  2  is  placed  at  55  intervals  from 
No.  1,  and,  consequently,  that  the  divergence  in  this 
example  is  = -|^.  It  may  readily  be  understood,  by  any 
person  accustomed  to  mathematical  investigations,  that 
the  first  term  common  to  the  two  arithmetical  series,  1, 
35,  69,  &c.,  and  2,  91,  180,  &c.  (and  which  is  1871), 
will  be  the  number  on  the  bractea  intersected  by 
that  spiral,  which  is  represented  by  the  first  of  these 
K  3 


134 


DESCRIPTIVE    BOTANY. 


arithmetical  series,  and  the  vertical  line  through  No.  2, 
represented  by  the  second ;  and  also  that  one  less  than 
the  number  of  terms  in  the  first  series  represents  the 
angular  distance  of  2  from  1.  Several  other  interesting 
mathematical  considerations  might  be  given,  but  they 
would  appear  to  be  misplaced  in  a  treatise  of  this  de- 
scription. 

(129.)  Tabular  View  of  Vegetable  Organs.  —  In  con- 
cluding this  part  of  our  subject,  we  shall  present  the 
reader  with  a  tabular  view  of  the  various  organs  we  have 
been  describing,  so  arranged  as  to  display  the  subordin- 
ation which  subsists  between  them ;  giving  a  reference 
to  the  separate  articles  in  which  each  is  described. 


I.   ELEMENTARY  ORGANS  (!".)• 


Membrane  (13.) 
Fibre  (U) 


f  Vesicle 

)  Trache 

)  Ducts 

I  Vital  v 


Vesicle*  (16.) 
'     :he«e  (23.) 
is  (24.) 
'essels  (27.) 


Modifications. 
Cellular  tissue  (16) 
Vascular  tissue  («2.) 


Pellicle  (29 )       > 
Slomata  (30.)     J 


II.  COMPOUND  ORGANS  (28.). 

Epidermis  (29.) 

Hair  (31.) 
Stings  (31.) 
Glands  (31.) 


III. 


ponpoles  (39.)    7 
•ibrils  (39.)          \ 


Pith  («.) 
Medullary  sheath  (49.) 
Woody  layers  (50.) 
Alburnum  (50.) 
Medullary  rays  (51.) 
Liber  (52.) 
Cortical  layers  (52.) 

Petiole  (69.)  J   7 
Limb  (69.)        j 


COMPLEX    ORGANS  (32.). 
*  Nutritive  (38.). 

Roots  (39.) 
Appendages  (41.) 


Stems  '440  and 
"Branches  (59.) 


Leaf  (69.) 
Stipules  (77.) 


Thorns  (62.) 
Bulbs  (65.) 
Tubers  (64.) 
.Suckers  (62.) 
Kunners  (62.) 


Phyllodia  (75.) 
Spines  (78.) 
Tendril* 
Pitchers  (80.) 


TAXONOMY    AND    PHYTOGRAPHY.  135 

**    Reproductive  (85.). 

Bractea  Involucrum  (91.) 

(91.) 
Sepals -Calyx     }  Peri. ' 

'anth 
(93.) 


—  Calyx     ") 

(9*0      ( 

—  Corolla  { 

(95.)    3 

sftTi"^  I 

Filament   C 

(97.)        J 


Fovilla 

Granules  (99.)    )  ^\"s  (     (98.)     1  J-    Flower  (92.) 

'Stamen  (95.) 
•nt    \ 
^(97.) 
Carpels  (100.) 
Ovules  (112.) 


COMPOSITION  OF  THE  RIPE  FRUIT  (105.)- 


Pericarp 

(106.) 

Radicle  (111.)  }         ,-,    . 

Cotyledon  (112.)       {        ™f*?° 
Plumule  (111.)        3  11L) 

Spermoderm 
(109.) 


SECTION  II. 

TAXONOMY    AND    PHYTOGRAPHY. 

CHAP.  VII. 

NATURAL    GROUPS    (131.).  VALUES    OF    CHARACTERS    (192.) 

SUBORDINATION    OF    CHARACTERS    (133.).  NATURAL    OR- 
DERS   (135.).  ARTIFICIAL    ARRANGEMENTS    (136.).  LIN- 

N^EAN    SYSTEM    (137.) APPLICATION    OF    IT    (140.). 

(130.)  Taxonomy.  —  WE  have  no  space  to  devote  to 
any  extended  review  of  the  various  methods  and  sys- 
tems which  have  been  proposed  for  the  classification 
of  plants ;  and  it  is  not  necessary  for  us  to  explain 
K  4 


I3  DESCRIPTIVE    BOTANY.  PART  I. 

the  uses  which  a  systematic  arrangement  of  natural 
bodies  is  intended  to  serve.  This  subject  has  been 
thoroughly  and  sufficiently  discussed  by  Mr.  Swainson, 
in  our  sixty-sixth  volume.  We  may  just  remark,  that 
the  number  of  species  already  named  and  classified  in . 
works  of  botany,  amounts  to  about  60,000 ;  and  this 
fact  alone  must  satisfy  us,  how  necessary  it  is  that 
botanists  should  possess  those  means  of  intercommuni- 
cation, which  a  systematic  classification  alone  can  afford 
—  whenever  they  wish  to  announce  the  discovery  of  a 
new  species,  or  to  refer,  with  certainty,  to  one  which  has 
been  previously  noticed.  But,  if  we  have  the  higher 
object  in  view,  of  searching  after  the  laws  and  princi- 
ples which  regulate  the  structure  and  fix  the  properties 
of  plants,  then  it  is  a  necessary  and  immediate  conse- 
quence of  every  discovery  of  this  kind,  that  we  thereby 
obtain  a  nearer  conception  of  those  affinities  by  which 
plants  approach,  and  of  those  differences  by  which  they 
recede  from  each  other  ;  and  this,  in  fact,  amounts  to 
a  closer  insight  into  that  hitherto  undiscovered  system,  or 
plan,  upon  which  we  must  feel  satisfied  that  the  Author 
of  nature  has  proceeded  in  creating  all  natural  objects. 

(131.)  Natural  Groups.  —  We  have  already  (art. 
33.)  mentioned  the  leading  characteristics  of  the  three 
primary  groups,  or  classes,  into  which  plants  seem 
to  be  naturally  divisible.  Each  of  these,  again,  admits 
of  subdivision  into  minor  groups,  which  severally  con- 
tain such  species  as  are  more  nearly  related  to  each 
other  than  to  those  of  other  groups.  By  further  sub- 
divisions of  this  kind,  a  subordination  of  groups,  of 
smaller  and  smaller  dimensions,  is  obtained,  until  we 
arrive  at  those  groups  which  do  not  readily  admit  of 
further  subdivision,  and  which  are  termed  "genera." 
It  must,  however,  be  obvious  that  this  method,  of 
analysis,  is  not  the  actual  process  in  which  the  primary 
groups  were  originally  established.  This  was  effected 
by  a  synthetical  mode  of  procedure  —  by  comparing 
separate  individuals,  and  by  selecting  those  which  most 
nearly  resembled  each  other ;  and  thence  establishing, 


SECT.  II.      TAXONOMY  AND  PHYTOGRAPHY.        137 

in  the  first  place,  the  limits  within  which  a  given 
species  might  be  supposed  to  vary.  Then,  by  com- 
paring different  species,  and  selecting  those  which  had 
the  greatest  resemblance,  a  genus  was  constructed. 
Then  the  genera  were  grouped  into  orders ;  and  lastly, 
those  orders  which  possessed  only  a  few  general  but  im- 
portant points  of  resemblance,  were  arranged  under  the 
three  classes  alluded  to.  But  when  these  several  groups 
were  once  established,  a  further  refinement  in  their 
classification  could  be  made ;  and  the  principles  upon 
which  this  was  effected,  may  be  explained  by  the  ana- 
lytical process  to  which  we  have  just  had  recourse, 
when  we  said  that  all  species  are  comprised,  first,  in  a 
class;  secondly,  in  an  order,  or  family ;  and  thirdly, 
in  a  genus.  In  very  many  cases,  a  further  subordination 
may  be  established  among  the  several  groups ;  and, 
from  various  considerations,  they  may  either  be  aggre- 
gated into  larger,  or  subdivided  into  smaller  groups  ;  to 
which  other  names  are  applied,  of  which  we  have 
given  an  example  in  art.  102.  .  When  any  group  is 
subdivided  into  larger  groups  than  those  which  it 
is  supposed  to  contain  under  the  system  of  subordin- 
ation already  described,  these  are  generally  recognised 
by  the  addition  of  the  word  "  sub"  to  the  name  of 
the  original  group ;  thus  we  have  sub-classes,  sub- 
orders, and  sub-genera.  Certain  groups  are  also  termed 
"  Tribes,"  "  Cohorts,"  "  Sections,"  and  «  Divisions ; " 
and  some  of  these  terms  are  used  indiscriminately  for 
subordinate  groups  among  the  classes,  genera,  and  even 
species.  When  a  "  variety"  of  any  species  is  repro- 
ducible by  seed,  and  retains  its  peculiarities  pretty 
steadily,  without  returning  to  the  more  common  type, 
it  is  termed  a  "race;"  but  when  its  distinguishing 
characters  are  transient,  and  may  be  modified  by  a 
change  of  soil  or  situation,  it  is  only  a  "variation." 
In  this  way  then,  we  establish  a  subordination  among 
the  natural  groups  into  which  plants  may  be  arranged, 
and  which  may  be  exemplified  by  the  following  in- 
stance. 


138  DESCRIPTIVE    BOTANY.  PART  I. 

I.   Class         ....     Dicotyledones. 

*  Sub-class         -  -     Calyci  flora1. 
II.    Order  -     Lcguminosa1. 

*  Sub-order  -         -     Papilionaceae. 
**  Tribe                            -  -     Lotea. 

***  Sub-tribe  -         -  Genisteae. 

III.   Genus            -  -  Antliyllis. 

*  Sub-genus  (or  Section)  -      -  Vulneraria. 
IV.   Species  -  Vulneraria. 

*  Variety  -         -  Dillenii. 

**   Race     ...  -     Florilms  coccineis. 

***  Variation  -         -     Foliisliirsutissiniis. 

(132.)  Value  of  Characters.  —  In  determining  the 
particular  group  to  which  a  plant  belongs,  it  is  neces- 
sary to  compare  its  "  characters"  with  those  of  other 
species.  By  the  term  "  characters/'  we  mean  the  pecu- 
liar appearances  presented  by  different  organs.  Thus, 
a  leaf  may  be  round,  lanceolate,  &c. ;  the  petals  may 
be  united,  abortive,  &c. ;  and  these  adjectives  denote  the 
peculiar  characters  of  these  organs.  It  will  readily  be 
understood,  that  some  characters  must  be  of  much 
greater  importance  than  others,  in  determining  the 
affinities  of  different  species.  Thus,  the  first  degree 
of  affinity  in  phsenogamous  plants,  is  almost  always  to 
be  ascertained  by  a  single  character,  residing  in  the 
embryo ;  and  we  may  determine  at  once,  to  which  of 
the  two  primary  groups  it  belongs,  by  attending  to  this 
circumstance  alone.  But  even  here,  this  primary  cha- 
racter may  be  so  far  disguised  or  modified,  as  inevit- 
ably, in  some  instances,  to  lead  us  into  error,  if  it 
were  not  possible  for  us  to  check  our  observations  by 
other  considerations,  of  secondary  importance  in  most 
cases,  but  which,  in  the  present  instance,  are  quite 
sufficient  to  correct  our  judgment,  and  to  satisfy  us 
of  the  real  affinities  of  the  plant  in  question.  Thus, 
in  the  genus  Cuscuta,  the  character  of  the  flower, 
the  structure  of  the  stem,  and  other  circumstances, 
clearly  indicate  that  it  belongs  to  the  class  "  Dicotyle- 
dones"—  although  the  embryo  has  no  cotyledons,  and  the 
stem  is  leafless.  The  inference  to  be  drawn  from  these 


SECT.  II.  TAXONOMY    AND    PHYTOGRAPHY.  139 

facts  is,  that  the  cotyledons  and  leaves  are  abortive ; 
and  hence  we  might  expect,  if  ever  such  a  phenomenon 
should  occur  as  a  leafy  Cuscuta,  that  its  cotyledons 
would  certainly  resemble  those  of  other  Dicotyledones. 
When  the  class  of  any  plant  has  been  determined  by 
the  presence  of  some  one  character,  or  by  the  com  bin. 
ation  of  several,  we  next  renew  our  search  for  other 
characters  of  a  less  general  description,  to  ascertain  the 
ee  order"  to  which  it  belongs.  And  when  we  have  found 
the  order,  we  must  descend  to  still  more  minute  particu- 
lars for  fixing  the  "  genus."  It  is,  therefore,  of  the 
utmost  consequence  to  these  inquiries,  that  an  accurate 
subordination  of  characters  should  be  established  ;  and 
for  this  purpose  a  few  rules  have  been  framed,  which 
are  the  result  of  an  extended  examination  of  facts,  or 
the  deductions  of  common  sense.  We  must  remark, 
that  a  direct  comparison  can  only  be  made  between 
two  organs  which  belong  to  the  same  class  of  functions: 
the  nutritive  organs  must  therefore  be  compared  toge- 
ther, and  the  reproductive  together,  in  order  to  esta- 
blish a  subordination  in  each  series  respectively.  We 
may,  however,  afterwards  determine,  whether  one  of 
these  two  functions  can  not  be  considered  more  im- 
portant than  the  other ;  and  then  we  shall  also  be  able 
to  establish  something  like  a  fresh  relation,  between  the 
several  degrees  which  had  been  previously  settled  for 
the  two  series  of  organs.  Suppose,  for  example,  it  were 
determined,  that  the  cotyledons  are  among  the  organs 
of  most  importance  to  the  nutritive  system,  and  the 
root  among  those  of  the  next  degree.  Suppose,  also, 
the  stamens  were  determined  to  be  organs  of  the  highest 
importance  to  the  reproductive  function,  and  the  co- 
rolla among  those  of  the  next.  Now,  if  it  were  also 
determined  that  the  nutritive  function  was  of  more  im- 
portance than  the  reproductive,  then  the  cotyledons  will 
be  of  more  value  than  the  stamens.  But,  although  the 
root  may  be  of  more  importance  than  the  corolla,  it 
does  not  follow  that  it  is  necessarily  of  more  than  the 
stamens  ;  it  may  be  of  equal  or  less  importance.  In 


140  DESCRIPTIVE    BOTANY.  PARTI. 

this  latter  case,  we  are  comparing  an  organ  of  second- 
rate  importance  in  the  one  series,  with  one  of  first-rate 
in  the  other. 

If  we  could  determine  the  natural  affinities  of  all 
plants,  from  a  comparison  of  the  characters  deduced 
from  one  series  alone,  and  could  likewise  determine  their 
natural  affinities  from  characters  belonging  to  the  other 
series,  it  is  evident  that  the  two  arrangements  thus 
established  would  strictly  coincide.  In  the  establishment 
of  the  minor  groups,  botanists  have  recourse  almost 
exclusively  to  the  reproductive  organs ;  as  their  cha- 
racters are  much  better  defined,  and  more  varied  than 
those  of  the  nutritive  organs.  The  larger  groups,  how- 
ever, are  chiefly  determined  by  characters  belonging  to 
the  nutritive  and  elementary  organs,  as  we  have  shown 
(art.  33.),  where  the  exogenous  structure  tallies  with 
the  dicotyledonous  embryo,  and  the  endogenous  with  the 
monocotyledonous. 

(133.)  Rules  for  firing  Subordination  of  Character*. 
—  The  following  rules  may  be  advantageously  con- 
sulted, for  determining  a  subordination  of  characters  in 
one  or  the  other  series. 

1.  Where  two  organs,  belonging  to  different  classes 
of  functions,  have  the  same  relative  value  in  their  re- 
spective series,  that  organ  will  possess  the  greatest  value 
which  belongs  to  the  most  important  function. 

2.  Those  organs  of    the  same   series,   are  of  the 
greatest  value,  which  are  of  most  general  occurrence. 
Thus  the  cellular  tissue,  which  is  universally  present,  is 
the  most  important  element  in  vegetation. 

3.  The  adhesion  which  frequently  subsists  between 
an  inferior  and  a  superior  organ,  serves  to  point  out  the 
relative  value  of  any  two  of  the  former  ;  since  it  will 
be  the  same  as  that  which  was  previously  established 
for  those  of  the  latter,  to  which  they  respectively  adhere. 

4.  The  greater  degree  to  which  an  organ   is  liable 
to  vary,  indicates  an   inferiority   in   its  value.     Thus 
the  shape  of  the  leaves,  is  of  little  importance  beyond 
determining  the  specific  distinctions  of  plants,  and  in 


TAXONOMY    AND    PHYTOGEAPHY. 


HI 


many  cases  is  even  of  no  further  use,  than  in  discrimi- 
nating certain  varieties  of  the  same  species. 

5.  The  relative  periods  at  which  different  organs 
are  formed  and  developed,  may  also  be  taken  as  some 
test  of  their  relative  importance  ;  those  which  are  the 
earliest  formed,  being  considered  more  important  than 
others  with  which  they  are  immediately  connected,  and 
of  the  same  class. 

By  attention  to  these  and  a  few  other  rules  of  less 
general  application,  a  subordination  of  characters  has 
been  established,  of  which  the  chief  results  are  exhibited 
in  the  following  table  :  — 


Relative 
Values. 


Elementary. 

Cellular  Tissue 
Vascular  Tissue 
(a)  Tracheae 
(6)  Ducts 
Stomata 


Nutritive. 


Reproductive. 


5. 


Embryo   and        'j 
Sporule 

(a)  Cotyledons  > 
(6)  Radicle 
(c)  Plumule    J 

"(1)  Stamens  and 

Pistils. 

(2)  Fruit,    Peri- 
[^     carp,  Theca. 

{Perianth. 
(a)  Corolla. 
(6)  Calyx. 
|"  Inflorescence, 
J  Torus,  Nectary, 
"J  Bractea,     Invo- 
(_      lucre. 


Root,     Stem, 
Leaf,    Frond, 
Thallus 


(134.)  Relative  Importance  of  similar  Organs. — Be- 
sides the  relative  values  of  different  organs,  established 
in  this  table,  we  may  estimate  the  relative  value  which 
two  organs  of  the  same  kind  bear  to  each  other,  in  dif- 
ferent species.  This  will  depend  upon  the  greater  or  less 
perfection  which  they  exhibit  in  their  respective  modes 
of  development ;  also,  upon  their  position,  connection 
with  other  organs,  and  numerous  other  particulars  which 
it  is  impossible  to  define  with  any  degree  of  precision, 


142  DESCRIPTIVE    BOTANY.  I'AHT   I. 

and   which  practice  alone  can    enable   the  systematic 
botanist  duly  to  appreciate. 

(135.)  Xatnrnl  Orders. — As  we  make  no  pretensions 
in  this  volume  to  enter  upon  the  details  of  systematic 
botany,  we  do  not  consider  it  advisable  to  present  the 
reader  with  a  bare  enumeration  of  the  characters  of  the 
natural  orders  which  have  been  hitherto  established  in 
the  most  recent  works.  We  shall  content  ourselves  with 
explaining  the  connection  which  subsists,  between  the 
principal  groups  under  which  Jussicu  arranged  the 
natural  orders,  so  far  as  they  had  been  established  in 
his  time,  with  the  principal  groups  in  the  recent  system 
of  De  Candolle,  under  which  this  eminent  botanist  has 
arranged  the  natural  orders  as  they  are  at  present  un- 
derstood. Jussieu  threw  the  natural  orders  or  families 
with  which  he  was  acquainted,  into  fifteen  groups, 
which  he  termed  classes,  and  these  he  further  com- 
bined into  six  principal  groups  or  divisions ;  of  which 
four  belonged  to  Dicotyledones,  and  one  each  to  Mono- 
cotyledones  and  Acotyledones.  De  Candolle  has  also 
four  groups  for  the  Dicotyledones  and  one  for  the  Mo- 
nocotyledones,  but  somewhat  differently  arranged  ;  and 
he  has  split  up  the  Acotyjodones  into  two  parts,  one  of 
which  (although  cryptogamic  like  the  other)  he  classes 
with  the  Monocotyledones,  and  retains  the  other  only 
as  Acotyledones.  He  further  arranges  the  whole  of 
vegetation  under  two  principal  heads,  according  as  plants 
possess,  or  are  entirely  without,  any  portion  of  a  vascular 
structure. 


TAXONOMY  AND  PHYTOGRAPHY. 


143 


Comparative  View  of  the  Systems  of  De  Candolle  and 
Jussieu. 


Primary  Divisions  of  De 
Candolle. 

Subordinate  Groups 
(  Classes  of  Jussieu) 
common  to  both. 

Primary  Divisions 
of  Jussieu. 

*  Vasculares  sen  Cotyle- 

don ea>. 

A.  Dicotyledoneae  seu 

C.  Dicotyledones. 

Exogenje. 

I.  Thalamiflora?. 
f 

14.  Hypopetalas             } 
13.  Peripetala? 

III.  Polypetala?. 

12.  Epipetala?                 J 

11.  Epicorolhe  corisan-"! 

II.  Calyciflorae.             4 

thera; 

10.  Epicorollae    synan-  ! 
therae 

II.  Monopetala;. 

I 

9.  Pericorollaj 

III.  Corolliflorae. 

8.  Hypocorolla?           J 

f 

7.  Hypostaminea;        ~i 

6.  Peristaminea; 

I.  Apetale. 

IV.  Monochlamydeaj    ^ 

5.  Epistaminea?           J 
15.  Diclines                   1 
*   Angiosperma?          Y 

IV.  Diclines. 

L  **   Gymnosperma?        3 

B.  Monocotyledonea?  sett 

B.  Monocotyledones. 

Endogena? 

f 

4.  Monoepigyna? 

V.  Phanerogam  as          •< 

3.  Monoperigyna? 

C 

2.  Monohypogynaj 

A.  Acotyledones. 

VI.  Cryptogamse           } 
**  Cellulares  sen  Aco-f 
tyledonea?                 ( 

1.  Acotyledones 

VII.  Cellulares             3 

We  have  explained  in  art.  102.  the  meaning  of  the  terras 
which  designate  the  principal  groups  of  De  Candolle  in 
the  first  column  of  this  table;  and  we  shall  now  explain 
those  which  have  been  proposed  for  the  classes  of  Jussieu, 
in  the  second  column,  as  their  etymology  may  assist  the 
reader  in  recollecting  them.  They  are  combinations 
of  words  expressive  of  the  three  modes  of  floral  arrange- 
ment described  in  art.  101.,  applied  respectively  (in  the 
Dicotyledones)  to  the  "petals,"  when  these  organs  do 
not  cohere  together;  to  the  "  corollae,"  when  they  are  mo- 
nopetalous;  and  to  the  "  stamens,"  when  the  perianth  is 
single.  Thus,  Epicorollae  indicates,  that  a  monopetalous 
corolla  is  epigynous  in  the  10th  and  llth  classes;  which 
are  further  distinguished  from  each  other  by  the  anther 


144  DESCRIPTIVE    BOTANY.  PART  I. 

being  united  together  (<rv»)  in  the  10th,  and  separate 
(xof«;)  in  the  llth.  The  term  Diclines  indicates  the 
flowers  of  the  l.'jth  class  to  be  unisexual  ;  and  in  the 
two  subdivisions  of  this  class,  the  seeds  are  contained  in 
a  pericarp  or  distinct  vessel  (a-yyc?)  in  the  one,  and  art- 
without  it,  or  naked  (yv/xvo?),  in  the  other.  The  deri- 
vation of  the  classes  of  the  Alonocotyledones  is  evident. 

(136.)  Artificial  Arrangements. — An  artificial  arrange- 
ment proceeds  upon  the  fact,  that  certain  organs,  in  nearly 
all  the  species  included  under  the  same  genus,  have  a 
great  degree  of  constancy  as  to  their  number,  relative 
size,  position,  and  other  characters  ;  and  these  organs 
are  selected  as  the  basis  of  the  systematic  arrangement. 
Thus,  for  example,  every  species  of  the  genus  Ranun- 
culus has  more  than  twenty  stamens,  and  these  organs 
are  similarly  circumstanced  with  respect  to  the  other 
floral  whorls.  The  species  of  the  genus  Papaver,  have 
their  stamens  arranged  like  those  of  the  last-mentioned 
genus,  and  they  are  also  numerous.  These  two  genera 
belong  to  different  natural  orders,  but  they  and  many 
others  are  thrown  together  into  the  same  artificial  class, 
characterised  by  the  species  having  their  stamens  nume- 
rous, and  not  attached  to  the  calyx,  the  flowers  also 
containing  both  stamens  and  pistils. 

The  natural  groups,  then,  which  we  term  genera,  and 
which  are  the  lowest  in  the  rank  of  subordination,  are 
not  subdivided  to  suit  the  purposes  of  an  artificial  arrange- 
ment ;  but  it  is  the  higher  groups  only  which  are  so. 
There  are  certain  cases,  however,  where  it  is  advisable  to 
break  through  this  rule,  and  to  retain  under  the  sarae 
artificial  class,  several  genera  of  a  natural  order,  which  do 
not  agree  with  the  rule  laid  down  for  fixing  their  posi- 
tion in  the  system.  In  other  words,  it  would  be  too  great 
a  violation  of  the  natural  group  to  which  such  genera 
belong,  to  separate  them  from  it.  Thus,  for  example, 
the  greater  number  of  those  genera  of  the  natural  order 
Leguminosse  which  have  papilionaceous  flowers,  forming 
the  tribe  Papilionaceie,  have  their  filaments  united  round 
the  pistil,  so  thatnine  are  blended  together,  and  one  stands 


SECT.  II.      TAXONOMY  AND  PHYTOGRAPHY.        145 

by  itself  (see  art.  97-)  ;  and  an  artificial  class  (Diadel- 
phia)  has  been  constructed  to  admit  all  flowers  which 
have  their  stamens  united  into  two  bundles.  Now,  there 
are  a  few  genera  of  the  Papilionaceae,  where  the  union 
of  the  ten  filaments  is  complete;  and  these  therefore 
strictly  belong  to  another  artificial  class  (Monadelphia), 
characterised  by  this  circumstance.  But  in  this  case 
the  natural  affinity  is  so  striking,  that  the  artificial 
arrangement  is  broken  through,  and  they  are  all  classed 
together.  We  shall  presently  explain  how  the  diffi- 
culty of  such  a  false  position  is,  to  a  certain  extent, 
obviated.  (Art.  1 38.  bis.} 

An  artificial  system  which  should  disregard  the  con- 
struction of  genera,  and  group  species  according  to 
the  principles  of  that  system,  would  be  the  most  per- 
fect ;  but  this  would  be  descending  to  a  degree  of 
precision  unnecessary  for  obtaining  the  sole  purpose  for 
which  an  artificial  system  should  be  employed,  viz. 
the  detection  of  the  name  of  a  plant ;  and  the  devices 
adopted  for  referring  the  anomalous  species  to  their 
proper  genus,  and  the  anomalous  genera  to  their  pro- 
per class,  are  sufficient  to  counteract  the  smaller  in- 
convenience of  establishing  >a  system  at  variance  with 
these  few  cases. 

(137-)  Linneean  System. —  The  most  celebrated  of 
the  several  artificial  systems  which  have  been  proposed, 
is  that  which  Linnaeus  established,  from  considerations 
deduced  from  the  number  and  disposition  of  the  sta- 
mens and  pistils ;  these  organs  maintaining  a  greater 
general  resemblance  in  all  the  species  of  the  same 
genus,  and  through  many  genera  of  the  same  natural 
group,  than  any  others.  They  are  at  the  same  time 
sufficiently  modified  in  different  groups,  to  allow  of 
these  being  thrown  into  several  orders  and  classes,  cha- 
racterised by  some  definite  and  striking  peculiarity. 
This  system  has  been  styled  the  sexual  system,  In 
his  arrangement,  Linnaeus  established  twenty-four 
classes ;  the  last  of  which  embraces  the  whole  of 
the  natural  class  of  Acotyledones,  or  flowerless  plants. 


146 


DESCRIPTIVE    BOTANY. 


The  Dicotyledones  and  Monocotyledones  are  distributed 
unequally  throughout  the  other  twenty-three  classes ; 
some  of  these  consisting  entirely,  or  chiefly,  of  the 
one,  and  others  of  the  other,  whilst  several  of  them 
are  made  up  from  both  of  these  natural  classes.  The 
fundamental  principles  upon  which  his  arrangement 
proceeds,  are  of  the  simplest  possible  description,  but 
in  the  practical  application  of  them,  the  beginner 
will  unfortunately  meet  with  several  anomalies,  and 
without  repeated  caution  he  is  sure  to  be  misled. 
The  following  table  exhibits  the  names  of  the  clas-< •- 
and  orders  of  the  Linntcan  system  ;  and  we  shall 
explain  their  etymology,  as  this  is  intended  to  con- 
vey the  leading  characteristic  upon  which  each  de- 
pends. 


Tabular  View  of  the  Classen  and  Orders  of  the 
Linruean  System. 


Classes. 

1. 

Monandria. 

2. 

Diandria. 

3. 

Triandria. 

4. 

Tetrandria. 

5. 

Pentamlrin. 

6. 

Hexandria. 

7. 
8. 

Ili-ptandria. 
Octandria. 

9. 

Enncandria. 

10. 

Decandria. 

11. 

Doderandria. 

12. 

Icosandria. 

13. 

Polyandria. 

14. 

Didynamia. 

15. 

Tetradynamia. 

Ifi. 
17. 
18. 

Monadelphia. 
Diadelphia. 
Polyadelphia. 

Orders. 


fJLOVOS. 

Si,. 

Tpflt. 

rtrpas 

TTfVTf. 

firra. 

OKTtll. 
tVVfO.. 


"I  Monogynia. 

Digynia. 

Trigynia. 

Tetragynia. 

Pentagynia. 

Hexagynia. 
)-Hepta<ryiiia. 

Octogynia. 

Enneagynia. 

Decagynia. 

Dodecagynia. 

Polygynia. 
J 

f  Gymnospermia. 
\  Angiospermia. 

f  Siliculosa. 
\  Siliquosa. 

I  Triandria, 
f      Classes. 


&c.    as    in    the 


SECT.  II. 


TAXONOMY  AND  PHYTOGRAPHY. 


14? 


1 9.    Syngenesia. 


20.  Gynandria. 

21.  Monoecia. 

22.  Dioecia. 

23.  Polygamia. 

24.  Cryptogamia. 


'Polygamia  aequalis. 
superflua. 
frustranea. 
necessaria. 
segregata. 
Monogamia. 

I  Monandria,   &c.    as  in  the 
f      Classes. 

Monoecia,  Dioecia,  Trioecia. 
Filices,  Musci,  &c. 


(138.)  Linneean  Classes.  —  The  first  eleven  classes 
are  characterised  by  the  "  number"  merely,  of  the 
stamens,  which  the  species  (or  nearly  all  of  them)  in 
the  respective  genera  contain ;  and  their  names  are  a 
compound  of  two  Greek  words,  one  of  which  signifies 
that  number,  and  the  other  is  av»ip  (a  man).  The 
number  eleven  is  not  employed,  as  no  flowers  are  found 
to  possess  that  number  of  stamens.  In  the  first  ten 
classes,  the  species  are  pretty  constant  in  the  num- 
ber of  stamens  by  which  their  class  is  designated  • 
but  in  the  eleventh  class  the  number  is  not  so  certainly 
fixed.  There  are,  however,  very  few  species  included 
in  it ;  and  when  the  genera  to  which  they  belong  have 
been  once  pointed  out,  the  student  is  not  afterward < 
likely  to  refer  them  to 
another  class. 

Although  the  name  of 
the  twelfth  class  would 
indicate  that  the  species 
referred  to  it  contained 
twenty  stamens,  whilst  ' 
those  of  the  thirteenth 
contained  more  than  that 
number,  the  real  dis- 
tinction between  these 
two  classes  depends  more  upon  the  position,  than 
upon  the  number  of  these  organs.  In  both  classes 
the  stamens  are  numerous  —  that  is  to  say,  are  above  a 
dozen  in  number ;  but  in  Icosandria  they  adhere  to  the 


148  DESCRIPTIVE    BOTANY.  PART  1. 

calyx  (fig.  144.),  or  are  perigynous  (see  art.  101.)  ; 
whilst  in  Polyandria  they  are  free  from  the  calyx,  or 
are  hypogynous. 

The  fourteenth  and  fifteenth  classes  are  characterised 
by  a  twofold  consideration,  —  the  number  and  relative 
lengths  of  the  stamens.  In  Didynamia  there  are 
four,  and  in  Tetradynamia  there  are  six ;  but  the 
former  is  distinguished  from  Tetrandria,  by  two  of  the 
stamens  being  always  shorter  than  the  other  two ;  and 
he  latter  from  Hexandria  by  two  being  shorter  than 
the  other  four.  This  is  expressed  by  the  word  8t>ya/xo< 
(power),  signifying  that  some  of  the  stamens  have  an 
ascendancy  over  others,  and  this  is  combhu'd  with  the 
word  which  expresses  their  number.  These  circum- 
stances are  not  always  readily  recognised  by  begin- 
ners ;  and  they  should  take  into  consideration  a  few 
other  particulars  which  may  enable  them  to  correct 
their  judgment.  Thus,  in  Didynamia,  the  four  stamens 
are  not  symmetrically  disposed  round  the  axis,  but  are 
thrown  together  on  one  side  of  the  flower,  which  is 
always  monopetalous  *  and  never  strictly  regular.  The 
lipped  flowers  (Labiattp,  art.  95.  and  fig.  93.)  form  a 
large  portion  of  this  class,  except- 
ing a  few  of  them,  as  the  genus 
Salvia,  in  which  two  stamens  are 
abortive,  and  which  is  there- 
fore placed  under  Diandria.  The 
class  Tetrandria  is  readily  re- 
cognisable, from  the  circumstance 
of  all  its  species  having  six  sta- 
mens, but  only  four  petals,  and 
four  sepals.  It  agrees  precisely 
with  the  natural  order  Crucifera?, 
60  named  from  the  petals  being  dis- 
posed in  such  a  manner  as  to  re- 
present a  cross  (fig.  145.  a).  (6) 
shows  the  relative  position  of  the  floral  organs. 

The  names  of  the  three  next  classes  indicate  that  the 
filaments  are  united  into    bundles,    expressed   by    the 


SECT.  II.      TAXONOMY  AND  PHYTOGRAPUV.        ]  49 


word  a&eX^of  (a  brother)  ;  these  bundles  or  brother- 
hoods of  stamens,  being  either  one,  two,  or  more  than 
two  respectively.  Where  there  is  only  one  (in  Mona- 
delphia),  the  filaments  must  necessarily  form  a  cylin- 
drical tube  round  'the  pistil  (fig.  97-  «)•  The  greater 
portion  of  Diadelphia  is  composed  of  a  large  section  of 
a  natural  tribe,  the  Papilionacese,  belonging  to  the  natural 
order  Leguminosae.  (See  art.  136.)  A  small  section  of 
the  Papilionacea?,  in  which  the  filaments  are  perfectly 
free  from  any  adhesion,  is  classed  under  Decandria, 
in  the  same  way  as  a  few  of  the  Labiatae  are  placed 
under  Diandria.  The  remainder  of  this  artificial  class 
is  almost  entirely  composed  of  the  few  genera  which 
belong  to  the  Fumariaceae  and  the  Polygalese  ;  the 
former  having  six,  and  the  latter  eight  stamens,  united 
into  two  bundles. 

The  class  Polyadelphia  is  exceedingly  small,  (the  genus 
Hypericum  forming  its  most  prominent,  feature,)  and 
the  stamens  are  here  placed  in  little  tufts  or  bundles 
round  the  pistil. 

The  nineteenth  class  is  also  strictly  natural,  like  the 
fifteenth,  coinciding  with  the  natural  order  Compositse, 
so  named  from  the  inflorescence  being  composed  of  a 
dense  mass  of  small  flowers,  or  florets  (as  they  are 
here  termed),  closely  invested  by  an  involucrum.  The 
whole  head,  in  popular  language  is  called  a  single 
flower.  (Seefg.  87.)  The  name  of  the  artificial  class 
signifies  that  the  anthers  are  united,  a-w  (together,)  and 
7EVEO-K  (generation). 

Although  the  several  parts  of  the  florets  are  very 
minute,  and  the  adhesion  of  the  anthers  into  a  tube 
round  the  style  not  readily  recognisable,  yet  there  is 
very  little  difficulty  in  referring  any  species  of  this 
class  to  its  right  position.  There  are  a  few  flowers  in 
some  other  natural  orders,  arranged  in  heads  resem- 
bling those  of  the  Compositse,  but  their  anthers  are 
free. 

The  twentieth  class  is  named  from  jury  (a  woman), 
and    avijp    (a  man)  ;     the    centre  of   the   flower    not 
L  3 


150  DESCRIPTIVE    BOTANY.  PART   /. 

having  the  pistils  and  stamens  separate  in  distinct 
whorls,  but  grafted  together  into  one  column,  on  the 
summit  of  which  the  anthers  are  seated  near  the 
stigma.  This  class  is  principally  made  up  of  the 
natural  order  Orchidese,  which  includes  all  those  sin- 
gular flowers  commonly  known  by  the  name  of  orchises 
and  air-plants. 

The  next  two  classes  are  characterised  by  having 
unisexual  flowers,  expressed  by  the  word  GJXO;  (a  house)  ; 
intimating  that,  in  Monoecia,  flowers  of  both  sexes 
are  found  on  the  same  plant ;  whilst  in  Dioecia  the 
stameniferous  flowers  are  on  one  plant,  and  the  pistili- 
ferous  on  another. 

In  Polygamia,  7*<*«{  (marriage),  we  have  three 
kinds  of  flowers,  which  may  all,  or  some  only,  be 
placed  on  the  same  plant.  In  these  cases,  it  should 
seem  that  the  flower  in  its  most  perfect  form  contains 
both  stamens  and  pistils ;  and  that  in  those  flowers, 
where  either  of  these  organs  is  wanting,  it  is  from  abor- 
tion, and  not  that  any  difference  of  construction  pre- 
cludes its  development. 

And  lastly,  Cryptogamia,  from  xpvirTo?  (hidden), 
and  yxpos  (marriage),  there  being  no  flowers  apparent 
from  whence  seeds  are  produced. 

(139-)  lAnnaean  Orders.  —  The  orders  of  the  se- 
veral classes  depend  upon  circumstances,  connected  either 
with  the  stamens  or  pistils. 

In  the  thirteen  first  classes,  the  orders  are  fixed  en- 
tirely by  the  number  of  the  pistils,  and  this  is  expressed 
by  the  word  ",uvij  (a  woman)  in  composition  with  the 
Greek  words  signifying  the  number  present.  In  some 
compound  pistils,  however,  this  number  is  calculated 
from  the  number  of  the  styles  or  stigmas  rising  from 
the  top  of  the  ovarium,  when  those  organs  happen  to  be 
remarkably  distinct. 

In  class  fourteen,  there  are  two  orders,  characterised 
by  the  manner  in  which  the  ovaria  are  developed  into 
seed-vessels.  One  (Angiospermia)  is  named  from  ayyo/; 
(a  vessel)  and  a-nif^y,  (a  seed),  and  in  this  case  the 


SECT.  II.      TAXONOMY  AND  PHYTOGBAPHY.        151 

pericarp  is  composed  of  two  carpels  blended  together 
into  a  single  two-celled  capsule,  containing  many  seeds 
attached  to  a  central  placenta.  The  other  order  (Gym- 
nospermia)  was  so  named  from  a  mistaken  opinion 
that  the  seeds  were  destitute  of  any  pericarp,  or  naked 
(jv^vot-).  In  this  order  the  pistil  is  composed  of  four 
carpels,  each  containing  a  single  seed,  and  agglutinated 
together  into  a  compound  ovarium  with  one  style. 
As  the  fruit  ripens,  the  carpels  separate,  and  ulti- 
mately become  four  nuts,  seated  at  the  bottom  of 
the  calyx.  The  two  orders  are,  therefore,  readily  dis- 
tinguished, by  the  former  containing  only  one  seed- 
vessel  with  many  seeds,  and  the  latter  four  seed-vessels 
which  resemble  four  naked  seeds. 

The  fourteenth  class  also  contains  only  two  orders, 
which  are  characterised  by  the  comparative  lengths  of 
the  seed-vessels.  They  are  composed  of  two  carpels 
united  by  their  edges,  and  are  divided  into  two  cells  by  a 
transverse  membranous  partition  (see  art.  109-  fig.  123.). 
When  the  length  of  the  seed-vessel  exceeds  its  breadth 
three  or  four  times,  it  is  termed  a  siliqua,  and  the 
order  to  which  it  belongs  is  named  "  Siliquosa."  When 
the  length  and  breadth  of  the  seed-vessel  are  nearly  the 
same,  the  order  is  named  "  Siliculosa."  These  dis- 
tinctions are  apparent  in  the  flower,  from  the  earliest 
stages  of  the  ovarium,  and  long  before  it  becomes  a  true 
seed-vessel. 

In  the  sixteenth,  seventeenth,  and  eighteenth  classes, 
the  orders  depend  upon  the  number  of  the  stamens  ; 
and  in  this  respect  they  resemble  the  thirteen  first 
classes  themselves. 

The  nineteenth  class  was  originally  divided  into  six 
orders  ;  in  five  of  which  the  flowers  were  aggregated 
into  heads,  and  thence  distinguished  under  the  name 
of  "Polygatniaj"  whilst  the  sixth  contained  those  simple 
flowers,  whose  anthers,  as  in  the  violets  (Violse),  were 
more  or  less  united.  But  this  last  order  has  been  abolished 
by  the  universal  consent  of  botanists  ;  and  the  species 
which  it  contained,  are  now  referred  to  their  position  in 
fc  4 


152  DESCRIPTIVE    BOTANY.  PART   I. 

the  system,  without  regard  to  the  syngenesious  cha- 
racter of  their  anthers.  Of  the  five  orders,  then,  which 
it  now  possesses,  the  first,  "  JEqualis,"  is  so  named  from 
all  the  florets  being  "  alike ;"  each  containing  both 
stamens  and  a  pistil  (fig.  14-6  a).  In  "  Superflua,"  the 
outer  florets  have  a  pistil 
but  no  stamens  ;  whilst 
the  florets  in  the  centre 
contain  both  (/>).  In  this  T  TT  T  * 
case,  the  outer  florets,  as  in  4^\  QC-\  J£'^.  . 
(he  daisy,  are  "ligulate,"  H  EIL  F'M'  KH' 
or  "  strap-shaped,"  and  constitute  what  is  termed  the 
"  ray  ;"  whilst  the  inner  florets  are  all  "  tubular,  "  or 
"  floscular,"  and  form  the  "  disk "  of  the  capitulum. 
The  inner  florets  being  the  most  perfect,  and  sufficient 
to  secure  the  production  of  seed,  the  outer  florets  ap- 
pear as  it  were  "  superfluous,"  from  whence  the  name 
has  been  given  to  the  order.  In  "Necessaria,"(c)the  outer 
florets  contain  pistils  only  ;  and  the  inner,  stamens  only ; 
and  consequently  both  are  "  necessary  "  for  perfecting 
the  seed.  In  "Frustranea,"  (d)the  central  florets  are  per- 
fect, or  contain  both  stamens  and  a  pistil ;  whilst  those 
in  the  ray  contain  neither,  and  hence  appear  to  be 
formed,  as  it  were,  in  "'vain  "  (frustra),  as  regards  the 
perfecting  of  seed.  The  corolla  of  the  latter  florets 
is  generally  very  highly  developed,  and  assumes  a 
handsome  appearance,  as  in  the  genus  "  Centaurea  " 
(fig. 87-).  In  "Segregata"  (i),  each  floret  is  surrounded 
with  a  distinct  and  well-defined  involucrum  of  its  own, 
which  "  separates  "  it  completely  from  the  other  florets 
in  the  same  capitulum.  In  the  diagram  (fig.  146'.),  these 
different  arrangements  of  the  pistils  and  stamens  are 
represented,  and  the  capital  letters  further  refer  to  the 
kind  of  florets  of  which  the  capitula  are  composed,  viz. 
H  (hermaphrodite),  M  (male),  F  (female),  N  (neuter), 
I  (involucrate). 

In  the  two  next  classes,  Monrccia  and  Dioecia,  the 
orders  depend  upon  the  number  and  arrangement  of 
the  stamens,  precisely  as  in  the  several  classes  al- 


SECT.  II.       TAXONOMY  AND  PHYTOGRAPHY.      153 

ready  enumerated  ;  whilst  in  Polygamia  the  orders 
are  characterised  by  the  flowers  being  monoecious, 
dioecious,  or  trioecious. 

There  is  no  connection  betweeu  the  nomenclature 
of  the  orders  of  the  class  Cryptogamia,  and  the  charac- 
ters of  the  plants  they  contain ;  but  some  of  them  are 
familiar  to  most  persons,  as  the  ferns  (Filices),  mosses 
(Musci),  seaweeds  (Algae),  mushrooms  (Fungi). 

(138.  bis.)  Application  of  the  Linntean  System. — Not- 
withstanding the  apparent  great  simplicity  of  this 
system,  there  are  many  anomalous  cases  to  which  it 
cannot  be  directly  applied.  In  order  to  meet  these, 
Linnaeus  made  use  of  an  expedient  by  which  such 
species  as  do  not  strictly  belong  to  the  class  and 
order  under  which  their  genus  is  arranged,  may  still  be 
ascertained.  Their  names  are  placed  in  Italics  at  the  end 
of  the  order  to  which  they  really  belong,  and  in  which 
they  would  naturally  be  sought  for  ;  so  that  the  student, 
who  has  not  been  able  to  detect  them  among  the  genera 
there  enumerated,  may  refer  to  the  index,  and  search 
among  these  anomalous  cases.  Thus,  for  example,  the 
genus  Gentiana  is  classed  under  Pentandria  Digynia  ; 
but  Gentiana  campestris  has  generally  only  four  sta- 
mens, and  would  be  sought  for  under  Tetrandria  Di- 
gynia. Not  being  found  among  the  genera  there 
enumerated,  it  must  be  one  of  the  few  anomalous 
species,  whose  names  are  mentioned ;  and  these  must 
be  all  referred  to,  before  it  can  be  determined  which 
of  them  it  may  be.  The  very  unequal  distribution 
of  the  classes  is  another  inconvenience  in  this  system. 
The  great  bulk  of  plants  are  included  in  about  one 
half  of  them,  whilst  the  others  contain  comparatively 
few.  If,  however,  attention  be  paid  to  the  general 
form  of  the  flowers,  the  relationship  which  usually 
subsists  between  the  divisions  of  the  perianth  and  the 
number  of  the  stamens,  in  such  as  have  a  regular 
corolla,  and  a  few  other  particulars,  the  knowledge  of 
which  a  little  practice  alone  can  bestow,  these  diffi- 
culties are  soon  greatly  diminished,  and  many  large  na- 


DESCRIPTIVE    BO  TANS'.  PART  I. 

tural  groups  will  be  instantly  referred  to  thsir  proper 
class  and  order,  without  the  necessity  of  searching 
for  the  characters  upon  which  their  arrangement  de- 
pends. It  will  be  soon  seen  that  Triandria,  Hex- 
andria,  and  Gynandria  contain  the  great  bulk  of 
the  Monocotyledones,  and  that  there  are  very  few 
of  this  natural  class  among  the  other  artificial  classes. 
This  circumstance  is  connected  with  the  ternary  ar- 
rangement of  the  subordinate  parts  of  the  floral 
whorls,  to  which  we  have  alluded  (art.  120.).  On  the 
other  hand,  tlie  great  bulk  of  Dicotyledons  are  included 
in  those  classes  where  some  trace  or  other  of  a  quinary 
disposition  is  observable.  Thus,  Pentandria,  Decan- 
dria,  Icosandria,  and  Polyandria  are  large  classes  an- 
swering to  this  description ;  and  Syngenesia,  which 
is  the  largest  of  any,  has  always  five  stamens,  and  the 
corolhr  generally  exhibit  a  tendency  to  a  subdivision 
into  five  separate  petals,  indicated  by  five  teeth  at  the 
end  of  the  florets.  Didynamia  is  eminently  irregular  ; 
but  even  here,  the  normal  character  of  the  species  seems 
to  repose  upon  a  quinary  arrangement,  which  is  some- 
times manifested  by  a  monstrous  development  of  the 
suppressed  organs,  as  in  the  varieties  termed  "  Peloria," 
of  the  genera  Antirrhinum  and  Linaria  (see  art.  114.). 
Tetradynamia  is  not  unsymmetrical,  but  equally  irregu- 
lar, as  regards  the  more  usual  characteristic  of  a  dico- 
tyledonous flower. 


155 


PART  II. 

PHYSIOLOGICAL    BOTANY. 


CHAPTER  I. 

VITAL    PROPERTIES    AND    STIMULANTS. 

VEGETABLE    LIFE     (139.)'  PROPERTIES     OP     TISSUES     (141.). 

KNDOSMOSE    (144.).  VITAL     PROPERTIES      (145.).  STIMU- 
LANTS   TO    VEGETATION    (152.). 

(13.Q.  bis.)  Vegetable  Life —  HITHERTO  we  have  been 
occupied  with  the  forms  only  which  the  various  organs 
of  plants  assume,  and  the  manner  in  which  they  may 
be  considered  to  be  mutually  related.  We  have  been 
examining  merely  some  of  the  details  of  that  exquisite 
mechanism  by  means  of  which  the  vital  principle  is 
enabled  to  act  and  may  be  acted  upon  ;  and  thus 
produce  all  the  varied  and  complicated  results  which 
the  phenomena  of  vegetation  present.  In  this  second 
part  of  our  treatise,  we  propose  to  examine  the  vegetable 
machinery  in  a  state  of  action,  and  to  search  for 
indications  of  those  laws  by  which  vegetable  life 
enables  the  organic  bodies  to  which  it  is  united  to 
grow  and  multiply.  It  would  be  an  unnecessary 
waste  of  words  to  offer  any  proof  that  plants  are 
organised  bodies  endowed  with  life.  No  one  is  so 
little  observant,  as  to  be  ignorant  of  the  more  ge- 
neral phenomena  of  vegetation,  that  plants  originate 
from  seed,  that  they  are  gradually  developed,  and, 


156  PHYSIOLOGICAL    BOTANY.  PART   II. 

after  having  attained  perfection,  that  they  as  gra- 
dually decay,  die,  and  are  decomposed.  In  fact  the 
general  phenomena  of  life  and  death,  are  scarcely  less 
striking  in  the  vegetable  than  in  the  animal  king- 
dom ;  and  probably  the  vital  principle,  considered 
apart  from  sensibility,  is  something  of  the  same  kind, 
if  not  the  very  same  thing,  both  in  animals  and  vege- 
tables. This  similarity  or  unity  in  essence  must  lead 
us  to  expect,  what  experience  has  shown  to  be  the  fact, 
that  a  considerable  analogy  exists  between  the  functions 
of  animal  and  vegetable  life.  Although  every  argu- 
ment which  may  be  derived  from  this  analogy,  cannot 
be  too  severely  scrutinised  before  we  admit  the  particular 
conclusion  which  it  may  seem  to  establish,  yet  we  may 
confidently  reckon  upon  the  certainty  of  its  existence,  as 
one  of  the  best  guides  which  we  now  possess,  towards 
obtaining  a  more  perfect  elucidation  of  the  general  laws 
of  physiology. 

(140.)  Vital  Stimulants.  —  Life,  though  at  the  best 
of  only  temporary  duration  in  organised  bodies,  cannot 
be  maintained  in  them  at  all,  without  the  continued 
application  of  certain  stimulants.  All  require  peculiar 
kinds  of  food,  according  to  their  respective  natures  ;  a 
sufficiency  of  air,  of  moisture,  of  heat,  &c.  If  entirely 
deprived  of  these  stimulants,  they  soon  die  ;  and  even 
when  they  are  only  partially  subjected  to  their  influence, 
in  a  less  proportion  than  is  requisite  for  a  free  exercise 
of  their  functions,  they  languish  and  become  sickly. 
But,  besides  the  various  salutary  influences  to  which 
all  living  bodies  must  be  submitted,  in  order  to  secure 
for  them  a  due  and  healthy  performance  of  their 
several  functions,  there  are  others  to  which  they 
may  be  subjected,  which  are  decidedly  noxious  under 
all  conditions,  and  which  must  ultimately  prove  fatal 
to  them,  if  they  had  not  the  power  of  escaping  from 
their  presence,  or  at  least  of  modifying  their  effects. 
In  proportion  as  a  living  being  possesses  a  greater 
power  of  choice,  either  in  profiting  by  those  circum- 


CHAP.   I.     VITAL    PROPERTIES    AND    STIMULANTS.  157 

stances  which  are  favourable,  or  in  avoiding  those 
which  are  hurtful  to  its  existence,  we  may  con. 
sider  it  to  be  more  elevated  in  the  scale  of  nature,  and 
further  removed  from  the  condition  of  mere  brute 
matter.  Most  animals,  by  the  faculty  which  they  pos- 
sess of  locomotion,  have  a  great  advantage  in  this 
respect  over  plants  ;  and  even  those  among  the  very 
lowest  tribes  of  animals  which  are  permanently  fixed  to 
one  spot  during  the  whole  period  of  their  existence,  still 
possess  a  certain  power  of  selecting  their  food,  and  re- 
jecting what  is  noxious  to  them,  which  vegetables  have 
not.  The  consequence  is,  that  the  continued  influ- 
ence of  external  agents,  is  found  to  be  far  greater 
in  modifying  the  characters  of  plants  than  of  animals. 
As  a  sort  of  compensation  however,  the  vital  prin- 
ciple in  plants  is  so  much  less  energetic  than  in 
animals,  that  they  are  not  so  readily  affected  as  these 
latter,  under  any  merely  casual  or  temporary  altera- 
tion in  the  external  conditions  under  which  they  may 
be  placed. 

(141.)  Properties  of  Tissue.  —  Before  we  describe 
the  functions  performed  by  the  vegetable  tissues,  it  will 
be  necessary  to  remark  upon  a  few  of  the  properties 
which  these  tissues  themselves  possess.  In  the  com- 
plex phenomena  which  vegetation  furnishes,  it  is  very 
difficult  to  separate  so  much  of  each  result  as  may  be 
strictly  ascribed  to  the  operation  of  the  vital  principle, 
from  such  as  may  be  due  to  the  action  of  purely  physical 
causes,  the  chemical  effects  of  affinity,  and  the  mere 
mechanical  properties  of  the  tissue.  The  most  obvious 
means  which  we  can  employ,  for  ascertaining  the  precise 
properties  of  the  tissue,  is  to  perform  experiments  upon 
it  in  the  dead  vegetable,  and  as  nearly  as  possible 
before  any  chemical  change  may  have  taken  place  in  it. 
It  will  not  be  necessary  for  us  here  to  notice  all  the 
properties  which  the  vegetable  tissues  possess  in  com- 
mon with  other  substances ;  but  there  are  two  on 
which  we  shall  make  a  few  remarks,  as  the  pheno- 
mena to  which  they  give  rise  might  in  some  cases 


158  PHYSIOLOGICAL,    BOTANY.  PAST   II 

be  attributed  to  the  operation  of  the  vital  force  :  these 
are,  the  elastic  and  hygroscopic  powers  of  some  vege- 
table tissues. 

(142.)  El'ixticity  <;/'  7V,w//r. — This  property  is 
eminently  conspicuous  when  the  tissue  is  distended  with 
fluid  ;  and,  unless  its  effects  be  duly  appreciated,  we 
might  be  misled,  and  inclined  to  consider  certain  phe- 
nomena as  the  direct  result  of  an  irritability  residing  in 
the  plant,  whilst,  in  fact,  they  may  be  easily  accounted 
for  by  the  action  of  elasticity  alone.  Thus,  in  the  flower* 
of  the  common  nettle  (fiy.  147- «)'  ^u'  filaments  are  at 


first  curved  inwards,  and  the  anthers  meet  in  the  centre. 
When  the  flower  is  completely  expanded,  the  filaments 
have  become  highly  elastic ;  but  are  still  retained  in 
their  original  curved  position  by  the  mutual  pressure 
which  they  exert  upon 'each  other.  If  this  state  of 
equilibrium  be  disturbed,  either  by  slightly  displacing 
the  anthers  with  the  point  of  a  pin,  or  by  the  further 
progress  made  in  vegetation,  the  stamens  are  suddenly- 
thrown  back  by  the  elasticity  of  their  filaments,  the 
anthers  burst  and  the  pollen  is  scattered  by  the  shock 
(6).  This  appearance  is  very  like  that  of  some  other 
sudden  motions,  which,  as  we  shall  hereafter  show, 
must  be  referred  to  the  direct  influence  of  some  stimulus 
upon  the  vital  principle.  Many  seed-vessels  when 
fully  ripe,  burst  as  it  were  spontaneously,  by  the  in- 
creased elasticity  of  their  tissue,  and  the  seeds  are  often 
scattered  to  a  considerable  distance  by  this  means ;  but 
although  all  the  organs  of  plants  when  replete  with 
fluid,  are  generally  elastic,  a  remarkable  exception  oc- 
curs in  the  pedicels  of  Dracocephalum  moldavicum. 


CHAP.  I.     VITAL    PROPERTIES    AND    8TJMTJ1ANTS.  159 

When  these  are  turned  in  any  particular  direction,  they 
retain  the  position  in  which  they  are  placed,  without 
any  effort  to  return  again  to  that  in  which  they  were 
previously  disposed. 

(143.)  Hygroscopicity  of  Tissue.  —  The  hygroscopic 
properties  of  some  tissues  are  very  great,  and  are  the 
cause  of  certain  motions,  which  might  be  mistaken  for 
the  direct  effects  produced  by  the  vital  force.  If  the 
awn  or  bristle  of  the  wild  oat  be  moistened,  it  imme- 
diately untwists ;  the  teeth  of  mosses  suddenly  collapse 
when  moistened  by  the  breath,  and  readily  expand  upon 
drying  again.  In  estimating  the  hygroscopic  properties 
of  the  tissue,  we  must  distinguish  between  the  action  of 
the  whole  mass,  and  the  property  of  the  membrane 
which  forms  the  separate  vesicles  and  tubes  of  which 
the  tissue  is  composed.  It  seems  easy  to  account  for 
the  hygroscopicity  of  the  mass  of  the  tissue,  when  we 
remember  that  it  is  penetrated  in  all  directions  by  inter- 
cellular passages,  and  thus  resembles  a  sponge,  which 
absorbs  moisture  by  the  common  properties  of  capillary 
attraction.  This  action  is  found  to  be  much  more 
powerful  in  proportion  as  the  vegetable  tissue  is  but 
slightly  charged  with  foreign  matter.  Some  plants,  as 
the  mosses,  readily  imbibe  water,  however  long  they 
may  have  been  dried ;  and  reassume  an  appearance  of 
freshness  nearly  equal  to  that  which  they  possessed  in  a 
living  state ;  but,  in  these  cases,  the  effect  is  most  pro- 
bably due  to  the  hygroscopic  action  of  the  elementary 
membrane  composing  the  vesicles,  and  not  to  the  capil- 
larity of  the  tissue  itself.  The  immediate  result  of  any 
hygroscopic  action  upon  a  portion  of  the  tissue  is  to 
enlarge  it;  and  consequently,  where  two  portions 
are  in  contact,  one  of  which  is  more  hygroscopic  than 
the  other,  there  exists  a  tendency  to  separation. 
When,  however,  they  do  not  separate,  the  portion 
which  is  the  least  hygroscopic,  becoming  less  dis- 
tended than  the  other,  necessarily  produces  an  incurv- 
ation of  the  mass  upon  that  side  on  which  it  is  placed. 

(144.)  Endosmose. — Connected    with    the    hygro- 


160 


PHYSIOLOGICAL    BOTANY. 


scopicity  of  the  vegetable  membrane,  we  may  here  men- 
tion a  property  of  all  membrane,  which  has  probably  a 
considerable  influence  in  the  economy  both  of  animal 
and  vegetable  life.  When  a  membrane  is  viewed  under 
the  highest  powers  of  the  microscope,  it  appears  to 
possess  a  perfectly  homogeneous  texture,  without  pores 
of  any  kind  ;  and  yet  water,  milk,  and  other  fluids, 
placed  under  certain  circumstances,  are  capable  of  pass- 
ing through  it  with  considerable  facility.  The  con- 
ditions required  for  producing  this  effect  are  these :  — 
Any  two  fluids  which  exert  a  mutual  affinity  towards 
each  other,  being  placed  on  opposite  sides  of  a  mem- 
brane, their  immediate  intermixture  will  commence, 
each  of  them  passing  through  the  substance  of  the 
membrane.  If,  for  instance,  a  little  treacle  be  enclosed 
in  a  piece  of  bladder,  and  this  immersed  in  water,  a 
portion  of  the  treacle  will  soon  be  found  to  haveexudi  •<!. 
whilst  a  still  larger  quantity  of  water  will  have  pene- 
trated into  the  bladder  ;  and  this  action  will  continue 
until  the  fluids  have  acquired  the  same  density.  The 
remarkable  circumstance  attending  this  phenomenon ,  i< 
the  fact  of  the  lighter  fluid  having  penetrated  the  mem- 
brane with  greater  velocity 
than  the  denser  fluid.  •  In 
consequence  of  this,  the 
bladder  becomes  distended. 
By  a  simple  contrivance, 
styled  an  endosmometer, 
we  may  measure  the  degree 
of  force  or  velocity  by 
which  the  current  of  water 
exceeds  that  of  the  current 
of  the  denser  fluid.  In 
fig.  148  A  is  a  glass 
funnel  with  the  mouth 
downwards,  and  covered 
with  a  piece  of  bladder. 

The  other  end  of  this  funnel   is  furnished  with  a  tube 
twice  bent,  the  stems  of  which  are  vertical ;    treacle 


VITAL    PROPERTIES    AND    STIMULANTS.  l6l 

is  placed  in  the  body  of  the  funnel,  and  the  mouth 
immersed  in  water ;  mercury  is  poured  into  the  open 
extremity  of  the  tube,  and  ascends  in  the  other  stem 
until  it  meets  the  fluid  in  the  funnel.  So  soon  as  the 
endosmose  commences,  the  rising  fluid  pushes  the  mer- 
cury before  it ;  and  the  amount  of  the  force  by  which 
this  is  effected,  is  ascertained  by  pouring  in  more  mer- 
cury until  the  further  rise  of  the  fluid  is  checked.  The 
height  of  the  column  of  mercury  affords  an  estimate  of 
the  pressure  of  the  ascending  fluid,  which  is  of  course 
due  to  the  force  of  the  endosmose.  In  this  way  it  may 
be  shown,  that  a  syrup  three  times  the  density  of  water 
produces  an  endosmose  capable  of  sustaining  a  pressure 
equal  to  the  weight  of  three  atmospheres. 

(145.)  Vital  Properties.  —  After  abstracting  all  that 
can  reasonably  be  allowed  to  the  physical  properties  of 
the  tissue,  arid  to  the  chemical  or  other  effects  which 
operate  in  modifying  every  vital  phenomenon,  whatever 
still  remains  unaccounted  for  in  the  functions  of  ve- 
getation, must  be  ascribed  to  the  direct  operation  of  the 
vital  force  itself.  What  life  is,  whether  it  is  a  simple 
quality,  the  effects  of  which  are  variously  modified  ac- 
cording to  the  nature  of  the  tissue  in  which  it  resides, 
and  by  means  of  which  it  acts,  or  whether  it  possesses 
several  distinct  properties,  which  are  severally  capable  of 
acting  only  upon  and  through  particular  tissues,  is  quite 
unknown  to  us.  For  the  sake  of  convenience,  and  pro- 
visionally merely,  the  physiologist  considers  animal  life 
to  be  compounded  of  certain  properties,  and  that  its 
various  functions  are  performed  by  these  properties, 
acting  through  the  intervention  of  different  kinds  of 
tissue.  There  are  three  of  these  properties  attached  to 
animal  life,  which  may  be  styled  respectively  its  ex- 
citability, irritability,  and  sensibility. 

(146.)  Excitability. — The  excitability  of  animal  life, 
which  is  also  termed  the  "  vis  formativa,"  is  manifested 
through  the  cellular  tissue,  by  which  the  function  of 
nutrition  is  carried  on  ;  it  is  that  property  by  which 
this  tissue  takes  cognizance  of  the  action  of  external 


l6'2  PHYSIOLOGICAL    BOTANY.  PART   II. 

influences  upon  it,  and  by  which  it  resists  those  mechan- 
ical and  chemical  efforts  which  otherwise  would  soon 
succeed  in  decomposing  its  substance.  The  existence 
of  such  a  property  is  equally  evident  in  the  vegetable  as 
in  the  animal  kingdom.  No  one  will  deny  that  ve-. 
getables  live ;  and  we  may  perhaps  believe,  that  the 
general  law  of  life  by  which  they  resist  destruction,  is 
the  very  same  in  kind,  however  different  it  may  be  in 
degree,  as  that  by  which  animals  are  also  maintained  in 
a  state  of  existence.  In  animals  indeed,  the  intensity 
with  which  this  vital  property  acts  is  greater  than  in 
vegetables ;  but,  as  a  sort  of  compensation,  we  find  that 
vegetables  are  much  more  tenacious  of  life  than  animals. 
A  plant  may  be  mutilated  to  a  very  great  extent,  and 
its  separate  parts  will  still  live,  and  are  frequently  ca- 
pable of  becoming  distinct  individuals  ;  and,  although 
there  are  certain  creatures  possessing  a  compound  struc- 
ture, among  the  lowest  tribes  of  animals,  yet  even  in 
them  this  property  does  not  reside  in  so  eminent  a 
decree  as  in  certain  vegetables,  every  elementary  organ 
of  which  appears  capable  of  existing  in  a  detached 
form,  and  of  reproducing  an  individual,  similar  to  the 
original  of  which  it  formed  a  trifling  and  subordinate 
part.  This  therefore,  the  "  excitability"  of  life  as  it 
has  been  termed,  is  a  property  which  we  may  consider 
common  to  both  kingdoms  of  organised  nature. 

(147.)  Tenacity  of  Life.  —  A  plant  may  lose 
nearly  half  its  weight  by  drying,  and  yet  be  restored 
by  care.  De  Candolle  has  recorded  an  instance  of  a 
Srinpervivum  ccespitosum,  which  had  been  placed  in  a 
herbarium  for  eighteen  months,  and  from  which  he 
afterwards  detached  a  living  bud  and  reared  a  plant. 
But  the  tenacity  of  vegetable  life  is  best  exhibited 
in  the  property  which  seeds  possess,  of  retaining 
their  powers  of  germination  after  having  been  exposed 
to  very  considerable  extremes  of  heat  and  cold.  Some 
also,  which  have  partially  germinated,  may  be  again 
dried  and  kept  for  months,  without  losing  the  power  of 
germinating  afresh,  although  they  are  sensibly  weakened 


CHAP.   I.      VITAL    PROPERTIES    AND    STIMULANTS.  1 6'3 

by  such  treatment.  The  revival  of  plants  among  the 
cryptogamic  tribes,  after  a  very  long  suspension  of  the 
vital  functions,  is  well  authenticated. 

(148.)  Irritability. —  Besides  the  excitability  of  ve- 
getable Hfe,  there  are  certain  striking  phenomena  ex- 
hibited by  some  plants,  which  seem  to  indicate  the 
presence  of  a  property  analogous  to  that  of  animal 
"  irritability."  A  closer  examination,  however,  of  the 
circumstances  under  which  this  "  vegetable  irritability  " 
manifests  itself,  rather  inclines  us  to  believe  with  De  Can- 
dolle,  until  sufficient  proof  be  brought  to  show  the  con- 
trary, that  these  are  only  extreme  cases  of  the  operation 
of  the  property  of  excitability.  The  sudden  inclination 
of  the  stamens  in  the  berberry  towards  the  pistil,  when 
the  filaments  are  touched  near  the  base  on  the  inside, 
the  well-known  phenomena  exhibited  by  the  sensitive- 
plant,  and  several  other  singular  movements  of  particular 
organs  in  some  other  plants,  are  the  phenomena  which 
have  led  to  the  conclusion,  that  some  few  vegetables  are 
endowed  with  an  irritability  analogous  to  that  which 
exists  in  all  animals.  But  on  the  other  hand  it  has 
been  observed,  that  in  animals  this  property  is  confined 
to  the  muscular  fibre,  whilst  in  vegetables  there  does 
not  appear  to  be  any  particular  tissue  to  which  it  is 
peculiarly  restricted.  In  animals,  again,  the  effects  of 
irritability  are  apparent  during  the  whole  course  of  their 
life,  and  are  not  destroyed  by  repetition  of  the  experi- 
ments by  which  they  are  elicited  ;  whereas  this  property 
can  be  traced  only  under  peculiar  conditions  of  vege- 
table existence,  and  then  only  in  certain  organs  of  a 
very  few  species.  Several  of  these  instances,  also,  are 
only  special  modifications  of  certain  actions,  which  are 
constantly  produced  by  the  operation  of  more  general 
causes.  For  instance,  the  folding  of  the  leaflets  of  the 
sensitive-plant,  which  takes  place  when  we  touch  them, 
is  the  very  same  sort  of  effect  which  we  daily  witness 
in  a  vast  number  of  other  plants,  where  it  is  elicited 
by  the  agency  of  light,  only  in  a  more  gradual  and 
M  2 


PHYSIOLOGICAL    BOTANY. 


imperceptible  manner.  In  these  latter  cases,  the  effect 
is  denominated  the  sleep  of  plants,  and  may  be  more 
especially  witnessed  in  the  leguminose  tribes,  whose 
leaves  remain  folded  during  a  certain  portion  of  tin- 
day,  and  assume  an  appearance  of  languor  and  inaction 
singularly  analogous  to  the  periodical  state  of  repose 
exhibited  in  the  animal  kingdom.  In  cases  therefore, 
where  similar  effects  are  brought  about  by  the  action  of 
certain  stimuli,  in  a  yet  more  violent  or  rapid  succession, 
we  may  imagine  that  they  are  nevertheless  the  results 
of  the  same  vital  property,  which  is  here  exhibited 
under  some  peculiar  degree  of  excitement. 

(149.)  Examples  of  Vegetable  Irritability.  —  As 
some  of  the  phenomena  exhibited  by  vegetable  irrita- 
bility are  very  striking,  we  shall  here  insert  a  brief 
uotice  of  a  few  of  the  most  interesting  examples. 

(1.)  Sensitive- Plants.  —  There  are  several  species 
of  sensitive-plants,  which 
possess  the  property  of 
moving  their  leaves 
when  they  are  touched, 
or  otherwise  stimulated. 
The  most  common  is  an 
annual  (Mimosa  pudica}, 
with  compound  digitate 
leaves,  with  four  pinnules 
(_/?</.!  4*9.); — each  partial 
petiole  being  furnished 
with  numerous  pairs  of 
leaflets,  expanded  hori- 
zontally as  at  (a).  One 
of  the  most  striking 
means  of  eliciting  the  phenomenon  in  question,  is  by 
scorching  a  single  leaflet  in  a  candle,  or  by  concen- 
trating the  sun's  rays  upon  it  with  a  lens.  This 
leaflet  will  immediately  move,  together  with  the  one 
opposite  to  it,  both  bringing  their  upper  surfaces 
into  contact,  and  at  the  same  time  inclining  forwards, 


CHAP.   I.      VITAL    PROPERTIES    AND    STIMULANTS.  l65 

or  towards  the  extremity  of  the  partial  petiole  on 
which  they  are  seated  (6).  Other  pairs  of  leaflets, 
nearest  to  the  one  first  stimulated,  will  then  close  in 
succession  in  a  similar  manner  ;  and  at  length  the 
partial  petioles  themselves  fold  together,  by  inclining 
upwards  and  forwards.  Last  of  all,  the  influence  is 
transmitted  to  the  common  petiole,  which  bends  down- 
wards with  its  extremity  towards  the  ground  (c) ;  in 
a  direction  the  reverse  of  those  which  were  taken  in 
the  former  cases.  The  effect  is  next  continued  to  the 
other  leaves  nearest  to  the  one  first  stimulated,  and 
they  fold  their  leaflets  and  depress  their  petioles  in 
a  similar  manner.  When  the  plant  is  shaken,  all  the 
leaflets  close  simultaneously,  and  the  petioles  droop 
together  ;  but  if  the  agitation  be  long  continued,  the 
plant  will  at  length  become  accustomed  to  the  shock, 
and  after  a  lapse  of  some  time,  the  leaflets  expand 
again.  The  mechanism  by  which  these  movements 
are  produced  resides  in  the  thickened  or  swollen  joints, 
seated  at  the  bottom  of  each  leaflet  and  petiole;  for 
if  the  upper  part  of  these  swellings  are  cut  away, 
the  leaf  remains  erect ;  but  if  the  lower  part  is  re- 
moved it  continues  depressed.  Hence  it  appears  that 
the  elevation  and  depression  of  the  leaf,  is  owing  to 
the  elasticity  of  the  tissue  of  which  the  swollen  joint  is 
composed ;  and  that  the  stimulus  employed  to  produce 
motion,  tends  to  weaken  the  upper  parts  of  these  joints 
in  the  case  of  the  leaflets  and  partial  petioles,  but  the 
lower  part  of  those  belonging  to  the  main  petioles  — 
the  contrary  sides  continuing  elastic,  as  before.  But 
how  the  effect  is  produced,  and  what  may  be  the  law 
which  regulates  its  action,  is  not  known.  The  causes 
are  active  from  the  earliest  stages  of  the  plant's  exist- 
ence ;  the  cotyledons  themselves  exhibiting  the  property 
so  soon  as  they  have  expanded.  The  transmission  of 
the  stimulus  from  one  leaf  to  another  along  the  stem 
of  the  plant,  has  been  shown  by  Dutrochet  to  take 
place  through  the  intervention  of  the  ducts  contained  in 
M  3 


166 


PHYSIOLOGICAL    BOTANY. 


PART  II. 


the  woody  parts.  For,  if  both  the  pith  and  the  corti- 
cal portions  are  removed,  the  effects  are  not  stopped  ; 
whilst,  if  the  woody  parts  are  abstracted,  which  con- 
tain the  ducts,  they  cease  entirely. 

(2.)  Denmodium  gyrans.  —  The  Desmodium  gy- 
rans  is  another  plant  of  the  same  natural  order  as  the 
sensitive-plants,  the  motion  of  whose  leaflets  is  still 
more  striking  than  in  the  latter  ;  for  here  the  motion 
is  continued,  without  the  necessity  of  applying  any 
external  stimulus.  The 
leaves  are  composed  of  a 
pair  of  small  leaflets,  and 
a  terminal  one  of  larger 
dimensions  (fig-  150.). 
The  motion  consists  of  a 
succession  of  little  jerks, 
produced  at  intervals  of 
a  few  seconds.  One  of 
the  two  lateral  leaflets 
is  gradually  elevated, 
whilst  the  other  is  de- 
pressed ;  and  when  both 
have  attained  the  maxi- 
mum amount  of  movement  in  one  direction,  they  begin 
to  proceed  in  the  opposite.  At  the  same  time  the 
terminal  leaflet  becomes  inclined  by  similar  inter- 
rupted movements  ;  first  on  one  side,  and  then  on  the 
other. 

(3.)  Common  Berbery.  —  The  flowers  of  the  com- 
mon Berbery  contain  six  stamens,  which  surround  a 
single  piftil.  When  first  expanded,  the  stamens  are 
inclined  back  upon  the  petals  or  away  from  the  pistil. 
If  the  filaments  are  touched  near  the  base  on  the  in- 
side, they  immediately  start  forward  towards  the  pistil, 
so  that  the  anther  is  brought  close  to  the  stigma.  In  a 
little  time  they  recover  their  original  position,  and  may 
be  again  stimulated  as  before.  When  the  anther  is 
ripe,  the  violence  of  the  motion  causes  it  to  burst,  and 
the  pollen  is  projected  on  the  stigma ;  and  we  may 


CHAP.   I.      VITAL    PROPERTIES    AND    STIMULANTS. 


167 


unquestionably  consider  the  mechanism  by  which  this 
effect  is  produced  as  designed  for  effecting  this  very 
purpose. 

(4.)  Dionaea  muscipula. —  The  leaves  of  the  Dio- 
naea  muscipula,  or  Venus's  Flytrap,  consist  of  a  flat- 
tened petiole  (fig.  151.  a),  at  the  extremity  of  which 
are  two  fleshy  lobes  (6), 
which  lie  when  ex- 
panded in  the  same 
plane  with  the  petiole. 
These  lobes  are  capable 
of  being  elevated  and 
brought  together  in- 
to a  position  perpen- 
dicular to  the  surface 
of  the  petiole  (c). 
They  are  furnished 
with  "ciliae,"or  bristles, 
round  their  margins, 
which  stand  nearly  at 
right  angles  to  their 
upper  surface ;  and 
there  are  besides  these,  three  little  short  bristles  placed 
upon  the  upper  surface  of  each  lobe  in  a  triangular 
order.  When  a  fly  or  other  insect,  crawling  over  the 
surface  of  the  lobes,  touches  either  of  these  latter 
bristles,  the  irritability  is  excited,  the  lobes  suddenly 
close,  and  the  insect  is  imprisoned  like  a  rat  in  a  com- 
mon gin.  Some  little  time  after  the  death  of  the 
insect,  the  lobes  unfold  and  wait  for  another  victim. 
The  only  plausible  conjecture  which  has  been  made, 
to  account  for  the  use  and  intent  of  this  singular  con- 
trivance, supposes  this  plant  to  require  animal  manure 
for  the  healthy  performance  of  some  function  or  other  ; 
and  in  corroboration  of  this  opinion,  it  has  been  stated 
that  Mr.  Knight,  after  having  secured  some  plants  from 
the  possibility  of  providing  themselves  with  flies,  fur- 
nished some  of  them  with  scraped  beef,  and  left  the 
rest  without  any  such  provision.  The  result  of  the 
M  4 


168  PHYSIOLOGICAL    BOTANY.  PART  II. 

experiment  showed  the  more  flourishing  condition  of 
the"  provisioned  specimens. 

(5.)  Sundews.  —  To  the  above  list  we  may  add  one 
more  example,  taken  from  a  British  genus  of  plants, 
the  Droserse  or  Sundews,  of  which  three  species  are 
natives  of  this  country.  The  leaves  of  these  plants  are 
furnished  on  their  upper  surface  with  long  hairs,  tipped 
with  glandular  and  viscous  globules.  When  an  insect 
settles  upon  them  it  is  retained  by  the  viscosity  of  the 
gland,  and  in  a  little  while  the  hairs  exhibit  a  consider- 
able degree  of  irritability,  by  curving  inwards,  and  thus 
holding  it  secure. 

(150.)  Sensibility. —  If  we  do  not  consider  it  clearly 
established  that  plants  are  endowed  with  an  irritability 
strictly  analogous  to  that  which  exists  in  animals,  then. 
seems  still  less  reason  for  supposing  them  to  possess  that 
"  sensibility,"  by  which  all  animals,  but  more  espe- 
pecially  the  higher  tribes,  are  so  eminently  characterized. 
In  them  this  property  resides  in  their  nervous  system, 
to  which  there  appears  to  be  nothing  analogous  among 
vegetables.  Even  in  the  lower  tribes  of  animals,  their 
nervous  system  is  so  little  developed,  that  they  may  be 
mutilated  and  otherwise  injured,  to  an  extent  which 
would  speedily  cause  their  death,  if  the  intensity  of 
the  pain  which  they  felt  were  at  all  proportionable  to 
what  animals  of  a  higher  grade  experience  under  si- 
milar treatment ;  and  yet  they  scarcely  appear  to  suf- 
fer any  inconvenience.  If  there  were  no  better  ar- 
gument to  satisfy  us  that  plants  are  utterly  devoid  of 
sensibility,  we  have  the  general  consent  of  mankind, 
founded  on  their  daily  observation,  in  favour  of  the 
non-existence  of  such  a  property.  The  only  plausible 
arguments  in  support  of  the  probability  of  plants  being 
endowed  with  something  analogous  to  a  nervous  system, 
rest  upon  the  effects  produced  on  them  by  different 
poisons.  When  corrosive  poisons  are  imbibed  into 
their  system,  they  destroy  the  tissue  much  in  the  same 
way  as  in  the  animal  frame  ;  but  when  narcotic  poi- 
sons are  imbibed,  although  they  kill  the  plants,  they  do 


CHAP.    I.     VITAL    PROPERTIES    AND    STIMULANTS.  lp 

not  appear  to  have  produced  any  derangement  or  disor- 
ganisation in  their  tissue.  But  it  has  been  argued  that, 
as  these  latter  poisons  act  upon  the  nervous  system  of 
animals,  we  may  suspect  something  analogous  to  this 
system  to  exist  in  vegetables  also.  A  long  list  has 
been  given  of  substances  which  act  as  poisons  on 
plants  ;  and  it  has  been  ascertained  that  very  nearly 
all  such  as  are  deleterious  to  animal  are  so  likewise  to  ve- 
getable life,  and  many  others  besides,  which  animals  may 
take  with  impunity.  Some  of  those  which  it  is  necessary 
to  administer  in  large  quantities  in  order  to  produce 
death  in  animals,  are  sufficiently  powerful  to  kill  plants 
when  given  in  very  small  doses  —  as  alcohol,  ethers, 
and  oils ;  whilst  on  the  other  hand,  the  oxides  of  lead 
and  zinc,  which  poison  animals  when  administered  in 
small  portions,  produce  little  or  no  effect  on  plants, 
probably  because  they  are  incapable  of  being  absorbed 
by  the  spongioles.  Most  vegetable  extracts  and  ex- 
cretions act  as  poisons  on  all  plants  (even  upon  those 
from  which  they  were  obtained)  when  they  are  imbibed 
by  the  roots.  Gases  diffused  in  water  are  harmless. 
Many  salts  are  highly  noxious,  but  most  of  the  salts  of 
lime  produce  no  effect.  Fortunately  for  the  permanence 
of  vegetation  on  the  surface  of  the  earth,  the  natural 
poisons  are  not  very  generally  diffused  in  places  where 
plants  are  likely  to  grow. 

(151.)  Periodicity.  — In  tracing  the  various  ana- 
logies which  exist  between  the  phenomena  of  animal 
and  vegetable  life,  we  find  a  remarkable  example  in 
what  may  be  termed  the  individual  temperament,  or 
idiosyncracy  of  a  living  organic  being.  Besides  that 
general  resemblance  between  the  manner  in  which  the 
same  functions  are  performed  by  all  individuals  of  the 
same  species,  there  are  certain  modifications  in  the  re- 
sults which  are  peculiar  to  particular  individuals,  and 
which  must  be  attributed  to  some  peculiarity  in  their 
temperament.  This  is  remarkably  exhibited  in  the 
differences  observable  among  separate  individuals  of 
the  same  species,  as  regards  their  periods  of  leafing 


170  PHYSIOLOGICAL    BOTANY.  PART  If. 

or  flowering ;  for  although  it  is  evident  that  the  re- 
gular return  of  the  seasons  stimulates  all  plants  to  a 
periodic  execution  of  these  functions,  and  although 
the  great  majority  of  individuals  of  the  same  species 
and  under  the  same  circumstances  perform  them  at 
nearly  the  same  time,  yet  it  often  happens  that  some 
individuals  are  considerably  retarded  or  accelerated  in 
these  respects.  But  further  than  this,  the  functions 
themselves,  independently  of  the  action  of  any  external 
stimuli,  appear  to  have  a  natural  inherent  tendency  to 
periodic  returns  of  activity  and  repose.  Thus  in  the 
animal  kingdom,  the  return  of  night  and  day  are  met 
by  a  desire  to  sleep  and  to  be  awake  ;  and  although 
these  desires  may  be  so  modified  in  different  individuals 
that  some  require  less  sleep  than  others,  there  are  cer- 
tain limits  beyond  which  it  is  not  safe  to  carry  any 
unnatural  attempts  to  live  without  it.  Now  as  in 
these  cases  we  do  not  attribute  the  periodic  desire 
to  sleep  to  the  regular  return  of  night,  but  to  the  cha- 
racter of  the  function  itself  ;  so  in  the  case  of  the 
diurnal  opening  and  closing  of  flowers,  the  phenomenon 
must  primarily  be  ascribed  to  some  inherent  quality 
in  the  plant,  assisted  indeed  by  the  stated  returns  of 
the  stimuli  to  which  it  is  subject. 

(152.)  Functions  of  Vegetation.  —  Whether  we  con- 
sider life  in  the  vegetable  kingdom  as  possessing  more 
than  one  property  or  not,  the  various  operations  which 
result  from  its  action,  upon  and  through  the  instru- 
mentality of  the  several  organs  of  which  plants  consist, 
are  termed  "  functions  of  vegetation."  Although  there 
are  a  multiplicity  of  operations  carried  on  in  different 
parts  of  the  vegetable  structure,  they  may  all  be  con- 
sidered subordinate  to  one  or  other  of  the  two  general 
functions  of  nutrition  and  reproduction.  By  the  former 
the  life  of  each  individual  is  preserved,  and  by  the  latter 
the  continuance  of  the  species  is  secured. 

(153.)  Stimulants  to  Vegetation.  —  Life,  in  order 
to  act  through  the  instrumentality  of  the  vegetable 
structure,  requires  to  be  stimulated  by  the  influence  of 


CHAP.   I.      VITAL    PROPERTIES    AND    STIMULANTS.  1?1 

external  agents.  Unless  such  be  present,  the  vital  force 
remains  dormant,  even  where  it  is  not  extinguished. 
Thus  for  example,  seed  will  not  germinate  unless  it  be 
placed  under  peculiar  circumstances  with  regard  to 
moisture,  temperature,  and  the  atmosphere  ;  but  when 
a  sufficient  supply  of  these  three  stimulants  is  provided, 
the  seed  swells,  bursts,  and  the  plant  is  gradually  de- 
veloped. The  principal  stimulants  to  vegetation  are 
light,  heat,  air,  and  water ;  and  the  conjoint  action  of 
at  least  three  of  these  four  is  generally  requisite  to  se- 
cure a  healthy  condition  to  most  plants. 

(154.)  Light. —  The  action  of  light,  as  we  shall  show 
more  distinctly  when  we  are  describing  some  of  the 
functions  of  vegetation,  is  of  the  greatest  importance. 
We  shall  here  notice  only  onq  phenomenon,  to  which 
we  have  already  alluded  (art.  148.),  where  the  presence 
of  this  stimulant  exerts  a  decided  influence. 

(155.)  Sleep  of  Leaves. — The  phenomenon  to  which 
we  allude  is  termed  the  sleep  of  plants.  This  consists  in 
a  periodic  change  in  the  position  of  an  entire  leaf,  or  of 
the  several  leaflets  of  which  a  compound  leaf  is  formed. 
The  petioles,  or  leaf  stalks,  either  bend  upwards  or 
downwards,  so  that  the  flattened  surface  or  limb  of  the 
leaf  is  elevated  or  depressed.  There  are  about  a  dozen 
different  modifications  in  the  manner  in  which  the 
leaves  are  inclined  to  the  stalks  on  which  they  grow ; 
some  raise  their  leaflets  so  that  their  upper  surfaces  are 
brought  into  contact,  and  others  depress  them  so  that 
the  under  surfaces  meet  together.  This  phenomenon 
is  best  exhibited  by  various  species  of  the  two  natural 
orders,  the  Leguminosae  (which  includes  both  the  pea- 
flowering  plants,  as  clover,  &c.,  and  the  acacias  and 
mimosas,  &c.  which  have  regular  flowers)  and  the 
Oxalidese.  These  phenomena  depend  upon  a  special 
physiological  law,  subject  in  some  degree  to  the  sti- 
mulating effects  of  light  and  heat,  which  elicit  and 
control  them,  but  which  are  not  themselves  the  pri- 
mary causes  of  these  effects.  When  the  sensitive-plants 
are  confined  in  a  dark  room,  their  leaflets  periodically 


172  PHYSIOLOGICAL    BOTANY.  PART  II. 

fold  and  open  as  usual,  excepting  that  the  periods 
are  somewhat  lengthened ;  on  the  other  hand,  when 
they  are  exposed  to  a  continued  light,  these  periods  are 
shortened.  When  exposed  to  strong  lamplight  by 
night,  and  excluded  from  all  light  by  day,  their  periods 
of  sleep  become  extremely  irregular  for  a  time  ;  but, 
in  the  end,  the  specimens  generally  close  their  leaves 
during  the  day,  and  unfold  them  at  night.  The 
alternate  opening  and  closing  of  flowers  is  a  similar 
function  to  that  of  the  sleep  of  leaves.  The  time  of 
day  in  which  flowers  close  is  very  different  for  different 
species,  and  even  differs  for  that  period  during  which 
the  leaves  are  asleep  on  the  very  same  plant.  Bertho- 
let  mentions  an  acacia  in  the  garden  at  Orotava  in 
Teneriffe  whose  leaflets  closed  at  sunset  and  unfolded 
at  sunrise,  whilst  its  flowers  closed  at  sunrise  and 
expanded  at  sunset. 

(I5f).)  Electricity.  —  Nothing  very  decisive  is 
known  of  the  effects  which  so  important  an  agent  as 
electricity  produces  on  vegetation.  It  is,  indeed,  sup- 
posed to  act  as  a  stimulant,  and  the  supposition  is 
countenanced  by  the  increased  vigour  with  which  plants 
are  observed  to  grow  during  the  prevalence  of  stormy 
weather.  It  seems  to  be  not  unlikely,  that  some 
trees  are  more  liable  to  be  struck  by  lightning  than 
others  ;  but  they  are  all  so  constructed  as  to  present 
numerous  conducting  points  in  the  extremities  of  their 
branches,  well  adapted  for  drawing  off  the  electricity 
in  the  clouds. 

(157-)  Temperature.  —  The  influence  of  temper- 
ature on  vegetation  is  a  very  important  consideration, 
whether  we  regard  the  physical  or  physiological  effects 
which  it  produces.  When  the  temperature  is  below 
the  freezing  point  plants  can  obtain  no  nutriment,  be- 
cause the  water  in  which  it  is  conveyed  is  solidified. 
But  further,  it  is  essential  to  the  healthy  condition  of 
every  plant  that  its  internal  temperature  should  be  sup- 
ported within  certain  limits,  which  differ  for  different 
species.  The  opposite  extremes  of  temperature  under 


CHAP.   I.      VITAL    PROPERTIES    AND    STIMULANTS.  1  "3 

which  different  plants  are  capable  of  existing  are  widely 
apart.  Some  flourish  within  the  influence  of  hot  springs, 
where  they  are  stated  to  be  constantly  exposed  to  a  tem- 
perature of  62°  R.,  or  17H°  F.,  and  even  to  80°  R., 
which  is  equivalent  to  212°  F. ;  whilst  the  oak  sustains 
the  rigours  of  a  winter  in  latitudes  where  the  thermo- 
meter falls  to  -25°  R.,  or  -24-i°  F.,  and  the  birch  will 
resist  a  cold  of  -36°  R.,  or  -49°  F.  The  latter  is  well 
protected  against  the  effects  of  extreme  cold  by  the  man- 
ner in  which  its  trunk  is  defended  with  several  loose  coats 
of  epidermis.  The  chief  protection,  however,  against 
the  sap  freezing  in  the  trunks  of  trees,  is  the  circum- 
stance of  its  being  contained  in  extremely  minute  ve- 
sicles and  capillary  vessels  ;  for  it  has  been  shown  that 
water  will  resist  a  temperature  of  -?°  R.  or  l6-^-°  F. 
under  similar  circumstances ;  and  all  viscid  fluids  are 
still  more  difficult  to  freeze  than  water.  Whenever 
the  sap  does  freeze,  it  produces  the  effect  technically 
termed  "  shakes  "  in  timber  trees,  which  consists  in  a 
tendency  in  the  separate  layers  of  wood  to  disunite. 

(158.)  Internal  Temperature.  —  In  animals,  the 
function  of  respiration  is  the  means  by  which  caloric  is 
set  free,  for  the  purpose  of  maintaining  the  temperature 
of  their  bodies  at  a  sufficient  elevation  to  protect  them 
against  the  influence  of  cold,  and  perspiration  cools  them 
when  they  are  exposed  to  excessive  heat.  As  vegetables 
perform  two  functions  of  a  similar  kind,  we  might  per- 
haps be  led  to  expect  that  the  influence  of  similar 
effects  would  regulate  their  internal  temperature.  But, 
if  such  be  the  fact,  the  results  are  on  too  minute  a 
scale  to  be  rendered  sensible  by  our  instruments ;  and 
in  the  winter,  when  these  functions  nearly  cease,  we 
cannot  suppose  that  they  operate  at  all  in  resisting  any 
atmospheric  changes  which  might  be  injurious  to  vege- 
tation. Still  it  has  been  observed  as  a  general  law,  that 
the  temperature  of  a  tree  is  higher  between  autumn  and 
spring  than  the  average  temperature  of  the  air,  and 
that  it  is  lower  between  spring  and  autumn.  But 
there  are  physical  causes  which  seem  to  be  sufficient 


174  PHYSIOLOGICAL    BOTANY.  PART  II. 

to  account  for  these  facts  without  the  necessity  of  as- 
cribing them  to  the  results  of  any  physiological  action. 
The  roots  penetrate  the  earth  to  a  depth  where  the  soil 
is  always  warmer  than  the  atmosphere  in  winter  and 
cooler  in  summer,  and  the  moisture  which  they  imbibe 
will  consequently  partake  of  this  influence.  Hence  it 
has  been  observed,  that  the  internal  temperature  of  trees 
is  about  the  same  as  the  soil  at  one-half  the  depth  to 
which  their  roots  penetrate.  The  maintenance  of  an 
internal  temperature  distinct  from  the  external  is  as- 
sisted by  the  nature  of  the  wood  itself,  which  is  a  bad 
conductor  of  heat;  and  also  by  the  property  which  it 
possesses  of  conducting  heat  better  in  a  longitudinal 
than  in  a  transverse  direction.  As  an  example,  we  may 
mention  that  the  milk  of  the  cocoa-nut  is  kept  cool 
during  the  hottest  part  of  the  day  by  the  thick  fibrous 
coating  of  the  pericarp,  which  is  a  very  bad  conductor 
of  heat. 


175 


CHAP.  'II. 

FUNCTION  OF  NUTRITION  —  Periods  1,  2,  3,  4. 

ABSORPTION    (160.).  ASCENT     OF      SAP      (163.) CAUSES     OF 

PROGRESSION      (165. ).—  EXHALATION       (169.)-  RETENTION 

OF    SAP    (172.).  RESPIRATION    (173.).  FIXATION    OF    CAR- 
BON     (176.).  ORGANIZABLE     PRODUCTS GUM       (177.).  

ETIOLATION   (179.). COLOURS  AND  CHROMATOMETER   (182.). 

RESULTS    OF    RESPIRATION     (189.). 

(159-)  Function  of  Nutrition.  —  THE  first  of  the  two 
general  functions  (art.  152.),  that  of  nutrition,  may 
be  conveniently  subdivided  into  about  seven  distinct 
processes  or  subordinate  functions,  which  are  all  car- 
ried on  simultaneously  in  different  parts  of  the  vege- 
table structure,  more  especially  during  those  seasons 
of  the  year  in  which  the  powers  of  vegetation  are 
the  most  active.  Sometimes,  only  one  of  them  is 
in  activity,  whilst  the  rest  are  either  partially  or 
entirely  suspended.  But  as  the  whole  of  the  materials 
which  serve  to  nourish  the  plant  must  have  been 
subjected  to  these  several  processes  in  succession, 
we  may  consider  the  function  of  nutrition  to  be 
carried  on  during  as  many  successive  periods,  be- 
fore it  is  completed.  We  will  briefly  mention  what 
these  successive  processes  are,  before  we  enter  upon 
the  details  necessary  for  the  more  accurate  description 
of  each  of  them.  In  the  first  place,  plants  absorb 
their  nutriment  by  the  roots ;  this  nutriment  is  then 
conveyed  through  the  stem  into  the  leaves ;  there  it 
is  subjected  to  a  process  by  which  a  large  proportion 
of  water  is  discharged;  the  rest  is  submitted  to  the 
action  of  the  atmosphere,  and  carbonic  acid  is  firA 
generated,  and  then  decomposed  by  the  action  of  light : 


1  7fi  PHYSIOLOGICAL    BOTANY.  PART  II. 

carbon  is  now  fixed  under  the  form  of  a  nutritive  ma- 
terial, which  is  conveyed  back  into  the  system  ;  and  this 
material  is  further  elaborated  for  the  development  of  all 
parts  of  the  structure,  and  for  the  preparation  of  certain 
secreted  matters,  which  are  either  retained  within  or 
ejected  from  the  plant.  These  several  processes  may 
be  designated  :  1 .  Absorption  ;  2.  Progression  of  sap  ; 
.'{.  Kxhalation ;  4.  Respiration;  5.  Retrogression  of 
proper  juice ;  6.  Secretion  ;  7-  Assimilation. 

FIRST    PERIOD    OF    NUTRITION. 

(l6'0.)  Abtorption.  —  That  plants  absorb  moisture 
from  the  soil  in  which  they  grow  admits  of  easy  proof. 
The  extremities  of  the  fibres  in  which  their  roots  ter- 
minate, are  not  covered  with  an  epidermis  like  the  rest 
of  the  surface,  and  consequently  the  cellular  texture  is 
there  exposed,  and  constitutes  the  "  spongiole,"  or  true 
absorbing  organ.  As  plants  do  not  possess  the  power 
of  locomotion,  it  is  essential  that  their  food  should  be  so 
universally  distributed  that  they  may  run  no  risk  of 
perishing  from  want  of  a  constant  supply.  It  is  further 
requisite  that  their  food  should  be  offered  them  in  a 
fluid  form  ;  for  it  is  an  established  principle  in  ve- 
getable physiology,  that  the  spongioles  are  incapable 
of  absorbing  any  matter  in  a  solid  state.  Whatever 
therefore,  is  to  be  received  into  the  system  for  the  pur- 
pose of  nutrition  must  be  held  in  a  state  of  solution 
in  water.  The  three  most  important  ingredients  to  be 
found  among  the  products  of  vegetation,  are  oxygen, 
hydrogen,  and  carbon  (see  art.  14.)  ;  the  two  former  are 
the  elements  of  water,  and  the  third  is  an  element  of 
carbonic  acid,  a  gas  which  is  every  where  present  in  the 
atmosphere,  and  which  may  be  detected  in  almost  all 
springs  and  other  waters  on  the  surface  of  the  earth. 
Water,  again,  in  a  state  of  suspension  in  the  air,  is  also 
present  every  where.  Plants,  therefore,  receive  a  constant 
supply  of  these  three  elements  wherever  they  are  placed 
on  the  surface  of  the  earth,  in  situations  adapted  to  their 


CHAP.   II.  FUNCTION    OP    NUTRITION'.  177 

growth.  Besides  the  three  elementary  substances,  oxygen, 
hydrogen,  and  carbon,  essential  to  the  composition  of  all 
organized  matter,  whether  animal  or  vegetable,  there 
are  other  elements  to  be  met  with  in  slight  proportion 
in  some  vegetables.  Azote  is  an  element  more  espe- 
cially essential  to  the  formation  of  animal  substances ; 
but  it  seems  probable,  that  it  is  also  a  fundamental 
ingredient  in  certain  vegetable  compounds,  in  which 
it  exists  in  considerable  abundance.  As  this  gas 
also  forms  a  component  part  of  the  atmosphere,  plants 
may  as  readily  be  furnished  with  it,  as  with  either 
of  the  other  three  ingredients  universally  essential  to 
their  nature.  Whether  the  other  elements  occasion- 
ally found  in  plants  ever  constitute  an  essential  part 
of  their  structure,  is  uncertain.  Several  of  them  exist 
under  combinations,  such  as  common  salt  for  example, 
which  appear  to  be  useful  to  some  plants ;  possibly  as  a 
stimulus  necessary  for  the  preservation  of  their  health, 
since  they  languish  and  die  when  wholly  removed  from 
their  influence.  In  all  cases,  however,  whatever  be  the 
nature  of  the  various  saline,  earthy,  metallic,  and  other 
compounds  found  in  small  quantities  in  the  ashes  of 
plants,  they  must  have  been  introduced  in  a  state  of  so- 
lution through  the  spongioles. 

(l6l.)  Cause  of  Absorption.  —  This  absorption  by 
the  spongioles  continues  during  the  lifetime  of  the  plant, 
and  it  becomes  a  question  for  the  physiologist  to  deter- 
mine, upon  what  cause  the  action  depends  ;  whether  it 
may  be  ascribed,  for  instance,  to  the  known  hygroscopic 
powers  of  the  cellular  tissue,  or  whether  it  be  wholly  or 
partly  due  to  a  vital  action.  This  question  can  scarcely 
be  considered  as  satisfactorily  settled.  If  we  suppose 
the  plant  capable  of  removing  the  imbibed  fluid  as  fast 
as  it  is  absorbed  by  the  spongioles,  then  we  may  imagine 
the  possibility  of  a  supply  being  kept  up  by  the  mere 
hygroscopic  property  of  the  tissue,  much  in  the  same 
way  as  the  capillary  action  of  the  wick  in  a  candle 
maintains  a  constant  supply  of  wax  to  the  flame  by 

N 


178  PHYSIOLOGICAL    BOTANY.  I'AHT  II. 

which  it  is  consumed.  This  view  is  further  sup- 
ported by  the  fact,  that  the  facility  with  which  dif- 
ferent liquids  are  absorbed,  appears  to  depend  entirely 
upon  their  degrees  of  fluidity ;  and  thus  even  the  most 
noxious  materials  will  be  more  readily  imbibed  than  such 
as  are  nutritious,  provided  they  are  presented  to  the 
spongioles  in  the  more  fluid  state.  Now  if  their  ab- 
sorption were  the  result  of  a  vital  action,  we  might  have 
expected  that  a  greater  degree  of  energy  would  have 
been  exerted  in  favour  of  the  more  nutritious  matter, 
and  that  the  noxious  ingredient  would  have  been  ab- 
sorbed with  difficulty. 

(162.)  Stimulants  to  Absorption Whatever  be  the 

immediate  cause  of  absorption,  it  does  not  depend  upon 
the  action  of  light ;  for  plants  absorb  by  night  as  well 
as  by  day,  and  the  absorbing  organs  are  most  frequently 
placed  under  ground,  and  in  the  dark.  In  an  indirect 
manner,  however,  light  does  certainly  exert  a  consider- 
able effect  upon  the  quantity  of  fluid  absorbed  ;  because 
it  is  the  stimulant  by  which  a  large  portion  is  con- 
tinually removed  by  the  function  of  exhalation  ;  and 
we  consequently  find  that  when  plants  are  placed  in  the 
dark,  although  the  absorption  continues  it  is  consider- 
ably checked,  so  that '  the  water  imbibed  accumulates 
until  they  become  dropsical,  and  their  leaves  fall  off  upon 
the  slightest  touch.  An  increase  of  temperature  aug- 
ments the  quantity  of  water  absorbed  ;  but  this  again 
may  depend  upon  some  local  stimulus  upon  another 
function.  Thus  if  a  branch  from  a  plant  growing 
in  the  open  air  be  introduced  within  a  stove  during 
the  winter,  it  will  immediately  begin  to  push  its  leaves, 
and  become  the  remote  cause  of  accelerating  the  ab- 
sorption of  the  sap,  which  had  been  going  on  very  lan- 
guidly. 

SECOND    PERIOD    OP    NUTRITION. 

(lf)3.)  Ascent  of  the  Sap — The  fluid  introduced  by 
the  absorption  of  the  spongioles  bears  the  general  name 


CHAP.   II.  FUNCTION    OF    NUTRITION.  179 

of  sap  or  "  lymph."  Essentially,  this  sap  is  nearly  pure 
water ;  but  in  order  that  it  may  become  effective  in 
nourishing  the  plant,  it  must  contain  carbonic  acid,  or 
at  least  some  carbonaceous  material  capable  of  being  con- 
verted into  carbonic  acid  by  a  subsequent  process,  which 
we  shah1  presently  describe.  In  Dicotyledonous  woody 
stems,  it  has  been  clearly  ascertained  that  the  course  of 
the  sap  is  up  the  woody  fibre,  and  especially  through  the 
alburnum,  but  that  it  does  not  ascend  in  any  appreciable 
quantify  through  the  pith  or  bark.  It  is  then  carried 
onward  through  the  branches  and  into  the  leaves.  In 
the  internal  parts  of  old  trunks,  the  sap  accumulates  in 
large  quantities  about  the  spring  of  the  year,  and  is  there 
retained  under  a  certain  degree  of  compression  ;  for  if 
the  tree  be  felled  at  this  season,  it  flows  most  readily 
from  those  central  parts  which  have  ceased  to  possess 
any  vitality,  and  sometimes  it  even  issues  in  a  jet  during 
a  few  seconds,  when  the  trunk  is  first  severed.  Whether 
or  not  any  distinct  modification  takes  place  whilst  the 
sap  is  moving  onward,  analogous  to  the  effects  of  diges- 
tion in  animals,  has  not  been  clearly  ascertained.  It  is 
certain,  indeed,  that  if  a  tree  is  tapped  at  different 
heights,  when  the  sap  is  rising  with  the  greatest  energy, 
the  liquid  obtained  from  the  lower  parts  of  the  stem  is 
purer  than  that  which  is  derived  from  the  upper  parts. 
But  this  may  be  ascribed  to  the  complete  admixture 
which  takes  place  between  the  juices  previously  elabo- 
rated and  the  ascending  sap.  which  thus  becomes  thick- 
ened by  them  as  it  moves  onward. 

(164.)  Channels  for  the  Sap. — Some  authors  suppose 
the  sap  to  be  propelled  through  the  vascular  system, 
whilst  others  consider  it  to  rise  through  the  intercellular 
passages,  and  others  again  imagine  that  it  passes  from 
cell  to  cell,  through  the  elementary  membrane  of 
which  they  are  formed.  The  great  difficulty  in  de- 
termining the  precise  channel  through  which  the  pro- 
gression of  the  sap  takes  place,  must  be  ascribed  to  the 
perfect  transparency  of  the  vegetable  membrane,  and  the 
extreme  minuteness  of  these  organs  themselves.  By 
N  2 


180  PHYSIOLOGICAL    BOTANY.  PART  II. 

placing  a  branch  in  coloured  fluids,  such  as  a  decoction 
of  Brazil-wood  or  cochineal,  they  are  absorbed  and  the 
course  of  the  sap  through  its  whole  passage  into  the 
leaf  may  be  readily  traced  ;  but  on  examining  micro- 
scopically the  stains  which  have  been  left,  it  is  scarcely 
possible  to  feel  satisfied  whether  they  are  on  the  outer 
or  inner  surface  of  the  vessels  and  cells  which  they  have 
discoloured.  The  mutilated  state  of  the  stem,  when 
subjected  to  experiments  of  this  description,  lias  also 
introduced  errors  into  the  results,  and  the  coloured 
liquids  have  been  observed  to  rise  up  certain  vessels 
which  under  ordinary  circumstances  appear  destined  to 
convey  air.  Since  there  are  many  plants  which  possess 
no  vascular  structure,  in  them  at  least  we  must  allow  the 
cellular  tissue  to  be  the  true  channel  through  which  the 
sap  is  conveyed.  But  whatever  may  be  the  manner  in 
which  the  effect  is  produced  in  the  more  succulent  parts 
of  plants,  it  seems  to  be  unquestionable  that  a  more  di- 
rect mode  of  progression  than  that  of  a  gradual  trans- 
mission from  cell  to  cell,  must  exist  in  the  older  parts 
of  woody  stems.  If  for  instance  we  take  a  long  branch 
of  the  vine  and  bend  it  in  the  middle,  the  sap  imme- 
diately exudes  at  the  extremities,  but  chiefly  on  those 
sides  which  are  towards-the  concave  surface  produced  by 
the  flexure;  which  not  only  indicates  a  continuity,  but 
also  a  rectilinear  course  in  the  channels  through  which 
the  sap  is  conveyed.  It  is  further  evident  that  a  general 
intercommunication  must  subsist  between  these  several 
channels  ;  for  the  stem  may  be  notched  to  the  very 
centre,  at  different  altitudes  and  on  different  sides,  so  as 
completely  to  intercept  every  r.ectilinear  communication 
between  the  lower  and  upper  parts,  and  the  sap  will 
still  find  its  way  into  the  leaves.  The  probability 
therefore  seems  to  be,  that  the  crude  sap  really  rises, 
at  least  in  woody  stems,  through  the  intercellular  pas- 
sages, where  it  bathes  the  surface  of  the  cells  and  ves- 
sels, all  of  which  are  so  many  distinct  organs  destined 
to  act  upon  it  —  and  more  especially  when  it  has  after- 
wards become  intermixed  with  the  proper  juices  of  the 


CHAP.   II.  FUNCTION    OF    NUTRITION.  181 

plant.  If  this  view  of  the  subject  should  prove  correct, 
then  the  intercellular  passages  must  be  considered  ana- 
logous to  the  stomachs  of  animals,  mere  recipients  of  a 
crude  material,  which  is  afterwards  modified  and  ren- 
dered available  for  the  purposes  of  nutrition. 

(165.)  Cause  of  Progression.  —  The  progression  of 
the  sap  appears  to  be  influenced  by  several  causes.  De 
Candolle  supposes  it  to  be  carried  forward  through  the 
intercellular  passages  by  successive  contractions  and  dila- 
tations of  the  cells.  But  there  appears  to  be  no  warrant 
for  the  supposition ;  on  the  contrary,  it  seems  impos- 
sible that  such  an  effect  could  be  produced  in  cells 
which  are  replete  with  an  incompressible  fluid.  If 
contraction  were  to  take  place,  an  expulsion  of  the  con- 
tained fluid  must  ensue,  and  every  dilatation  of  the  cells 
would  require  that  the  ambient  fluid  should  enter  them. 
Whether  therefore  the  sap  rises  or  not  through  the  in- 
tercellular passages,  the  hypothesis  which  he  has  framed 
to  explain  its  progression  appears  to  be  inadmissible. 

(166.)  Propulsion  of  the  Sap.  —  The  first  and  most 
important  cause  of  the  rise  of  the  sap,  resides  in  the 
spongioles.  The  water  imbibed  by  them,  is  also  by 
them  propelled  forward  with  considerable  force,  and 
the  effects  are  strikingly  analogous  to  those  exhibited 
by  the  endosmometer  (art.  144.).  Hales  cut  off  the 
stem  of  a  vine  in  the  spring,  when  the  sap  rises  with 
the  greatest  velocity,  and  luted  a  tuba  to  the  top  of  the 
stump,  bent  in  the  manner  we  have  described  in  the 
construction  of  the  endosmometer.  As  the  sap  rose  into 
the  tube,  mercury  was  introduced  at  the  open  end  ;  and 
a  measure  of  the  force  of  the  rising  sap  was  thus  ob- 
tained, and  found  to  equal  the  pressure  of  an  atmosphere 
and  a  half.  If  a  piece  of  bladder  be  tied  over  the  sur- 
face of  a  v^ne-stump,  when  the  sap  is  rapidly  rising, 
it  soon  becomes  tightly  distended,  and  will  ultimately 
burst.  These  effects  manifestly  bespeak  an  action  very 
different  from  the  ordinary  results  of  capillarity,  and 
indicate  the  presence  of  a  powerful  force,  a ' '  vis  a  tergo." 
N  3 


182  PHYSIOLOGICAL    BOTANY.  PART  II. 

residing  in  the  lowest  extremities  of  the  roots  by  which 
the  propulsion  of  the  sap  is  regulated.  Although  these 
results  so  closely  resemble  those  of  endosmose,  there 
still  exists  a  difficulty  in  connecting  the  two  phenomena  ; 
for  whilst  we  may  admit  the  possibility  of  an  inter- 
change between  the  contents  of  the  vesicles  composing 
the  spongioles,  and  the  water  in  the  soil  which  sur- 
rounds them,  by  the  ordinary  operation  of  endosmose, 
it  is  difficult  to  explain  how  the  sap  may  be  propelled 
forward  so  violently  as  it  appears  to  be,  in  the  open 
channels  through  the  centre  of  the  stem,  which  contain 
crude  sap  of  nearly  the  same  specific  gravity  as  water 
itself.  It  would  be  further  necessary  to  account  for  the 
manner  in  which  a  continued  supply  of  fresh  materials 
is  obtained  for  carrying  on  the  endosmose,  which  must 
otherwise  soon  cease  when  the  fluid  within  has  become 
much  diluted.  We  shall  find,  however,  that  a  constant 
supply  of  fresh  material  is  actually  provided  by  the 
direct  action  of  the  vital  force,  during  a  subsequent 
period  in  the  function  of  nutrition  ;  and  hence  it  is  not 
impossible,  though  it  has  not  been  proved,  that  both 
the  propulsion  as  well  as  the  absorption  of  the  sap  may 
principally  if  not  entirely  be  owing  to  the  operation 
of  mechanical  causes  ;  "dependent  however  for  their 
lengthened  continuance  upon  the  existence  of  the  vital 
energy  by  which  those  conditions  are  perpetually  re- 
newed, and  without  which  the  endosmose  would  of  neces- 
sity soon  cease.  Although  therefore  it  is  quite  evident 
that  the  immediate  effects  of  the  vital  force  must  be  some- 
where present,  and  co-operative  with  the  two  pheno- 
mena we  have  described,  these  themselves  may  be  only 
the  secondary  results,  and  not  the  direct  effects  of  its 
action. 

(ifi?.)  Adfluxion.  —  Another  cause  which  promotes 
the  rise  of  the  sap,  is  the  continued  discharge  of  moisture 
which  takes  place  from  the  surface  of  the  leaves  and 
other  parts,  by  a  process  to  be  described  presently  (art. 
l68.).  This  effect  produces  a  constant  absorption  from  be- 
low ;  and  thus  a  branch  placed  in  water  gradually  imbibes 


CHAP.  II.  FUNCTION    OP    NUTRITION.  183 

a  large  quantity  at  its  cut  extremity.  This  "  adfluxion  " 
of  the  sap,  as  it  has  been  termed,  is  clearly  the  result 
of  a  different  cause  from  that  of  its  propulsion,  explained 
in  the  last  article. 


THIRD    PERIOD    OP    NUTRITION. 

(168.)  Exhalation.  —  A  large  portion  of  the  water 
imbibed  by  the  spongioles  is  afterwards  discharged  at 
the  surface  of  the  leaves,  in  a  manner  analogous  to  the 
insensible  perspiration  of  animals.  This  discharge  may 
be  attributed  to  the  operation  of  two  distinct  causes.  A 
very  small  portion  is  carried  off  by  the  ordinary 
effects  of  evaporation,  but  a  far  greater  quantity  by 
a  process  which  has  been  named  "  exhalation,"  and 
which  is  ascribed  to  the  immediate  action  of  the 
vital  force.  That  a  certain  portion  of  the  discharge 
must  be  due  to  the  evaporation  of  the  contained 
fluid  through  the  membranous  coats  of  the  vesicles,  is 
proved  by  the  gradual  desiccation  of  the  succulent 
parts-  of  dead  plants,  and  by  the  effects  observed,  in  the 
preservation  of  pulpy  fruits.  But  still,  the  effects  of 
evaporation  alone  are  scarcely  perceptible,  when  com- 
pared with  the  rapid  manner  in  which  the  fluid  is  dis- 
charged from  the  surface  of  the  leaf.  It  has  been 
ascertained  that  a  common  sunflower  of  three  feet  in 
height,  will  exhale  about  twenty  ounces  of  water  every 
day ;  and  a  common-sized  cabbage  discharges  moisture 
at  the  same  rate :  so  that  the  surfaces  of  these  plants 
exhale  at  a  rate  which  is  seventeen  times  greater  than 
that  at  which  the  insensible  perspiration  is  given  off 
from  the  surface  of  the  human  body. 

(169.)  Exhaling  Organs. — By  comparing  the  effects 
produced  by  the  leaves  of  different  species,  it  has  been 
found  that  those  exhale  the  most  which  possess  the 
greatest  number  of  stomata ;  whilst  those  surfaces  which 
possess  none,  produce  very  little  or  no  effect  beyond  the 
ordinary  loss  sustained  by  evaporation.  It  is  quite  as 
evident  therefore  that  the  stomata  are  the  true  exhaling 
N  4 


184  PHYSIOLOGICAL    BOTANY.  PART  II. 

organs  of  plants,  as  that  the  spongioles  are  their  real 
absorbing  organs.  As  the  under  surfaces  of  leaves  are 
in  general  more  plentifully  supplied  with  stomata  than 
their  upper  surfaces,  the  exhalation  is  there  the  most 
abundant.  Plants  which  live  under  water  have  no  sto- 
mata ;  but  as  they  have  no  true  epidermis  either,  they 
rapidly  fade  when  exposed  to  the  air,  from  the  more  de- 
cided effects  of  evaporation  alone. 

(170.)  Stimulants  to  Exhalation.  —  The  manner  in 
which  the  stomata  act  is  unknown  ;  and  consequently 
we  are  compelled  to  ascribe  the  function  which  they 
perform  to  the  immediate  operation  of  the  vital  force. 
The  stimulus  by  which  their  activity  is  sustained,  is 
u.ainly  if  not  entirely  due  to  the  influence  of  light ;  for 
the  exhalation  ceases  when  the  plant  is  carried  into  a 
darkened  chamber,  and  is  restored  upon  its  return  to 
the  light.  Even  lamplight  is,  to  a  certain  extent,  suf- 
ficient for  maintaining  this  action.  The  effects  of  ex- 
halation are  remarkably  apparent  about  sunrise,  when 
the  temperature  is  low,  and  the  moisture  exhaled  is  not 
readily  carried  off;  it  then  accumulates,  and  is  deposited 
in  innumerable  drops  upon  the  surface  and  edges  of  the 
leaves,  and  is  generally  mistaken  for  the  effects  of  dew  : 
but  as  it  collects  equally  on  plants  which  are  under  shel- 
ter as  on  those  which  are  openly  exposed,  this  cannot  be 
the  true  cause.  It  is  by  no  means  clear  that  an  elevation 
of  temperature  has  any  effect  in  modifying  this  func- 
tion ;  but  since  it  undoubtedly  increases  the  quantity  of 
the  evaporation,  it  becomes  difficult  to  decide  whether 
any  portion  of  the  result  is  due  to  an  increased  ex- 
halation also.  The  manner  in  which  the  direct  rays  of 
the  sun  act  in  stimulating  this  function,  is  well  known 
to  those  who  are  aware  how  necessary  it  is  in  order  to 
preserve  the  beauty  and  freshness  of  a  nosegay,  to  keep  it 
constantly  in  the  shade.  There  are  certain  succulent 
plants  which  possess  so  few  stomata  that  they  may  be 
preserved  out  of  the  ground  for  many  days  and  even 
months,  without  perishing  from  want  of  moisture ;  and 
it  will  frequently  happen  that  Sedums,  and  other  plants 


CHAP.   II.  FUNCTION    OF    NUTRITION.  185 

of  this  character,  will  even  push  considerable  shoots 
whilst  placed  under  pressure,  when  preparing  for  the 
herbarium :  such  specimens  should  first  be  killed  by 
immersion  for  a  few  seconds  in  scalding  water.  As 
juicy  plants  require  most  light  to  secure  for  them  a 
regular  discharge  of  moisture,  we  may  mention  as  a 
piece  of  practical  information,  the  propriety  of  exposing 
as  many  leaves  as  possible  in  the  melon  frame  to  the 
action  of  the  sun's  rays,  at  the  same  time  providing 
against  the  accumulation  of  moisture  in  the  confined 
situation  in  which  such  plants  are  placed. 

The  operation  of  transplanting  should  be  carried  on 
either  in  the  spring  or  autumn,  when  plants  are  des- 
titute of  leaves ;  otherwise  the  exhalation  is  too  strong 
at  a  time  when  the  absorption  has  been  checked,  owing 
to  injury  sustained  at  the  root.  Provided  the  plants 
are  well  watered,  the  latter  inconvenience  may  to  a 
certain  extent  be  obviated.  The  water  exhaled  is  so 
nearly  pure,  that  scarcely  any  trace  of  foreign  matter  is 
discoverable  in  it,  certainly  not  more  than  would  be 
found  in  distilled  water  prepared  with  the  greatest  care. 
Even  that  which  is  exhaled  by  aromatic  plants  is  scarcely 
tainted  by  any  odour.  The  stomata  are  in  fact  the 
most  perfect  and  delicate  stills  to  be  met  with  in  the 
laboratory  of  nature. 

(171.)  Retention  of  Sap.  — About  two  thirds  of  the 
fluid  imbibed  by  the  spongioles  is  thus  exhaled  by  the 
stomata,  and  consequently  about  one  third  must  be 
still  retained  in  the  plant.  As  this  portion  now  in- 
cludes all  the  saline,  earthy,  carbonaceous,  and  other 
materials,  which  happened  to  be  dissolved  in  the  sap 
when  it  was  first  absorbed,  the  obvious  effect  produced 
by  the  exhalation  is  to  condense  these  matters,  so 
that  the  sap  becomes  a  comparatively  denser  fluid 
than  it  was  before.  As  many  of  the  materials  thus 
introduced  are  not  adapted  to  the  purposes  of  nutrition, 
they  are  deposited  in  those  parts  where  the  exhalation 
has  been  going  on ;  but  the  various  carbonaceous  ma- 
terials, furnished  chiefly  by  decomposing  animal  and 


186 


PHYSIOLOGICAL    BOTANY. 


vegetable  substances,  are  brought  into  a  situation  favour- 
able for  receiving  a  peculiar  modification,  which  we 
shall  describe  in  the  fifth  period  of  nutrition.  Of  the 
three  elements  more  especially  essential  to  the  compo- 
sition of  all  vegetable  matter,  we  find  that  two  of  them, 
the  oxygen  and  hydrogen,  may  be  furnished  by  the 
water  retained  after  the  process  of  exhalation  has  been 
completed. 


FOURTH    PERIOD    OP    NUTRITION. 

(172.)  Respiration.  —  The  first  actual  change  pro- 
duced in  the  sap  is  effected  by  a  process  analogous  to 
animal  respiration.  The  air  is  inhaled  by  the  leaf  and 
the  fresh  surfaces  of  other  parts  of  the  plant,  and 
its  oxygen  then  unites  with  the  carbonaceous  matters 
contained  in  the  sap,  and  the  result  is  the  formation  of 
carbonic-acid.  The  greater  part  of  this  gas  is  then 
held  in  solution  by  the  sap ;  and  the  whole  or  very  nearly 
all  the  azote  which  was  separated  from  the  oxygen, 
is  exhaled.  Besides  the  carbonic  acid  thus  formed  by 
the  plant  itself,  the  trifling  proportion  every  where 
found  in  the  atmosphere  is  also  inhaled ;  and  a  still 
larger  quantity  is  introduced  in  the  water  absorbed 
by  the  spongioles.  Hence  it  appears  that  a  threefold 
provision  is  made  for  maintaining  a  supply  of  this  ne- 
cessary ingredient.  So  long  as  plants  remain  in  the 
dark,  no  fresh  change  takes  place  in  this  condition  of 
things ;  the  carbonic  acid  is  retained,  but  is  not  fixed 
in  the  form  of  an  organic  compound.  This  further 
result  requires  the  additional  stimulus  of  light,  and  then 
the  decomposition  of  the  carbonic  acid  is  effected,  the 
carbon  becomes  fixed  under  the  form  of  an  organisable 
compound,  which  we  shall  presently  describe  (art.  1 76.), 
and  all  or  nearly  all  the  oxygen  with  which  it  was  united, 
is  exhaled  into  the  atmosphere.  So  long  then  as  plants 
continue  to  vegetate  in  the  dark  they  tend  to  vitiate  the 
atmosphere  by  abstracting  its  oxygen,  and  also  by  the 


CHAP.   II.  FUNCTION    OF    NUTRITION.  187 

emission  of  some  portion  of  the  carbonic  acid  which 
they  generate ;  but  when  they  are  exposed  to  the  light, 
they  not  only  restore  the  oxygen  which  they  had  pre- 
viously abstracted  from  the  atmosphere,  but  also  give 
out  another  portion  of  this  gas,  which  they  set  free  by 
the  decomposition  of  the  carbonic  acid  contained  in  the 
air,  as  well  as  that  which  was  in  the  water  imbibed  by  the 
spongioles.  In  animal  respiration,  the  carbonic  acid  is 
immediately  expelled  from  the  lungs  as  soon  as  it  is 
formed,  and  the  function  is  then  considered  complete ; 
and  perhaps  it  would  be  more  logical  to  divide  the 
function  of  vegetable  respiration  into  two  processes,  one 
of  which  should  comprise  the  formation,  and  the  other 
the  decomposition,  of  carbonic  acid. 

(173.)  Formation  of  Carbonic  Acid.  —  The  formation 
of  carbonic  acid  takes  place  in  the  leaf,  beneath  the 
epidermis ;  but  whether  the  air  penetrates  through  the 
stomata  or  not,  is  still  uncertain.  That  it  cannot  uni- 
versally be  introduced  through  these  organs  is  apparent, 
since  many  leaves  have  no  stomata;  and  in  these  cases 
at  least,  the  action  takes  place  through  the  intervention 
of  the  delicate  membrane  of  which  the  vesicles  of  the 
cellular  tissue  are  composed.  If  a  section  perpendicular 
to  both  surfaces  of  a  leaf  be  examined  under  the  highest 
powers  of  the  microscope  (fig.  152.),  the  interior  will  be 
observed  to  be  chiefly 
made  up  of  cellular 
matter,  or  "  paren- 
chyma," whose  vesi- 
cles are  loosely  ag- 
gregated, so  that  large 
intercellular  passages 
exist  in  communica- 
tion with  each  other, 
through  its  whole  sub- 
stance. That  these  passages  are  filled  with  air  is  readily 
shown  by  placing  a  leaf  under  water,  and  beneath  the  re- 
ceiver of  the  air-pump.  Upon  exhausting  the  receiver,  the 
air  contained  in  the  leaf  will  be  seen  to  escape  through  the 


188 


PHYSIOLOGICAL    BOTANY. 


petiole ;  and  upon  removing  the  receiver,  the  water  will 
then  find  its  way  into  the  leaf,  and  occupy  the  in- 
terstices which  were  originally  filled  with  air.  This 
effect  is  rendered  particularly  striking  in  those  leaves 
whose  under  surfaces  are  of  a  paler  colour  than  their 
upper,  in  consequence  of  the  larger  dimensions  of  the 
intercellular  passages  in  those  parts.  When  the  water 
is  introduced  and  occupies  the  whole  of  these  passages, 
the  two  surfaces  become  equally  coloured. 

(1?4.)  Air  Cells.  —  Besides  the  air  in  the  leaves,  some 
also  is  found  in  the  stems  and  other  parts  of  plants,  where 
its  precise  use  has  not  been  fully  ascertained.    In  many 
aquatics,  indeed,  it  is  contained  in  large  cavities,  termed 
"lacunae,"  as  we  have  stated  (art.  21.).  The  obvious  use 
of  such  reservoirs  as  these,  is  to  float  the  leaves  and  other 
parts  in  which  they  exist.     The  Pontiih-rw  mm/>!# 
has  its  petioles  (fig.  1 53  rt.)  remarkably  distended  with 
air.     The  roots  of  the  Utri- 
cularia?  are  furnished  with  a 
multitude  of  little  bladders 
(fig.  32.)  by  which  they  are 
floated  to  the  surface  during 
the  season  of  flowering  ;  and 
a  number  of  other  instances 
might  be    mentioned  where 
some    provision  or  other  of 
this  kind  exists.      But,  be- 
sides   the   mere  mechanical 
effects  which  are  thus  pro- 
duced, it    is    probable    that 
the  air  introduced   into  the 
system  may    in    many  instances    serve    some    physio- 
logical purpose.      It    seems    to    be    sufficiently   ascer- 
tained, that  some  portions  at  least  of  the  vascular  system 
are  destined  to  convey  air  from  one  part  of  the  plant  to 
another.     The  spiral  vessels  and  some  ducts  are  often 
found  filled  with  it;  and  in  these  positions,  according  to 
some   experimenters,    it   contains  rather  more  oxygen 


CHAP.   II.  FUNCTION    OF    NUTRITION.  189 

than  the  atmosphere.  At  present  so  little  has  been 
ascertained  of  the  conditions  under  which  this  air  has 
been  introduced  into  the  vessels,  or  of  the  peculiar  office 
which  it  is  destined  to  perform,  that  we  can  do  no  more 
than  just  mention  the  fact,  and  state  the  opinion  of 
some  botanists,  who  have  considered  it  probable  that  in 
these  situations  also  it  is  subservient  to  the  process  of 
respiration,  and  who  conclude  that  it  is  not  impossible 
there  may  exist  a  strong  analogy  between  the  manner 
in  which  this  function  is  performed  by  plants  and  by 
some  of  the  inferior  tribes  of  animals.  Insects  for 
example  breathe  by  introducing  air  through  several 
spiracles  ranged  along  each  side  of  their  abdomen, 
and  which  open  into  certain  ducts  or  pipes,  singularly 
resembling  in  their  general  appearance  the  tracheae  or 
spiral  vessels  of  plants. 

(1?5.)  Fixation  of  Carbon.  —  When  all  those  parts 
of  plants  which  are  capable  of  assuming  a  green  tint,  but 
more  especially  the  leaves,  receive  the  stimulus  of  light, 
they  immediately  decompose  the  carbonic  acid  contained 
in  the  sap.  The  result  of  this  action  is  the  retention  of 
the  carbon,  and  the  expiration  of  the  greater  part  of  the 
oxygen  into  the  surrounding  atmosphere.  The  most 
obvious  effect  produced  by  this  fixation  of  carbon  is  the 
appearance  of  that  green  colour  which  we  find  in  nearly 
all  leaves,  and  in  some  other  organs.  In  the  few 
cases  which  militate  against  this  rule,  we  may  reason- 
ably imagine  the  existence  of  some  other  cause  in 
operation  which  speedily  modifies  the  initial  result. 
Thus  for  instance,  the  peculiar  tinge  assumed  by  the 
leaves  of  the  red-beech,  may  possibly  be  owing  to  the 
presence  of  an  acid  secreted  simultaneously  with  the 
fixation  of  the  carbon,  which  converts  the  green  to 
red.  The  fixation  of  the  carbon  by  plants  appears 
to  be  the  first  step  in  that  elaborate  process  by  which 
brute  matter  is  converted  into  an  organisable  compound  ; 
that  is  to  say,  into  a  material  capable  of  being  afterwards 
assimilated  into  the  substance  of  an  organised  body. 


J90  PHYSIOLOGICAL    BOTANY.  PART  II. 

Many  effects,  popularly  ascribed  to  the  action  of  air,  are 
in  fact  due  to  the  agency  of  light.  Thus  trees  which 
grow  in  elevated  or  in  isolated  situations,  are  more 
vigorous  than  others  of  the  same  species  which  grow  in 
forests  or  in  shady  places;  and  those  on  the  skirts  of  a 
wood  are  finer  than  those  in  the  interior.  When  fields 
are  arranged  into  alternate  strips  of  fallow  and  crop, 
the  produce  is  much  greater  from  a  given  portion  of 
land  than  where  the  whole  field  is  regularly  sown,  and 
this  effect  must  be  attributed  to  the  increased  in- 
fluence of  light  in  such  cases.  The  loss  of  light  in 
stoves  and  green-houses,  by  diminishing  the  effects  of 
exhalation,  renders  plants  more  liable  to  be  frozen  than 
others  of  the  same  description  which  are  growing  in  the 
open  air. 

(176-)  Organisable  Products. — When  we  proceed  to 
inquire  in  what  form  the  carbon  appears  after  it  has  be- 
come fixed,  the  subject  assumes  a  degree  of  uncertainty, 
which  it  seems  almost  hopeless  to  get  rid  of  in  the  pre- 
sent state  of  our  knowledge.  Since  this  fixation  is  effected 
by  the  leaf  and  other  green  parts  of  the  plant,  it  is  con- 
sequently in  them  that  we  may  expect  to  find  the  organ- 
isable  product,  whatever  it  be,  which  is  the  primary 
and  immediate  result  df  this  action.  Now  unluckily 
for  our  inquiry,  there  are  so  many  different  compounds 
contained  in  solution  among  the  sap  and  various  juices 
of  plants,  —  such  as  gums,  sugars,  resins,  oils,  acids, 
alkaloids,  &c.,  all  of  which  are  composed  of  different 
modifications  of  the  same  three  elements,  carbon,  oxygen, 
and  hydrogen,  —  that  it  becomes  a  task  of  the  greatest 
delicacy  to  determine  which  of  them  ought  to  be  con- 
sidered as  the  immediate  result  of  the  process  of  fixation. 
If  we  may  presume  that  this  result  is  the  same  in  all 
plants,  or  so  nearly  the  same  that  we  may  designate  it 
(like  the  blood  of  animals)  by  some  name  which  em- 
braces all  the  subordinate  modifications,  we  must  ex- 
pect to  find  it  among  those  products  which  are  the 
most  generally  dispersed  in  vegetables,  and  which  are 


CHAP.   II.  FUNCTION    OF    NUTRITION.  IQ1 

also  known  to  be  eminently  beneficial  to  them.     These 
requisites  will  at  once  exclude  a  large  class  of  com- 
pounds, to  be  met  with  only  in  certain  families  of  plants, 
as  well  as  several  others  which  are  known  to  exercise 
noxious  effects  upon   vegetation.     And  thus  we  find, 
upon  careful  inquiry,  that  our  choice  is  restricted  to 
about  four  substances,  all  of  which  possess  nearly  the 
same  chemical  characters,  and  which  are  the  most  uni- 
versally present  among  the  juices  of  plants.     These  are 
gum,  sugar,  fecula,  and  lignine.     The  first  of  these  ap- 
pears by  far  the  most  universally  diffused,  and  has  been 
obtained  from  nearly  every  plant  in  which  it  has  been 
sought  for  ;  and  moreover  as  it  possesses  decidedly  nutri- 
tious qualities,  it  may  be  considered  with  every  proba- 
bility in  its  favour,  as  the  first  or  proximate  organisable 
compound  formed  by  the  action  of  vegetable  life,  acting 
under  the  stimulus  of  light.    The  other  three  substances, 
which  so  nearly  resemble  gum  in  chemical  composition, 
appear  to  be  slight  modifications  of  it,  which  have  re- 
sulted from  some  further  elaborations  perfected  by  the 
vesicles  in  different  parts  of  the  vegetable  structure,  and 
we  shall  defer  their  description  to  our  account  of  the 
sixth  period  of  nutrition. 

(177.)  Gum  exudes  naturally  from  certain  trees, 
and  especially  from  some  acacias,  which  furnish  the 
common  gum-arabic  of  commerce.  It  is  purer  when 
obtained  in  this  way  than  when  it  has  been  separated 
by  some  chemical  process  from  the  sap.  Its  specific 
gravity  varies  from  1-316  to  1-482.  It  is  extremely 
soluble  in  water,  but  is  insoluble  in  alcohol,  ether,  and 
and  oil.  It  possesses  slight  modifications  in  its  qua- 
lities, according  as  it  is  extracted  from  different  plants  ; 
and  the  following  analysis  will  show  its  composition,  as 
it  has  been  stated  by  three  eminent  chemists  :  — 


Thenard. 

Berzelius. 

Prout. 

Carbon    - 

-     42-23 

41-906 

41-4 

Oxygen 

-     50-84 

51-306 

52-1 

Hydrogen 

-       6-93 

6-288 

6-5 

1Q2  PHYSIOLOGICAL    BOTANY.  PART  II. 

For  the  present  then,  we  may  consider  this  substance 
as  most  probably  the  material  which  is  primarily  pre- 
pared for  the  nourishment  of  all  parts  of  the  vegetable 
structure,  and  which  is  afterwards  further  modified  by 
the  different  vesicles  and  glands  distributed  through  the 
system,  according  as  the  nature  of  different  parts  may 
require. 

(178.)  Etiolation.  —  When  any  part  of  a  plant  capa- 
ble of  decomposing  carbonic  acid  is  entirely  excluded 
from  the  light,  it  remains  white.  This  "etiolation," 
as  botanists  term  the  phenomenon,  consists  in  a  combin- 
ation of  an  excess  of  water  with  the  vegetable  matter 
previously  prepared  ;  so  that  the  quantity  of  carbon 
already  fixed  becomes  as  it  were  diluted,  and  diffused 
over  a  wider  space.  If  the  etiolated  parts  are  exposed 
to  the  light,  the  green  colour  makes  its  appearance  in 
less  than  eight-and-forty  hours,  and  the  plant  gradually 
assumes  a  natural  and  healthy  character.  The  parts 
which  have  once  become  green  are  incapable  of  being 
completely  etiolated  afterwards.  Among  the  various 
vegetable  matters  used  by  man  as  food,  those  which 
are  the  least  sapid  are  among  the  most  alimentary  ; 
whilst  the  more  highly  flavoured  are  generally  more  or 
less  deleterious,  and  some  of  them  extremely  poisonous. 
In  order  to  obtain  a  food  which  shall  be  both  whole- 
some and  grateful,  the  horticulturist  contrives  by  vary- 
ing his  mode  of  culture  to  moderate  the  proportion  in 
which  the  deleterious  ingredients  are  naturally  secreted, 
and  thus  renders  them  harmless.  The  most  common 
mode  of  producing  this  effect  is  by  removing  the  sti- 
mulus of  light  from  such  parts  as  are  intended  to  be 
eaten  ;  this  both  diminishes  the  activity  of  the  organs 
employed  in  secreting  the  deleterious  matters,  and  at  the 
same  time  causes  them  to  absorb  a  superabundant  supply 
of  moisture.  In  this  way  the  blanched  stems  of  celery, 
which  in  its  natural  state  is  a  poisonous  plant,  become  a 
grateful  food.  The  leaves  of  the  endive,  and  many 
others  which  would  be  far  too  bitter  or  tough  in  their 


CHAP.   II.  FUNCTION    OF    NUTRITION.  IQ3 

natural  state  to  be  eaten,  are  rendered  useful  and  agree- 
able additions  to  our  salads. 

(1 79-)  Action  of  Sun's  Rays. — Although  the  decom- 
position of  carbonic  acid  by  the  green  parts  of  plants, 
is  perpetually  carried  on  under  the  stimulus  of  diffused 
light,  and  its  effects  may  even  be  rendered  apparent  by 
the  action  of  lamp-light,  which  gives  a  slight  tinge  of 
green  to  plants  when  grown  in  a  cellar,  yet  in  these  cases 
the  process  is  carried  on  too  slowly  to  allow  of  our  col- 
lecting the  oxygen  which  is  set  free.  But  when  plants 
are  placed  in  the  direct  rays  of  the  sun,  the  action  is  so 
much  more  rapid,  that  the  oxygen  may  then  be  collected 
in  sufficient  quantity  to  produce  a  striking  result.  If  a 
plant  be  immersed  in  pump  water,  under  an  inverted 
glass  jar  placed  in  the  direct  light  of  the  sun,  in  a 
short  time  the  surface  of  its  leaves  becomes  covered  with 
minute  bubbles,  which  presently  collect  at  the  top  of 
the  jar,  and  are  found  to  be  nearly  pure  oxygen.  When 
boiled  or  distilled  water  is  used  from  which  all  the 
carbonic  acid  has  been  expelled,  no  such  effect  takes 
place.  But  if  another  jar  filled  with  carbonic  acid  be 
also  inverted  over  the  same  pan  in  which  the  jar  con- 
taining the  plant  is  placed,  and  the  surface  of  the 
water  in  the  pan  protected  by  a  coat  of  oil,  to  prevent 
the  escape  of  the  gas  as  it  is  gradually  imbibed  by 
the  water,  it  will  then  be  decomposed  as  before,  and  the 
oxygen  will  collect  in  the  upper  part  of  the  jar  which 
contains  the  plant,  whilst  an  equal  bulk  of  carbonic 
acid  will  disappear  from  the  other  jar.  It  does  not  ap- 
pear that  the  epidermis  is  essential  to  the  success  of 
this  experiment,  and  the  decomposition  of  the  carbonic 
acid  is  equally  effected  by  leaves  which  have  been  de- 
prived of  it. 

(180.)  Action  of  Oxygen. — A  certain  portion  of  free 
oxygen  is  necessary  for  the  formation  of  the  carbonic 
acid  generated  by  the  process  of  respiration  ;  but  when 
this  carbonic  acid  is  decomposed  and  the  carbon  fixed, 
the  same  oxygen  which  is  set  free,  will  serve  again 
for  a  fresh  formation  of  carbonic  acid  so  long  as  there 
o 


19*  PHYSIOLOGICAL    BOTANY.  PART  11. 

remains  any  carbonaceous  materials  in  the  sap.  This 
may  assist  us  in  explaining  an  interesting  fact  described 
in  the  "  Gardener's  Magazine,"  vol.  x.  p.  208.  It  is 
there  stated  that  many  plants,  especially  ferns,  have 
been  readily  grown  in  the  smoky  atmosphere  of  Lon- 
don, by  placing  them  in  boxes  furnished  with  glass 
coverings  hermetically  sealed.  In  this  state  they  have 
lived  and  increased  in  size  during  several  years,  without 
any  immediate  communication  with  the  atmosphere. 
The  same  mode  of  treatment  has  been  successfully 
practised  in  transporting  plants  during  a  long  voyage, 
the  influence  of  the  sea  breeze  charged  with  saline  par- 
ticles forming  the  greatest  obstacle  to  their  safe  con- 
veyance. When  performing  experiments  to  ascertain  the 
decomposition  of  carbonic  acid  by  the  process  of  respir- 
ation, great  precaution  is  necessary  to  ensure  accurate 
results.  The  plants  being  placed  under  conditions 
which  are  not  strictly  natural,  are  soon  apt  to  become 
sickly  and  exhibit  a  tendency  to  decompose.  When 
this  is  the  case  the  formation  of  hydrogen,  water,  and 
other  substances  takes  place,  and  vitiates  the  results. 
Those  who  are  anxious  to  pursue  these  researches  in 
further  detail  may  peruse  the  admirable  treatises  of 
De  Saussure  and  Ellis;  where  they  will  find  a  multitude 
of  experiments  recorded  and  a  patience  of  investigation 
exhibited,  which  has  been  rarely  surpassed  by  the  la- 
bours of  other  philosophers. 

(181.)  Vegetable  Colours. — Not  only  the  green  colour 
of  those  parts  which  decompose  carbonic  acid,  but  all 
the  various  colours  of  plants,  depend  upon  the  presence 
of  minute  grains  of  matter  contained  in  the  vesicles 
of  the  cellular  tissue.  The  grains  which  give  the 
green  tinge  to  the  leaf  are  termed  "  chromule,"  and 
it  is  probable  that  all  the  others  are  only  modifications 
of  the  same  substance.  From  observations  made  upon 
the  leaf  at  different  seasons  of  the  year,  it  appears  that 
towards  autumn  this  organ  ceases  to  give  out  oxygen  by 
day  though  it  continues  to  imbibe  it  by  night;  and 
hence  it  seems  highly  probable  that  the  chromule  passes 


CHAP.  II.  FUNCTION    OF    NUTRITION.  195 

into  different  states  of  oxidation,  each  of  which  possesses 
some  peculiar  tint,  as  in  the  case  of  the  various  oxides 
of  iron.  Although  carbon  is  the  principle  ingredient  in 
the  composition  of  chrpmule,  it  is  not  likely  as  some 
have  supposed  to  be  this  substance  in  a  perfectly  pure 
state.  Although  different  colours  in  plants  appear  to 
depend  upon  that  action  of  light  which  effects  the  de- 
composition of  carbonic  acid,  yet  we  find  that  many 
sea- weeds  are  intensely  coloured  when  they  grow  at  a 
depth  where  the  illuminating  power  of  the  sun's  rays  is 
some  hundreds  of  times  less  than  it  is  at  the  surface  of 
the  earth.  Humboldt  mentions  having  obtained  the 
Fucus  vitifolius  from  a  depth  of  190  feet,  where  the 
light  which  it  received  was  two  hundred  and  three 
times  less  than  that  of  a  common  candle  placed  at  the 
distance  of  one  foot  from  the  object  illuminated.  All 
white  flowers  are  only  different  tints  extremely  diluted 
—  a  fact  of  which  the  celebrated  flower  painter  Redoute 
availed  himself.  By  placing  the  flower  on  a  white 
sheet  of  paper  he  could  observe  the  exact  tint,  however 
delicate,  which  ought  to  form  the  ground  of  his  drawing. 
All  blacks  on  the  other  hand  are  only  intense  shades 
of  some  of  the  darker  colours,  or  of  grey. 

(182.)  Colours  of  Flowers.  —  Colour  is  (generally 
speaking)  of  very  little  importance  as  respects  the  de- 
termination of  species  among  flowering  plants ;  but  it 
often  furnishes  characters  of  considerable  value  for  the 
discrimination  of  many  among  the  cryptogamic  tribes. 
In  some  other  branches  of  natural  history  it  is  of  much 
greater  consequence;  and  we  shall  here  explain  a  method 
by  which  an  accurate  and  comprehensive  nomenclature 
may  be  established  for  defining  colours,  so  far  as  may  be 
required  in  the  description  of  objects  of  natural  history. 
The  scheme  is  little  more  than  a  modification  of  a  plan 
suggested  by  M.  Mirbel ;  and  consists  in  referring  all 
natural  colours  to  certain  absolute  tints  and  shades*, 
determined  according  to  fixed  rules. 

(183.)   Composition  of  Colours. — All  colours  may  be 

*  By  "  shade  "  we  here  mean  the  depth  or  intensity  of  a  tint. 
o  2 


196  PHYSIOLOGICAL    BOTANY.  PART  II. 

referred  to  different  degrees  of  mixture  between  three 
colours,  which  are  considered  as  "  primary."  These 
we  may  assume  to  be  red,  blue,  and  yellow.  A  mix- 
ture of  red  and  blue  makes  purple ;  of  red  and  yellow 
makes  orange  ;  of  blue  and  yellow  makes  green  ;  and 
innumerable  binary  compounds  may  be  formed  by  unit- 
ing the  primaries  two  and  two  in  different  proportions. 
Innumerable  shades  also  of  each  of  these  may  be  ob- 
tained, between  the  deepest  that  can  be  formed  and 
the  faintest,  by  diluting  each  colour  to  a  greater  or 
less  extent.  In  order  that  we  may  consider  every 
colour  to  be  formed  on  some  regular  principle,  we 
divide  a  circle  into  three  equal  parts  (fig.  154.  in. 
nermost),  and  place  the  Blue  (B),  Red  (R),  and  Yellow 
(Y),  in  each  of  them  re- 
spectively. Around  this 
circle  a  second  is  de- 
scribed, and  divided  into 
six  equal  compartments 
containing  respectively 
the  three  primaries,  and 
also  those  three  binaries 
which  are  exactly  inter, 
mediate  between  the"m ; 
viz.  the  Orange  (R  +  Y), 
the  Purple  (B  -f  R),  and 
the  Green  (B  +  Y)  ;  as- 
suming these  also  of  the  same  shade  as  before.  Another 
circle  containing  twelve  equal  compartments  is  described 
round  the  last,  and  in  these  are  placed  the  last  six 
colours,  together  with  six  new  ones  formed  by  uniting 
each  contiguous  pair  in  the  same  way  as  before.  An- 
other circle  would  contain  twenty-four  colours  and 
so  on  ;  each  fresh  addition  being  always  formed  from 
the  combination  of  two  contiguous  colours  in  a  former 
circle,  and  between  which  it  is  to  be  exactly  inter- 
mediate ;  and  the  whole  is  then  reduced  to  a  uniform 
shade.  By  proceeding  in  this  way  it  is  evident  that 
we  may  form  every  conceivable  binary  compound,  or 


CHAP.   II.  FUNCTION    OP    NUTRITION.  197 

"  pure  colour."  But  as  the  colours  in  contiguous  com- 
partments will  differ  less  and  less  from  each  other  as 
we  extend  our  circles,  it  will  not  be  necessary  that  we 
should  proceed  further  than  we  are  able  readily  to  ap- 
preciate their  difference.  Now  it  is  considered  that 
the  third  circle  of  twelve  colours  will  satisfy  the  re- 
quired purpose,  and  these  we  name  the  fundamental  or 
"  basial  "  colours  of  our  scheme.  Their  composition 
is  expressed  in  our  diagram  (fig.  154.),  and  the  usual 
names  employed  to  designate  them  would  be  — 

B.        Blue. 

2  B  +  R.  Bluish  Purple,  or  Purplish  Blue. 
B  +  R.     Purple. 
2  R  +  B.    Reddish  Purple,  or  Purplish  Red. 

R.        Red. 

2  R  +  Y.  Reddish  Orange,  or  Orange  Red. 
R  +  Y.     Orange. 
2  Y  +  R.  Yellowish  Orange,  or  Orange  Yellow. 

Y.        Yellow. 

2  Y  +  B.   Greenish  Yellow,  or  Yellowish  Green. 
Y  +  B.     Green. 
2  B  +  Y.   Bluish  Green. 

(184.)  Pure  Colours.  —  It  may  be  here  observed 
that  if  the  three  colours  purple,  orange,  and  green, 
or  any  other  three  taken  at  equal  intervals  round  a  cir- 
cle constructed  on  the  above  principle,  had  been  assumed 
as  our  three  primaries,  and  these  had  been  combined 
two  and  two,  we  should  have  obtained  all  the  pure 
colours  as  before,  and  among  them  the  three  former 
primaries  (blue,  red,  and  yellow)  under  the  character 
of  binary  compounds.  This  will  be  apparent  when  we 
recollect  that  the  union  of  three  primaries  in  equal  pro- 
portions forms  white  light  with  the  colours  of  the 
spectrum,  and  a  grey  or  neutral  tint  (N),  when  ma- 
terial colours  are  employed. 


Now,  Green  +  Orange=(B  + 

Orange  -t-Purple=(R+Y)  +  (B+-R)  =  (B  +  R  +  Y)  +  R=N+  R. 
Green+  Purple=i;B+  Y;  +  (B-t-  R}=  (B  +  R  +  Y)  +  B  =  N  +  B. 

o  3 


198  PHYSIOLOGICAL    BOTANY.  PART   II. 

In  these  three  mixtures  of  the  binaries,  we  have  respect- 
ively the  three  original  colours,  Y,  11,  B,  combined  with 
N.  And  thus,  if  N  be  white  light  a  restoration  of  the 
three  original  primaries  is  effected,  but  if  (N)  represent 
grey,  obtained  by  mixing  material  colours,  then  the 
three  primaries  will  appear  dull  or  "impure."  This  dull 
appearance  always  results  from  the  mixture  of  any  two 
material  colours,  however  brilliant  or  "pure"  they  may 
naturally  be.  These  remarks  are  perhaps  sufficient  to 
show  that  all  brilliant  or  "  pure  "  colours  may  be  con- 
sidered equally  as  primaries  or  binaries,  combined  with 
a  greater  or  less  proportion  of  white  light ;  whilst  all 
dull  or  "  impure "  colours  result  from  mixing  pure 
colours  with  grey.  In  order  to  obtain  any  truly  bril- 
liant tint  we  must  procure  our  colour  from  some  na- 
tural substance  and  not  form  it  by  admixture.  Such 
pure  colours  are  comparatively  rare  in  nature,  and  even 
those  which  approach  the  nearest  to  brilliancy  gene- 
rally contain  more  or  less  grey.  Although  it  is  par- 
ticularly difficult  to  obtain  either  of  the  three  colours 
which  we  have  adopted  as  our  primaries  perfectly  pure 
from  admixture  with  one  of  the  other  two,  we  may 
state  our  theory  and  then  we  must  practically  contrive 
to  make  as  close  an  approximation  to  such  a  scheme  as 
the  nature  of  the  case  will  admit. 

It  will  be  evident,  that  any  pure  colour  in  nature, 
when  reduced  to  the  same  shade  as  those  in  our  scale 
{fig.  154.),  will  either  exactly  coincide  with  one  of  the 
twelve  basial  colours  or  lie  between  two  which  are 
contiguous.  Thus  a  colour  whose  composition  is  5  B 
-f  3  Y,  lies  between  (B  +  Y)  and  (2  B  +  Y),  and  its 
exact  position  may  be  ascertained,  by  forming  fresh 
combinations  between  these  two  colours  and  their  re- 
sultants as  before  described.  Thus, 

Since  (2  B  +  Y)  and  (B  +  Y)  are  contiguous  in  the  third  circle, 

So  will  (2  B  +  Y)  —  (3  B  +  2  Y)  —  (B  +  Y)  be  in  the  fourth, 

And  (2  B  +  Y)  —  (5  B  -I-  3  Y)  —  (3  B  +  2  Y)  —  (4  B  +  3  Y)  —  (B  -4-  Y)  in 

the  tilth,  &c. 


CHAP.   II.  FUNCTION    OF    NUTRITION.  199 

This  colour  therefore  is  one  of  forty-eight  pure  co- 
lours which  would  compose  a  fifth  circle  constructed 
on  the  plan  alluded  to.  We  may  remark  that  any 
two  colours  arranged  in  opposite  compartments  added 
together  make  white  or  grey,  and  are  hence  styled 
complementary  colours.  Thus  (2B  +  Y)  is  exactly 
opposite  to  (2  R  +  Y),  and  these  added  together 
make  up  (2  B  +  2  R  +  2  Y)  or  2  N ;  and  so  of  any 
others. 

(185.)  Impure  Colours.  —  From  what  we  have  said 
it  appears,  that  every  tertiary  or  other  compound  among 
material  colours,  that  is  to  say  every  dull  or  "  impure" 
colour,  must  be  some  pure  colour  mixed  with  a  greater 
or  less  proportion  of  grey.  Thus,  a  colour  com- 
posed of  (9  B  +  7  Y  +  4  R)  is  the  same  as  (4  B  +  4 
1T-M  R)  4  (5  B  +  3  Y),  which  is  the  same  as  (4  N) 
•-f-  (5  B  -f-  3  Y),  or  a  combination  of  grey  (4  N)  with 
the  pure  colour  represented  by  (5  B  +  3  Y)  which  is 
one  of  the  bluish  greens.  Many  ternary  compounds  have 
obtained  specific  names;  thus  the  different  "  browns" 
result  from  various  proportions  of  grey  mixed  with  some 
pure  colour  of  which  red  is  a  constituent  part ;  and  the 
"  Olives"  are  some  of  the  greens  similarly  rendered 
impure. 

In  order  to  conceive  how  every  possible  impure  colour 
may  be  formed  by  combining  the  pure  colours  with 
grey,  we  may  take  the  deepest  shades  of  all  the  former 
and  having  placed  them  in  the  compartments  of  a  circle 
divided  as  before,  combine  them  with  all  the  shades 
of  grey  beginning  with  the  palest  in  the  centre  and 
proceeding  to  the  darkest  in  the  circumference ;  and 
then  in  another  circle  concentric  with  the  former,  com- 
bine every  shade  of  all  the  brilliant  colours  with  the 
deepest  shade  of  grey.  This  double  arrangement  gives 
us  every  possible  mixture  between  the  basial  colours  and 
grey;  that  is  to  say  every  possible  ternary  compound  or 
impure  colour.  Thus  in  the  annexed  figure  (155.),  if  the 
deepest  shade  of  blue  extends  from  (a)  to  (6),  and  the 


200  PHYSIOLOGICAL    BOTANY.  PART  II. 

deepest  shade  of  grey  from  (6)  to  (c),  then  all  the  shades 
shades  of  grey  may  be 
added,   increasing   in 
their    intensity    from 
(n)    to    (6),   and   all 
those  of  blue  from  (6) 
to    (c),   and   the  re-' 
quired  results  will  be 

obtained  for  this  single  basial  colour.     The  impure  co- 
lours thus  formed  will  also  be  of  their  deepest  shades. 

As  we  have  assumed  twelve  pure  colours  out  of  the 
innumerable  sets  which  might  be  formed  so  we  may 
assume  two  impure  colours  corresponding  to  each  of 
our  basial  colours,  as  sufficient  for  representing  the 
tertiary  compounds.  Those  may  be  selected  which  lie 
exactly  intermediate  between  («)  and  (f>),  and  (6)  and 
(c)  (fig.  155.).  The  former  will  evidently  contain  a 
double  proportion  of  a  pure  colour  mixed  with  one  of 
grey ;  and  the  latter  a  double  proportion  of  grey 
mixed  with  one  of  pure  colour.  Thus  we  shall  have 
one  set  of  "impure"  and  another  of  "very  impure" 
colours. 

(186.)  Chromatometer. —  It  will  be  seen  that  we 
have  considered  the  construction  of  twelve  "  pure" 
colours,  twelve  "impure"  colours,  and  twelve  "very  im- 
pure" colours  to  be  sufficient  for  our  scheme.  But  we 
may  further  adopt  three  separate  shades  of  each  of 
these  thirty-six  colours,  to  which  we  may  also  refer  the 
shades  of  all  natural  colours ;  and  this  gives  us  108 
different  shades.  If  to  these  we  add  three  correspond- 
ing shades  of  grey  we  shall  have  in  all  111  to  complete 


he  scheme.     These   may  be  arranged    in   a  diagram 
termed  a  "Chromatometer,"  which  will  serve  for  purposes 


'CHAP.   II.  FUNCTION    OF    NUTRITION.  201 

of  immediate  reference  whenever  we  wish  to  describe 
any  colour.  The  annexed  figure  (156.)  may  be  taken  as 
a  representation  of  one  of  its  sectors,  containing  the  three 
shades  of  grey  (a  6),  and  those  of  the  "  very  impure" 
(b  c),  "  impure"  (c  d),  and  "  pure"  (d  e)  blues.  If 
the  other  eleven  basial  colours  were  similarly  disposed 
round  the  same  centre  the  chromatometer  would  be 
complete. 

It  seems  unnecessary  to  include  in  this  scale  the 
different  tinges  commonly  ascribed  to  white,  black,  and 
grey ;  as  these  after  all  are  only  very  faint  or  dark 
shades  of  some  defined  colour,  and  may  be  recognised 
by  comparison  with  the  nearest  shades  expressed  in  the 
chromatometer. 

(187.)  Limitation  of  Colour.  —  It  has  often  been 
observed  by  horticulturists,  that  among  different  va- 
rieties of  the  same  species  a  limited  number  of  colours 
is  found,  among  which  are  not  more  than  two  out  of 
three  of  the  basial  colours  similarly  disposed  upon  the 
chromatometer.  Thus  there  are  blue  and  red  hyacinths, 
but  none  that  are  pure  yellow;  there  are  yellow  and 
red  dahlias,  but  none  that  are  blue.  The  rule  is  not 
free  from  exceptions,  still  less  does  it  apply  to  those 
flowers  which  have  different  bands  of  colour  on  their 
corolla.  It  has  been  conjectured  that  those  colours 
which  pass  from  green  through  yellow  to  red  arise  from 
combinations  of  oxygen  with  the  chromule  in  its 
green  or  neutral  state ;  whilst  those  which  pass  from 
green  through  blue  to  red  contain  a  less  proportion  of 
oxygen  than  the  green  chromule  itself.  But  as  these 
two  series  meet  in  the  same  colours  at  both  ends  of 
such  a  scale  it  is  not  easy  to  understand  how  this  can 
be  the  case,  since  the  red  would  equally  result  from  a 
union  of  the  chromule  with  a  maximum  and  with  a 
minimum  of  oxygen. 

(188.)  Results  of  Vegetable  Respiration.  —  From 
what  has  been  said  it  seems  necessary  to  conclude 
that  carbon,  in  order  to  be  fixed  in  vegetation  must  be 
presented  to  a  plant  in  the  form  of  carbonic  acid ;  and 


202  PHYSIOLOGICAL    BOTANY.  PART  II. 

that  the  decomposition  of  this  gas  by  the  direct  Gyr- 
ation of  the  vital  principle  furnishes  the  first  step  to- 
wards the  organisation  of  brute  matter. 

The  ultimate  effects  of  vegetable  respiration  being  the 
reverse  of  those  which  result  from  the  analogous  func, 
tion  in  animals,  have  been  often  regarded  as  a  remark- 
able provision  against  the  gradual  deterioration  of  our 
atmosphere.  But  the  effects  produced  by  the  respiration 
of  animals,  by  combustion,  and  by  various  other  processes 
by  which  carbonic  acid  is  added  to  the  atmosphere,  are 
of  too  trifling  a  description  to  enable  us  to  appreciate 
their  consequences  under  the  lapse  of  many  ages.  The 
continued  spontaneous  decomposition  of  a  large  portion 
of  dead  vegetable  matter,  is  also  perpetually  counter- 
acting some  portion  of  the  beneficial  effects  which  the 
fixation  of  carbon  by  plants  might  produce.  Still  it 
is  evident  that  every  particle  of  carbon  in  living  vege- 
tables, and  likewise  all  that  exists  in  those  fossil  bodies, 
coal,  jet,  &c.  which  are  the  altered  remains  of  primaeval 
vegetation,  must  have  resulted  from  the  decomposition  of 
carbonic  acid  whose  oxygen  has  been  set  free  during 
the  process  of  vegetable  respiration.  To  this  we  may 
also  add  whatever  carbon  is  found  in  animals,  since 
this  has  been  derived  from  their  food  primarily  ob- 
tained from  the  vegetable  kingdom.  We  should  possess 
something  like  a  measure  of  the  extent  to  which  vege- 
tation has  been  active  in  altering  the  state  of  our  atmo- 
sphere, if  we  could  obtain  an  estimate  of  how  much 
oxygen  would  be  required  to  convert  into  carbonic  acid 
all  the  carbon  now  fixed  in  organised  beings,  recent  and 
fossil ;  and  hence  we  might  ascertain  whether  the  at- 
mosphere thus  modified  would  still  be  fitted  for  our 
respiration  or  not.  But  in  other  respects  there  can  be 
no  doubt  of  the  important  results  to  which  the  respiration 
of  vegetables  gives  rise.  It  is  this  process  which  pre- 
pares the  organisable  materials  from  whose  subsequent 
elaboration  are  derived  those  infinitely  varied  conditions 
of  organised  matter  which  are  essential  to  the  develop- 
ment of  the  numerous  tribes  of  plants  which  gladden 


CHAP.  II.  FUNCTION    OF    NUTRITION.  203 

the  fair  face  of  nature,  and  serve  to  nourish  the 
myriads  of  animated  beings  which  people  the  earth, 
the  ocean,  and  the  atmosphere.  And  lastly  and  most 
incomprehensibly,  from  these  same  materials  are  con- 
structed those  organised  substances  which  seem  to 
stand  as  portals  to  the  intellectual  and  spiritual  world 
—  channels  of  direct  communication  by  which  reason 
and  revelation  may  tell  the  frail  tenants  of  a  few  mould- 
ering atoms,  of  that  more  glorious  condition  which  will 
as  certainly  be  their  heritage  hereafter  as  their  hopes 
and  yearnings  after  immortality  are  within  the  actual 
experience  of  their  present  state. 


CHAP.  III. 

FUNCTION    OF    NUTRITION    CONTINUED  Periods    5,    6. 

DIFFUSION    OF    PROPER    JUICE     (189.).  INTERCELLULAR    ROTA- 
TION    (193.).  LOCAL     CIRCULATIONS     (195.).  VEGETABLE 

SECRETIONS     (196.).  FECULA,      SUGAR,     LIGNINE    (197.).  

PROPER  JUICES  (202.)  TASTE  AND  SCENT  (210.).  EX- 
CRETIONS (212.).  ROTATIONS  OF  CROPS  (218.).  EX- 
TRANEOUS DEPOSITS  (219.). 

FIFTH    PERIOD    OF    NUTRITION. 

(189-)  Diffusion  of  proper  Juice. —  THE  crude  sap  hav- 
ing been  subjected  to  the  action  of  the  atmosphere  and 
the  carbonic  acid  decomposed,  the  result  is  termed  the 
"  proper  juice"  or  elaborated  sap  of  the  plant.  This 
liquid  has  now  to  find  its  way  back  again  into  the 
system  for  the  purpose  of  nourishing  and  develop- 
ing the  various  parts.  There  are  three  distinct  kinds 
of  movement  to  which  the  proper  juices  of  plants 


204  PHYSIOLOGICAL    BOTANY.  PART  II. 

are  subjected.  The  first  of  these  is  its  descent  and 
transfusion ;  the  second  is  a  very  singular  rotation 
of  the  juices  contained  in  the  vesicles  and  short  tubes 
of  some  plants ;  and  the  third  is  a  sort  of  actual 
though  local  circulation  more  nearly  resembling  the 
circulation  of  blood  in  animals.  We  propose  to  describe 
each  of  these  under  the  present  period,  though  certainly 
they  can  hardly  be  all  considered  as  subordinate  pro- 
cesses of  the  same  function. 

(190.)  Descent  of  Sap. —  When  a  ring  of  bark  is  re- 
moved from  a  stem  or  branch  of  a  dicotyledonous  plant 
a  tumour  is  formed  at  the  upper  edge  of  the  ring,  which 
indicates  a  stoppage  to  have  taken  place  in  the  descent 
of  the  elaborated  sap.  This  stoppage  by  causing  an 
excess  of  nutriment  to  accumulate  above  the  ring,  oper- 
ates in  improving  the  size  and  quality  of  fruits,  and 
will  even  occasion  a  tree  to  flower  and  produce  fruit 
when  it  would  otherwise  have  developed  nothing  but 
leaves.  No  increase  or  at  most  a  very  slight  one  takes 
place  in  the  diameter  of  the  trunk  below  the  ring;  but  the 
part  above  it  is  more  developed  than  it  otherwise  would 
have  been.  If  a  potato  be  ringed  in  this  way  the  buds 
in  the  axillte  of  its  leaves  are  developed  in  the  form 
of  little  tubers,  whilst  none  are  produced  on  the  under- 
ground stems  or  rhizomata.  Similar  effects  are  produced 
by  a  tight  ligature;  and  most  persons  have  observed  the 
appearance  which  a  woodbine  causes  on  the  branches  of 
trees  by  twining  round  them.  A  spiral  protuberance 
is  formed  immediately  above  and  below  the  stricture, 
but  more  especially  above  it,  and  in  process  of  time 
these  swellings  often  become  so  large  as  to  meet  com- 
pletely over  the  woodbine  and  embed  it  in  the  sub- 
stance of  the  tree.  The  parts  which  lie  above  a  ring 
or  ligature  become  specifically  heavier  than  those  which 
are  below  it  as  Mr.  Knight  found  in  the  oak,  the 
wood  above  having  a  specific  gravity  of  1'14,  and  that 
below  only  I'll.  All  these  facts  seem  to  indicate 
that  the  chief  passage  of  the  descending  sap  is  down 
the  bark,  and  towards  the  surface  of  the  stem.  It  was 


CHAP.  III. 


FUNCTION    OF    NUTRITION'. 


205 


supposed  by  some  persons  that  an  important  advantage 
might  be  taken  of  this  circumstance ;  and  that  by 
stripping  a  tree  of  its  bark  some  time  before  it  was 
felled,  the  sap  would  be  forced  to  descend  along  the 
newly  formed  wood  and  thus  ripen  or  harden  it  more 
speedily  than  would  have  been  the  case  in  the  natural 
course  of  things.  But  experience  has  shown  that  such 
timber  is  very  brittle  and  unfit  for  the  purposes  of 
building. 

(191.)  Progression  of  the  Sap. —  Although  the  proper 
juice  appears  to  descend  more  especially  by  the  bark 
and  those  portions  of  the  tree  which  are  towards  the 
surface,  and  which  are  in  fact  the  parts  where  the 
vitality  of  the  trunk  resides,  there  still  appears  to  be 
a  very  general  diffusion  of  the  nutritious  juice  con- 
tinually taking  place  throughout  all  parts  of  the  tree, 
sometimes  in  one  direction  and  sometimes  in  another. 
This  may  be  shown  by  a 
contrivance  of  M.  Biot  (fig. 
157.)-  A  wooden  wedge  boiled 
in  wax  and  oil  to  render  it 
impervious  to  moisture,  has  a 
groove  cut  in  the  upper  part, 
and  is  then  driven  into  a  ca- 
vity which  it  exactly  fits  in  the 
trunk  of  a  tree ;  a  space  is 
hollowed  out  both  above  and 
below  this  wedge  ;  the  roof  of 
the  cavity  above  it  shelves 
towards  the  middle,  so  that 
the  descending  sap  collects  there  and  drops  into  the 
open  extremity  of  a  pipe  placed  in  the  groove  to  re- 
ceive it.  The  ascending  sap  rises  into  the  lower  cavity 
which  is  also  cut  into  a  groove,  and  it  is  there  re- 
ceived into  another  pipe  placed  in  the  bottom.  In 
this  manner  a  flow  of  sap  is  obtained  either  simul- 
taneously from  both  pipes,  or  at  separate  times  and  in 
different  proportions  according  to  the'  state  of  the  at- 
mosphere, season  of  the  year,  and  other  circumstances 


206 


PHYSIOLOGICAL    BOTANY. 


which  influence  the  flow.  It  is  observed  that  the  de- 
scending current  is  generally  denser  and  more  saccharine 
than  the  ascending,  although  the  reverse  is  occasionally 
the  case  after  violent  rains.  Light  appears  to  be  the 
principal  agent  in  modifying  the  conditions  of  the  flow. 
Mild  weather  promotes  the  ascent,  and  a  sudden  cold 
succeeding  causes  a  rapid  descent  by  contracting  the 
trunk  of  the  tree.  If  the  cold  continue  and  the  ground 
become  frozen,  the  sap  is  again  forced  to  ascend.  When 
a  thaw  succeeds  a  frost  the  exhausted  roots  are  to  be 
replenished,  and  the  downward  current  is  re-established. 
The  rapid  ascent  which  commences  in  spring  when  the 
buds  are  beginning  to  burst,  ceases  as  soon  as  the  leaves 
are  completely  expanded.  After  midsummer  the  power 
of  the  solar  rays  being  less  energetic,  and  the  deposition 
of  earthy  particles  having  obstructed  the  vessels  of  the 
leaf  less  sap  is  exhaled  from  them  and  the  tree  attains 
a  state  of  plethory,  indicated  by  an  increasing  flow  at 
the  upper  tube  of  the  instrument. 

(192.)  Cause«  of  Progression.  —  Although  these  ex- 
periments of  M.  Biot  clearly  indicate  that  there  is  an 
influence  produced  by  a  change  of  temperature  and 
probably  also  by  other  atmospheric  causes  on  the  pro- 
gression of  the  sap,  it  is 'neither  to  these  nor  yet  to  the 
effects  of  gravity  that  we  must  entirely  attribute  the 
descent  and  general  diffusion  of  the  nutritious  jukes. 
We  find  that  if  a  branch  is  ringed  and  its  extremity 
bent  towards  the  ground,  the  tumour  now  is  produced 
upon  that  edge  which  is  the  lowest  in  position  though 
furthest  from  the  root,  and  consequently  the  return- 
ing sap  has  been  compelled  to  rise  into  the  pendent 
branch.  Its  progression  is  decidedly  facilitated  by 
mechanical  causes,  such  as  the  wind  continually  agitat- 
ing the  stem  and  branches.  Mr.  Knight  confined  the 
stem  of  a  tree  so  that  it  could  vibrate  only  in  one 
plane  ;  and  at  the  end  of  some  years  lie  observed  that 
its  section  was  an  ellipse,  whose  greater  axis  lay  in  this 
plane. 

(193.)    Intercellular     Rotation. —  In     the    ascent, 


CHAP.  III.  FUNCTION    OF    NUTRITION.  20? 

descent  and  general  transfusion  of  the  sap,  we  can 
trace  the  operation  of  physical  causes  modifying  and 
controlling  to  a  considerable  extent,  if  indeed  they  do 
not  originate  and  entirely  regulate  these  movements. 
We  have  now  to  describe  a  more  remarkable  movement  of 
the  juices  of  some  plants,  which  more  decidedly  evinces 
a  vital  action.  This  movement  consists  in  a  constant 
rotation  of  the  fluid  contained  in  their  vesicles  and  tubes, 
and  rendered  apparent  by  the  presence  of  minute  glo- 
bules of  vegetable  matter  floating  in  it.  The  original 
disovery  of  this  phenomenon  was  made  about  a  century 
ago  by  Corti,  who  first  observed  it  in  the  Cauliniafra- 
gilis,  a  maritime  plant  found  on  the  shores  of  Italy. 
His  observations  appear  to  have  been  generally  neg- 
lected until  lately,  when  the  re-discovery  of  the  pheno- 
menon in  other  plants  has  excited  the  attention  of 
botanists.  It  may  readily  be  seen  with  a  good  lens 
in  Valisneria,  Hydrocharis,  Potamogeton,  and  other 
aquatic  genera,  but  more  especially  in  the  genus  Chara. 
It  has  also  been  observed  in  the  terrestrial  genera  Cu- 
curbita,  Cucumis,  Pistia,  and  others ;  and  is  more  es- 
pecially observable  in  the  hairs  of  many  species.  It 
appears  to  be  a  universal  property  of  the  cellular 
tissue  though  it  is  impossible  in  many  cases  to  de- 
tect it,  either  on  account  of  the  want  of  sufficient 
transparency  in  the  membrane  or  from  the  absence  of 
the  granular  matter  by  whose  presence  alone  the  ro- 
tation of  the  fluid  itself  can  be  observed.  We  shall 
explain  the  phenomenon  as  it  may  be  seen  in  the 
Chara  with  a  lens  of  about  the  tenth  of  an  inch  focal 
distance  or  even  of  less  power. 

(194.)  Rotation  of  Fluid  in  Chara.  —  This  genus 
may  be  divided  into  two  sections,  which  are  considered 
as  distinct  genera  by  Agardh.  In  one  of  them,  the 
true  Chara,  the  stems  are  composed  of  a  central  tube 
jointed  at  intervals  and  surrounded  by  a  row  of  smaller 
tubes.  In  the  other  section,  or  genus  Nitella,  the 
stems  consist  of  single  tubes  jointed  as  before.  If  we 
select  a  species  of  the  first  section  it  will  be  necessary 


208  PHYSIOLOGICAL    BOTANY.  PART  II. 

to  clear  away  the  outer  tubes  which  are  always  more 
or  less  encrusted  with  carbonate  of  lime,  in  order  to 
expose  the  inner  tube  in  which  the  rotation  of  the 
fluid  may  be  seen.  This  is  an  operation  requiring  some 
little  delicacy  ;  and  the  choice  of  a 
species  of  the  other  section  (Nitella)  is  £ 
to  be  preferred,  in  which  the  tubes  are 
generally  very  transparent  and  require 
no  preliminary  preparation  to  clean  their 
surface.  At  the  joints  of  the  stem  are 
whorls  of  branches  (fig.  158.)  com- 
posed also  of  short  tubes,  in  each  of 
which  the  same  rotation  of  the  con- 
tained fluid  may  be  seen.  If  an  entire 
tube  occupying  the  space  between  two 
joints  be  detached  and  placed  under  the  microscope, 
its  inner  surface  appears  to  be  studded  with  minute 
green  granules  arranged  in  lines,  which  do  not  run 
parallel  to  the  axis  of  the  tube  but  wind  in  a  spiral 
direction  from  one  extremity  to  the  other.  They  are 
studded  over  the  whole  of  the  interior,  with  the  exception 
of  two  narrow  spaces  on  opposite  sides  of  the  tube  form- 
ing two  spiral  lines  from  end  to  end.  The  globules  of 
transparent  gelatinous  matter  dispersed  through  the  fluid 
are  in  constant  motion,  being  directed  by  a  current  up 
one  side  of  the  tube  and  back  again  by  the  other.  The 
course  of  this  current  is  regulated  by  the  spiral  arrange- 
ment of  the  granules,  and  it  moves  in  opposite  directions 
on  contrary  sides  of  the  clear  spaces  on  the  inner  surface  of 
the  tube.  The  rotation  continues  in  a  detached  portion, 
for  several  days ;  and  if  the  tube  is  tied  at  intervals 
between  the  joints  the  fluid  between  two  ligatures  still 
continues  to  circulate,  even  though  the  extremities  of  the 
tube  should  be  cut  away.  The  motion  here  described 
is  precisely  similar  to  what  takes  place  in  the  tubes  of 
Corallines,  and  must  unquestionably  be  considered  as 
the  result  of  a  vital  action. 

(195.)   Local    Circulation*.  —  It   was  in    the    year 
1820,  that    a    distinguished    naturalist,    M.  Schultes, 


CHAP.  III.  FUNCTION    OP    NUTRITION.  209 

first  announced  his  discovery  of  a  peculiar  movement 
in  the  juices  of  plants,  which  more  nearly  resembles 
the  circulation  of  the  blood  in  animals  than  any  thing 
which  had  formerly  been  observed.  The  existence 
of  such  a  circulation  had  been  strongly  suspected  be- 
fore ;  but  as  the  experiments  upon  which  his  actual 
detection  of  the  phenomenon  depended  were  difficult  to 
verify,  his  account  was  much  disputed  until  recently 
when  he  obtained  the  prize  which  the  Academy  of 
Sciences  at  Paris  had  proposed  for  the  purpose  of  elicit- 
ing further  investigations  on  the  subject.  His  memoir 
has  not,  hitherto  we  believe  made  its  appearance  ;  but 
the  committee  appointed  to  examine  its  merits  have 
made  a  favourable  report  of  its  contents  published 
in  the  "Archives  de  Botanique"  for  1833;  and  from 
this  and  a  former  paper  in  the  "Annales  des  Sciences," 
we  have  gleaned  *the  following  particulars  :  —  The 
liquid,  whose  movement  is  described  and  which  M. 
Schultes  terms  the  "  latex,"  is  sometimes  transparent 
and  colourless  but  in  many  cases  opaque,  and  either 
milk-white,  yellow,  red,  orange,  or  brown.  The 
colours  depend  upon  the  presence  of  innumerable  mi- 
nute globules  which  are  constantly  agitated  as  if  by 
a  spontaneous  motion,  and  appear  to  be  alternately 
attracted  and  repelled  by  each  other.  This  liquid 
is  considered  to  be  the  proper  juice  of  the  plant 
secreted  from  the  crude  sap  in  the  intercellular  pas- 
sages and  consequently  analogous  to  the  blood  of  ani- 
mals as  was  long  since  suggested  by  Grew,  who 
further  likened  the  lymphatic  or  crude  sap  to  their 
chyle.  It  is  contained  in  delicate  transparent  mem- 
branous tubes,  which  become  cylindrical  when  iso- 
lated, but  when  packed  together  in  bundles  assume  a 
polygonal  shape.  In  young  shoots  it  is  difficult  to  de- 
tect them,  on  account  of  their  extreme  transparency  and 
tenuity  ;  but  they  may  be  extracted  with  considerable 
facility  from  older  parts.  They  have  been  observed  very 
generally  in  Monocotyledons  and  in  Dicotyledons,  ex- 


210  PHYSIOLOGICAL    BOTANY.  PART   II. 

cepting  in  the  few  species  in  which  no  tracheae  have  been 
hitherto  noticed.  They  frequently  intercommunicate  or 
anastomose  by  means  of  lateral  branches,  and  sometimes 
form  a  regular  network  (see  art.  27-  fig,  15.).  They 
occur  in  the  woody  fibre,  in  the  bark,  occasionally 
even  in  the  pith,  and  very  frequently  surround  the 
tracheae.  They  exist  in  greatest  complexity  in  the 
root,  from  whence  they  proceed  in  parallel  lines  up 
the  stem  into  the  leaves  and  flowers  and  then  return 
again  to  the  root,  the  ascending  and  descending  branches 
anastomosing  throughout  their  course.  The  movement 
of  the  latex  can  be  witnessed  only  in  those  parts  which 
happen  to  be  very  transparent ;  and  it  has  not  been 
actually  seen  in  many  plants.  The  fr'it-ux  i-/mttica, 
Che/iduninui  innjiix,  and  Al'minn  pluntiitjn,  are  the 
species  upon  which  most  of  the  observations  hitherto 
recorded  have  been  made.  Distir&t  currents  are  ob- 
served traversing  the  vital  vessels,  and  passing  through  the 
lateral  connecting  tubes  or  branches  into  the  principal 
channels.  These  currents  follow  no  one  determinate 
course,  but  are  very  inconstant  in  their  direction  —  some 
proceeding  up  and  others  down,  some  to  the  right 
and  others  to  the  left ;  the  motion  occasionally  stop- 
ping suddenly,  and  theji  recommencing.  In  detached 
fragments  of  the  plant  it  will  continue  from  five  minutes 
to  half  an  hour,  according  to  circumstances  ;  but  M. 
Schultes  has  been  able  so  to  adjust  his  lens  as  to  witness 
the  flow  in  the  growing  plant.  The  action  is  sud- 
denly checked  by  cold,  and  again  recommences  with 
an  elevation  of  temperature.  The  effect  does  not  seem 
to  depend  upon  a  contractile  power  of  the  tubes,  be- 
cause the  latex  flows  chiefly  or  entirely  from  one  end 
of  a  tube  even  when  it  has  an  orifice  open  at  both 
extremities.  The  appearance  is  very  similar  to  the 
circulation  of  the  blood  in  the  foetus  contained  in  a 
bird's  egg  before  the  heart  is  formed ;  but  is  more  es- 
pecially analogous  to  the  circulation  of  some  of  the 
lowest  tribes  of  animals,  as  in  the  Diplozoon  paradoxum, 
which  may  be  divided  into  two  parts  and  the  blood 


CHAP.  III.  FUNCTION    OF    NUTRITION.  211 

still  continue  to  circulate  for  three  or  four  hours  in  each. 
By  a  strong  electric  shock,  the  force  by  which  the  latex 
is  propelled  is  paralysed,  and  its  motion  arrested. 


SIXTH    PERIOD    OF    NUTRITION. 

(196.)  Vegetable  Secretions.  —  In  describing  the  pro 
cess  by  which  we  have  supposed  the  first  step  to  be 
made  towards  the  organisation  of  those  materials  which 
enter  into  the  vegetable  structure,  we  have  considered 
gum  to  be  the  immediate  result  of  the  fixation  of  car- 
bon in  combination  with  the  two  elements  of  water  ; 
and  that  this  substance  is  formed  by  all  those  parts  of 
plants  which  almost  universally  acquire  a  green  tinge. 
We  further  stated  that  there  were  three  other  sub- 
stances nearly  allied  to  gum  in  chemical  composition, 
which  might  also  be  considered  as  destined  for  the 
nourishment  of  the  plant.  It  is  probable  that  these 
substances  are  only  slight  modifications  of  gum,  produced 
by  its  subsequent  elaboration  in  the  cellular  tissue.  It 
is  impossible,  however,  to  point  out  the  specific  organs 
which  are  appropriated  to  this  office.  In  some  cases 
a  distinct  glandular  structure  is  very  apparent,  and 
the  immediate  secretions  effected  by  it  are  collected  in 
an  isolated  form  ;  but  in  others  there  is  no  apparent 
difference  between  the  organisation  of  those  parts  in 
which  the  secretions  are  produced  and  the  rest  of  the 
cellular  tissue. 

(197-)  Fecula. —  The  first  of  the  three  alimentary 
products  which  we  shall  further  notice  is  fecula.  This 
substance  forms  minute  spheroidal  grains  in  the  cellu- 
lar tissue,  and  must  be  considered  rather  as  a  dis- 
tinctly organised  product  than  as  a  secreted  matter. 
Each  grain  consists  of  an  insoluble  pellicle  or  integu- 
ment, containing  a  soluble  substance  which  seems  to 
be  pure  gum,  or  some  material  scarcely  differing  from 
it  in  any  essential  character.  These  grains  are  not 
p  2 


212  PHYSIOLOGICAL    BOTANY.  PART  II. 

altered  by  the  action  of  alcohol,  ether,  or  cold  water ; 
but  in  hot  water  the  pellicle  bursts,  the  contained 
matter  exudes,  and  the  whole  mass  becomes  a  paste. 
The  specific  gravity  of  fecula  is  about  1'53.  It 
may  be  obtained  from  the  pulp  of  fruits,  tubers,  succu- 
lent stems,  and  other  parts  of  various  plants.  That 
which  is  derived  from  corn  and  the  potato  is  fami- 
liarly termed  starch.  Sago  (from  the  stems  of  a  palm), 
tapioca  (from  the  tubers  of  the  Jatropha  manihot), 
arrow-root  (from  the  rhizomata  of  the  Maranta  arun- 
dinacea),  are  all  so  many  varieties  of  fecula.  This 
substance  is  highly  alimentary  and  is  largely  stored 
up  in  various  parts  of  vegetables  where  it  forms 
magazines  of  nutriment,  apparently  destined  for  the 
future  development  of  the  buds  and  ripening  of  the 
seed.  It  is  a  material  of  all  others  the  most  im- 
portant as  an  article  of  human  food,  and  is  providen- 
tially provided  for  our  use  in  the  greatest  abundance. 
It  bears  a  striking  analogy  to  the  fat  of  animals,  even 
in  the  general  structure  of  its  component  parts  accord- 
ing to  some,  but  more  evidently  in  the  uses  to  which 
it  is  subservient  in  the  economy  of  vegetation.  The 
formation  and  subsequent  re-absorption  of  fecula  is 
rendered  very  evident,  by  comparing  the  different  quan- 
tities found  in  plants  of  the  same  species  at  different 
seasons  of  the  year.  The  following  table  shows  us 
fhe  gradual  accumulation  which  takes  place  in  100 
,  pounds  of  potatoes  between  August  and  November,  and 
the  subsequent  diminution  from  March  to  May : — 

Aug.     Se])t.      Oct.      Xov.  March.      April.      May. 

10         14£       14|       17  17  13$          10 

(198.)  Plants  containing  Fecula.  —  The  following 
list  contains  a  few  of  the  principal  plants  which  furnish 
fecula  in  the  greatest  abundance,  and  the  figures  givi- 
the  percentage  yielded  by  the  several  organs  from 
which  it  is  extracted.  These  numbers  may  also  be 
considered  to  a  certain  extent  indicative  of  the  degrees 
of  nourishment  which  each  is  capable  of  affording  :  — 


CHAP.   III. 


FUNCTION    OP    NUTRITION. 


213 


Maize 

Rice 

\VTieat 

Rye 

Oats 

Peas 

French  beans     - 

Kidney  beans 

Lentils     - 

Amomum  curcuma 

Dioscorea  triloba 

Potato         - 

Tapioca  (Jatropha  manihof) 

Sweet  Potato  (Ipomaea  batatas} 


80  to  92") 
80  to  85 

70  to  77 

-  61  . 

59  I"  seed. 
50 

-  46 
34 
32 

-  26 
25 
24 

-  13-5 
13-3 


Arrow-root  (Marantaarundinacea)  12-5 
Canna  coccinea  -  -      12'5 

Breadfruit  (Artocarpus  incisd]  .       3 '2 


rhizoma. 

tuber. 

root. 


rhizoma. 
fruit. 


(199-)  Sugar.  —  There  are  numerous  modifications 
of  sugar,  all  of  which  may  be  referred  to  two  general 
heads.  The  one  class,  as  the  sugars  of  the  sugar- 
cane and  beet-root,  contains  a  less  proportion  of  water 
in  combination  with  an  equal  quantity  of  carbon  than 
the  other  class,  which  includes  the  sugars  extracted 
from  raisins,  manna,  &c.  Some  are  crystallisable 
others  not.  The  purest  obtained  from  the  sugar-cane 
has  a  specific  gravity  of  1-605,  and  is  composed  of 
about  42  per  cent,  of  carbon  and  58  of  water.  In  the 
East  Indies  the  canes  yield  about  17  per  cent.,  and 
in  America  14  per  cent,  of  sugar;  but  in  our  hot- 
houses they  produce  scarcely  any.  All  sugars  are 
readily  soluble  in  water  but  less  so  in  alcohol,  into 
which  latter  fluid  they  may  themselves  be  converted 
by  the  process  of  fermentation ;  thus  the  quantity  of 
ardent  spirits  which  may  be  extracted  from  any  vege- 
table is  in  proportion  to  the  sugar  it  contains.  This 
substance  bears  a  striking  affinity  to  gum  in  its  che- 
mical composition,  and  is  very  commonly  dissolved 
p  3 


214  PHYSIOLOGICAL    BOTANY.  PART  II. 

in  the  juices  of  plants.  After  it  has  been  formed 
it  is  again  very  easily  altered  during  the  progress  of  vege- 
tation; a  fact  of  considerable  importance  to  the  cultivator, 
who  must  be  cautious  to  collect  the  produce  of  his  canes 
at  the  season  when  the  sugar  is  most  abundantly  gener- 
ated and  before  it  sustains  such  alteration.  The  flowering 
of  the  cane  exhausts  the  sugar  in  the  stem;  and  that 
which  is  so  abundantly  contained  in  the  cortical  sys- 
tem of  the  root  of  the  beet  is  ultimately  carried  into 
the  upper  parts  of  the  plant,  and  similarly  exhausted 
during  its  inflorescence. 

(200.)  Lignine.  —  This  substance  is  contained  in 
the  elongated  vesicles  termed  closters(art.  1 6.  fig.  3.  c),  of 
which  the  woody  fibre  is  composed.  It  does  not  ap- 
pear that  it  has  ever  been  submitted  to  a  careful  analy- 
sis, or  accurately  examined  in  a  detached  form.  After 
various  matters  have  been  abstracted  from  the  woody 
fibre,  such  as  certain  salts,  gummy  particles,  and  others, 
there  then  remains  about  96  per  cent,  of  an  in- 
soluble substance,  composed  of  nearly  equal  propor- 
tions of  water  and  carbon.  But  this  is  a  compound 
material,  consisting  both  of  the  thin  pellicle  which 
formed  the  vesicles  themselves  as  well  as  of  the  lignine 
which  they  contained.  The  resemblance  which  lignine 
bears  to  gum  is  not  so  striking  as  in  the  case  of  the  two 
materials  just  described,  nor  does  it  appear  to  answer  any 
ulterior  purpose  of  nutrition  after  it  has  become  secreted ; 
but  it  remains  unchanged  in  the  cells,  and  imparts 
to  wood  the  varied  qualities  and  colours  which  different 
species  present.  Its  specific  gravity  varies  being  1-459 
in  the  maple,  and  1  -.5.34  in  the  oak. 

(201.)  Vegetable  Products. —  Besides  the  four  ma- 
terials gum,  fecula,  sugar,  and  lignine,  which  we 
consider  as  the  simplest  modifications  which  the  nutri- 
tious and  organisable  materials  found  in  the  vegetable 
structure  can  assume,  there  is  an  interminable  catalogue 
of  other  substances  which  may  be  extracted  from  the 
juices  of  different  plants,  all  of  which  have  been  formed 
by  secretion  in  some  part  or  other  of  their  structure. 


CHAP.   III.  FUNCTION    OF    NUTRITION.  215 

Some  are  the  results  of  disease,  whilst  others  are  more 
abundantly  formed  when  the  plants  which  produce 
them  are  placed  in  peculiar  soils  and  situations.  Some 
occur  in  a  very  few  species  only,  whilst  others  are 
characteristic  of  whole  families.  None  of  them  are 
so  abundantly  diffused  as  the  four  nutritive  sub- 
stances already  described  ;  and  they  all  materially 
differ  from  these,  by  having  either  the  oxygen  or  the 
hydrogen  which  they  contain  in  greater  excess  than 
would  be  necessary  to  form  water.  These  may  there- 
fore be  termed  hyperoxygenated  and  hyperhydrogen- 
ated  products,  when  contrasted  with  the  others. 
Little  is  at  present  known  of  the  exact  manner  in 
which  these  various  products  are  formed.  Their  com- 
plete enumeration  belongs  to  the  department  of  che- 
mical Botany ;  and  we  can  here  pretend  to  do  no 
more  than  point  out  some  of  the  principal  groups,  and 
mention  a  few  of  their  most  striking  peculiarities. 

(202.)  Proper  Juices.  —  Several  of  the  products 
elaborated  in  the  leaves  and  cortical  parts,  are  dissolved 
in  those  proper  juices  of  plants  which  in  art.  1.Q5. 
we  described  as  the  latex  or  vital  fluid,  analogous  to 
the  blood  of  animals.  But  as  these  juices  are  very 
different  in  their  characters  in  different  species,  as  they 
are  not  clearly  defined  in  some  and  above  all  as  they 
act  as  poisons  when  imbibed  by  the  roots,  De  Candolle 
imagines  that  they  ought  more  properly  to  be  con- 
sidered as  secretions  of  a  recrementitial  nature,  ana- 
logous to  the  bile  and  others  in  the  animal  economy. 
Some  of  these  products  even  contain  azote,  and  by 
this  circumstance  are  brought  into  closer  resemblance 
with  animal  matter.  The  more  remarkable  materials 
found  in  the  proper  juices  of  plants  are  milks,  resins, 
and  oils. 

(203.)  Milks These  are  generally  of  an  opaque 

white,  though  some  are  variously  coloured.  They 
abound  in  many  species,  and  are  highly  characteris- 
tic of  certain  natural  families,  as  the  Euphorbiaceae, 
p  4 


216 


PHYSIOLOGICAL    BOTANY. 


Apocyneie,  Artocarpete,  &c.  They  differ  very  remark- 
ably in  their  characters;  for  although  a  large  portion 
are  noxious,  and  even  highly  poisonous,  some  on  the 
contrary  are  wholesome  and  nutritious.  There  are 
several  substances  found  in  the  composition  of  these 
milks,  of  which  we  may  mention  the  following :  — 

1.  Caoutchouc,  or  Indian    rubber    is    abundant  in 
some  of  them,  and  may  be  readily  obtained  from  several 
trees  of  different  families  growing  in  tropical  climates. 
All  that  is  requisite  for  the  purpose  of  procuring  this 
material,  is  to  receive  the  milk  into  suitable  vessels  as 
it  flows  from  a  wound  in  the  bark   and  to  allow  its 
aqueous  particles  to  evaporate,  when  the  caoutchouc  re- 
mains in  a  solid  form. 

2.  Opium  is  procured  by  inspissating  the  milk  of 
the  poppy,  and  is  also  found  in  other  plants. 

3.  The  Cow. Tree. —  One  of  the  most  remarkable 
phenomena   of    the  vegetable  world    is    the    cow-tree 
described    by   Humboldt   in   the   following    terms,   as 
growing  in  the  Cordilleras  of  South  America :  —  "  On 
the  barren  flank  of  a  rock  grows  a  tree  with  dry  and 
leather-like  leaves ;  its  large  woody  roots  can  scarcely 
penetrate  into   the  stony  soil.     For  several  months  in 
the  year  not  a  single  shower  moistens  its  foliage.     Its 
branches  appear  dead  and  dried  ;  yet  as  soon  as  the 
trunk  is  pierced,  there  flows  from  it  a  sweet  and  nou- 
rishing milk.     It  is  at  sunrise  that  this  vegetable  foun- 
tain  is  most  abundant.     The  natives  are  then  to  be 
seen  hastening  from  all  quarters,  furnished  with  large 
bowls  to   receive  the  milk,   which   grows  yellow  and 
thickens  at  the  surface.     Some  empty  their  bowls  under 
the   tree,  while  others  carry  home   the  juice  to  their 
children.     The  milk  obtained  by  incisions  made  in  the 
trunk  is  glutinous,  tolerably  thick,  free  from  all  acri- 
mony, and  of  an  agreeable  and  balmy  smell.     It  was 
offered   to  us  in  the  shell  of  the  tutuno,  or  calabash 
tree.     We  drank  a  considerable  quantity  of  it  in  the 
evening,  before  we  went  to  bed,  and  very  early  in  the 
morning,   without  experiencing  the  slightest  injurious 


CHAP.   III.  FUNCTION    OF    NUTRITION.  21? 

effect.  The  viscosity  of  the  milk  alone  renders  it  some- 
what disagreeable.  The  negroes  and  free  labourers 
drink  it,  dipping  into  it  their  maize,  or  cassava  bread." 
Mr.  Lockhart  has  subsequently  afforded  the  following 
additional  particulars  concerning  this  tree :  —  "  The 
Palo  de  vaca  is  a  tree  of  large  dimensions.  The  one 
that  I  procured  the  juice  from  had  a  trunk  seven  feet 
in  diameter,  and  it  was  one  hundred  feet  from  the  root 
to  the  first  branch.  The  milk  was  obtained  by  making 
a  spiral  incision  into  the  bark.  The  milk  is  used  by 
the  inhabitants  wherever  it  is  known.  I  drank  a  pint 
of  it  without  experiencing  the  least  inconvenience.  In 
taste  and  consistence  it  much  resembles  sweet  cream, 
and  possesses  an  agreeable  smell." 

(204.)  Receptacles  for  Milk. — All  the  various  milky 
juices  reside  in  the  bark  and  leaves,  and  are  not  found 
in  the  wood.  They  are  contained  in  distinct  receptacles, 
and  may  be  extracted  by  means  of  incisions  chiefly 
in  the  upper  parts  of  plants,  and  which  do  not  ex- 
tend deeper  than  the  bark ;  otherwise  they  would  be 
diluted  and  impoverished  by  mixing  with  the  as- 
cending sap.  M.  Bertholet  has  recorded  a  remarkable 
instance  of  the  harmless  quality  of  the  sap  in  the 
interior  of  a  plant,  whose  bark  is  filled  with  a  milky 
proper  juice  of  a  poisonous  nature.  He  describes  the 
natives  of  Teneriffe  as  being  in  the  habit  of  removing 
the  bark  from  the  Euphorbia  canariensis,  and  then 
sucking  the  inner  portion  of  the  stem  in  order  to 
quench  their  thirst,  this  part  containing  a  consider- 
able quantity  of  limpid  and  non-elaborated  sap.  The 
reservoirs  which  contain  the  milky  juice  of  the  wild 
lettuce  (Lactuca  virosa)  are  so  remarkably  irritable 
that  the  slightest  touch  is  sufficient  to  cause  it  to  be 
ejected  from  them  with  considerable  force.  When 
this  plant  is  about  to  flower,  if  an  insect  happens  to 
crawl  over  the  surface  of  the  stalk  any  where  near  its 
summit  a  jet  of  milk  is  propelled.  In  general  plants 
which  secrete  these  milky  juices  love  the  light;  few 
are  found  to  affect  shady  situations,  and  none  are  aqua- 


'218  PHYSIOLOGICAL    BOTANY.  PART  II. 

tics.  By  cultivation,  their  noxious  properties  may  be 
greatly  subdued. 

(205.)  Jtesins.  —  This  class  contains  certain  sub- 
stances separated  from  the  proper  juice  by  some  pro- 
cess of  secretion  ;  and  not  having  any  peculiar  channels 
appropriated  to  their  reception,  they  form  cavities  and 
force  passages  for  themselves  in  the  cellular  tissue.  Oc- 
casionally they  exude  from  the  surface  of  the  stem  ;  but 
this  must  be  considered  accidental  and  not  the  result  of 
any  provision  made  for  their  excretion,  as  is  the  case 
with  some  substances  which  exude  from  certain  glands 
on  the  surface. 

(206'.)  Oils.  —  There  are  two  classes  of  oils  secreted 
by  plants  :  the  one  contains  the  highly  volatile  or  essen- 
tial oils  as  they  are  termed,  which  impart  the  fragrant 
or  disagreeable  odours  peculiar  to  different  plants  ;  and 
the  other  the  fixed  oils,  such  as  those  extracted  ^  from 
the  fruit  of  the  olive,  the  seeds  of  flax,  &c. 

(207.)  Volatile  Oily.  —  The  first  kind  are  gener- 
ally contained  in  spherical  or  oblong  cells  in  the  leaves 
and  cortical  parts  of  plants  ;  when  held  to  the  light 
these  parts  appear  as  if  they  were  punctured,  owing 
to  the  superior  transparency  of  the  receptacles  in 
which  the  oil  is  deposited.  The  St.  John's-wort 
(Ifi/jH-rii-uin  /ifrfnrtitiiin)  and  any  of  the  myrtle  tribe 
are  familiar  examples  of  this  fact  In  the  Umbellifera: 
the  oil  accumulates  in  oblong  club-shaped  receptacles, 
termed  "  vitta?,"  which  are  placed  between  the  coats  of 
the  seed-vessel ;  and  it  is  remarkable  that  their  num- 
ber and  general  appearance  is  so  constantly  the  same 
for  each  separate  species  that  important  generic  cha- 
racters are  derived  from  this  circumstance. 

(208.)  Camphor  is  deposited  upon  the  evaporation  of 
certain  volatile  oils,  especially  those  extracted  from  some 
of  the  Labiata?,  as  the  common  lavender. 

(20<>.)  Fixed  Oils.  —  These  are  rarely  found  in  the 
cortical  parts  like  the  others,  but  are  for  the  most 
part  extracted  from  the  seed  or  its  envelopes,  and 
sometimes  from  the  pericarp,  as  in  the  olive.  In 


CHAP.   III.  FUNCTION    OF    NUTRITION.  219 

these  cases  they  are  readily  convertible  by  some  natural 
process  into  a  nutritious  emulsion;  and  then  appear  to 
be  destined  to  feed  the  young  plant  during  the  early 
stages  of  its  development. 

The  following  table  shows  the  percentage  of  fixed 
oil  obtained  from  the  seeds  of  a  few  plants  : — 

Nut  -  -  60 

Cress  -  -  58 

Walnut  -  50 

Poppy  -  -  47 

Almond  -  -  46 

(210.)  Taste  and  Scent  of  Plants. —  It  will  readily 
be  conceived  that  the  peculiar  tastes  and  odours  met  with 
in  different  species,  must  depend  entirely  upon  the  nature 
of  the  various  matters  which  are  secreted  by  them. 
Attempts  have  been  made  to  classify  the  various  im- 
pressions which  are  thus  made  upon  the  sensorium,  and 
odours  have  been  arranged  into  classes,  under  the 
terms  aromatic,  foatid,  acrid,  alliaceous,  musky,  &c. 
Such  classifications  at  the  best  are  highly  empyrical, 
and  any  arrangement  which  could  be  founded  on  an 
accurate  knowledge  of  the  chemical  nature  of  these 
substances  would  be  far  preferable ;  but  our  extreme 
ignorance  on  these  points  will  not  justify  the  attempt 
at  present.  The  delicate  perfumes  emitted  by  certain 
flowers,  as  well  as  the  more  powerful  and  often  disagree- 
able scents  afforded  by  the  herbage  of  some  plants, 
generally  depend  upon  the  diffusion  of  a  volatile  oil. 
In  some  cases  this  oil  is  magazined  in  the  stalks  and 
leaves,  and  is  rendered  more  sensible  the  more  these 
parts  are  rubbed  or  bruised.  In  the  flower  especially, 
the  oily  particles  which  produce  the  odour  seem  to  be 
diffused  as  fast  as  they  are  secreted  ;  and  hence  it  hap- 
pens that  the  greater  number  of  plants  are  more  power- 
fully scented  at  one  particular  part  of  the  day  and 
that  almost  all  flowers  are  most  fragrant  towards  night. 
There  are  some,  specially  termed  "  night-scented," 
which  are  extremely  powerful  after  sunset  though 


220  PHYSIOLOGICAL    BOTANY.  PART  II. 

they  emit  little  or  no  odour  by  day ;  and  several  of 
these  as  the  night-scented  stock,  geranium,  wallflower, 
gladiolus,  &c.,  are  further  remarkable  from  possess, 
ing  a  peculiar  brown  and  lurid  tint.  The  flowers  of 
the  splendid  Cereus  grandiflorus  begin  to  expand  about 
seven  o'clock  in  the  evening,  attain  their  full  beauty 
and  put  forth  their  powerfully  fragrant  odour  before 
midnight,  and  are  completely  faded  before  sunrise. 
Some  of  the  singular  tribe  of  Stapelias  are  disgustingly 
nauseous  in  the  scent  which  they  emit,  strongly  resem- 
bling the  most  offensive  carrion  ;  so  much  so  indeed 
that  even  flies  and  other  carnivorous  insects  are  de- 
ceived by  the  similarity,  and  very  frequently  deposit 
their  eggs  in  their  blossom. 

(211.)  Impressions  made  by  Odours.  —  The  scents 
emitted  by  certain  flowers  make  very  different  impres- 
sions upon  the  nerves  of  different  people;  and  some 
persons  can  readily  perceive  a  powerful  odour  where 
others  are  nearly  or  entirely  insensible  to  its  impression, 
although  they  may  not  be  defective  in  other  instances  in 
the  sense  of  smelling.  Very  deleterious  impressions  are 
made  on  some  constitutions  by  the  odours  of  strong- 
scented  flowers.  The  most  dangerous  symptoms  have 
occurred  in  persons  especially  females  with  weak  nerves, 
merely  by  their  remaining  in  a  room  where  certain 
flowers  have  been  placed  ;  and  even  violets  are  not 
exempt  from  a  bad  reputation.  Instances  of  death 
have  been  recorded  which  were  considered  to  have 
been  occasioned  by  effects  of  this  kind ;  and  Linnaeus 
mentions  a  case  where  the  odour  from  the  Rose-bay 
(Nereum  oleander}  was  supposed  to  have  proved  fatal 
to  the  constitution  of  one  person.  Prussic  acid  may 
be  instanced  as  abounding  in  the  leaves  of  the  common 
laurel  (Pr units  lauroceratus)  to  so  great  an  extent, 
that  if  one  of  them  be  cut  into  small  pieces  and  placed 
under  a  wine-glass,  and  a  wasp  or  other  insect  be  in- 
troduced under  the  glass  it  will  be  completely  stupefied 
in  two  minutes. 

(212.)    Excretions.  —  We  have  still   to   allude  to 


CHAP.  III.  FUNCTION    OF    NUTRITION.  221 

a  class  of  substances  which  are  excreted  from  plants  by 
various  glands  seated  on  the  surface  of  their  stems, 
leaves,  and  other  organs.  Many  of  them  are  of  the 
same  description  as  those  which  are  formed  within 
the  plant  by  internal  secretions,  such  as  acids,  oils,  &c. ; 
but  some  of  them  are  peculiar.  They  may  be  con- 
sidered as  more  strictly  analogous  to  the  various  ex- 
crementitious  matters  ejected  by  animals  than  those  of 
the  former  class;  and  the  glands  by  which  they  are 
formed  are  for  the  most  part  more  complex  and 
better  defined  than  those  which  are  seated  in  the 
interior  of  plants.  The  external  glands  (see  art.  31. 
andyz^.  20.)  by  which  these  matters  are  excreted  often 
form  a  sort  of  clammy  pubescence  upon  the  epidermis. 
They  frequently  resemble  hairs  tipped  with  a  little 
globular  mass  by  which  the  excreted  matter  is  more 
especially  elaborated. 

(213.)  Fraxinella. —  The  common  Fraxinella  is 
covered  with  minute  glands  which  excrete  a  volatile 
oil.  This  is  continually  evaporating  from  its  surface, 
and  on  a  calm  still  evening  forms  a  highly  inflammable 
atmosphere  round  the  plant.  If  a  candle  be  brought 
near  it,  the  plant  is  enveloped  by  a  transient  flame 
without  sustaining  any  injury  from  the  experiment. 

(214.)  Stings,  —  The  stinging  plants  prepare  a 
caustic  juice  which  is  contained  in  a  cellular  bag  sur- 
mounted by  a  hollow  bristle.  When  the  bristle  is 
gently  pressed  the  fluid  is  forced  through  it  and  flows 
out  at  the  summit  through  a  minute  orifice,  as  we  have 
stated  (art.  31.  and^.20.  a).  If  the  bristle  enters  a  pore 
of  the  skin,  the  caustic  fluid  is  introduced  and  produces 
the  painful  sensations  familiar  to  all  who  have  ever  handled 
a  common  nettle.  The  Loaste  have  stings  which  give 
a  still  more  irritating  sensation  than  the  nettles.  The 
Malpighise  are  furnished  with  a  multitude  of  doubly 
pointed  bristles  which  lie  parallel  to  the  surface  of  their 
leaves,  to  which  they  are  attached  by  a  short  hollow  stem. 
These  contain  a  slightly  caustic  fluid. 

(215.)  Glue. — The  gummy  excretions  on  the  stems  of 


222  PHYSIOLOGICAL    BOTANV.  PART   IT. 

certain  plants,  as  the  fly-catching  Lychnises  (Lychnis 
nrmeria  and  others)  appear  to  be  composed  of  a 
material  of  the  same  nature  as  common  birdlime 
extracted  from  the  bark  of  the  holly.  Several  kind  of 
leaf-buds,  as  those  of  the  horse-chestnut,  are  coated 
over  with  a  glutinous  insoluble  excretion  apparently 
intended  to  secure  them  from  the  ill  effects  of  moisture. 

(2 16.)  Wax  —  is  a  very  abundant  excretion  from 
many  plants.  It  forms  a  delicate  powder  on  the  sur- 
face of  certain  fruits,  as  the  substance  termed  the 
"  bloom  "  on  the  plum.  It  is  so  plentiful  on  the  sur- 
face of  poplar  leaves,  that  a  manufactory  was  at  one 
time  established  in  Italy  for  the  purpose  of  procuring 
it  from  them  as  a  material  for  commerce.  It  is  very 
abundantly  furnished  by  some  palms  in  tropical  countries, 
where  it  is  advantageously  employed  for  economical 
purposes  ;  but  the  Myrica  cerifera  is  the  plant  which 
affords  it  in  the  greatest  abundance.  Its  fruit  is 
completely  enveloped  in  a  coat  of  wax,  and  when 
thrown  into  boiling  water  the  wax  melts  and  floats  to 
the  surface  where  it  is  skimmed  off.  It  has  a  slightly 
green  tinge  which  can  be  removed  by  chlorine,  and  it 
may  then  be  formed  into  candles  resembling  sper- 
maceti. This  fruit  yields  about  one  ninth  per  cent,  of 
its  weight  in  wax.  All  the  kinds  of  vegetable  wax  are 
closely  allied  to  common  bees'  wax  in  several  proper- 
ties, though  essentially  distinguished  from  it  by  others. 

(217.)  Radical  Excretion*.  —  But  of  all  excretions 
proceeding  from  plants,  some  of  the  least-known  are 
perhaps  the  most  important  in  an  economical  point  of 
view.  It  was  not  until  very  recently  that  their  pro- 
perties had  been  made  a  subject  of  experimental  in- 
quiry, or  even  that  their  existence  had  been  clearly 
established  ;  but  the  partial  results  hitherto  obtained 
have  opened  a  wide  field  for  speculation.  The  excre- 
tions to  which  we  allude  are  discharged  from  the 
root,  and  may  be  detected  by  a  very  simple  experi- 
ment. If  young  French  beans,  for  example,  be  placed 
in  a  glass  containing  distilled  water,  at  the  end  of 


CHAP.  III.  FUNCTION    OF    NUTRITION.  223 

a  few  days  this  water  will  be  found  strongly  im- 
pregnated by  a  matter  excreted  from  the  roots.  A 
fresh  plant  should  be  placed  daily  in  the  water,  to  avoid 
the  effects  which  might  otherwise  be  produced  by  an 
incipient  decomposition.  It  is  also  found  that  the 
matters  thus  procured  from  plants  of  different  families 
are  dissimilar.  Thus  that  which  is  excreted  by  the 
Leguminosae  contains  an  abundance  of  mucilage,  whilst 
that  which  exudes  from  the  Gramineae  has  very  little. 
The  Chicoraceae  excrete  a  bitter  matter  analogous  to 
opium;  the  Euphorbiaceae  a  gum-resinous  matter,  &c. 

(218.)  Rotation  of  Crops. —  So  far  as  observations 
have  hitherto  been  made,  it  appears  probable  that 
the  excretions  given  out  by  plants  of  different  fami- 
lies possess  very  different  qualities,  and  act  differently 
upon  other  plants.  It  had  been  long  known  to  gar- 
deners that  flowers  and  fruit-trees  will  not  prosper  so 
well  when  they  have  been  planted  in  a  situation  where 
others  of  the  same  kind  had  previously  grown,  as  if 
they  were  planted  in  situations  where  they  succeeded 
to  others  of  a  different  kind.  It  is  also  a  well-esta- 
blished fact  in  forestry,  that  when  a  wood  principally 
composed  of  one  species  of  timber  trees  has  been 
cleared,  the  trees  which  then  spring  up  spontaneously 
and  supply  the  place  of  the  former  growth  are  for 
the  most  part  of  a  different  species.  And  lastly, 
the  agriculturist  has  established  a  rotation  of  crops 
upon  experimental  proof  that  grain  of  one  kind  suc- 
ceeds better  when  it  follows  certain  other  kinds,  than 
when  it  is  sown  immediately  after  a  crop  of  the 
same  plant.  The  various  theories  which  had  formerly 
been  proposed  to  account  for  these  facts  were  all  liable 
to  serious  objections ;  but  M.  De  Candolle  has  suggested 
the  probability,  that  the  excretions  of  any  one  plant 
although  they  may  be  noxious  to  others  of  the  same 
species,  genus,  or  family,  may  nevertheless  be  per- 
fectly harmless  or  even  beneficial  to  plants  of  other 
families.  In  this  manner  he  would  account  for  the 
fact,  that  plants  of  the  natural  order  Leguminosae  (as 


~~  }•  PHYSIOLOGICAL    BOTANY.  PART  II. 

vetches,  tares.  &c.),  prepare  or  improve  the  soil  for 
those  of  the  Grammes  (various  kinds  of  corn,  &c.).  If 
the  farmer  by  further  experimental  research  should 
ever  be  able  to  establish  an  extensive  series  of  facts  of 
this  description,  he  may  expect  to  grow  a  succession 
of  crops  with  comparatively  little  manure  and  without 
ever  being  obliged  to  let  his  land  lie  fallow.  In  the 
present  state  of  this  inquiry  it  would  be  idle  to 
say  much  upoh  the  possible  advantages  which  may 
be  expected  from  the  confirmation  of  this  theory; 
but  it  must  be  evident  to  the  most  prejudiced  admirer 
of  old  customs,  that  we  cannot  expect  to  make  any  real 
progress  in  the  various  branches  of  human  knowledge, 
agriculture  among  the  rest,  until  we  have  obtained 
clearer  notions  and  a  sounder  theory  respecting  the 
fundamental  principles  upon  which  the  successful  prac- 
tice of  any  pursuit  depends. 

(219-)  Extraneous  Matters. —  Besides  those  numer- 
ous products  directly  secreted  by  plants,  and  which  are  the 
immediate  results  of  vegetable  action,  there  are  many 
others  which  have  either  been  accidentally  absorbed 
with  the  water  that  enters  through  the  spongioles  and 
pores,  or  else  have  resulted  from  subsequent  combin- 
ations chemically  effected  between  matters  so  introduced 
and  the  undoubted  products  of  vegetation.  All  matters 
however  which  are  accidentally  introduced,  form  only 
a  very  slight  per  eentage  of  the  weight  of  the  whole  mass. 
They  compose  the  various  earthy,  saline,  metallic,  and 
other  ingredients  found  in  the  ashes  of  plants,  after 
combustion  has  dissipated  all  the  purely  vegetable  pro- 
ducts. They  generally  exist  in  the  greatest  quantity  in 
those  plants,  or  parts  of  plants,  where  the  process  of  ex- 
halation has  been  carried  on  with  the  greatest  rapidity. 
Hence  they  abound  more  in  the  leaves  than  in  other 
parts,  and  more  in  the  bark  than  in  the  wood.  Herba- 
ceous plants  for  similar  reasons  furnish  more  ashes 
than  trees. 

(220.)  Earths. — Lime  is  the  earth  which  is  most  uni- 
versally present  in  the  ashes  of  plants,  generally  in  tin 


CHAP.   III.  FUNCTION    OF    NUTRITION.  225 

form  of  a  carbonate,  but  also  in  union  with  other  mineral 
and  vegetable  acids.  Carbonate  of  lime  is  largely  deposit- 
ed in  the  stems  of  some  of  the  Charge,  which  it  completely 
incrusts  with  stony  matter.  —  Silica  is  the  earth  which 
next  to  lime  occurs  in  the  greatest  abundance,  especially 
among  some  of  the  monocotyledonous  tribes.  The  glossy 
surfaces  of  canes,  reeds,  and  other  grasses,  are  com- 
posed of  a  very  large  percentage  of  it ;  and  if  two  canes 
be  rubbed  together  in  the  dark,  they  emit  a  flash  of  light 
similar  to  that  which  is  obtained  by  the  friction  of  two 
quartz  pebbles.  When  a  stack  of  corn  or  hay  has  been 
rapidly  consumed,  the  ashes  are  fused  into  a  semi-vitri- 
fied mass :  the  straw  abounding  both  with  silica  and  an 
alkali,  the  two  chief  ingredients  necessary  to  the  form- 
ation of  such  a  compound.  In  the  hollow  portions 
of  the  stem  between  the  joints  of  the  bamboo,  a  sub- 
stance named  tabasheer  is  deposited  in  lumps  which 
very  much  resemble  fragments  of  opaque  and  semitrans- 
parent  opal.  This  remarkable  deposit  contains  70  per 
cent,  of  pure  silica,  and  possesses  very  peculiar  and 
curious  optical  properties.  Silica  is  also  deposited  in 
little  semi-crystalline  lumps  along  the  angles  of  the 
stems  of  some  species  of  Equiseta,  especially  the  Equi- 
setum  hyemale  or  Dutch  reed,  which  from  this  circum- 
stance is  serviceable  to  watchmakers  and  others  in 
polishing  their  work. 

(221.)  Salts.  —  The  salts  of  potash  are  particularly 
abundant  in  most  plants,  but  the  salts  of  soda  are  more 
especially  confined  to  such  as  grow  near  the  sea.  It  is 
however  remarkable,  that  plants  which  abound  in  the 
salts  of  soda  whilst  growing  in  these  latter  situations, 
secrete  the  salts  of  potash  when  they  are  no  longer 
within  the  influence  of  the  sea.  In  such  plants,  it  is 
difficult  not  to  believe  that  the  presence  of  one  or  other 
of  these  alkalis  is  in  some  way  beneficial  to  their  health, 
even  though  it  may  not  form  any  essential  part  of  their 
structure.  The  common  soda  of  commerce  is  a  carbon- 
ate obtained  from  the  incineration  of  several  maritime 


~'2I)  PHYSIOLOGICAL    BOTANY.  PART  II. 

plants  and  sea  weeds,  and  is  largely  prepared  on  the 
shores  of  the  Mediterranean  for  the  European  market. 

(i^ii.)  Origin  of  extraneous  Deposits.  —  The  various 
other  products,  such  as  oxides,  metallic  salts,  &c.,  which 
occur  in  small  quantities  in  the  ashes  of  plants,  have  all 
been  either  derived  immediately  from  the  soil  or  intro- 
duced in  some  way  by  absorption  from  the  atmosphere. 
It  seems  clearly  established  that  none  of  them  ought  to 
be  considered  as  the  direct  product  of  any  vegetative 
function,  as  was  once  supposed  ;  and  it  has  been  satis- 
factorily shown  that  however  carefully  the  experiments 
may  have  been  made  which  favour  such  a  theory,  and 
however  cautiously  the  means  may  have  been  taken  for 
excluding  all  foreign  matters  from  access  to  the  grow- 
ing plant,  error  was  unavoidable.  The  extreme  mi- 
nuteness of  the  elementary  organs  of  plants,  and  the 
more  delicate  nuinipnlutitms  of  a  natural  chemistry,  are 
capable  of  separating  the  minutest  portions  of  foreign 
matters  from  the  materials  with  which  they  are  brought 
in  contact,  however  carefully  and  accurately  these  ma- 
terials may  have  been  purified  and  cleansed  by  artificial 
processes.  It  seems  to  be  impossible  for  instance  to 
provide  even  distilled  water  so  pure,  but  what  some 
traces  or  other  of  foreign  matter  may  be  detected  in  it. 


FUNCTION    OF    NUTRITION.  227 


CHAP.  IV. 

FUNCTION    OF    NUTRITION    CONTINUED Period  7- 

ASSIMILATION     (223.).  PRUNING  (225.).  GRAFTING  (227.). 

DEVELOPMENT       (230.). NUTRITION       OF       CRYPTOGAMIC 

PLANTS    (233.).  PARASITIC    PLANTS  (234.).  DURATION  OF 

LIFE      (235.).  VEGETABLE     INDIVIDUALS     (236.).  LONGE- 
VITY   OF    TREES    (239.). 

SEVENTH    PERIOD    OF    NUTRITION. 

(223.)  Assimilation.  —  THE  chief  end  and  object  of 
the  various  processes  which  we  have  been  describing,  is 
the  manufacture  of  the  materials  which  are  ultimately 
to  be  assimilated  into  the  vegetable  structure,  and  by 
which  it  is  to  be  nourished  and  developed  in  all  its 
parts.  Of  the  precise  manner  in  which  the  assimilation 
of  this  nutriment  takes  place  we  know  nothing,  and 
the  first  steps  towards  the  formation  and  development 
of  any  organised  being  are  entirely  concealed  from  us. 
We  may  indeed  observe  when  a  gradual  organisation  of 
matter  is  taking  place;  but  there  is  no  stage  in  the 
process  from  whence  we  may  not  refer  back  to  some 
previous  state,  out  of  which  it  appears  to  have  emerged 
imperceptibly  and  inexplicably ;  and  it  is  utterly  im- 
possible to  note  with  any  degree  of  accuracy,  either  the 
precise  manner  or  exact  time  when  the  first  traces  of 
any  new  condition  of  organisation  commenced.  In  other 
words,  as  soon  as  we  can  distinguish  an  organ  it  already 
exists  in  a  developed  form,  however  faintly  its  subor- 
dinate parts  may  be  indicated. 

(224.)  Growth  of  the  Tissues  — In  dicotyledonous 
trees,  as  we  have  observed  (art.  34.  2.),  the  new  tissue 
makes  its  appearance  between  the  old  wood  and  old 


228  PHYSIOLOGICAL    BOTANY.  PART   II. 

hark.     In  the  earliest  stage  in  which  it  is  discoverable 
it  appears  as  a  thick  clammy  fluid  termed  the  cambium, 
which    gradually  assumes    the    character  of    a    newly 
formed  cellular  tissue  intermixed  with  vessels  which  are 
disposed  longitudinally  through   the  stem.     It  should 
seem  that  the  cellular  tissue  at  least  is  developed  from 
the  old    tissue,   as   may  be  shown  experimentally   by 
grafting  a  branch  containing  a  wood  of  one  colour  on  a 
tree  whose  wood  is  of  a  different  colour  as  a  peach  on 
a  plum.     The  new  wood  retains  the  distinctive   cha- 
racters of  the  parts  round  which  it  is  formed,  the  graft 
increasing  by  pale  coloured  layers  and  the  stock  by  layers 
of  a  reddish  colour,  even  though  these  latter  have  been 
nourished  by  the  descending  sap  elaborated  in  the  leaves 
of  the  former.    Different  theories  have  been  proposed  in 
order  to  account  for  the  manner  in  which  the  cellular 
tissue  increases.     Some  suppose  that  the  young  cells 
are  developed   within  the  old    ones,   which   they  ulti- 
mately rupture  and  replace ;   but  of  this  there   is   no 
good  evidence.     Others  consider  the  opaque  dots  dis- 
cernible  on   the  surface  of  some  cells  to   be  nascent 
vesicles,  which  are  afterwards  developed  on  the  outside 
of  the  old  ones ;  and  this  is  a  more  probable  hypothesis 
than  the  last.     According  to  a  third  opinion,  an  old 
cell  becomes  separated  into  compartments  by  the  form- 
ation   of  a  transverse  diaphragm,    and  each    compart- 
ment   afterwards  develops   into  a  separate  cell.     The 
formation  of  the  fresh  vessels  is  still  more  ambiguous 
than  that  of  the  cells.     One  theory  considers  them  ana- 
logous to  descending  roots  proceeding  from  the  buds 
placed  in  the  axillae  of  the  leaves,  and  supposes  them 
to  be  continuous  throughout  the  whole  length  of  the 
longest  stems.     But  as  vessels  are  formed,  though  of 
small  dimensions,  in  those  parts  of  the  stem  which  are 
below  the  place  where  a  ring  of  bark  has  been  removed, 
this  supposition  is  untenable.     It  seems  more  probable 
that  the  vessels  have  a  common  origin  with  the  vesicles, 
or  are  modifications  of  them  ;  and  that  a  long  vessel  was 
originally  composed  of  sevetal  parts. 


CHAP.  IV.  FUNCTION    OF    NUTRITION.  229 

(225.)  Effects  of  Pruning.  —  The  objects  to  be  ob- 
tained by  pruning  are  various.  The  gardener  employs 
this  resource  as  the  means  of  improving  the  general 
form  which  he  wishes  his  ornamental  shrubs  to  assume ; 
and  he  prunes  his  fruit  trees  in  order  that  they  may 
bear  fruit  of  larger  size  and  improved  flavour.  With 
these  questions  we  have  nothing  to  do  in  this  place. 
The  results  of  pruning  which  we  propose  to  notice 
are  such  as  are  produced  internally  at  places  where 
the  knife  has  been  employed,  particularly  for  the  pur- 
pose of  improving  the  quality  of  timber.  This  is  at- 
tempted by  removing  superfluous  branches,  which  com- 
pels the  main  trunk  to  become  a  straight  clean  shaft.  The 
effect  of  every  wound  of  this  kind  is  to  expose  a  portion 
of  the  older  or  innermost  parts  of  the  woody  layers, 
which  are  incapable  of  generating  fresh  tissue.  The 
consequence  is  that  such  parts  cannot  be  healed  over, 
excepting  by  the  growth  of  the  newest  tissue  round  the 
edge  of  the  wound.  This  tissue  gradually  extends 
itself  from  the  edges  over  the  whole  surface  of  the 
wound  until  the  opposite  sides  meet,  and  then  grafting 
together  unite  into  one  continuous  mass  :  but  the  new 
wood  contracts  no  union  with  the  surface  of  the  old 
wood  exposed  by  the  operation  of  pruning.  As  the 
growing  tissue  which  coats  over  a  wound  depends 
upon  the  returning  sap  for  its  supply  of  nutriment,  no 
wound  produced  by  cutting  off  a  branch  at  some  dis- 
tance from  the  main  trunk  can  ever  heal.  In  this  case 
there  are  no  leaves  beyond  the  exposed  surface  to  supply 
it  with  proper  juice,  and  whatever  descends  from  the 
main  stem  is  carried  into  the  branch,  and  consumed 
in  developing  the  buds  and  tissue  on  the  lower  part 
of  it  before  it  can  arrive  at  its  extremity.  But  where 
the  branch  is  lopped  near  the  trunk  and  a  "snag" 
(as  it  is  technically  termed)  has  been  left,  the  descending 
sap  flows  into  this  stump  in  sufficient  abundance  to 
enable  the  tissue  to  close  over  the  exposed  extremity. 
As  the  trunk  increases  these  snags  are  completely  em- 
bedded and  greatly  injure  the  timber ;  especially  as  they 
Q  3 


230  PHYSIOLOGICAL    BOTANY.  PART  II. 

generally  become  more  or  less  rotten  at  the  exposed 
extremity  before  the  new  tissue  has  had  time  to  coat  it 
over.  Of  all  descriptions  of  wounds  those  which  are 
the  nearest  to  the  main  stem  heal  the  quickest,  and 
this  shows  us  the  propriety  of  pruning  as  close  as  pos- 
sible to  the  trunk,  whenever  a  branch  is  to  be  removed 
for  the  purpose  of  improving  the  timber.  The  new 
tissue  increases  with  great  rapidity  chiefly  from  above 
downwards,  but  also  from  the  sides  of  the  wound,  and 
a  little  likewise  at  the  base,  until  it  has  spread  over  the 
whole  surface.  The  extent  of  the  injury  introduced 
into  the  timber  is  best  seen  by  forcibly  separating  the 
new  wood  from  the  surface  over  which  it  has  spread  ; 
when  the  latter  will  always  be  found  exactly  as  it  was 
left  at  the  time  it  was  covered  up,  with  the  mark  of  the 
knife  upon  it  or  with  any  portions  of  decay  which  may 
afterwards  have  taken  place.  This  is  sometimes  seen 
in  trees  upon  which  deep  inscriptions  have  been  carved. 
Wherever  the  letters  have  penetrated  below  the  bark 
into  the  woody  layers  an  impression  is  left  in  them  ;  and 
however  long  the  new  wood  may  have  been  formed 
over  them,  they  will  be  found  beneath  it  whenever  the 
outer  portion  is  removed.  Birds'  nests,  stags'  horns, 
an  image  of  the  Virgin  Mary,  and  many  other  articles 
are  described  as  having  been  found  in  the  very  heart  of 
some  trees,  where  they  were  unquestionably  embedded 
by  the  enlargement  of  the  stem  in  the  way  we  have  de- 
scribed. 

(226.)  Precautions  to  be  observed  in  Prwniuj. — 
From  what  we  have  stated  it  is  evident,  that  wherever 
a  branch  has  been  pruned  off  a  blemish  is  inevitably 
introduced ;  and  consequently  where  pruning  can  be 
avoided  'it  should  never  be  resorted  to  ;  but  where  it 
is  really  necessary  it  should  be  performed  as  early  as 
possible,  before  the  branch  has  attained  any  consider- 
able dimensions.  Even  rubbing  off  the  buds  should  be 
preferred  to  regular  pruning.  The  cut  also  should  be 
made  close  to  the  stem,  and  as  nearly  vertical  as  pos- 
sible; the  latter  precaution  prevents  the  accumulation 


CHAP.  IV.  FUNCTION    OF    NUTRITION.  231 

of  water  upon  the  surface  of  the  wound,  after  the  newly 
developed  wood  has  formed  a  swollen  border  round  its 
edges.  If  the  cut  is  perfectly  smooth  it  will  be  the 
sooner  healed ;  and  its  surface  may  be  protected  by 
some  compost  (such  as  that  which  is  known  by  the 
name  of  Forsyth's  mixture)  whenever  the  wound  is  un- 
avoidably large.  An  opinion  has  gone  abroad  that  it  is 
possible  to  diminish  the  blemish  which  pruning  neces- 
sarily occasions  in  timber,  by  lopping  the  extremities  of  a 
branch  and  causing  them  to  die  and  rot  off  in  a  natural 
manner.  Supposing  it  were  true  that  a  branch  thus 
treated  always  did  die, — which  is  by  no  means  a  neces- 
sary consequence, — all  that  could  be  gained  by  such  a 
mode  of  proceeding  would  be  the  introduction  of  the 
rotten  stump  of  the  lopped  branch  into  the  heart  of  the 
tree  instead  of  the  clean  scar  which  close  pruning  pro- 
duces. It  is  not  true,  as  some  suppose,  that  any  na- 
tural sloughing  off  of  the  decayed  part  takes  place 
or  that  the  old  and  new  wood  can  ever  completely 
unite  together ;  but  in  all  cases  it  will  be  found  that 
the  new  wood  has  grown  over  the  old  wound,  and  that 
the  surface  of  the  latter  is  preserved  exactly  in  the 
state  in  which  it  was  embedded.  The  knots  in  deal 
and  other  timbers  are  defects  produced  by  the  process 
of  "  natural  pruning,"  as  it  has  been  termed,  and  such 
defects  are  inevitably  greater  than  those  which  result 
from  artificial  pruning  performed  on  branches  of  the 
same  dimensions  and  cut  off  close  to  the  stem. 

(227.)  Grafts.  —  Every  one  is  acquainted  with  the 
fact,  that  certain  portions  of  some  plants  may  be  grafted 
upon  others,  and  that  the  tissues  of  the  "  graft "  and 
"  stock "  as  the  two  are  named  will  completely  unite 
and  vegetate  together  as  though  they  were  parts  of  the 
same  individual.  The  effects  thus  artificially  produced 
are  occasionally  observed  to  take  place  naturally :  two 
branches  of  the  same  tree  being  sometimes  found 
grafted  together,  where  they  have  been  wounded  by 
mutual  attrition.  When  ivy  has  grown  to  a  consider- 
able size  its  branches  often  interlace  and  graft  together 
Q  4 


PHYSIOLOGICAL    BOTANY.  PART  II. 

in  various  places,  till  the  whole  forms  a  rude  network 
upon  the  trunk  of  the  tree  up  which  it  has  climbed. 
Although  it  is  so  easy  for  two  parts  of  different  in- 
dividuals of  the  same  species  to  graft  together,  it 
requires  great  care  and  precaution  to  secure  such  a 
union  between  two  different  species.  In  dicotyledonous 
plants  the  two  alburnums  and  the  two  libers  must  be 
placed  in  contact,  and  then  the  line  of  junction  between 
the  two  cambiums  will  also  be  complete  and  the  newly 
formed  tissues  will  readily  unite.  De  Candolle  thinks  it 
likely,  in  contradiction  to  the  common  opinion,  that  the 
ascending  sap  being  attracted  by  the  graft  will  first 
produce  a  union  between  the  two  alburnums,  and  that 
the  descending  sap  then  effects  the  union  of  the  two 
libers.  The  chief  requisite  in  this  operation  is  the 
near  relationship  of  the  two  species ;  and  it  never  suc- 
ceeds excepting  between  such  as  are  of  the  same  genus 
or  at  least  between  allied  genera  of  the  same  family. 
The  ancients  were  of  a  very  different  opinion,  and  con- 
sidered it  possible  to  graft  any  two  plants  together. 
Thus  Virgil :  — 

"  Et  stcriles  platani  malos  gesserc  valentw, 
Cattaiies*  fagos,  ornutque  incanuit  albo 
Flore  Tyri,  glandemque  sues  Iregere  sub  ulmis." 

Pliny  has  recorded  a  marvellous  instance  of  a  grafted 
tree  bearing  a  variety  of  different  fruits,  which  he  tells 
us  he  himself  saw.  "  Tot  modis  insitam  arborem 
vidimus,  omni  genere  pomorum  ornustum  :  alio  ramo 
nucibus,  alio  baccis,  aliunde  vite,  ficis,  piris,  punicis, 
malorumque  generibus.  Sed  huic  brevis  fuit  vita."  * 

As  we  must  not  doubt  that  Pliny  saw  the  specimen 
to  which  he  here  so  pointedly  alludes,  we  cannot  other- 
wise explain  the  fact,  than  by  supposing  him  to  have 
been  imposed  upon  by  a  practice  which  it  is  said  is  still 
resorted  to  in  Italy,  for  amusement  or  deceit.  The 
French  have  termed  it  the  "  (Jreffe  des  Charlatans." 
It  consists  in  cutting  down  a  tree,  as  the  orange,  to 

•  Lib.  xvii.  ch.  17.  sect.  20. 


CHAP.  IV.  FUNCTION    OF    NUTRITION.  233 

within  a  short  distance  of  the  ground ;  then  hollowing 
out  the  stump  and  planting  within  it  several  young 
trees  of  different  species  and  families.  In  a  few  years 
the  whole  grow  up  together  so  as  completely  to  fill  the 
cavity,  and  on  a  superficial  observation  appear  to  have 
become  blended  or  grafted  into  a  single  stem.  The 
deception  is  still  more  perfect  if  a  few  buds  have  been 
left  upon  the  stump  to  keep  this  alive  also. 

(228.)  Kinds  of  Grafts.  —  M.  Thouin  has  de- 
scribed about  a  hundred  different  ways  in  which  the 
process  of  grafting  may  be  varied.  These  may  however 
be  referred  to  the  three  following  general  classes. 

1 .  By  Approach.  —  Two    plants    are    placed    near 
each   other,  and   their  boughs  grafted  together  whilst 
they  are  still  on  the  stems.     When  they  have  become 
completely  united,   one  is  then   severed  from  its  own 
stock  and  left  to  grow  on  that  of  the  other. 

2.  By  Slips.  —  A  shoot  is  taken  from  one  tree  and 
placed  on  the  extremity  of  a  branch  of  another  properly 
prepared  to  receive  it.     The  branch  is  cleft  and    the 
graft  inserted  into  the  notch  in  various  ways,  which 
more  peculiarly  form  the  study  of  the  gardener.     This 
graft  is  made  in  the  spring  when  the  sap  is  rising. 

3.  Budding.  —  A  piece  of  bark  is  removed  from  a 
tree  at  a  place  where  there  is  a  bud  ;  and  a  piece  of  the 
same  dimensions  is  taken  from  another  tree  also  con- 
taining a  bud  and  is  then  placed  on  the  exposed  alburnum 
of  the  former  tree.     The  branch  is  tied  tightly  above 
the  graft  in  order  to  force  the  rising  sap  into  it.     This 
graft  is  practised  both  in  spring  and  autumn. 

(229.)  Effects  of  Grafting.  —  It  does  not  appear  that 
the  graft  produces  any  decided  effect  upon  the  stock,  as 
we  have  already  remarked  (art.  224.) ;  but  in  certain 
instances  the  reverse  seems  unquestionably  to  be  the  case. 
The  influence  is  rather  to  be  attributed  to  some  dif- 
ference in  the  mode  of  growth  in  the  two  subjects, 
than  to  any  dissimilarity  between  the  two  saps  of  the 
stock  and  graft.  Thus  the  lilac  grafted  on  the  ash  be- 
comes a  tree,  and  the  Mespilus  japonica  on  the  haw- 


234  PHYSIOLOGICAL    BOTANY.  FART  II. 

thorn  is  capable  of  sustaining  a  greater  degree  of  cold 
than  it  otherwise  could.  In  some  cases  the  crop  of 
fruit  is  increased,  in  others  it  is  diminished ;  and  some 
plants  which  are  naturally  climbers  become  more 
bushy,  &c. 

(230.)  Development.  —  The  process  of  development 
never  appears  to  be  entirely  stationary  in  the  living 
plant,  not  even  during  winter  when  the  repose  of  vege- 
table life  is  the  most  marked  ;  but  a  slight  progression 
of  the  sap  is  still  going  on  and  a  trifling  enlargement  of 
the  buds  is  gradually  taking  place.  As  the  spring  ad- 
vances the  vital  energies  revive  and  vegetation  seems 
to  awaken  ;  a  sudden  and  rapid  flow  of  the  sap  towards 
the  extremities  takes  place,  and  the  buds  begin  to  de- 
velop with  great  rapidity.  It  is  evident  that  the  in- 
creased temperature  of  the  atmosphere  is  a  stimulating 
cause  in  producing  these  effects ;  and  they  may  be  par- 
tially accelerated  or  retarded  by  artificial  means.  If 
for  instance  a  branch  of  any  tree  growing  in  the  open 
air  is  introduced  into  a  hothouse  during  the  winter, 
the  buds  upon  it  swell  and  put  forth  leaves  although 
the  rest  of  the  tree  continues  bare. 

(231.)  Vernal  Development.  —  The  different  degrees 
of  vigour  with  whicK  buds  burst  forth  in  spring  in 
different  years,  is  probably  regulated  by  the  quantity 
of  nutriment  which  has  been  prepared  and  laid  up  in 
the  stem  during  the  previous  summer ;  so  that  a  more 
rapid  development  will  take  place  after  a  fine  season 
than  after  a  bad  one.  The  extraordinary  activity  which 
vegetation  evinces  in  the  spring,  appears  to  depend  upon 
the  great  freshness  of  those  parts  by  which  the  several 
processes  of  nutrition  are  then  conducted.  New  fibres 
have  been  formed  at  the  roots  during  the  winter,  and 
their  absorbing  powers  now  act  with  the  fullest  energy  ; 
the  young  leaves  have  their  vessels  and  vesicles  quite 
fresh,  and  unobstructed  by  the  deposition  of  those 
earthy  matters  which  are  afterwards  found  in  them 
when  the  exhalation  of  moisture  from  their  surface 
has  been  going  on  for  some  time.  If  a  branch  of  the 


CHAP.  IV.  FUNCTION    OF    NUTRITION.  235 

vine,  sycamore,  and  many  other  trees  be  cut  off  at  this 
period^  the  sap  often  flows  with  sufficient  rapidity  to 
fill  a  bottle  in  a  few  hours.  As  the  summer  advances 
this  action  gradually  diminishes ;  but  in  the  autumn  it 
is  again  partially  renewed. 

(232.)  Autumnal  Development.  —  The  buds  formed 
in  the  axils  of  the  leaves  of  many  plants  have  attained 
by  autumn  a  sufficient  size  to  attract  the  sap  towards 
them,  and  then  they  undergo  a  partial  development, 
which  however  is  soon  checked  on  the  approach  of 
winter.  In  a  few  cases,  as  in  the  Lombardy  poplar,  this 
autumnal  development  is  sufficient  to  furnish  the  ex- 
tremities of  some  branches  with  leaves  which  remain 
for  some  time  after  the  older  leaves  have  fallen.  This 
always  takes  place  in  mulberry  trees  in  those  countries 
where  they  are  stripped  for  the  purpose  of  feeding  silk- 
worms. The  buds  then  become  the  centres  of  attraction 
to  the  rising  sap,  and  soon  developing  furnish  the  trees 
with  fresh  leaves  which  replace  those  that  have  been 
removed.  Such  a  tree  lives  as  it  were  two  years  in 
one,  but  is  always  proportionably  stunted  and  injured  in 
its  growth. 

(233.)  Nutrition  of  Cryptogamic  Plants.  —  The 
higher  tribes  of  cryptogamic  plants  possess  true  roots 
and  leaves ;  and  we  may  suppose  their  function  of  nu- 
trition to  be  carried  on  in  a  way  which  differs  little 
from  that  in  which  it  proceeds  among  phanerogamic 
species.  But  the  manner  in  which  the  lower  tribes 
whose  nutritive  organs  are  not  distinguishable  into  roots 
and  leaves  Complete  the  function  is  in  great  obscurity, 
and  few  attempts  have  hitherto  been  made  to  elucidate 
the  subject. 

(234.)  Parasitic  Plants.  —  There  are  certain  plants 
which  are  without  the  means  of  providing  nutriment 
for  themselves  or  of  elaborating  the  crude  sap  into 
proper  juice  but  obtain  their  nourishment  immediately 
from  other  plants  to  which  they  attach  themselves, 
and  whose  juices  they  absorb.  Such  plants  are  true 
"  Parasites."  They  are  distinguished  from  "  Epi- 


236 


PHYSIOLOGICAL    BOTANY.  PART   II. 


phytes,"  which  also  grow  on  the  stems  and  branches 
of  trees,  but  do  not  penetrate  their  bark  or  absorb 
their  juices.  There  are  a  vast  number  of  cryptogamic 
plants  among  the  ferns,  mosses,  and  lichens,  which 
are  epiphytic,  as  are  also  several  species  of  certain 
phanerogamous  tribes.  This  is  particularly  the  case 
with  those  Orchidete  which  are  termed  "  air  plants," 
whose  roots  imbibe  moisture  from  the  atmosphere  as 
we  noticed  in  art.  39.  Among  the  true  parasites, 
some  cryptogamic  species  live  wholly  within  the  plant 
and  may  be  considered  analogous  to  intestinal  worms ; 
whilst  such  as  are  external  (both  cryptogamic  and 
phanerogamic)  may  be  likened  to  the  ticks  and  lice 
which  infest  animals.  Different  species  are  parasitic 
on  different  parts  of  plants  as  on  the  root,  stem,  or 
leaves.  Some  of  the  cryptogamic  species  are  highly 
destructive  to  our  crops,  as  those  which  cause  the 
"  smut"  and  "  rust"  in  corn.  It  is  difficult  to  as- 
certain in  what  manner  the  impalpable  powder  into 
which  their  sporules  disperse  is  introduced  within  the 
very  substance  of  the  plants  attacked  ;  but  it  seems  not 
improbable  that  it  may  be  imbibed  with  water  by  the 
roots.  Some  suppose  it  may  be  introduced  through  the 
stomata,  but  this  is  not. so  plausible  an  opinion  as  the 
former.  All  the  phanerogamic  species  except  those  of 
the  natural  order  Loranthea?  (to  which  the  common 
misseltoe  belongs)  are  destitute  of  green  leaves ;  these 
organs  appearing  only  in  the  form  of  small  brown 
scales  without  stomata,  and  incapable  of  performing 
the  functions  of  respiration.  Hence  these  plants  have 
a  livid  and  discoloured  appearance.  They  are  furnished 
with  suckers  which  penetrate  the  bark  and  absorb  the 
proper  juices  of  the  plants  on  which  they  grow,  and 
which  are  always  dicotyledonous.  It  is  remarkable, 
that  the  flower  of  largest  dimensions  hitherto  discovered 
is  a  parasite  of  this  description.  This  is  the  Rajfletia 
Arnold!  (Jig.  159-)  whose  corolla  measures  a  yard  in 
diameter  and  is  fifteen  pounds  in  weight.  It  grows  in 
the  island  of  Sumatra  upon  the  woody  stems  and  roots 


CHAP.  IV. 


FUNCTION    OF    NUTRITION. 


237 


of  a  trailing  plant  (Cissus  angustifolia).     In  our  own 
country  the  genera  Orobanche,  Cuscuta,  Lathraea,  Mono- 


tropa,  and  Epipactis  afford  us  leafless  parasitic  species. 
These  do  not  appear  to  be  very  injurious  to  any  woody 
plants  which  they  attack;  but  such  as  grow  on  herba- 
ceous species  are  highly  mischievous.     The  species  of 
"  Cuscuta"  are  among  the  most  curious  of  this  kind. 
When  they  first  germinate  they  have  a  stem  formed 
like  a  delicate  thread,  which  is  leafless  and  soon  coils 
itself  round  the  stem  of  some  plant  growing  in  the 
neighbourhood.     To  this  it  adheres  by  means  of  suck- 
ers formed  of  wart-like  protuberances  at  intervals  along 
its  stem.     When  it  has  obtained  firm  hold  of  the  plant 
round    which   it  has  coiled,   its  root   decays  and  the 
stem  ceases  to  have  any  connection  with  the  soil,  but 
vegetates  and  produces  flowers  at  the  expense  of  the 
proper  juices  of  the  plant  to  which  it  is  attached.     The 
common  misseltoe  and  other  Loranthese  being  furnished 
with  green  leaves  are  able  to  elaborate  crude  sap  into 
proper  juice ;    but    as  they  are  destitute  of  any  true 
root  they  possess  the  property  of  penetrating  through' 
the  bark  of  the  trees  to  which  they  are  attached,  and 
of  fixing  the  base  of   their  stems  into  the  wood  be- 
neath.    Thus  they  absorb  the  rising  sap  in  its  progress 
towards  the  leaf.      It  is  asserted  that  a  branch  of  mis- 
seltoe when  placed  in  water  has|po  power  of  absorbing 
this  fluid,  but  that  when  the  branch  to  which  it  is  still 


~.'>'S  PHYSIOLOGICAL    BOTANY.  PART   II. 

attached  is  immersed,   then   the   water  is  readily  ab- 
sorbed and  penetrates  into  the  misseltoe  itself. 

(235.)  Duration  of  Life.  —  Some  plants  exist  only 
for  a  few  days  or  weeks,  others  for  about  a  twelve- 
month or  two  years,  and  others  again  for  a  very  length- 
ened   period.      Some  when   they    have   once   flowered 
and  perfected  their  seeds  immediately  die  ;  and  these 
in   consequence  are  termed  "  Monocarpeans."     Others 
annually  produce  a  fresh  crop  of  seeds,  and  are  termed 
"  Polycarpeans."    The  difference  between  them  is  more 
apparent  than  real ;  for  although  in  the  ordinary  course 
of   things    the    Monocarpeans    soon    die,    the    natural 
period  of  their  existence  may  be  considerably  extended 
beyond  the  usual  period,  by  merely  preventing  the  form- 
ation  or  development  of  their  seed.      This  shows  us 
that  it  was  the  effort  of  the  plant  to  form  seed  which 
checked   the  functions  of  nutrition,    and  not  that  the 
period  of  its  existence  was  necessarily  so  limited  as 
its  early  death  would  seem  to  indicate.     Some  plants 
which  are  annuals  in  our  stoves  are  perennials  in  their 
native  country.     The  American  aloe  (Agave  americann) 
is  a  striking  example  of  a  plant,  the  ordinary  period 
of  whose  existence  may  be  very  considerably  extended 
by  preventing  its  flowers-  from  developing.     In  its  na- 
tive climate  it  comes  into  blossom  when  four  or  five 
years  old,  and  afterwards  dies  ;  but  in  our  greenhouses 
it   continues  to  vegetate  for  fifty  or  a  hundred   years 
without  showing  any   symptoms  of  putting   forth  its 
flowers.     If  then  we  make  abstraction  of  those  checks 
which  are  given  to  the  vital  function  by  the  process  of 
fructification,  and  which  do  not  appear  formidable  in 
any  degree  to  the  life  of  perennial  species,  we  might 
imagine  it  possible  for  plants  to  continue  vegetating  for 
a  much  longer  period  than  they  naturally  would ;  and 
that  the  life  of  some  might  be  extended  indefinitely, 
provided  the  external  or  accidental  causes  which  tend  to 
produce  decay  and  death  were  continually  removed.     By 
this  we  mean,  that   certain  plants  never  die  from  the 
effects  of  old  age  in  the  same  sense  in  which  we  apply 


CHAP.  IV.  FUNCTION    OP    NUTRITION.  239 

this  term  to  animals,  but  are  as  well  qualified  to  perform 
all  their  functions  with  vigour  and  precision  after  they 
have  existed  for  many  years  as  when  they  were  young. 
The  causes  why  such  plants  perish  are  not  merely  those 
common  accidents  which  result  from  the  influence  of 
the  weather,  the  ravages  of  animals,  and  the  like  ex- 
ternal accidents,  but  likewise  the  continually  increasing 
difficulty  they  meet  with  in  procuring  sufficient  nutri- 
ment. The  increasing  length  of  their  branches  affords 
greater  hold  to  the  wind,  and  renders  them  proportion- 
ably  more  liable  to  be  broken  off  and  rottenness  to  be 
introduced  in  consequence.  But  in  speaking  of  the  dura- 
tion of  life  in  plants,  we  ought  to  have  some  definite 
notion  of  what  we  mean  by  a  vegetable  individual. 

(236.)  Individuality  of  elementary  Organs.  —  Some 
persons   consider  every   vesicle    and   other  elementary 
organ  of  which  plants  are  composed,  to  possess  a  dis- 
tinct and  separate  existence  of  its  own ;  and  therefore 
they  look  upon  every  specimen  as  an  aggregate  of  ve- 
getable individuals,  closely  packed  together  and  con- 
stituting a  compound  individual.     The  main  facts  upon 
which  this  singular  hypothesis  reposes  are  the  follow- 
ing. —  There  are  certain  plants  among  the  lowest  tribes 
which  consist  of  only  one  or  at  most  of  very  few  distinct 
vesicles,  which  indicates  the  possibility  of  a  single  de 
tached   vesicle   existing  as    a  separate    individual.     It 
may  be  observed  however  that  these  plants  are  among 
some  of  the  most  minute  objects  of  organised  matter, 
and  that    we  know  very  little  of  their  actual  history 
and  scarcely  any  thing  of  their  physiology.     Another 
argument  in  favour  of  the  individuality  of  each  vesicle 
is  deduced  from  a  belief  that  the  cellular  tissue  in  every 
part  of  the  vegetable  structure  is  capable  of  producing 
buds  or  gems,  each  of  which  is  able  to  exist  separate 
from  the  plant  on  which  it  was   developed,  and   by 
proper  treatment  to  become  an  individual  plant  similar 
to  its  parent.      M.  Turpin    has    recorded    a    very  in- 
teresting and  remarkable  instance  of  this  description, 
where  a  leaf  of   an  Ornithogalum   after   it  had   been 


£40  PHYSIOLOGICAL    BOTANY.  PART   II. 

placed  between  some  sheets  of  paper  for  the  purpose  of 
being  dried  for  the  herbarium,  threw  out  a  multitude 
of  minute  bulbs  from  all  parts  of  its  surface.  He  con- 
cludes that  each  separate  bulb  was  only  a  more  deve- 
loped state  of  a  single  cell,  and  hence  lie  would  draw 
die  inference  that  each  cell  must  be  a  distinct  individual. 
But  if  this  conclusion  were  admitted,  the  same  thing 
might  be  asserted  of  every  organ  which  produces  an 
embryo  of  any  kind.  It  would  perhaps  have  been  more 
logical  to  have  considered  each  cell  as  an  embryonic 
sac,  capable  of  originating  a  distinct  individual  of  the 
same  complicated  form  and  structure  of  which  it  was 
itself  only  a  subordinate  organ.  If  each  vesicle  were 
an  individual  plant,  its  offspring  if  we  argue  from 
analogy  ought  to  resemble  itself,  and  to  be  a  vesicle 
and  not  a  bud  with  a  complicated  arrangement  of 
parts  representing  in  miniature  the  several  organs  of  the 
entire  plant.  This  hypothesis  of  the  individuality  of 
each  vesicle  according  to  our  acceptance  of  the  term 
appears  to  be  untenable. 

(237-)  Individuality  of  Buds.  —  A  second  hypo- 
thesis considers  each  bud  as  a  separate  individual,  pos- 
sessed of  a  vitality  independent?  of  that  of  the  whole 
plant.  This  view  is  considerably  supported  by  the 
great  analogy  which  exists  between  the  structure  of 
a  plant  considered  in  this  light  and  that  of  some  of 
the  lower  tribes  of  animals.  The  reproduction  of  po- 
lypi is  effected  by  means  of  little  bud-like  protuber- 
ances on  their  surface,  which  having  attained  a  cer- 
tain degree  of  development  quit  the  body  of  the  parent 
and  become  separate  individuals.  Thus  also  if  the 
buds  on  the  stem  of  a  tree  are  removed  and  treated 
with  proper  precaution,  they  will  grow  and  become 
trees  themselves.  Some  buds  are  detached  by  a  natural 
process,  and  the  plant  is  ordinarily  propagated  by  this 
means.  Thus  the  death  and  decay  of  the  orange  lily 
(Liliinii  InUiifi-nnn}  causes  the  little  bulbs  which  are 
produced  in  the  axils  of  its  leaves  to  detach  from  the 
stem  ;  and  these  upon  falling  to  the  ground  become 


CHAP.  IV.  FUNCTION    OF    NUTRITION.  241 

so  many  individual  plants.  The  runners  of  the  straw- 
berry, decay  when  the  buds  at  their  extremities  have 
obtained  a  firm  root  in  the  ground,  and  thus  the 
parent  plant  becomes  separated  from  the  numerous 
progeny  scattered  around  it.  But  the  closest  ana- 
logy between  a  plant,  considered  as  an  aggregate 
of  individuals,  and  any  living  animal,  is  that  which 
exists  in  certain  marine  tribes  still  lower  in  the  scale  of 
organisation  than  the  polypi  to  which  we  have  referred. 
A  number  of  these  animals  are  grafted  and  blended  to- 
gether into  a  compound  mass,  in  which  each  still 
possesses  its  separate  individuality,  and  is  capable  of 
existing  in  a  detached  form.  It  is  by  the  joint  labours 
of  these  compound  animals  that  a  coral  reef  is  raised 
from  the  bottom  of  deep  seas  to  the  surface.  The 
innermost  and  oldest  parts  of  the  reef  consist  of  the 
untenanted  cells  of  those  animals  which  have  died, 
whilst  a  fresh  crop  is  continually  developing  towards 
the  surface.  Thus  also  in  a  tree,  the  oldest  parts  of 
the  trunk  and  branches  is  composed  of  matter  in  a  dead 
or  dying  state,  and  it  is  the  newly  developed  portions 
alone  which  contain  the  living  materials  capable  of  per- 
forming the  functions  of  vegetation.  As  these  latter 
portions  originate  from  successive  crops  of  fresh  buds, 
the  analogy  alluded  to  is  very  complete. 

It  has  been  further  observed,  that  if  each  bud  be  not 
a  separate  individuality,  we  might,  by  grafting  several 
buds  on  the  same  stock,  produce  a  tree  composed 
of  a  multitude  of  species ;  which  would  be  an  ab- 
surdity. 

(238.)  Individuality  of  Plants. — Any  cutting,  layer, 
or  bud,  which  has  been  detached  from  a  plant,  and 
grown  in  an  isolated  state,  always  retains  the  exact  pe- 
culiarities of  the  individual  plant  from  which  it  was 
obtained ;  but  a  seedling.,  raised  from  the  same  plant, 
will  frequently  deviate  more  or  less  from  the  original 
type,  and  present  us  with  certain  peculiarities  of  its 
own.  This  fact  appears  to  favour  another  hypothesis, 


24-2  PHYSIOLOGICAL    BOTANY.  PART  II. 

distinct  from  the  two  already  explained,  which  con- 
siders the  vegetable  individual,  in  the  most  usual  ac- 
ceptation of  the  term,  as  an  entire  plant  which  has 
originated  from  the  development  of  a  single  seed.  But 
this  definition  of  an  individual  involves  the  seeming 
absurdity,  that  an  organised  being  may  consist  of  several 
detached  portions,  each  of  which  may  exist  apart  from 
the  others.  Thus  a  cutting  from  a  tree  is  a  part  of 
the  individual  from  whence  it  was  taken ;  and  though 
it  may  also  become  a  tree,  it  is  no  more  than  the 
developed  state  of  a  portion  of  the  former.  Since  all 
the  weeping  willows  in  Europe,  for  instance,  are  said 
to  have  originated  from  cuttings  taken  from  a  single 
tree;  according  to  this  hypothesis,  there  is  no  more  than 
one  weeping  willow  in  Europe,  and  that  also  can  only 
be  a  portion  of  one  which  may  be  still  growing  in  Asia. 
But  whatever  be  the  speculations  of  physiologists,  we 
must  admit  the  truth  of  the  remark,  "  that  in  ordinary 
parlance  we  require  some  more  precise  mode  of  express- 
ing ourselves,  when  we  would  speak  of  the  individual 
weeping  willow  which  shades  the  grave  of  Napoleon 
at  St.  Helena,  as  being  the  same  plant  which  decorates 
the  tomb  of  J.  J.  Rousseau  at  Ermenonville,  although 
each  may  probably  have  originated  from  the  same  em- 
bryo." But  if  we  cannot,  in  the  present  state  of  know- 
ledge, exactly  determine  the  requisites  which  constitute 
the  individuality  of  vegetables,  and  may  possibly  con- 
sider as  a  separate  existence  what  in  reality  constitutes 
the  duration  of  a  succession  of  individuals  ;  yet  whilst 
we  choose  to  put  such  a  limitation  to  our  ideas,  we  may 
speak  of  the  duration  of  life  in  a  plant  as  the  real  ex- 
istence of  an  individual,  whether  this  plant  may  have 
originated  from  a  seed,  bud,  cutting,  or  from  any  other 
mode  by  which  it  could  be  propagated. 

(239.)  Longevity  of  Trees. — When  we  consider  each 
separate  plant  as  an  individual  being,  there  is  this  ma- 
nifest and  important  distinction  between  the  mode  in 
which  its  life  is  maintained,  and  that  in  which  it  is 
continued  in  any  animal ;  —  the  plant  annually  renews 


CHAP.  IV.       FUNCTION  OF  NUTRITION.  243 

all  the  different  organs  by  which  its  various  functions 
are  carried  on,  and  which  are  consequently  as  vigorously 
performed  in  the  oldest  tree  as  in  the  youngest.  But 
although  the  organs  which  every  animal  possesses  are 
continually  sustaining  a  certain  degree  of  repair,  yet 
they  are  gradually  wearing  out,  or  ultimately  become 
choked  up  in  old  age ;  and  thus  a  definite  period  is 
naturally  allotted  to  the  existence  of  the  individual 
from  this  cause  alone.  But  the  period  of  life  to  which 
plants  attain  is  no  way  dependent  on  these  conditions ; 
but  is  regulated  by  a  combination  of  external  causes 
and  internal  influences  of  a  very  different  kind.  Those 
trees  are  most  likely  to  endure  the  longest,  which  grow 
the  slowest,  and  which  attain  the  least  height  in  pro- 
portion to  the  diameter  of  their  trunks  ;  and  the  anti- 
quity of  some  trees  of  this  description  appears  to  be 
prodigiously  great. 

(240.)  Estimation  of  the  Age  of  Trees.  —  It  is  only  the 
ages  of  Dicotyledons  which  can  be  ascertained  with  any 
degree  of  certainty.  In  Monocotyledons  the  diameter  of 
the  tree  is  not  enlarged  by  annual  additions  of  fresh 
cylinders  of  wood,  as  is  the  case  with  the  former,  whose 
ages  may  be  accurately  ascertained  by  inspecting  a 
transverse  section  of  their  trunks.  By  placing  a  strip 
of  paper  upon  this  section  from  the  centre  to  the  cir- 
cumference, and  marking  it  along  the  edge  where  it 
intersects  the  concentric  circles  on  the  section,  a  con- 
venient register  may  be  obtained,  not  only  of  the  ages 
of  different  trees,  but  of  their  comparative  rates  of  in- 
crease at  different  periods  of  their  growth.  As  the  pith 
is  seldom  exactly  in  the  centre  of  the  tree,  the  best  mode 
of  obtaining  the  average  annual  growth  is  by  measuring 
the  circumference  of  the  trunk,  and  then  calculating  for 
the  mean  thickness  of  each  layer  by  dividing  the  semi- 
diameter  by  the  whole  number  of  layers.  These  mea- 
surements should  be  made  at  a  little  distance  above  the 
soil,  generally  about  four  feet,  where  the  trunk  is  free 
from  protuberances  and  of  an  average  thickness. 
K  2 


244  PHYSIOLOGICAL    BOTANY.  PART  II. 

Where  a  complete  section  cannot  be  obtained,  a  la- 
teral incision  may  be  made,  and  by  counting  the  number 
of  rings  in  the  portion  exposed,  an  approximation  may 
be  made  to  the  whole  number ;  care  being  taken  to  make 
allowance  for  the  more  rapid  increase  of  the  trunk  in 
the  early  stages  of  its  growth. 

In  other  cases,  some  judgment  may  be  formed  of  the 
ages  of  very  old  trees,  by  ascertaining  the  rate  at  which 
others  of  the  same  species  have  increased  within  known 
intervals  of  time,  and  by  then  applying  the  rule  thus 
obtained  to  the  tree  in  question.  The  observer  must 
be  cautious  when  he  is  examining  very  large  trees,  lest 
he  should  be  deceived  by  several  trunks  having  become 
blended  into  one. 

('21 1.)  Examples  of  Longevity  in  Trees.  —  As  ex- 
amples of  the  mode  in  which  approximations  have  been 
made  towards  the  ages  of  very  old  trees,  we  may  men- 
tion certain  individuals  of  the  lime,  yew,  and  baobab. 

1 .  The  Lime.  —  A  tree  of  this  description  was 
planted  at  Fribourg  in  Switzerland,  on  the  day  when 
the  news  of  the  victory  of  Moral  arrived,  in  1476. 
In  1831,  this  tree  was  13  feet  [)  inches  in  circum- 
ference, which  gives  l£  lines  in  diameter  per  annum 
as  the  mean  rate  of  its  increase.  But  as  this  tree 
is  confined  in  a  town,  we  may  allow  2  lines  per  an- 
num as  the  rate  of  increase  for  other  trees  more  freely 
exposed,  whose  ages  we  may  wish  to  ascertain.  Now, 
there  is  a  lime  near  Neustadt  on  the  Kocher,  in  the 
kingdom  of  Wurtemberg,  which  was  of  large  dimen- 
sions in  the  year  1229  ',  since  it  is  stated  in  ancient 
records,  that  the  city  was  rebuilt  after  its  destruction 
in  that  year,  "  near  the  great  tree."  A  poem,  bearing  the 
date  of  1408,  describes  this  tree  as  having  its  branches 
at  that  time  supported  by  (>7  columns.  Evelyn,  in 
l6'6'4,  mentions  the  number  of  columns  then  to  have 
been  82  ;  and  in  1831  they  had  increased  to  106'. 
At  this  period,  the  trunk  was  37  feet  6'  inches  and 
.'>  lines  (\Vurtemberg  measure)  in  circumference,  be- 
tween 5  and  6  feet  from  the  ground.  This,  upon  an 


CHAP.  IV.  FUNCTION    OP    NUTRITION.  245 

estimate  of  2  lines  per  annum  for  its  growth,  would 
make  it  to  be  between  700  and  800  years  old.  But  as 
it  is  certain  that  it  has  not  increased  for  some  centuries 
at  so  rapid  a  rate,  it  may  fairly  be  considered  as  above 
1000  years  old. 

2.  The  Yew.  —  M.  De  Candolle  ascertained,  by  in- 
specting three  yews  which  had  been  felled,  that  they 
had  grown  at  the  rate  of  1  line  in  diameter  per  annum 
during  150  years;  and  that  one  of  them  had  in- 
creased somewhat  less  rapidly  during  the  succeeding 
century.  The  rate  thus  obtained,  he  applies  to  the 
growth  of  some  English  and  Scotch  yews,  whose  di- 
mensions were  given  by  Evelyn  in  1666,  and  Pennant 
in  1770.  Among  these,  is  a  yew  which  the  former 
describes  as  growing  in  the  churchyard  of  Braburn  in 
Kent,  which  was  58  feet  9  inches  in  circumference,  or 
2820  lines  in  diameter  ;  indicating  by  the  above  rule,  as 
many  years  for  its  age.  If  now  living,  this  tree,  according 
to  such  an  estimate,  would  be  more  than  3000  years  old. 
It  may  be  doubted  from  the  following  account,  whether 
the  rate  at  which  the  yew  increases  in  England  is  not 
more  rapid  than  in  France.  There  are  two  fine  healthy 
trees  of  this  kind  in  the  churchyard  at  Basildon  in 
Berkshire,  which,  according  to  the  parish  register,  were 
planted  in  17^6.  In  1834  they  were  very  nearly  of  the 
same  dimensions,  and  the  largest  measured  9  feet  3  inches 
in  circumference  at  4  feet  from  the  ground  :  this  gives 
444  lines  for  its  diameter,  or  4  lines  per  annum  as  the 
mean  rate  of  increase  for  a  century.  It  appears  how- 
ever by  some  other  entries  in  the  same  register,  that 
the  tree  had  grown  more  rapidly  during  the  former 
half  of  this  period  than  it  has  done  latterly.  Taking 
these  data  as  a  guide  for  estimating  the  ages  of  some 
old  yew  trees  in  the  churchyards  of  two  neighbouring 
parishes,  it  would  seem  that  De  Candolle's  calculations 
should  be  reduced  by  about  one  third,  in  order  to  ob- 
tain a  more  correct  approximation  than  that  which  he 
has  given  for  trees  of  this  description.  It  was  found, 
B  3 


246  PHYSIOLOGICAL    BOTANY.  PART  II. 

for  instance,  that  the  layers  of  wood  at  different  depths, 
in  a  hollow  yew  tree  at  Cholsey,  Berkshire,  varied  con- 
siderably in  thickness  ;  and  that  some  of  those  which 
had  been  very  recently  deposited  were  2£  lines,  whilst 
others,  which  were  more  than  a  century  older,  were 
only  half  a  line  in  thickness.  This  tree  is  between  14 
and  1 5  feet  in  circumference  ;  and  there  is  another  in 
the  churchyard  of  the  neighbouring  parish  of  Aldworth, 
which  is  more  than  19  feet  in  circumference,  which, 
estimated  by  De  Candolle's  rule,  ought  to  be  above  900 
years  old ;  but  may  rather  be  considered  as  nearer  ()00 
years. 

3.  The  Baobab  (Adansonia  digitata.)  —  The  last  ex- 
ample which  we  shall  select,  is  that  of  the  enormous 
baobabs,  or  monkey-bread  trees  of  Senegal,  whose  great 
ages  Adanson  has  attempted  to  estimate  from  the  fol- 
lowing data. 

Thevet  mentions,  in  his  "  Voyages  aux  Isles  Ant- 
arctikes,"  in  1555,  some  "  beaux  arbres,"  which  Adan- 
son found  to  be  6  feet  in  diameter  in  1749-  He 
judged,  from  Thevet's  expression,  that  these  trees  could 
not  have  been  less  than  4  feet  in  diameter  at  the  time 
when  he  saw  them  ;  and  this  opinion  was  strengthened 
by  observing  the  extent  to  which  the  letters  of  certain 
inscriptions  upon  them  had  become  deformed,  and  which 
inscriptions  were  dated  from  the  fourteenth  and  fifteenth 
centuries.  Allowing  therefore  that  these  trees  had  in- 
creased 2  feet  in  diameter  during  two  centuries,  he 
estimated  their  age  at  (>00  years.  But  there  are  trees 
of  this  species  which  are  30  feet  in  diameter;  and  these, 
at  the  above  rate,  would  be  3000  years  old.  But 
if  the  age  of  these  trees  be  calculated  upon  mathematical 
principles,  it  should  seem  that  they  must  be  much 
older  even  than  this.  Thus,  Adanson  having  ascer- 
tained that  a  tree  of  1  year  old  was  5  feet  in  height 
and  1  inch  in  diameter,  and  a  tree  of  30  years  was 
22  feet  high  and  2  feet  in  diameter,  he  applied  these 
data  to  construct  a  table,  which  bhould  give  the  heights 


CHAP.  IV.  FUNCTION    OP    NUTRITION.  24-7 

and  diameters  of  trees  from  1  year  to  5000  years  old. 
From  this  we  shall  make  the  following  extract :  — 

Age.  Height.  Diameter. 

1  year.  5  feet.  T^  feet. 

30  22  2 

100  29  4 

210  40          6 

660  53  11 

1050  58|  14 

2800  67  20 

5150  73  30 

It  will  be  observed,  according  to  this  table,  that  the 
ages  of  trees  whose  diameters  are  6  feet  would  be  no 
more  than  210  years;  whereas  it  was  satisfactorily 
shown  that  those  which  Thevet  had  described  must  at 
least  be  600.  So  far  then  this  table  would  underrate 
rather  than  exaggerate,  the  ages  of  these  trees.  It 
must  be  confessed  that  the  estimate  given  for  those  of 
the  largest  dimensions  is  too  startling  to  be  received 
with  implicit  confidence ;  and  that  we  need  further 
evidence  to  satisfy  us  that  these  calculations  are  good 
approximations  to  the  truth.  Be  this  as  it  may,  it 
seems  to  be  sufficiently  proved  that  the  world  is  pos- 
sessed of  living  monuments  of  antiquity,  whose  ages 
surpass  those  of  the  most  stupendous  fabrics  which 
the  labour  of  man  has  reared  to  perpetuate  the  memory 
of  his  folly  or  his  superstition. 

(242.)  Tables  of  Longevity  of  certain  Trees 

From  various  sources  of  information  —  some  the  re- 
sults of  direct  observation,  others  the  approximate  values 
obtained  from  the  kind  of  inferences  which  we  have 
referred  to  —  De  Candolle  has  furnished  us  with  the 
following  list  of  remarkable  trees,  whose  ages  he  con- 
siders that  he  has  succeeded  in  ascertaining  with  some 
degree  of  precision :  — 

R  4 


248 


PHYSIOLOGICAL    BOTANY. 


1.  Elm 

2.  Cypress 

3.  Cheirostemon 

4.  Ivy 

5.  Larch 

6.  Orange     - 

7.  Olive 

8.  Oriental  plane 
9-  Cedar 

JO.  Lime 
1  I .   ( )ak     - 
J2.  Yew 
IS.  Baobab 
14.  Taxodium 


Years. 

335. 

350  (about). 

400  (about). 

450. 

576. 

630. 

700  (about). 

720  (and  upwards). 

800  (about). 
1076—1117. 

810—1080—1500. 
1214—1458—2588—2820. 
51. ">0  (in  1757). 
4000  to  6000  (about). 


CHAP.  V. 

FUNCTION  OP  REPRODUCTION Periods  1,  2,  3. 

PROPAGATION      (243.).  ORIGIN     OF      FLOWER-BUDS     (245.).  

FLOWERING     (246.). FUNCTIONS    OF    THE    PERIANTH    ('252.). 

DEVELOPMENT       OF       CALORIC        (254.).    FERTILISATION 

(255.). FORMATION     OF     POLLEN      (261.).   MATURATION 

(265.).  FLAVOUR    AND    COLOUR    OF    FRUIT    (273.). 

(243.)  Propagation. —  THERE  are  two  distinct  modes, 
according  to  which  the  propagation  of  the  vegetable  species 
is  naturally  secured,  viz.  "  subdivision"  and  "reproduc- 
tion." In  the  first  the  individual  plant  may  be  subdivided 
into  several  parts,  each  of  which  when  detached  from  the 
parent  stock  is  capable  of  existing  as  a  separate  individual. 
A  familiar  example  of  this  mode  of  propagation  may 
be  seen  in  the  common  strawberry,  to  which  we  have 
alluded  in  art.  237.  It  is  very  common  to  find  elms, 
poplars,  and  other  trees  throwing  up  suckers  from  their 


CHAP.  V.  FUNCTION    OP    REPRODUCTION.  249 

roots  at  a  distance  from  the  trunk,  all  of  which  are 
capable  of  becoming  so  many  distinct  trees,  under  fa- 
vourable circumstances.  Man  has  availed  himself  of 
this  property,  to  extend  the  means  which  nature  has 
provided  for  the  propagation  of  the  species ;  and  by 
placing  cuttings,  slips,  and  buds  under  proper  treat- 
ment, he  forces  them  to  throw  out  roots ;  or  he  grafts 
them  on  other  stems,  where  they  adhere  and  develop 
as  so  many  separate  and  independent  individuals.  The 
process  by  which  any  detached  portion  of  a  plant  be- 
comes a  distinct  individual,  similar  to  that  from  which 
it  was  derived,  depends  upon  the  power  it  possesses 
of  reproducing  those  organs  or  parts  in  which  it  may 
be  defective.  Thus  the  ascending  organs  develop  roots; 
and  these  again,  produce  buds  from  which  the  ascend- 
ing organs  proceed. 

(244.)  Reproduction.  —  But  although  the  propa- 
gation of  many  plants  may  be  effected  by  the  means 
here  alluded  to,  and  although  some  species  are  more 
frequently  and  readily  propagated  by  subdivision,  than 
by  the  method  which  we  are  about  to  describe,  yet 
the  greater  number  of  plants,  and  at  least  all  those 
which  bear  flowers,  secure  the  continuation  of  their 
species  by  a  distinct  process,  of  a  very  different  nature. 
This  constitutes  the  function  of  "  reproduction,"  pro- 
perly so  called ;  which  consists  in  the  formation  of 
seeds,  containing  the  germs  of  future  individuals.  This 
function  of  reproduction  is  to  the  species,  what  life  is 
to  the  individual  —  a  provision  made  for  its  continued 
duration  on  the  earth.  The  more  minute  details  of  the 
process  by  which  the  function  of  reproduction  is  carried 
on,  and  the  germ  or  "  embryo"  of  the  future  plant  be- 
comes generated  in  the  seed,  were  never  understood  till 
of  late  years;  nor  are  they  even  yet  so  completely 
ascertained  as  we  may  one  day  hope  to  find  them. 
The  general  function  of  reproduction  may  be  consi- 
dered as  completed  in  five  different  periods ;  much  in  the 
same  manner  as  we  ascribed  seven  periods  or  processes 
to  the  function  of  nutrition. 


250  PHYSIOLOGICAL    BOTANY.  PART  II. 

(245.)  Origin  of  Flower-buds.  —  We  find  some  buds 
capable  of  developing  into  brandies  and  leaves,  and  others 
destined  to  produce  flowers :  but  it  is  beyond  the  limits 
of  our  present  faculties  to  ascertain  by  what  law  they  are 
thus  specially  inclined,  in  their  nascent  state,  to  as- 
sume the  one  rather  than  the  other  of  these  characters. 
That  leaf-buds  and  flower-buds  have  fundamentally  the 
same  origin,  is  apparent  from  an  extensive  review  of 
those  singular  deviations  from  the  ordinary  productions 
of  nature,  which  are  termed  Monstrosities,  as  we  have 
already  stated  in  art.  85.  The  organs  developed  from 
a  flower-bud  serve  a  temporary  purpose,  of  a  very  dif- 
ferent description  from  that  assigned  to  those  which 
are  developed  from  a  leaf-bud  ;  and  when  that  purpose 
is  completed,  they  soon  decay.  The  causes  which  pre- 
dispose the  plant  to  produce  a  flower-bud  rather  than  a 
leaf -bud  must  begin  to  operate  long  before  we  are  able 
to  detect  any  traces  of  the  bud  itself ;  and  from  the  very 
earliest  period  that  we  can  perceive  its  existence,  it  has 
already  assumed  the  peculiar  characters  with  which  it  is 
destined  to  develop.  It  is  asserted  that  in  some  palms, 
the  flower-buds  which  are  to  produce  flowers  during 
seven  successive  years  may  all  be  detected  at  one  time 
in  the  inner  parts  of  the.  stem.  We  may:further  notice 
the  manner  in  which  the  Lemna?  (Duckweeds)  are  pro- 
pagated, as  affording  a  striking  argument  in  favour  of 
the  common  origin  of  all  buds.  Each  plant  is  a  little 
green  lenticular  and  frond-like  mass,  which  produces  a 
long  pendent  root  from  its  under  surface  (fig.  31.). 
Its  usual  mode  of  propagation  is  by  a  bud  or  gem,  which 
makes  its  appearance  on  the  edge  of  the  frond,  and 
when  fully  developed,  detaches  itself  and  becomes  a 
separate  individual.  In  some  seasons  however,  and 
under  circumstances  suitable  to  such  an  event,  these 
plants  put  forth  diandrous  flowers,  which  originate 
precisely  in  those  spots  where  the  gems  are  usually  de- 
veloped. 


CHAP.   V.  FUNCTION    OF    REPRODUCTION.  251 


FIRST    PERIOD    OF    REPRODUCTION. 

(246.)  Flowering.  —  When  the  flower-bud  is  dis- 
tinguishable, the  parts  of  which  the  .flower  is  com- 
posed are  in  a  very  rudimentary  state.  The  perianth 
especially,  continues  for  some  time  very  small  in  pro- 
portion to  the  anthers,  which  are  more  early  deve- 
loped. A  gradual  enlargement  of  all  the  parts  of  the 
flower  continues  to  take  place  till  the  period  of  ex- 
pansion arrives.  This  expansion  may  be  likened  to 
the  age  of  puberty  in  animals ;  and  when  completed, 
terminates  the  first  period  of  the  function  of  reproduc- 
tion. In  herbaceous  plants,  it  is  very  frequently  effected 
the  same  year  in  which  they  have  germinated  from  the 
seed ;  but  there  are  some  which  do  not  flower  until  the 
second  year,  and  others  not  until  later.  Some  under- 
shrubs  also  begin  to  flower  within  the  year ;  others 
not  until  after  a  second,  third,  or  fourth  has  elapsed. 
Shrubs  and  trees,  with  very  few  exceptions,  never 
flower  before  the  second  or  third  year  at  least,  and 
very  many  of  them  attain  a  considerable  age  before 
they  show  any  symptom  of  flowering.  It  may  be  as- 
serted of  trees,  almost  as  a  general  rule,  that  the  period 
when  they  commence  flowering  is  protracted  in  pro- 
portion to  the  slowness  of  their  growth. 

(24-7.)  Stimulants  to  Inflorescence.  —  Although  we 
cannot  comprehend  the  primary  causes  upon  which 
the  formation  of  the  flower-bud  depends,  we  can  con- 
nect several  phenomena  which  attend  its  development 
with  the  operation  of  specific  influences.  For  instance, 
an  increase  of  temperature  accelerates,  and  a  dimi- 
nution retards  the  period  of  flowering ;  and  accord- 
ing to  the  nature  of  the  individual,  these  causes  also 
operate  in  predisposing  its  buds  to  assume  the  cha- 
racter of  leaf-buds  or  flower-buds.  Many  plants,  when 
removed  from  a  warm  climate  to  a  cold  one,  or  vice 
versa,  will  flourish  without  ever  producing  flowers ;  and 
others  which  are  able  to  flower,  never  perfect  their 


252  PHYSIOLOGICAL    BOTANY.  PART  II. 

fruit.  A  superabundance  of  moisture  retards  the  flower- 
ing, and  also  affects  the  formation  of  flower-buds  ;  and 
it  is  generally  observable,  that  where  the  functions  of 
nutrition  are  forced  into  a  state  of  unnatural  excite- 
ment, the  plant  has  an  increased  tendency  to  produce 
leaf-buds  rather  than  flower-buds.  Hence  it  is  re- 
marked, that  when  the  fruit  trees  of  temperate  climates 
are  transplanted  to  the  warm  and  moist  regions  of  tin- 
tropics,  they  frequently  become  barren,  although  they 
continue  to  push  their  shoots  with  vigour.  To  coun- 
teract this  effect,  a  practice  is  resorted  to  in  the  East 
Indies,  of  laying  bare  some  part  of  the  roots,  which 
checks  the  growth,  causes  the  leaves  to  fall,  and  thus 
predisposes  the  plant  to  form  flower-buds  instead  of 
leaf- buds.  At  the  period  of  flowering,  the  vital  energies 
of  the  plant  seem  to  be  called  into  extraordinary  activity, 
and  the  organs  of  inflorescence  are  developed  with 
great  rapidity.  An  Agave  fvetida  which  had  vegetated 
in  the  Paris  garden  for  nearly  a  century,  and  during 
that  period  had  scarcely  shown  any  signs  of  increase, 
during  a  warm  summer  began  to  show  signs  of  flowering. 
In  eighty-seven  days,  it  had  grown  twenty-two  feet 
and  a  half,  and  during  one  portion  of  this  interval  it 
increased  at  the  rate  of  nearly  one  foot  per  diem. 

(248.)  Periods  of  Floirrri lit/. —  The  precise  periods 
at  which  a  species  commences  flowering  in  different 
years,  range  within  certain  limits,  dependent  partly 
upon  the  state  of  the  weather  ;  but  it  is  very  difficult 
to  appreciate  all  the  causes  which  concur  in  modifying 
them.  It  is  evident  that  the  annual  distribution  of 
temperature  produces  a  marked  effect  upon  the  period 
of  flowering,  and  that  this  operates  more  decidedly  on 
those  plants  which  flower  in  the  spring,  than  on  such 
as  flower  later  in  the  year.  The  almond,  flowers  at 
Smyrna  in  the  early  part  of  February,  in  Germany 
about  the  beginning  of  April,  and  in  Christiania  not 
until  the  beginning  of  June.  The  vintage,  however, 
takes  place  at  Smyrna  the  beginning  of  September,  and 


CHAP.  V.      FUNCTION  OF  REPRODUCTION.         253 

in  Germany  about  the  middle  of  October ;  a  retardation 
in  this  case  which  is  less  than  in  the  former. 

When  a  perennial  has  once  begun  to  flower,  it  is 
subject  to  periodic  returns  of  this  function.  The  period 
of  the  year  in  which  the  flower  expands,  is  regulated  in 
all  cases  by  the  peculiar  character  of  each  individual, 
and  it  is  very  nearly  the  same  for  all  plants  of  the  same 
species.  There  are,  however,  remarkable  exceptions  to 
the  laws  by  which  the  periods  of  flowering  in  different 
species  are  regulated.  Advantage  is  taken  of  this  cir- 
cumstance ;  and  by  propagating  from  such  individuals 
as  are  both  the  earliest  and  latest  in  producing  their 
seeds,  peculiar  "  races  "  are  gradually  established,  which 
secure  to  the  cultivator  a  longer  succession  of  a  given 
crop  than  he  could  otherwise  have  obtained.  De  Can- 
dolle  mentions  an  instance  of  a  horse-chestnut  at 
Geneva,  which  always  flowers  a  whole,  month  before 
the  rest  in  its  neighbourhood,  without  any  apparent 
cause  for  such  precocity.  These  anomalies  indicate 
some  peculiarity  of  constitution,  or  "  idiosyncrasy,"  in 
the  separate  individuals  ;  but  they  determine  nothing 
against  the  existence  of  a  general  law,  by  which  each 
species  is  supposed  to  be  regulated  in  producing  its 
flowers  at  a  certain  period  of  the  year.  A  very  abun- 
dant crop  of  fruit  generally  absorbs  so  much  of  the 
nutriment  prepared  in  the  stem,  as  to  diminish,  and 
often  entirely  to  prevent  the  formation  of  flowers 
in  the  following  season  ;  and  hence,  some  trees  in 
orchards  bear  abundantly  only  on  alternate  years.  As 
double  flowers  produce  no  fruit,  their  stems  are 
not  so  thoroughly  exhausted  ;  and  perennials  of  this 
description  generally  flower  earlier  in  the  season  than 
single  flowers  of  the  same  species.  By  far  the  greater 
number  of  plants  flower  in  the  spring,  and  several 
do  so  even  before  they  expand  their  leaves.  In  these 
cases,  the  nutriment  which  has  been  prepared  for  the 
development  of  the  flower,  must  have  been  wholly 
provided  by  the  leaves  of  the  preceding  season,  and 
have  been  magazined  through  the  winter  in  the  stem. 


2:"i  I-  PHYSIOLOGICAL    BOTANY.  PART  II. 

The  peach,  apple,  and  almond  are  familiar  examples. 
It  sometimes  happens,  when  the  leaves  have  been  de- 
stroyed by  drought  or  other  causes,  that  a  second  crop 
of  flower-buds  is  developed  late  in  the  year ;  the  trees 
having  sustained  a  check  in  their  vegetation,  similar  to 
what  takes  place  in  the  winter,  break  out  again  as  if  it 
were  a  second  spring. 

(24.Q.)  Periodic  Iiijluriiwx. —  The  periods  at  which 
the  flowering  of  plants  commences  in  different  years,  at 
a  given  spot,  appear  to  depend  upon  the  mean  distri- 
bution of  temperature  per  month,  rather  than  upon  the 
mean  annual  temperature.  Since  some  process  or  other 
of  the  function  of  nutrition  is  carried  on  throughout  the 
year,  and  even  in  winter  this  is  not  entirely  dormant, 
there  may  very  likely  be  a  critical  season,  when  some 
defect  of  moisture,  light,  or  temperature  would  be  fatal 
to  the  progress  and  perfection  of  a  particular  process, 
and  retard  or  completely  prevent  the  flowering  of 
the  plant  at  the  proper  time.  When  by  a  com- 
bination of  circumstances  —  partly  dependent  on  the 
peculiar  constitution  of  the  individual,  partly  on  the 
character  of  the  species,  and  partly  on  external  influ- 
ences —  the  periodic  return  of  a  plant's  flowering  has 
been  fixed  within  certain  limits,  to  a  given  month  in 
the  year,  it  requires  a  certain  lapse  of  time  before 
any  alteration  in  the  external  circumstances  to  which 
it  may  be  subjected,  can  effect  a  decided  change  in  this 
period.  Thus,  it  is  observed  that  plants  which  are 
transported  from  the  southern  to  the  northern  hemi- 
sphere, do  not  immediately  accommodate  themselves  to 
the  opposite  condition  of  the  seasons  in  which  they  are 
placed,  but  for  a  while  continue  to  show  symptoms  of 
flowering,  at  the  same  period  of  the  year  in  which  they 
had  been  accustomed  so  to  do  in  their  native  climate.  In 
some  instances  they  are  several  years  in  accomplishing 
the  change,  and  sometimes  even  die  before  they  can 
effect  it.  The  usual  limits  within  which  the  periodic 
returns  of  flowering  in  each  species  take  place,  are 
always  mentioned  in  the  Floras  of  a  given  district ;  and 


CHAP.  V.  FUNCTION    OP    REPRODUCTION.  255 

Linnaeus  and  others  have  prepared  tables  of  different 
plants,  which  flower  in  each  month  of  the  year,  under 
the  title  of  Flora's  Calendars. 

(250.)  Horary  Expansion.  —  As  the  flowering  of 
different  species  takes  place  at  different  seasons  of  the 
year,  so  also  many  species  open  their  flowers  only  at 
certain  hours  of  the  day.  The  greater  number  are 
not  subject  to  any  very  marked  law  in  this  particu- 
lar ;  and  their  flowers,  wheri  once  expanded,  continue 
open  until  they  decay.  Some  flowers,  as  those  of  the 
purple  horned-poppy  (Rcemeria  violacea),  expand  early 
in  the  morning,  and  their  petals  are  so  very  fugacious, 
that  they  are  mostly  fallen  two  or  three  hours  before 
noon.  But  there  are  many  plants,  as  the  Convolvulus 
nil,  which  retain  their  corolla  for  several  days,  and 
regularly  open  and  shut  it  at  certain  hours.  Linnaeus 
prepared  tables  to  express  these  facts,  which  he  fanci- 
fully termed  Flora's  clocks.  The  following  list  may 
serve  as  a  specimen. 

A.  M. 

4.  Convolvulus  nil. 

5.  Papaver  nudicaule. 

5 — 6.  Convolvulus  tricolor. 

6' — 7-  Sonchus  oleraceus. 

8.  Anagallis  arvensis. 

9.  Calendula  arvensis. 

11.  Ornithogalum  umbellatum. 

12.  Mesymbrianthemum. 
p.  M. 

2.  Scilla  pomeridiana. 

5 — 6'.  Silene  noctiflora. 

6 — 7-  Nyctago  jalapa. 

7 — 8.  Cereus  grandiflorus. 

10.  Convolvulus  purpureus. 

He  named  those  flowers  "  Ephemeral,"  which  open 
once  only  at  a  given  time,  and  decay  within  the  period 
of  a  day ;  and  those  "  Equinoctial,"  which  open  and 
close  for  several  days  at  the  same  hour.  Of  these, 


256 


PHYSIOLOGICAL    BOTAXV.  PART  II. 


some  are  diurnal,  others  nocturnal.  "  Meteoric" 
flowers  are  such  as  are  influenced  by  the  state  of  the 
atmosphere.  A  few  of  these  as  the  Calendula  pluvialis 
close  at  the  approach  of  rain  ;  others  as  the  Campanula 
glomerata  when  the  sky  is  clouded. 

(-."'!.)  St'nniilnnts  to  L'.t/t'iitxion.  —  Light  and  not 
heat  appears  to  be  the  chief  stimulus  which  regulates 
the  expansion  of  the  blossom ;  and  the  influences  of 
moisture  alone  do  not  seem  to  affect  it  greatly;  at  least 
plants  when  wholly  immersed  in  water  expand  as 
freely  as  in  the  open  air.  The  phenomenon  of  their 
alternately  expanding  and  closing,  is  allied  to  the  sleep 
of  the  leaves  (art.  155.),  and  like  the  periodic  returns  of 
flowering,  appears  to  be  regulated  by  the  joint  operation 
of  several  causes,  among  which  we  must  allow  that  the 
peculiar  idiosyncracy  of  each  individual  plays  its  part. 
For  independently  of  the  effect  produced  by  the  external 
stimulus  of  light,  if  a  plant  aci-mstomed  to  flower  at  a 
given  period  of  the  day  be  removed  to  a  dark  room  it 
will  still  make  an  effort  to  expand  its  flowers  at  the 
wonted  hour.  De  Candolle  proved  this  by  shutting  up 
some  of  these  equinoctial  plants,  as  Linnfeus  termed 
them,  in  a  dark  chamber  by  day  and  exposing  them  by 
night  to  strong  lamp-light.  This  treatment  occasioned 
for  a  while  the  greatest  irregularity  in  their  periods  of 
expanding ;  but  at  length  they  became  accustomed  to  the 
change,  and  closed  their  petals  by  day  and  opened  them 
by  night.  In  some  cases  the  expansion  of  the  flower 
is  evidently  influenced  by  the  effects  of  light,  heat,  and 
moisture.  The  common  dandelion  (Leontodon  tarax- 
acum"), when  closed  on  a  cloudy  day,  upon  being 
brought  into  the  stove  will  immediately  expand  its  blos- 
soms, though  it  may  now  be  exposed  to  less  light  and 
more  moisture  than  before.  On  the  other  hand,  if  the 
same  plant  be  exposed  to  the  light  of  the  sun,  it  will  also 
expand  though  the  temperature  may  be  lower  than 
on  a  cloudy  day,  when  it  would  continue  shut.  It 
has  been  often  asserted  and  as  frequently  denied,  that 
the  common  sunflower  will  continue  to  turn  its  bios- 


CHAP.  V.      FUNCTION  OF  BEPROOUCTION.          257 

soms  to  the  sun  during  his  diurnal  course  through  the 
sky.  That  such  is  not  always  the  fact  is  easily  seen, 
for  it  often  happens  that  a  single  plant  is  covered  with 
blossoms,  which  face  all  quarters  of  the  heavens.  It  is 
possible  there  may  be  some  foundation  for  the  opinion, 
and  that  under  a  more  genial  climate  this  may  be  the 
fact ;  or  perhaps  the  notion  may  have  originated  in  some 
confusion  of  ideas  connected  with  the  name  of  the  plant, 
which  seems  at  least  as  much  entitled  to  its  appellation 
from  the  appearance  of  its  flowery  disk  surrounded  by 
the  glory  of  its  golden  rays,  as  from  the  very  doubtful 
property  which  has  been  assigned  to  it.  An  effect 
of  the  kind  alluded  to  is  sometimes  strikingly  exhibited 
in  such  flowers  as  Hypochceris  radicata,  and  Apargia 
autumnalis ;  which  may  often  be  seen  in  meadows 
where  they  abound,  most  evidently  inclining  their 
blossoms  towards  that  quarter  of  the  heavens  in  which 
the  sun  is  shining. 

(252.)  Functions  of  the  Perianth.— The  universal 
presence  of  the  stamens  and  pistils  in  every  species 
of  flowering  plant,  and  the  frequent  want  of  a  corolla 
and  in  some  cases  of  a  calyx  also,  appear  to  indicate 
that  the  functions  of  the  two  outermost  whorls  of 
the  flower  forming  the  perianth,  are  not  so  essential 
to  the  perfecting  of  the  seed  as  the  two  innermost.  In 
many  cases  indeed,  where  these  whorls  are  not  deve- 
loped, some  traces  of  their  existence  are  nevertheless 
apparent  in  the  form  of  glandular  protuberances  or 
nectaries  j  and  it  is  possible  that  these  may  still  perform 
whatever  "function"  more  especially  belongs  to  the 
perianth ;  just  as  the  green  surfaces  of  stems  which 
do  not  develop  leaves,  perform  the  function  of  respir- 
ation. One  obvious  use  of  the  calyx  and  corolla, 
when  they  are  present,  is  to  protect  the  inner  whorls 
from  injury  in  the  early  stages  of  their  develop- 
ment. It  seems  not  unlikely  that  they  may  pri- 
marily be  destined  in  some  way  to  modify  the  ma- 
terials which  are  provided  for  the  formation  of  the 
pollen  and  ovules.  In  addition  to  the  purpose  which 
s 


258  PHYSIOLOGICAL    BOTANY.  PART  II. 

the  calyx  and  corolla  serve,  of  protecting  the  stamens 
and  pistils  in  the  early  stages  of  their  development, 
they  occasionally  perform  a  similar  office  at  a  later 
period  in  protecting  the  seed.  In  some  cases  they 
remain  attached  to  the  seed-vessel  in  the  modified 
form  of  membranous  or  chaffy  appendages,  which 
serve  as  sails  to  waft  the  seed  to  a  distance.  Some 
of  the  most  familiar  and  effectual  contrivances  of  this 
description  are  to  be  seen  in  the  Composite? ;  such 
as  the  common  dandelion  and  thistles.  In  these  cases 
the  down  attached  to  each  seed  is  only  a  modified  form 
of  the  calyx. 

(253.)  Functions  of  the  Nectary.  —  As  the  nectary 
has  been  noticed  in  not  fewer  than  seventy-two  families, 
and  is  found  in  a  vast  number  of  species,  its  use  is 
probably  of  some  importance  in  the  general  economy  of 
reproduction,  though  we  do  not  know  what  this  may 
be.  The  most  plausible  conjecture  that  has  been 
offered  supposes  the  secreted  matter  or  nectar  to  be 
discharged  by  the  organ  on  which  it  is  seated  or 
near  which  it  is  placed,  whilst  it  is  elaborating  the 
juice  for  the  use  of  the  inner  whorls.  An  important 
secondary  purpose  which  it  serves  is  to  allure  bees  and 
other  insects,  which  crawling  over  the  flowers,  and  pass- 
ing from  one  to  the  other,  facilitate  the  dispersion  of 
the  pollen,  and  thus  promote  the  fertility  of  the  plant 
in  the  waywe  are  about  to  mention  under  our  second 
period. 

(254.)  Development  of  Caloric. — At  the  time  of  the 
flower's  expansion  a  considerable  development  of  heat 
takes  place  in  certain  species,  and  there  is  also  a  rapid 
formation  of  carbonic  acid.  This  phenomenon  is  most 
strikingly  exhibited  by  some  of  the  Arum  tribe.  The 
spadix  of  the  common  arum  (Arum  maculatum)  at- 
tains a  temperature  of  7  R-  or  47f  °  Fahr.  above  that 
of  the  atmosphere,  and  the  Arum  cordifolium  in  the 
Mauritius  has  been  observed  to  attain  a  temperature  of 
44°  to  49°  R.  or  131°  to  142^°  Fahr.  that  of  the  sur- 
rounding air  being  at  19°  R.  or  74  J°  Fahr.  These 


CHAP.  V.      FUNCTION  OF  REPRODUCTION.          25.9 

effects  take  place  once  only  for  each  plant,  and  it  seems 
most  likely  that  they  are  the  result  of  some  chemical 
action,  rather  than  of  any  physiological  property. 


SECOND    PERIOD    OF    REPRODUCTION. 

(255.)  Fertilization, —  Great  progress  has  been  made 
within  the  last  few  years  towards  attaining  an  accurate 
knowledge  of  the  process  by  which  the  fertility  of  the 
seed  is  secured.  It  had  been  long  ascertained,  that  the 
action  of  the  pollen  was  somehow  essential  to  this  pur- 
pose, and  that  the  effect  was  also  produced  through  the 
intervention  of  the  stigma ;  but  the  manner  in  which  it 
took  place  was  not  understood.  Even  the  ancients  had 
obtained  some  vague  notions  on  the  subject,  although 
their  speculations  regarding  this  as  well  as  most  other 
minute  details  in  natural  science  were  replete  with 
error  and  absurdity.  The  general  fact  had  forced  itself 
upon  their  attention  in  the  cultivation  of  the  date- 
palm.  As  the  blossoms  of  this  tree  are  dioecious,  the 
distinction  between  those  individuals  which  continued 
barren  and  such  as  always  bore  fruit  was  of  course 
soon  remarked ;  and  it  was  found  to  be  necessary  that 
either  some  of  the  barren  kinds  should  be  cultivated 
in  the  neighbourhood  of  those  which  bore  fruit,  or 
else  that  bunches  of  their  flowers  should  be  suspended 
near  them,  otherwise  the  fruit  never  attained  per- 
fection. Hence  originated  the  custom  of  cultivating 
only  fertile  plants,  and  of  annually  bringing  bunches  of 
the  sterile  flowers  from  the  wild  trees  —  a  practice 
which  has  prevailed  from  the  earliest  periods  of  history 
to  the  present  day  in  Egypt,  and  those  countries  of  the 
East  where  the  date  forms  a  most  important  article  of 
human  food.  When  the  French  were  in  Egypt  in 
1800,  the  events  of  the  war  prevented  the  inhabitants 
from  procuring  the  blossoms  of  the  sterile  or  male 
plant  (as  it  is  considered)  from  the  deserts,  and  none 
of  the  cultivated  plants  in  consequence  bore  any  fruit. 
(256.)  Erroneous  Theory  of  the  Ancients. —  A  prac- 
s  2 


260  PHYSIOLOGICAL    BOTANY.  PART   II. 

tice  has  long  prevailed  in  certain  countries  of  the  East 
with  respect  to  the  cultivated  fig,  of  a  similar  description 
to  that  which  is  employed  to  fertilize  the  date,  and 
although  the  results  are  very  different  in  the  two  cases, 
it  is  only  lately  that  this  fact  has  been  suspected. 
Both  phenomena  were  always  considered  of  the  same 
class  ;  and  an  erroneous  theory  was  formerly  founded  on 
the  mistake.  Bunches  of  the  flowers  of  the  wild  fig 
are  brought  from  the  woods  and  suspended  over  the 
cultivated  plants,  when  a  small  insect  (the  larva  of  a 
cynips)  imported  with  the  wild  flowers  punctures  tin- 
young  fruit  of  the  cultivated  individuals,  and  accelerates 
their  ripening  —  in  the  same  way  that  we  find  a  similar 
effect  produced  in  some  apples  and  pears  by  the  punc- 
ture of  the  caterpillar  of  a  small  moth,  which  causes  them 
to  ripen  before  the  rest,  and  to  fall  sooner  from  the 
tree.  In  consequence  of  the  earlier  ripening  of  the 
figs  occasioned  by  the  practice  alluded  to,  and  which  is 
styled  the  caprification  of  their  fruit,  a  second  crop  is 
secured  which  might  otherwise  have  failed,  from  being 
produced  too  late  in  the  season  to  allow  of  its  attaining 
perfection.  It  was  in  attempting  to  generalise  from  the 
facts  observed  in  the  caprification  of  the  young  fig,  that 
the  ancients  asserted  that  a  maggot  (t^v)  was  the  effi- 
cient cause  of  fertility  in  the  date,  and  that  this  insect 
crept  from  the  sterile  into  the  fertile  blossoms  before 
the  development  of  the  fruit  could  take  place. 

The  existence  of  a  sexual  distinction  between  indi- 
vidual trees  in  such  species  as  the  date  and  some  other 
dioecious  plants,  gave  rise  to  another  erroneous  opinion, 
and  it  was  supposed  that  even  plants  where  the  stamens 
and  pistils  were  contained  in  the  same  flower  were 
nevertheless  unisexual.  Thus  Claudian  asserts  — 

"  Vivunt  in  venerem  frondes,  arborque  vichsim 
Felix  arbor  amat ;  nutant  ad  mutua  palma1 
Fu'dcra  |iopuleo  suspirat  populus  ictu  : 
El  platani  plalanis,  alnoque  assibilat  alnus. " 

(257-)  Vegetable  Sexes.  —  A  more  careful  research 
and  the  results  of  direct  experiment  have  superseded 


CHAP.  V.      FUNCTION  OP  REPRODUCTION.          26'l 

the  vague  conjectures  of  the  old  philosophers;  and  it 
is  now  clearly  established  that  the  two  innermost  floral 
whorls,  the  stamens  and  pistils,  are  the  organs  essen- 
tial to  the  fertility  of  the  seed.  In  the  case  of  double 
flowers  where  all  the  stamens  have  assumed  the  condi- 
tion of  petals,  seed  is  never  produced  ;  but  if  the  pistil 
be  perfect,  it  may  be  supplied  with  pollen  from  another 
plant  of  the  same  species,  and  will  then  ripen  its  ovules. 
Some  apparent  anomalies  are  recorded  among  the  various 
experiments  which  have  been  made  to  prove  the  necessity 
of  the  action  of  the  pollen  in  securing  the  fertility  of  the 
seed.  The  females  of  certain  dioecious  plants  have  ma- 
tured their  seeds  although  they  were  carefully  excluded 
from  the  action  of  the  stameniferous  individuals ;  but 
in  some  of  these  cases,  this  was  probably  owing  to  the 
fact  that  dioecious  plants  are  frequently  partially  mo- 
noecious, and  that  a  stameniferous  flower  is  here  and 
there  developed  on  the  fertile  plants,  which  may  have 
furnished  sufficient  pollen  to  set  the  fruit.  Accord- 
ing to  some  recent  experiments,  however,  the  universality 
of  a  law  which  establishes  the  necessity  of  the  pollen's 
action  has  been  rather  shaken,  unless  there  be  some 
error  which  it  is  difficult  to  account  for.  If  they  are 
correct,  it  seems  to  have  been  proved  that  hemp  and 
a  few  other  annual  dioecious  species  are  capable  of  ri- 
pening their  seed  without  the  action  of  the  pollen  having 
taken  place.  Even  if  the  fact  should  be  satisfactorily 
established  it  will  in  no  way  disprove  the  general  neces- 
sity of  the  pollen's  action,  or  the  sexual  distinctions  of  all 
phanerogamous  plants.  But  such  isolated  exceptions 
may  possibly  be  considered  analogous  to  the  case  of  the 
Aphides,  in  which  insects  a  single  impregnation  is  suf- 
ficient to  enable  several  generations  to  become  fertile. 
But  after  all  we  have  such  marvellous  accounts  of  the 
distance  to  which  the  pollen  may  be  carried  and  yet 
preserve  its  proper  influence,  that  it  seems  hardly  pos- 
sible to  feel  quite  certain  that  the  plants  in  question 
may  not  have  been  fertilized  from  others  growing  in 
the  neighbourhood.  It  is  stated  that  in  the  year  1505 
s  3 


2(>2  PHYSIOLOGICAL    BOTANY.  PART  II. 

there  was  a  female  date-palm  growing  at  Brimles, 
which  flowered  regularly  but  never  bore  fruit.  At 
length  a  male  plant  of  the  same  species  growing 
thirty  miles  off  at  Otranto,  having  attained  a  sufficient 
height  to  overtop  the  trees  in  its  neighbourhood,  its 
pollen  was  then  wafted  by  the  wind  across  the  inter- 
vening space,  and  the  tree  at  Brimles  produced  its 
fruit.  The  poet  Pontanus  who  flourished  at  the  time, 
has  also  recorded  the  fact.  The  late  colonel  Wrilkes 
when  governor  of  St.  Helena,  procured  some  pollen 
from  dates  growing  on  the  continent  of  Africa,  with 
which  he  fertilized  some  trees  on  the  island  that  had 
never  before  perfected  their  fruit.  It  is  certainly  not 
necessary  that  the  ripe  pollen  should  immediately  be 
brought  into  contact  with  the  stigma ;  and  instances 
are  recorded  of  its  having  been  sent  in  a  letter  from  one 
part  of  the  country  to  another  and  still  retaining  its 
activity.  Dr.  Graham  mentions  that  a  female  specimen 
of  the  Chinese  pitcher-plant  (Nepenthe*  divtillatoria) 
was  fertilized  in  the  Edinburgh  Botanic  Garden,  by 
pollen  thus  procured  from  a  male  plant  which  happened 
fortunately  to  be  in  flower  in  another  part  of  Scotland. 

(258.)  Dispersion  of  Pollen.  —  Before  the  pollen  is 
scattered  from  the  anther,  some  plants  seem  to  make 
preparation  for  increasing  the  certainty  of  its  taking 
effect,  by  bringing  the  stamens  nearer  to  the  pistil. 
This  is  remarkably  evident  in  the  Grass-of- Parnassus 
(Parnassia  palustri*),  whose  stamens  on  the  first  ex- 
pansion of  the  flower  are  inclined  away  from  the  pistil, 
but  are  afterwards  brought  in  succession  towards  it 
when  their  anthers  are  about  to  burst.  In  Geranium, 
Kalmia,  &c.  the  filaments  bend  until  the  anther  is  placed 
immediately  over  the  stigma.  In  the  berberry  (as  we 
have  described  in  art.  149.  3.),  the  filament  may  be 
caused  to  incline  suddenly  towards  the  stigma  by  gently 
touching  it  near  the  base  on  the  inside.  The  genus 
Stylidium  affords  one  of  the  most  singular  examples  of 
this  kind  of  floral  irritability  ;  though  in  this  case  the 
object  is  not  so  clearly  to  be  perceived,  since  the  anthers 


CHAP.   V.  FUNCTION     OF    REPRODUCTION.  263 

are  at  first  close  to  the  stigma,  and  the  pistil  is  sud- 
denly removed  from  them. 

But  independently  of  any  means  which  some  species 
employ  for  assisting  the  dispersion  of  the  pollen  and  se- 
curing its  contact  with  the  stigma,  we  find  that  the 
mere  conditions  in  which  the  flower  is  placed  are  often 
such  as  are  most  likely  to  secure  these  results  with- 
out further  contrivance.  Thus,  when  the  flower  is 
erect  and  the  stamens  are  longer  than  the  pistil,  the 
pollen  on  falling  from  the  anthers  is  most  likely  to 
come  in  contact  with  the  stigma  placed  immediately 
below  them  ;  so  also  where  the  flower  is  pendent  and 
the  stamens  shorter  than  the  pistil,  the  same  effects 
will  be  produced.  In  cases  where  the  flower  is  erect 
and  the  stigma  stands  higher  than  the  anthers,  there  is 
often  a  closer  aggregation  of  the  flowers  as  in  the  nu- 
merous order  Composite,  so  that  the  chances  are  greatly 
increased  whereby  the  pollen  from  one  flower  may  be 
brought  into  contact  with  the  stigma  of  another,  either 
by  the  action  of  insects  crawling  over  them  or  by  the 
mere  agitation  of  the  wind.  These  and  a  thousand 
other  instances  might  be  adduced  of  a  provision  made 
for  securing  the  perfect  success  of  an  operation  of  so 
much  consequence  to  the  preservation  of  the  species. 

(259.)  Protection  of  Pollen. —  It  is  further  essential 
that  the  pollen  should  be  protected  from  the  influence 
of  moisture ;  and,  consequently  we  find  that  aquatics, 
as  the  water-lily  (Nymphcea  alba),  elongate  their  flower- 
stalks  until  the  blossoms  float  upon  the  surface  of  the 
water.  In  the  water-soldier  (Stratiotes  aloides),  water- 
violet  (Hottonia  palustris],  and  others,  the  entire  plants 
float  to  the  surface  of  the  water  during  the  period  of  flower- 
ing, but  live  submerged  at  other  times.  In  the  Zostera 
marina  the  flowers  are  arranged  within  a  cavity  filled 
with  air :  and  thus,  although  they  are  developed  beneath 
the  surface,  they  are  protected  from  the  immediate 
contact  of  the  water.  But  of  all  instances  that  might 
be  mentioned,  where  the  action  of  the  pollen  is  secured 
by  some  singularity  of  structure  or  contrivance,  the 
s  4 


~'l)t  PHYSIOLOGICAL    BOTANY.  PART  II. 

Valisneria  spirali*  is  one  of  the  most  remarkable.  This 
is  an  aquatic,  native  of  the  south  of  Europe.  Its 
flowers  are  dicecious.  The  females  are  attached  to 
long  peduncles  which  at  first  are  spirally  twisted,  so 
that  the  buds  are  completely  submerged.  They  after- 
wards untwist  until  the  buds  reach  the  surface,  and  the 
flowers  expand.  The  males  on  the  other  hand  have 
very  short  peduncles,  and  their  buds  are  in  the  form 
of  little  bladders  which  easily  detach  themselves  from 
the  peduncle  and  float  to  the  surface  of  the  water  when 
the  pollen  is  ripe.  Here  they  surround  the  female  blos- 
soms and  then  expand.  The  peduncles  of  the  female 
plants  coil  up  again,  the  flowers  are  submerged  and  the 
seed  is  then  ripened  below  the  surface  of  the  water. 

(260.)  Certainty  of  Reproduction,  —  No  one  who 
feels  as  he  ought  the  lessons  which  the  study  of  nature 
is  calculated  to  convey,  but  must  be  struck  with  admir- 
ation at  witnessing  the  multifarious  resources,  combined 
with  an  extreme  simplicity  in  the  means  employed,  for 
effecting  that  unity  of  purpose  which  is  manifested  in 
the  preservation  of  the  numerous  species  that  clothe 
and  beautify  the  surface  of  the  earth.  Independently 
of  that  security  which  every  species  possesses  in  its 
reproduction  by  seed  against  the  probability  of  utter 
annihilation,  some  are  further  enabled  to  maintain  their 
position  by  means  of  creeping  stems.  Many  aquatics,  as 
the  potamogetons,  are  thus  extensively  propagated  at 
the  bottom  of  rivers  and  lakes  and  their  perpetuity 
secured,  even  though  the  conditions  necessary  to  en- 
able them  to  perfect  their  seed  should  never  be  ful- 
filled. On  the  other  hand  the  occasional  produc- 
tion of  seed  in  such  plants  seems  to  be  necessary, 
if  we  remember  that  their  native  bed  may  possibly 
be  drained  in  the  lapse  of  ages  by  one  of  those 
events  which  characterise  the  geological  history  of  our 
planet ;  when  the  only  chance  which  would  possess 
of  being  preserved  must  consist  in  the  probability  of 
some  of  those  seeds  which  they  had  "  cast  upon  the 
waters,"  finding  a  new  station  equally  congenial  to 


CHAP.   V.  FUNCTION    OF    REPRODUCTION.  265 

their  growth.  The  chances  which  threaten  the  fail- 
ure of  seed  in  dioecious  species  are  diminished  by  the 
occasional  development  of  a  few  flowers  of  an  oppo- 
site sex  among  those  which  otherwise  characterize 
the  separate  individuals ;  and  it  is  well  authenticated 
that  cases  occasionally  occur,  where  willows  which  for 
many  years  had  borne  flowers  of  one  sex  only,  have 
afterwards  changed  their  character  and  begun  to  bear 
only  those  of  an  opposite  sex. 

(26l.)  formation  of  Pollen. — Before  we  describe  the 
action  of  the  pollen,  we  shall  say  a  few  words  upon  its 
formation.  In  this  case,  as  in  the  whole  account  of  the 
fertilization  and  development  of  the  ovule,  we  are  es- 
pecially indebted  to  the  admirable  researches  of  Adolphe 
Brongniart,  who  in  a  memoir  published  in  the  "  Annales 
des  Sciences,"  has  combined  an  extensive  series  of 
original  observations  with  whatever  was  previously 
known  on  the  subject ;  and  placed  the  main  facts  of  this 
interesting  and  curious  question  beyond  the  possibility 
of  successful  contradiction.  To  Robert  Brown  also  in 
this  as  in  every  department  of  botany,  we  are  pre- 
eminently indebted  for  important  and  accurate  details. 
His  invaluable  papers  on  the  fecundation  of  Asclepia- 
dea?  and  Orchideae  form  an  important  epoch  in  the 
progress  of  general  physiology. 

So  soon  as  the  anther  can  be  distinguished  in  the  flower- 
bud,  its  cells  are  filled  with  a  mass  of  cellular  tissue,'  each 
vesicle  of  which  contains  one  or  more  grains  of  pollen. 
As  the  anther  ripens  these  grains  enlarge  and  ultimately 
rupture  the  vesicles ;  and  the  debris  of  the  cellular  tis- 
sue then  forms  loose  fibres  intermixed  with  the  pollen. 
In  general  the  grains  are  separate,  but  in  some  plants  (as 
the  heaths)  three  or  four  grains  always  adhere  together. 
There  is  no  appearance  of  any  thing  like  a  pedicel  to  the 
separate  grains,  nor  any  scar  upon  them  like  the  hilum  on 
the  ovule,  which' might  indicate  an  original  attachment  to 
the  sides  of  the  vesicles  within  which  they  were  formed. 
In  most  plants  each  grain  is  composed  of  two  membranes; 
the  exterior  presenting  the  various  appearances  de- 


266 


PHYSIOLOGICAL    BOTANY. 


scribed  art.  99-  >  and  the  interior  being  an  exceedingly 
delicate  homogeneous  pellicle.  Whatever  may  be  the 
ultimate  determination  of  botanists,  respecting  the  form- 
ation and  origin  of  pollen,  yet  as  its  grains  in  a  very 
early  stage  of  their  development  are  free  and  unattached 
to  the  inner  walls  of  the  anther,  it  should  seem  that  from 
this  period  at  least  their  growth  must  depend  upon  the 
absorption  of  nutriment  through  their  surfaces. 

(262.)  Action  of  Water  on  Pollen.  —  If  ripe  pollen 
be  placed  in  a  drop  of  water  and  examined  under  a 
microscope,  in  a  few  seconds  it  will  be  seen  to  dilate, 
burst,  and  violently  expel  a  cloud  of 
minute  granules  (fit/.  1()0.).  These 
granules  are  still  contained  within 
the  inner  membrane  of  the  pollen 
grain  protruded  through  the  rup- 
tured outer  membrane,  but  which  is 
difficult  to  be  observed,  on  account 
of  its  extreme  tenuity.  It  thus  forms 
a  sort  of  rude  sack,  termed  a  "  pol- 
len tube,"  and  contains  a  liquid,  the  "  fovilla,"  in  which 
are  dispersed  a  number  of  very  minute  "  pollen  gra- 
nules." The  outer  skin  of  the  grains  is  ruptured  irre- 
gularly in  most  Monocotyledons;  but  in  Dicotyledons 
^here  are  one  or  more  determinate  points  on  its  sur- 
face where  a  regular  dehiscence  takes  place,  and  it  is 
through  these  that  the  inner  membrane  then  protrudes. 
In  consequence  of  the  effect  thus  produced  on  pollen  by 
water,  it  is  liable  to  injury  in  rainy  seasons  and  the  fer- 
tility of  the  seed  is  often  impaired.  Although  the  gra- 
nules are  destined  to  convey  that  influence  to  the  ovule 
which  is  necessary  to  secure  its  fertility,  yet  their  violent 
expulsion  from  the  grains  is  not  the  manner  in  which  this 
effect  is  produced.  This  process  constitutes  one  of  the 
most  curious  phenomena  which  have  been  observed  of 
late  years  among  the  many  wonders  which  the  micro- 
scope has  brought  to  light.  Considering  the  minuteness 
of  the  objects  and  the  delicacy  of  the  inanipulations  re- 
quisite for  these  investigations,  we  must  feel  surprised 


CHAP.    V.  FUNCTION    OF    REPRODUCTION.  26? 

at  the  progress  which  this  inquiry  has  already  made, 
although  much  yet  remains  to  be  done  before  a  complete 
elucidation  of  all  points  can  take  place. 

(263.)   Granules With    a   lens  which    magnifies 

about  300  times  in  linear  measure,  the  form  of  the  gra- 
nules in  the  fovilla  may  be  clearly  distinguished.  Whilst 
still  in  the  pollen  tubes  they  are  often  in  motion,  like 
the  globules  in  the  stems  of  the  Chara  (art.  194.).  A  few 
larger  molecules  are  found  dispersed  among  them,  appa- 
rently of  an  oleaginous  nature.  In  the  same  species 
all  the  granules  are  nearly  of  the  same  size  and  shape, 
but  they  differ  in  different  species.  They  are  always 
more  or  less  spheroidal  or  cylindrical.  They  are  cer- 
tainly to  be  considered  as  the  direct  agents  employed  in 
securing  the  fertility  of  the  ovules. 

(26'4.)  Action  of  the  Stigma.  —  When  the  grains  of 
pollen  fall  upon  the  stigma,  they  become  attached  to  it 
by  means  of  a  glutinous  exudation  with  which  it  is 
covered.  No  immediate  action  takes  place,  and  the 
grains  are  not  violently  exploded  with  the  pollenic 
tubes  as  when  they  are  placed  in  water ;  but  after  they 
have  remained  for  a  few  hours,  and  in  some  cases  even 
for  a  few  days  on  the  stigma,  each  grain  protrudes  one 
or  more  delicate  pollenic  tubes  which  penetrate  be- 
tween the  vesicles  of  the  cellular  tissue  of  the  stigma 
(fig.  16'l.a).  These  tubes  increase  rapidly  in  length, 
growing  as  it  should  seem  by 
meansof  thenourishmentwhich 
they  derive  from  the  granular 
matter  abounding  in  the  inter- 
stices or  intercellular  passages 
between  the  vesicles  of  the 
style.  In  some  cases  if  not 
in  all,  the  pollen  tubes  become 
extended  down  the  whole  length 
of  the  style,  and  penetrate  into  the  cavity  of  the 
ovarium,  where  they  run  along  the  surface  of  the  pla- 
centa, and  surround  the  ovules.  At  (6)  we  have  the 
section  of  a  stigma  on  whose  surface  are  numerous  pol- 


PHYSIOLOGICAL    BOTANY. 


PART  II. 


268 

len  grains  each  protruding  a  tube  and  appearing  like 
pins  on  a  cushion.  In  certain  families,  as  the  Orchi- 
deae  (Jig.  162.  a)  and  Asclepiadea?  (/;),  the  grains 
contained  in  one  cell  of  each  anther  are  agglutinated 
together  into  waxy  masses,  so  that  when  the  action 
takes  place,  a  number  of  tubes  are 
protruded  together  and  form  a  thick- 
ened cord  (as  at  c) ;  and  thus 
they  penetrate  into  the  <>\;irium  "en 
masse."  Even  some  grains  which 
are  composed  of  only  one  vesicle, 
exsert  more  than  one  pollen  tube.  * 
In  some  cases  the  tube  originates 
in  a  swelling  on  the  surface  of  the  grain,  which  then 
seems  to  be  formed  of  one  skin  only,  or  perhaps  the 
two  may  be  united. 


THIRD    PERIOD    OF    REPRODUCTION. 

(265.)  Maturation. —  After  the  action  of  the  pol- 
len has  taken  place,  the  ovules  contained  in  the  ovarium 
begin  rapidly  to  increase,  and  the  fruit  swells  and 
ripens.  But  in  order  to  understand  the  several  parts  of 
which  the  seed  is  composed,  it  is  necessary  to  trace 
the  changes  which  the  ovule  undergoes,  from  the 
earliest  period  in  which  it  is  distinguishable  in  the 
young  flower-bud,  up  to  the  time  when  the  complete 
maturation  of  the  fruit  is  effected. 

(2()6.)  Origin  of  the  Ovule. —  When  the  ovules  can 
first  be  seen  (as  in  some 
species  of  the  cucumber  or 
gourd),  they  are  small  pus- 
tules or  wartlike  excres- 
cences formed  upon  the 

inner  surface  of  a  cavity  in  the  ovarium;  and  are  with- 
out any  distinct  traces  of  organisation  (fg-  lG'3.  «)• 
Soon  after  their  first  appearance  we  find  them  lengthen- 
ing (/>),  and  assuming  traces  of  an  organised  structure  (c). 
They  are  observed  to  consist  of  an  internal  mass  of  eel- 


CHAP.   V. 


FUNCTION    OF    REPRODUCTION. 


269 

lular  tissue  termed  the  "nucleus"  (fig.  164.  a),  in- 
vested by  two  coats  or  skins  (6),  open  at  their  lower 
extremity,  and  allowing  a  portion  of  the  nucleus,  called 
its  "  apex,  "  to  protrude  through  them.  This  open- 
ing is  termed  the  "  fora- 
men." Shortly  afterwards 
these  skins  close  over  the 
nucleus,  and  leave  only  a 
small  orifice  to  the  fora- 
men (c).  The  outermost 
of  these  skins  is  termed 
the  " testa"  or  "primine,"  .-«< 
and  the  innermost  the 
"  tegmen  "  or  "  secun- 
dine."  Sometimes  there  is  only  one  skin,  or  more 
probably  the  two  are  so  blended  together  that  they  are 
not  distinguishable.  As  the  ovule  enlarges,  the  nucleus 
itself  is  also  found  to  be  a  closed  sack,  of  a  thick  or  fleshy 
consistency  ;  and  within  this  and  towards  its  apex,  an- 
other small  sack  or  vesicle  makes  its  appearance  called  the 
"embryonic  sack"  (fig.l65.  a).  The  ovule  may  there- 
fore generally  be  considered  in  its  early  165 
state  to  be  composed  of  two  closed  sacks 
which  together  constitute  the  nucleus, 
and  of  two  open  sacks  which  form  its 
integuments.  In  some  cases  the  two 
outer  skins  appear  to  be  blended  to 
gether,  for  one  only  can  be  seen.  The 
number  of  sacks  which  compose  the  nu- 
cleus sometimes  also  amounts  to  three ; 
so  that  the  whole  number  contained  in 
the  ovule  is  as  many  as  five,  and  these 
have  received  the  several  names  of  pri- 
mine, secundine,  tercine,  quartine,  and 
quintine  —  reckoning  from  without,  inwards.  Whilst 
the  enlargement  of  the  ovule  proceeds,  a  change  of 
position  also  takes  place  in  the  relation  of  its  parts, 
owing  to  an  unequal  development  of  the  sides  of  the 
primine.  The  apex,  which  at  first  was  on  the  side  of 


270 


PHYSIOLOGICAL    BOTANY. 


the  ovule  opposite  the  part  by  which  it  is  attached  to 
the  ovarium,  has  now  by  some  torsion  of  the  mass  been 
brought  close  to  its  base.  In  this  case  the  point  where 
the  secundine  is  attached  to  the  primine  (and  which  is 
called  the  "  Chalaze"  6)  is  distinct  from  the  "  Hiluin," 
or  place  where  the  funicular  cord  is  attached  to  the 
primine.  The  vessels  which  penetrate  the  funicular 
cord,  are  then  extended  through  the  substance  of  the 
outer  integument  from  the  hilum  to  the  chalaze  and 
form  a  vascular  bundle  termed  the  "  raphe"  («,•).  Figure 
166.  represents  a  section  of  the  developing  ovules  of 
plums,  almonds,  and  other  stone  fruits, 
and  may  serve  as  a  further  illustration  of 
the  facts  detailed  in  this  article.  When 
the  embryo  («)  makes  its  appearance  in 
the  embryonic  sack  (or  quartine)  (f>),  this 
latter  organ  is  observed  to  be  connected 
with  three  or  four  other  large  vesicles  in 
communication  with  the  raphe  where  it 
joins  the  chalaze  (r)  ;  the  hilum  being  at 
(rf).  The  testa  and  tegmen  already  appear  as  one  skin 
(/).  The  thick  nucleus  (*),  together  with  the  embryonic 
sack,  are  ultimately  exhausted  by  the  development  of 
the  embryo,  and  the  spermoderm  is  then  composed  of 
the  debris  of  the  four  integuments. 

(267.)  Modifications  of  the  Ovule,  —  When  the 
hilum  and  chalaze  are  contiguous  and  the  foramen  at 
the  opposite  extremity,  the  ovule  is  called  "  Ortho- 
tropous"  (fig.  167.  o),  and  this  is  the  condition  of  all 
ovules  in  their  earli-  ^^  157 
est  state.  In  many 
cases  the  integu- 
ments and  nucleus  ( 
develop  more  rapidly  y\  II  \\\  II 
on  one  side  than  on  \v  '//  _M 
the  other,  and  a  pe- 
culiar torsion  takes  place  in  the  body  of  the  seed,  by 
which  means  the  apex  is  brought  near  the  hilum.  The 
ovule  is  then  termed  "  Campulitropous "  (c).  When  the 


CHAP.  V.  FUNCTION    OF    REPRODUCTION.  27 1 

cha^ze  is  removed  from  the  hilum,  so  that  the  whole 
nucleus  is  inclined  upon  the  axis,  as  described  in  art. 
266'.  the  ovule  is  termed  "  Anatropous"  (A).  It 
more  frequently  happens  that  the  chalaze  is  immedi- 
ately opposite  to  the  hilum,  and  the  foramen  near  it 
(as  at  A)  ;  but  sometimes  the  former  is  placed  on  one 
side,  at  about  a  quarter  of  the  circumference  of  the 
ovule. 

(268.)  Formation  of  the  Embryo. —  Such  is  the 
state  of  the  ovules  previous  to  the  action  of  the  pollen 
upon  the  stigma.  Sooner  or  later  after  that  action,  the 
embryo  makes  its  appearance  under  the  form  of  a 
minute  vesicle,  attached  to  the  summit  of  the  inner- 
most or  embryonic  sack,  with  the  radicle  directed 
towards  the  foramen,  and  the  cotyledons  towards  the 
chalaze.  It  gradually  enlarges,  and  the  whole  ovule 
also  continues  to  increase. 

(269.)  Formation  of  Albumen.  —  Whilst  the  ovule 
is  increasing,  the  testa  and  tegmen  gradually  part  with 
their  juices,  for  the  support  and  increase  as  it  should 
seem  of  the  nucleus;  and  these  two  integuments  are 
ultimately  blended  together,  and  their  debris  then  forms 
only  a  single  skin  over  the  ripe  seed.  The  nucleus 
itself  is  sometimes  exhausted  in  a  similar  manner; 
whilst,  in  some  cases,  a  deposition  of  nutritious  matter 
takes  place  within  the  tercine,  and  round  the  quartine 
or  embryonic  sack.  In  some  kinds  of  seed  the  nutri- 
ment thus  provided  for  the  embryo  is  secreted  within 
the  embryonic  sack,  and  in  others  there  is  a  secretion 
of  this  description  going  on  simultaneously  within  this 
sack  and  the  tercine  also.  In  many  cases  this  nutri- 
ment, or  "  amnios,"  as  it  is  styled  in  its  earlier  state, 
Is  not  wholly  absorbed  by  the  ripening  ovule;  and  it 
ultimately  becomes  the  ' '  albumen"  or  "  perisperm"  of 
the  seed,  and  is  then  farinaceous,  hard,  or  oily.  This 
superabundant  supply  of  albumen  is  of  further  ser- 
vice to  the  embryo  during  its  germination,  and  supplies 
it  with  nutriment  in  the  early  stages  of  its  develop- 
ment, before  the  roots  have  sufficiently  enlarged  to 


272  PHYSIOLOGICAL    BOTANY.  PART  II. 

absorb  the  sap  from  the  surrounding  soil.  But  in  many 
cases  there  is  no  separate  provision  of  albumen  in  a  de- 
tached form,  but  this  material,  or  something  like  it,  is 
diffused  through  the  substance  of  the  cotyledons. 

(270.)     Development  of  the  Oruli: — So  soon  as  the 
embryo   makes   its  appearance  it  becomes  a  centre  of 
vital  action,  attracting  the  juices  of  the  plant  and  be- 
ginning an    independent   existence.       It    continues   to 
increase  at  the  expense  of  its  several  envelopes,  and  in 
the  end  constitutes  the  bulk  of  the  seed.     The  seed 
then  consists  of  this  body  enveloped  by  a  single  skin 
(the  spermoderm,  art.  109-),  which  is  composed  of  the 
debris  of  all  the  envelopes  blended  together,  and  in  some 
cases    there  is    also    superadded    a  store    of   albumen. 
Those  ovaries  which  are  not  fertilized  soon  wither  up  ; 
but  still  it  often  happens   that   the  ovaria  containing 
them  do  not  perish.     On  the  contrary  in  some  fruits, — 
as  in  the  cultivated  varieties  of  the  pine-apple,  where  the 
ovules  are  universally  abortive,  —  the  ovary  is  developed 
into  a  fleshy  pericarp ;  although  such  is  not  the  case  with 
the  wild   plants  which   possess  ovules.     The  same  is 
true  also  of  the  bread-fruit.     In  some  oranges  whose 
ovules  happen  to  be  abortive,  the  flavour  of  the  fruit  is 
much  improved ;  but  in-  many  plants,  when  the  ovules 
are    abortive  the  ovary  does  not  increase.      In  ovaria 
which  contain  numerous  ovules  it  often  happens  that 
some  only  are  fertilized  ;  and  sometimes  only  one  ovule 
arrives  at  perfection,  the  rest  being  either  starved  for 
want  of  sufficient  nutriment,  or  choked  by  the  more 
rapid  growth  of  that  which  becomes  a  perfect  seed. 
In  the  oak  for  example,  five  ovules  out  of  six  are  con- 
stantly abortive.     In  the  horse-chestnut  it  seldom  hap- 
pens that  more  than  one  arrives  at  perfection,  though  the 
pericarp  originally   contained  six  ;  and  though   all   of 
them,  for  some  time  after  their  fertilization  was   se- 
cured, had  every  appearance  of  health  and  vigour.      In 
the  stone  fruits  —  plums,  peaches,  &c.  —  we  generally 
find    only  one    ripe    kernel,    though    two    ovules    are 
always  present  in  the   early  stages  of  the  fruit ;  the 


CHAP.   V.  FUNCTION    OF    REPRODUCTION.  273 

other  may  be  seen  in  a  withered  state  attached  to 
the  inner  edge  of  one  suture  of  the  stone,  whilst  the 
perfect  seed  is  attached  to  the  other. 

(271.)  Maturation  of  the  Fruit.  —  Whilst  the  fruit 
continues  to  swell,  the  sap  is  drawn  with  increased 
energy  towards  those  branches  on  which  it  hangs,  and 
a  rapid  exhaustion  takes  place  of  the  nutritious  materials 
previously  deposited  in  the  stem.  As  these  materials 
are  distributed  among  the  whole  of  the  fruit,  the  ad- 
vantage of  thinning  it  early  is  evident,  as  the  share 
which  each  will  receive  must  be  proportionably  in- 
creased. We  may  compare  the  maturation  of  the  fruit 
to  the  period  of  gestation  in  animals ;  and  it  is  of  very 
varied  duration  in  different  species.  The  greater  num- 
ber of  plants  ripen  their  fruit  considerably  within  a 
year  from  the  time  when  the  flowers  first  expand,  and 
some  require  only  a  few  days  for  this  purpose.  But 
there  are  certain  trees,  as  some  oaks,  which  require 
eighteen  months ;  and  the  fruit  of  the  juniper,  and  the 
cones  of  many  of  the  fir  tribe,  hang  above  a  twelve- 
month. The  cedar  requires  twenty-seven  months  to 
bring  its  seed  to  perfection. 

The  following  list  contains  a  few  other  examples  of 
the  different  periods  required  by  some  plants  for  the 
maturation  of  their  seeds  : — 

Days        13.  Panicum  viride. 

14.  Avena  pratensis. 

16 — 30.  Most  other  Gramineae. 

Months      2.  Raspberry,  Strawberry,  Cherry,  Elm, 
Poppy,  &c. 

3.  Bird -cherry,  Lime,  Reseda-luteola. 

4.  Whitethorn,  Horse-chestnut. 

5 — 6.  Vine,  Pear,  Apple,  Walnut,  Beech. 

7.  Olive. 

8 — 9-  Colchicum  autumnale,  Missletoe. 

10—11.  Most  Fir  trees. 

No  uncombined  water  is  found  in  the  seed  when  it  is 
completely  ripe ;  but  it  is  now  chemically  united  in 


27  t  PHYSIOLOGICAL    BOTANY.  PART  II. 

their  fecula,  oils,  &c.,  and  the  proportion  of  carbon  also 
is  then  at  a  maximum.  Hence  it  acquires  an  increased 
power  of  resisting  decomposition,  and  of  preserving  its 
vitality  under  every  temperature  to  which  it  is  likely  to 
be  naturally  exposed. 

.Most  ripe  seeds  are  of  greater  specific  gravity  than 
water,  unless  (as  in  the  common  Indian  cress,  Tropa-oliun 
tntijna)  air  happens  to  be  contained  in  their  envelopes, 
when  they  will  float. 

('J7-.)  Stimulant*  to  Maturation. — An  increase  of 
temperature  materially  accelerates  the  period  in  which 
fruits  ripen,  and  also  improves  their  flavour.  Advan- 
tage is  taken  of  this  fact  to  wrap  fruit  in  thin  bags,  to 
place  it  under  glass,  or  upon  slates  of  a  dark  colour. 
That  elaboration  of  the  juices  by  which  the  fruit  is 
ripened  is  a  local  operation,  and  takes  place  within  the 
fruit  itself.  This  is  clearly  shown  where  a  tree,  whose 
fruit  possesses  a  peculiar  flavour,  has  been  grafted  upon 
the  stock  of  another  kind  whose  fruit  possesses  a  very 
different  quality :  no  alteration  is  produced  upon  the 
graft.  Also  where  fruit  has  been  gathered  before  it 
was  quite  ripe  it  will  nevertheless  ripen,  as  every  one  is 
aware  is  the  case  in  apples,  oranges,  and  many  others. 

The  process  of  ringing  the  branches  or  stems  of  fruit 
trees,  already  alluded  to  in  art.  190.,  considerably  acce- 
lerates, as  well  as  secures  the  maturation  of  the  fruit. 
In  the  vineyards  of  France  this  has  been  practised  on  a 
large  scale,  and  a  peculiar  instrument  invented  for  the 
purpose ;  and  the  results  have  shown  that  the  operation 
accelerates  the  ripening  of  the  grapes  from  twelve  to 
fifteen  days.  De  Candolle  mentions  a  vine  near  Geneva 
which  regularly  flowered  every  year,  but  had  never  pro- 
duced fruit  until  this  operation  was  performed  upon  it ; 
and  then  the  fruit  set,  and  proved  to  be  the  small 
Corinth  grape,  which  in  commerce  is  known  under  the 
name  of  dried-currants  or  plums. 

(273.)  Flavour  of  Fruit. — We  are  wholly  unac- 
quainted with  the  physiological  causes  upon  which  the 
different  flavours  of  fruits  depend.  In  the  earlier  state 


FUNCTION    OF    REPRODUCTION. 


275 


of  the  pericarp,  its  functions  are  analogous  to  those  of 
the  leaf ;  but  when  this  organ  possesses  no  stomata  and 
becomes  succulent,  at  first  there  is  a  superabundance  of 
water,  but  in  ripening,  an  increase  of  saccharine  matter 
takes  place  accompanied  with  a  diminution  of  the 
water. 

The  percentage  of  water  and  sugar  in  the  following 
fruits,  in  their  unripe  and  ripe  state,  has  been  thus 
stated,  viz. :  — 


WATER. 

SUGAR. 

Unripe.  ]    Ripe. 

Unripe. 

Ripe. 

Apricot 

89.39 

74.87 

6.64 

16-48 

Peach         -         - 

90.31 

80  24 

— 



Red  Currants 

— 

— 

0-52 

6-24 

Cherries  (royales) 

— 

— 

1-12 

18-12 

Plums  (reine-claude) 

— 

— 

17-71 

24-81 

The  solid  portion  of  succulent  fruits  consists  of  lignine  ; 
and  their  liquid  parts  are  chiefly  water  mixed  with  gum, 
malic-acid,  malate  of  lime,  colouring  matter,  and  vegeto- 
animal  matter.  The  whole  is  flavoured  with  an  aroma- 
tic substance  peculiar  to  each  fruit.  Much  wet  weather 
renders  these  fruits  insipid  ;  and  many  autumnal  fruits 
acquire  more  flavour  if  they  are  detached  from  the  tree 
before  they  are  perfectly  ripe. 

(274.)  Colours  of  Fruit. —  The  peculiar  colours  of 
fruit  depend  upon  some  local  secretions,  of  which  we 
are  not  able  to  give  an  account,  any  more  than  of  those 
which  produce  the  colour  of  the  flower.  These  two 
phenomena  have  this  property  in  common,  that  those 
parts  which  are  usually  coloured  may  become  white  in 
certain  varieties,  which  may  be  propagated  by  slips 
and  cuttings  ;  even  races  of  white-flowered  and  white- 
fruited  varieties  may  to  a  certain  extent  be  established 
by  seed.  The  colours  are  deepened  by  the  action  of 
light. 


T  2 


X70  PHYSIOLOGICAL    BOTANY.  PART  II. 

CHAP.  VI. 

I  t  MTION   OF  REPRODUCTION  CONTINUED. Periods  4,'5. 

DISSEMINATION     (275.).  MODES    OF    DISSEMINATION     (279.) 

PRESERVATION     OF     SEED     (281.).  GERMINATION    (283.). 

VITAI.ITT  OF  THE  EMBRYO  (29O.).  —  RELATION  OF  BTI)  AM) 
EMBRYO  (291.).  —  PROLIFEROUS  FLOWERS  (292.).  HY- 
BRIDS (295.  . 

FOURTH     PERIOD    OF    REPRODUCTION. 

(275.)  Dissemination.  —  THE  manner  in  which  the 
ripe  seed  is  disseminated,  forms  a  more  important  ele- 
ment in  the  history  of  the  preservation  of  species  than 
might  at  first  be  imagined.  It  may  be  considered  ana- 
logous to  the  period  of  labour  in  the  animal  kingdom, 
and  still  more  strictly  to  the  laying  of  eggs  among  such 
as  are  oviparous.  If  the  different  modes  of  dissemina- 
tion were  not  in  harmony  with  the  peculiar  character  of 
the  species,  we  might  expect  in  the  lapse  of  ages  that 
some  combination  of  Circumstances  would  arise  which 
should  so  far  interfere  with  the  reproduction  of  a  given 
species  that  it  would  disappear  from  the  earth.  This 
is  guarded  against  by  some  peculiar  adaptation  of  the 
mode  in  which  the  seed  is  disseminated  to  the  con- 
ditions under  which  each  species  naturally  thrives  the 
best.  In  some  cases,  the  seed  falls  immediately  around 
the  parent  plant ;  and  *vhere  many  seeds  are  contained 
in  the  same  seed-vessel,  the  young  plants  come  up  in 
a  crowded  manner  and  occupy  the  soil  in  society,  to 
the  exclusion  even  of  more  robust  species.  Other  seeds 
and  seed-vessels  are  furnished  with  the  means  of  being 
transported  by  the  influence  of  the  wind  or  by  some  other 
cause  to  a  considerable  distance.  The  great  diversity  in 
the  means  by  which  the  dissemination  of  the  seed  is  na- 
turally secured  forms  one  important  inquiry  to  the  bota- 


CHAP.   VI.  FUNCTION    OF    REPRODUCTION.  277 

nical  geographer ;  and  a  complete  description  of  the 
various  appendages  by  which  their  dispersion  is  assisted 
would  form  an  interesting  topic  of  inquiry.  We  may 
just  refer  to  three  forms  of  fruits  which  are  more  espe- 
cially connected  with  the  physiology  of  our  subject,  and 
which  exercise  a  marked  influence  on  the  dissemination 
of  the  seed. 

(276.)  In  pseudospermic  Fruits. —  In  this  class  we 
may  include  all  fruits  whose  pericarp  is  so  closely 
attached  to  the  seed,  that  it  cannot  readily  be  distin- 
guished from  one  of  its  integuments.  These  are  often 
erroneously  considered  as  naked  seeds,  and  not  as  com- 
plete fruits.  To  this  class  belong  the  various  kinds  of 
corn ;  the  seeds  of  the  umbelliferse,  as  carrots,  parsnips, 
&c. ;  and  of  the  composite  and  others.  In  these  cases, 
the  seed  is  sown  together  with  the  seed  cover  (or  peri- 
carp), and  the  young  plant  has  this  additional  obstacle  to 
overcome  before  it  can  grow.  Many  fruits  of  this  kind 
are  furnished  with  wing-like  appendages,  as  in  the  ash 
and  sycamore ;  or  with  down,  as  in  the  valerian,  but 
more  especially  in  some  of  the  compositae,  as  the  dande- 
lion, thistles,  and  others.  All  these  contrivances  are 
manifestly  intended  to  assist  in  the  dissemination  of  the 
seed ;  but  in  many  cases  the  pseudospermic  seeds  have 
no  such  provision,  and  are  even  so  arranged  on  the 
plant  as  to  secure  it  against  any  very  extended  dis- 
persion. 

(277-)  In  fleshy  Fruits. — The  soft  pulp  which  sur- 
rounds the  seeds  of  fleshy  fruits  does  not  appear  to  ac- 
celerate their  growth  when  sown  with  them  ;  and  by 
its  tendency  to  rot,  it  prevents  them  from  keeping  so 
long  as  when  they  are  divested  of  it.  As  a  sort  of 
compensation  for  the  injuries  which  they  might  receive 
on  this  account,  many  seeds  of  pulpy  fruits  are  encased 
in  a  hard  stone  or  bony  envelope  which  resists  the  action 
of  moisture,  and  protects  them  from  the  influence  of 
the  rotting  pulpy  mass  on  the  exterior.  All  fruits  of 
this  kind  fall  to  the  ground  close  to  the  plant  which 
bears  them,  and  must  depend  upon  accident  for  their 
T  3 


?78  PHYSIOLOGICAL    BOTANY.  PART   II. 

dispersion  ;  but  as  nature  has  destined  these  fruits  to 
be  the  favourite  food  of  many  birds  and  other  animals, 
they  become  instrumental  in  doing  this.  Animals  after 
swallowing  these  fruits  digest  the  pulp  only,  whilst  the 
seed  is  voided  by  them  in  a  state  better  fitted  for  ger- 
mination than  it  was  before. 

(278.)  In  capsuliir  Fruits. —  Under  this  denomina- 
tion may  be  included  all  fruits  whose  pericarp  consists 
of  a  dry  cover,  which  generally  becomes  detached  from 
the  seed,  and  bursts  regularly  along  a  line  of  suture, 
separating  it  into  distinct  valves.  Most  of  these  fruits 
are  many-seeded,  and  their  dispersion  is  commonly 
effected  by  the  agitation  of  the  wind,  which  shakes  a 
few  at  a  time  from  the  capsule.  In  some  cases  they 
are  so  arranged  that  their  dispersion  is  necessarily 
protracted,  whilst  in  others  it  is  speedily  accomplished. 
Some  fruits  retain  their  seed  long  after  they  are  ripe, 
as  though  it  were  necessary  they  should  be  thoroughly 
dried.  Some  capsular  fruits  project  their  seeds  to  a 
distance,  by  the  elastic  force  with  which  their  valves 
suddenly  burst  when  thoroughly  ripe.  The  Balsams 
(Iwjxitieiis)  are  a  familiar  instance  of  this,  in  which 
the  effect  is  acceleraled  or  suddenly  stimulated  by  the 
slightest  contact  of  the.  finger.  The  genus  O.ralis  has 
the  seeds  covered  with  an  elastic  arillus,  which  sud- 
denly bursts  after  the  capsules  have  opened,  and  turning 
the  inside  outwards  projects  the  seed  to  a  considerable 
distance. 

(279-)  Peculiar  Modes  of  Dissemination.  —  The 
ordinary  effect  produced  by  moisture  upon  the  valves  of 
a  seed-vessel  is  to  keep  them  closed  ;  but  there  are 
some  remarkable  exceptions  to  this  law.  In  the  Ona- 
yrarife,  which  grow  naturally  in  moist  places,  the  valves 
open  in  moist  weather,  and  the  seeds  are  then  scattered. 
There  is  a  small  annual  cruciferous  plant,  called  the 
Rose  of  Jericho  (Anastatica  hierochuntina),  which 
grows  In  the  driest  des'erts.  When  the  seeds  are  ripe 
the  plant  withers  and  the  branches  coil  together,  so 
that  the  whole  mass  forms  a  sort  of  ball.  As  the  root 


CHAP.  VI.     FUNCTION  OF  REPRODUCTION.          2?9 

is  very  small  and  unbranched,  it  is  easily  torn  up  by 
the  force  of  the  wind,  and  the  plant  is  then  blown 
along  the  surface  of  the  soil  until  it  happens  to  arrive 
at  some  pool  of  water,  when  the  branches  imbibe 
moisture  and  unrol :  the  pericarps  also  burst  and  the 
seeds  are  disseminated  in  a  spot  where  they  are  able  to 
germinate. 

(280.)  Hypocarpogean  Fruits.  —  There  are  some 
plants  which  possess  the  singular  property  of  ripening 
their  seed  under  the  ground.  In  some  of  these  the 
blossoms  expand  in  the  air,  and  then  the  pericarp  is 
drawn  down  or  forced  underground  by  the  incurvation 
of  the  pedicle,  as  in  the  Antirrhinum  Cymbalaria, 
Cyclamen,  &c.  The  Trifolium  subterraneum,  a  small 
species  of  clover  not  uncommon  in  the  sandy  districts 
of  England,  has  its  flowers  arranged  four  or  five  in  a 
head  :  the  end  of  the  pedicel  emits  some  succulent 
spinous  processes,  which  soon  harden,  and  the  whole  is 
gradually  thrust  under  the  surface  of  the  soil,  where 
the  seeds  ripen  and  germinate. 

Some  plants  possess  two  distinct  modes  of  flowering, 
the  one  aerial  and  the  other  subterranean  ;  and  these 
either  perfect  the  fruit  on  both  stems,  as  in  the  Vicia, 
amphicarpos ;  or  else  that  which  is  produced  on  the  un- 
derground stems  alone  arrives  at  perfection,  as  in  the 
Arachis  hypogcea,  or  ground-nut. 

(281.)  Preservation  of  Seeds. —  Notwithstanding 
the  ample  provision  which  is  made  for  securing  a  super- 
abundant crop  of  seeds,  infinitely  beyond  the  number 
of  individuals  destined  to  spring  up  from  their  disse- 
mination, there  is  another  circumstance  to  be  noticed  in 
their  history,  which  most  materially  diminishes  the 
chance  of  any  species  being  extirpated.  This  is  the 
property  which  seeds  possess  of  resisting  decomposition, 
and  of  retaining  their  vitality  whenever  they  are  placed 
under  circumstances  favourable  to  their  preservation. 
Seeds  are  capable  of  being  longer  preserved  in  propor- 
tion as  they  have  been  more  thoroughly  matured ;  and 
hence  it  is  advisable  to  allow  them  to  remain  for  a 

T    "t 


280  PHYSIOLOGICAL    BOTANY.  PART  II. 

certain  time  in  the  pericarp  after  they  have  been  ga- 
thered, in  order  that  they  may  more  completely  elabo- 
rate the  provision  there  prepared  for  their  use.  When 
thoroughly  mature  many  seeds  may  be  preserved  for  a 
very  great  length  of  time,  provided  they  are  not  exposed 
to  the  influences  of  those  causes  which  determine  their 
germination,  viz : —  a  certain  elevation  of  temperature, 
the  presence  of  oxygen,  and  the  influence  of  water. 
There  are  some  however  which  very  soon  lose  the 
faculty  of  germinating  after  they  an-  ripe,  though  they 
may  be  preserved  in  a  state  fit  for  food  for  a  long  time. 
The  seeds  of  coffee,  for  instance,  will  not  germinate 
unless  they  are  sown  within  the  space  of  a  few  weeks 
after  they  have  become  ripe. 

The  fact  that  seeds  retain  their  vitality  for  very 
many  years  is  well  authenticated.  De  Candolle  tells  us 
that  a  bag  of  seeds  of  the  sensitive-plant  gathered  about 
sixty  years  ago,  has  regularly  supplied  the  Paris  gar- 
den with  fresh  plants  every  year  since  then.  Young 
plants  have  been  raised  from  seeds  of  a  French-bean 
which  were  taken  from  the  herbarium  of  Tournefort, 
where  they  must  have  lain  for  more  than  a  century. 
These  examples  are  remarkable  exceptions  to  the  more 
general  rule,  that  seeds  'cannot  be  artificially  preserved 
in  a  living  state  for  many  years  together.  It  is  cer- 
tain that  most  of  those  found  in  ancient  tombs,  and 
in  the  catacombs  of  Egypt,  have  entirely  lost  their 
vitality ;  and  although  recent  accounts  have  been  pub- 
lished to  the  contrary,  the  fact  does  not  seem  to  have 
been  thoroughly  established,  and  may  possibly  have 
been  founded  on  some  mistake,  or  perhaps  imposition 
practised  upon  the  credulity  of  the  traveller  by  the 
cunning  of  the  natives.  M.  Rifaud,  a  recent  and  labo- 
rious investigator  of  the  antiquities  and  natural  history 
of  Egypt,  brought  to  Europe  a  large  collection  of  various 
seeds,  bulbs,  and  other  parts  of  plants,  which  he  had 
found  in  the  catacombs,  and  all  of  these  were  deprived 
of  any  vegetating  power.  Many  of  them  have  pre- 
served to  a  great  extent  the  appearance  of  freshness. 


CHAP.   VI.  FUNCTION    OF    REPRODUCTION.  281 

Some  spikes  of  maize,  obtained  from  the  tombs  of 
an  ancient  and  extinct  race  in  South  America,  still 
retain  their  original  colours,  the  pericarps  being  either 
red  or  yellow ;  the  variety  is  also  much  smaller,  and 
in  other  respects  different  from  those  at  present  in  cul- 
tivation. But  although  it  is  generally  impossible  to 
secure  the  vitality  of  seeds  by  artificial  means  for  such 
very  lengthened  periods,  it  should  seem  that  naturally 
and  under  peculiar  circumstances,  they  can  retain  the 
power  of  germinating  for  many  ages.  It  is  very 
common,  upon  turning  up  the  soil  from  great  depths, 
or  on  breaking  up  a  tract  of  ground  which  has  lain 
uncultivated  within  the  records  of  history,  to  find  a 
crop  of  plants  spring  up  from  the  newly-exposed  sur- 
face, whose  seeds  must  have  lain  dormant  for  centuries. 
In  the  fens  of  Cambridgeshire,  after  the  surface  has  been 
drained  and  the  soil  ploughed,  large  crops  of  our  mus- 
tards (Sinapis  arvmsis  and  alba)  invariably  spring  up. 
Ray  mentions  the  appearance  of  Siqymbrium  Irio  upon 
the  walls  of  the  houses  immediately  after  the  great  fire 
of  London,  though  the  plant  was  not  before  known  to 
exist  in  the  neighbourhood.  We  must  be  cautious  in 
not  confounding  such  facts  as  we  have  here  referred  to, 
with  the  delusive  effects  sometimes  produced  upon  soil 
which  has  been  brought  up  from  a  great  depth,  and 
taken  from  strata  which  have  never  been  disturbed  be- 
fore. The  seeds  of  plants  which  spring  up  in  such  soils 
have  been  accidentally  conveyed  to  them  by  the  wind. 
We  may  also  account  for  some  cases  where  plants  have 
appeared  spontaneously  on  soils  obtained  from  undis- 
turbed strata  at  great  depths,  by  supposing  the  seed  to 
have  been  carried  there  by  the  percolation  of  water. 

(282.)  Artificial  Preservation  of  Seed.  —  It  is  a 
vulgar  notion  that  some  seeds,  as  those  of  the  melon 
and  cucumber,  improve  by  being  kept  for  a  few  years ; 
and  that  the  plants  raised  from  them  will  produce  more 
fruit  and  fewer  leaves  than  they  would  have  done  had 
they  been  sown  immediately ;  but  this  opinion  appears 
to  be  without  sufficient  foundation.  In  an  economical 


~82  PHYSIOLOGICAL    BOTANY.  1'AHT   II. 

point  of  view,  the  preservation  of  fruits  and  seeds  in  a 
state  fitted  for  food  is  a  subject  of  considerable  import- 
ance ;  and  various  plans  have  been  proposed  which 
might  combine  both  cheapness  and  the  means  of  pro- 
tecting them  from  the  attacks  of  vermin,  with  security 
against  decomposition.  Some  wheat  preserved  at  Zu- 
rich for  a  space  of  250  years  was  found  to  make  ex- 
cellent bread.  One  of  the  simplest  and  at  the  same 
time  most  efficacious  modes  of  preserving  corn,  is  to 
inclose  it  in  wooden  casks  well  pitched,  and  secured 
against  the  influences  of  the  weather.  When  hYshy 
fruits  are  thoroughly  ripe  they  become  rotten,  by  the 
oxygen  uniting  with  their  carbon  and  forming  carbonic 
acid.  This  effect  may  be  prevented,  and  the  fruit  pre- 
served for  a  considerable  length  of  time  in  vessels  her- 
metically sealed,  and  from  which  the  air,  or  at  least  all 
the  oxygen,  has  been  previously  expelled. 

IIITH     PERIOD    OF    REPRODUCTION. 

(283.)  Germination.  —  When  the  maturation  of 
the  seed  is  complete,  all  further  development  of  the 
embryo  ceases,  and  it  then  enters  into  a  state  of  tor- 
pidity ;  and  thus  it  continues  until  it  meets  with  that 
peculiar  combination  of  circumstances  upon  which  tin- 
last  process  of  the  general  function  of  reproduction  de- 
pends. After  the  dispersion  of  the  seed  has  been 
secured,  we  might  properly  consider  the  function  of 
reproduction  to  be  terminated  ;  but  as  the  young  plant 
is  still  dependent  upon  the  nutriment  previously  pro- 
vided for  it,  and  has  not  yet  acquired  the  power  of 
preparing  its  own  nutriment,  we  may  perhaps  be  per- 
mitted to  include  the  process  of  "germination,"  of  which 
we  are  about  to  speak,  among  the  details  of  the  repro- 
ductive function.  Germination  commences  with  the 
revival  of  the  embryo  from  its  state  of  torpidity,  and  is 
considered  to  have  terminated  when  the  whole  of  the 
nutriment  previously  prepared  has  been  absorbed,  and 
the  young  plant  is  able  to  derive  its  nourishment  in  tin- 


CHAP.   VI.  FUNCTION    OF    REPRODUCTION.  283 

usual  way.  This  period  bears  some  analogy  to  that  of 
suckling  in  the  Mammalia,  or  still  more  strikingly  to 
that  of  incubation  in  birds. 

(284.)  Stimulants  to  Germination. —  There  are 
three  requisites  to  germination,  either  of  which  being 
wanting  the  process  will  not  take  place.  These  are 
moisture,  oxygen,  and  a  certain  elevation  of  temper- 
ature. When  the  conditions  requisite  for  the  germina- 
ation  of  a  seed  are  satisfied,  it  imbibes  moisture  through 
its  integuments,  the  embryo  swells,  and  the  radicle  is 
protruded  and  tends  downwards.  The  plumule  or 
terminal  bud  then  expands  and  rises  upwards  ;  the 
albumen,  either  free  or  contained  in  the  cotyledons,  is 
soon  exhausted ;  the  young  plant  takes  firm  hold  on  the 
ground  and  commences  its  independent  existence. 

Although  the  period  which  elapses  between  the  time 
when  seeds  are  sown  and  when  they  first  begin  to  ger- 
minate is  very  different  even  in  the  same  species,  ac- 
cording to  the  external  conditions  under  which  they  are 
placed,  yet  if  different  seeds  are  subjected  to  precisely 
the  same  influences,  we  find  a  still  more  remarkable  dif- 
ference between  the  periods  which  elapse  before  they  se- 
verally germinate.  The  following  list  exhibits  the  result 
of  some  experiments  made  at  the  Geneva  garden,  on 
seeds  similarly  watered  and  exposed  to  a  common  tem- 
perature of  95°  R.  It  was  ascertained  that  about  half 
the  species  of  the  following  families  germinated  after 
the  lapse  of  the  number  of  days  here  mentioned,  viz  : — 
Days. 

9-  Amaranthaceae. 

10.  Cruciferae. 

11.  Cariophyllaceae,  Malvaceae. 

12.  Composite,  Convolvulaceae. 

13.  Polygoneae. 

14.  Leguminosae,  Valerianeae. 

15.  Graminese,  Labiatse,  Solaneae. 
20.  Ranunculacese. 

22.  Onagrariae. 

23.  Umbelliferse. 


284  PHYSIOLOGICAL    BOTANY.  PART   II. 

(285.)  Action  of  Moist tire. —  It  has  been  found  that 
the  quantity  of  water  absorbed  by  seeds  varies  in  pro- 
portion to  their  bulk,  and  that  all  seeds  absorb  very 
nearly  a  weight  of  water  equal  to  their  own.  If  a  co- 
loured liquid  be  used,  it  will  be  found  to  traverse  the 
substance  of  the  seed  cover  (jparMMferm)  until  it  col- 
lects in  the  cellular  tissue  near  the  extremity  of  the 
radicle.  From  this  spot  it  is  imbibed  by  the  radicle,  and 
penetrates  into  the  cotyledons  of  dicotyledonous  plants, 
along  the  minute  and  ramifying  veins  which  traverse 
tin-in.  The  chief  use  of  the  imbibed  water  appears  to 
be,  to  dissolve  whatever  materials  have  been  prepared  in 
the  seed  for  the  nourishment  of  the  embryo,  and  to 
convey  them  into  its  substance.  Where  the  cotyledons 
are  learlike  and  not  fleshy,  they  contain  very  little  nutri- 
ment ;  and  if  there  is  no  free  albumen,  the  cotyledons 
themselves  are  furnished  with  stomata,,,  immediately  ex- 
pand, and  begin  to  elaborate  nutriment  by  decomposing 
carbonic  acid.  When  the  alburnum  is  free  and  surrounds 
the  cotyledons,  it  must  in  some  way  be  absorbed  by 
their  surface,  though  it  is  difficult  to  explain  how.  The 
process  bears  a  striking  analogy  to  the  suckling  of  the 
young  in  animals.  Seeds  will  not  germinate  in  boiled 
or  distilled  water,  from  which  the  oxygen  has  been  ex- 
pelled; and  if  they  are  placed  in  an  atmosphere  of  hydro- 
gen, azote,  carbonic  acid,  or  any  pas  which  contains  no 
portion  of  oxygen,  they  are  equally  incapable  of  ger- 
minating. They  succeed  best  in  a  mixture  of  one  part 
oxygen  with  three  of  azote,  and  this  is  not  very  far 
removed  from  the  proportion  in  which  these  gases  are 
united  in  the  atmosphere.  Where  the  oxygen  is  in 
larger  quantity  it  over-stimulates  the  seed. 

(286.)  Action  of  Oxygen. — One  use  of  oxygen  in  ger- 
mination is  to  unite  with  the  superfluous  carbon  which 
has  been  prepared  during  the  process  of  maturation  for 
the  better  preservation  of  the  seed :  thus  it  appears  that 
the  first  step  in  the  new  process  is  to  undo  the  last  by 
which  the  maturation  was  completed.  Consequently  it  is 


CHAP.  VI.     FUNCTION  OF  REPRODUCTION.          285 

found  that  if  the  nearly  ripe  seed  be  sown  immediately 
it  is  gathered,  it  will  vegetate  more  speedily  than  when 
it  has  remained  in  the  pericarp  until  the  complete  elabor- 
ation of  the  juices  has  taken  place.  This  fact  seems  to 
account  for  the  very  rapid  manner  in  which  corn  vege- 
tates in  moist  and  warm  weather,  after  it  has  been  cut 
and  whilst  still  in  the  sheaf,  or  even  before  it  is  reaped. 

(287-)  Action  of  Heat. — The  degree  of  heat  requisite 
to  produce  germination  is  different  for  seeds  of  different 
species ;  but,  within  certain  limits,  an  increased  tem- 
perature acts  as  a  stimulus  upon  all  of  them,  the  larger 
and  drier  seeds  requiring  a  longer  time  for  the  effect 
to  be  produced. 

(288.)  Action  of  Light.— The  action  of  light,  though 
not  fatal  is  decidedly  noxious  to  the  germination  of 
seeds ;  and  the  cause  why  it  is  so  is  obvious.  Seeds 
require  to  be  freed  from  their  superfluous  carbon,  by 
this  combining  with  oxygen ;  but  light  is  the  chief 
stimulus  which  operates  in  the  decomposition  of  carbonic 
acid,  and  in  the  fixation  of  carbon  in  the  green  parts. 

(289-)  Action  of  the  Soil. — After  germination  is 
complete,  most  plants  grow  in  some  soil  adapted  to  their 
nature,  which  serves  them  as  a  support,  and  more  es- 
pecially regulates  the  right  proportion  of  moisture  re- 
quisite for  their  roots. 

(290,)  Vitality  of  the  Embryo. — Every  part  of  the 
perfected  embryo  appears  to  be  equally  endowed  with 
life  ;  for  if  any  portion  be  cut  off,  the  remainder  con- 
tinues to  germinate  for  a  time,  and  will  often  repro- 
duce the  organ  which  has  been  detached.  Thus  the 
radicle  may  be  repeatedly  cut  away  whilst  it  is  de- 
veloping, and  the  plumule  will  nevertheless  elongate  ; 
or  the  plumule  may  be  cut  away  and  the  radicle  will 
develop.  There  is  of  course  a  limit  to  these  mutila- 
tions, beyond  which  the  young  plant  cannot  be  made  to 
grow  ;  but  whilst  it  is  still  germinating,  the  vital  force 
cannot  be  said  to  reside  in  any  one  part  of  the  indivi- 
dual rather  than  in  another. 

(291.)   Connection  between  Buds  and  Embryos — We 


286  PHYSIOLOGICAL    BOTANY.  r  \KT1I. 

have  already  given  several  instances  of  the  close  affinity 
which  subsists  between  the  various  foliaceous  appendages 
on  the  stem  (art.  85.),  and  have  further  mentioned  the 
community  of  origin  in  the  leaf-bud  and  flower-bud. 
There  also  exists  an  evident  and  striking  affinity  be- 
tween the  leaf-bud  and  the  embryo,  inasmuch  as 
each  of  them  when  detached  from  the  plant  on  which 
they  were  formed,  is  capable  of  becoming  a  perfect  in- 
dividual. The  chief  distinction  between  them  consists 
in  the  former  first  developing  its  ascending  organs  and 
then  its  descending  organs,  whilst  the  embryo  first 
emits  the  root  and  then  develops  the  plumule. 

(-<)-.)  Proliferous  Flowers.  —  In  "  proliferous  " 
flowers  especially,  the  identity  of  their  origin  is  strik- 
ingly exhibited.  In  these  instances,  every  bud  which 
in  ordinary  circumstances  would  have  been  developed  as 
a  flower,  assumes  the  characters  of  a  young  plant.  In 
the  onion  tribe  this  description  of  monstrosity  is  very 
common,  and  the  little  flowers  which  are  aggregated 
into  heads  become  small  bulbs,  and  germinate  as  young 
plants  even  whilst  they  are  still  attached  to  the  summit 
of  the  stem.  The  same  fact  very  often  takes  place  in 
certain  grasses,  and  especially  in  some  of  those  which 
affect  a  mountainous  situation.  This  appears  to  be  a 
provision  of  nature,  to  furnish  an  additional  security 
against  the  chance  of  failure  in  the  seed,  at  an  elevation 
whore  the  cold  might  offer  a  serious  obstacle  to  its  being 
perfected. 

(2f)3.)  Bud*  on  Leaves. —  The  Bryum  rnlju-inuni 
furnishes  one  of  the  most  satisfactory  examples  of  the 
connection  which  exists  between  the  bud  and  the  em- 
bryo. Its  leaves  are  very  fleshy,  and  when  they  are 
placed  in  a  moist  situation,  and  even  whilst  they  are 
still  attached  to  the  stem,  little  buds  are  formed  at  the 
bottom  of  the  crenations  on  their  margins  (fig.  1()8.), 
and  these  buds  soon  develop  into  perfect  plants.  Now 
if  we  only  suppose  a  leaf  of  this  plant  to  be  longitudi- 
nally folded  inwards,  and  that  its  margins  become 
grafted  together,  the  buds  will  then  correspond  to  the 


CHAP.  VI.     FUNCTION  OP  REPRODUCTION.          287 

ovules  arranged  on  the  placenta  of  a  carpel — an  organ 
which  we  have  considered  to  be  formed  on  this  prin- 
ciple (art.  100.). 


(294.)  Proportion  between  Seeds  and  Suds.  —  An 
argument  in  favour  of  the  common  origin  of  the  em- 
bryo and  bud  is  deduced  from  the  observed  fact,,  that 
many  plants  which  produce  the  one  in  abundance  are 
proportionally  defective  in  the  other  kind.  But  this 
after  all  may  depend  upon  the  plant  not  being  able  to 
provide  a  sufficiency  of  nutriment  for  both. 

(295.)  Hybrids.  —  If  the  pollen  of  one  species  is 
employed  to  fertilise  the  ovules  of  another,  the  seeds 
will  often  produce  plants  which  are  strictly  intermediate 
in  all  respects  between  the  two  parents.  Such  produc- 
tions are  termed  hybrids,  and  are  manifestly  analogous 
to  mules  among  animals.  The  conditions  necessary  for 
the  production  of  a  hybrid  are  not  ascertained,  beyond 
the  fact  that  those  species  only  are  capable  of  forming 
them  which  are  nearly  allied  to  each  other,  and  are 
either  of  the  same  genus,  or  of  genera  which  scarcely 
differ.  It  has  been  suggested  that  the  possibility  of 
producing  hybrids  was  limited  to  species  whose  pollen, 
or  rather  whose  pollen  granules,  were  nearly  of  the  same 


288  PHYSIOLOGICAL    BOTANY.  PART  II. 

form  and  dimensions  ;  but  this  is  at  present  mere  con- 
jecture. Not  more  than  forty  kinds  of  hybrids  have 
been  found  naturally  produced  in  a  wild  state  between 
well-defined  species,  and  all  of  these  are  described  as 
barren  or  incapable  of  perfecting  their  ovules ;  so  that 
they  can  never  be  reproduced  by  seed,  though  they 
may  be  propagated  by  other  means.  Numerous  hy- 
brids are  continually  produced  artificially  by  horticul- 
turists, for  the  purpose  of  obtaining  choice  flowers  and 
fruit  ;  and  it  has  been  asserted  that  many  of  these  are 
capable  of  fertilising  their  ovules,  and  thus  of  being  re- 
produced by  seed.  If  this  be  really  the  case,  it  would 
seem  to  be  impossible  for  us  to  draw  any  distinction 
between  true  species  and  hybrids.  But  sufficient  atten- 
tion has  not  hitherto  been  paid  to  this  intricate  subject, 
to  enable  us  to  feel  quite  satisfied  that  these  supposed 
hybrids  are  any  more  than  intermediate  forms  between 
marked  varieties  or  races  of  the  same  species.  It 
appears  to  have  been  ascertained  that  hybrids  may 
be  fertilised  by  the  pollen  taken  from  one  or  other 
of  the  parent  species,  and  that  the  seed  thus  obtained 
will  produce  plants  intermediate  between  that  species 
and  the  hybrid,  and  thus  a  return  may  gradually  .be 
made  to  one  of  the  original  types.  It  has  been  equally 
asserted  of  animals,  that  although  mules  never  produce 
young  between  themselves,  yet  a  female  mule  may  be- 
come productive  by  a  male  of  one  or  other  of  the  parent 
species. 

The  rarity  of  wild  hybrids  is  easily  accounted  for 
by  the  fact,  that  so  soon  as  the  stigma  has  been  affected 
by  the  contact  of  the  pollen,  it  becomes  incapable  of 
transmitting  an  additional  influence  from  any  fresh 
grains  that  may  afterwards  be  applied  to  it ;  and  conse- 
quently the  chances  of  every  stigma  being  first  affected 
by  the  pollen  of  its  own  stamens  (if  we  except  dioecious 
species),  is  infinitely  greater  than  its  receiving  any 
influence  from  others. 

(296'.)  Permanence  of  Specie*.  —  Every  thing  that 
has  hitherto  been  written  on  the  origin  and  limitation  of 


CHAP.  VI.  FUNCTION    OF    REPRODUCTION.  289 

species,  may  be  fairly  stated  as  purely  hypothetical. 
Linnaeus  supposed  that  only  a  few  species  or  distinct 
typical  forms  were  originally  created,  and  that  a  mul- 
titude of  others  had  since  been  derived  from  them  by 
repeated  intermixture  and  crossings.  He  supposed  the 
species  of  very  different  genera  might  be  capable  of  in- 
termixing and  producing  new  species,  and  even  new- 
genera.  These  speculations  are  wholly  unsupported  by 
facts  or  experiments.  De  Candolle  also  supposes  a  de- 
finite number  of  species  or  typical  forms  to  have  been 
originally  created,  but  he  does  not  imagine  any  de- 
cidedly new  form  or  type  to  have  ever  originated  from 
them.  He  considers  that  certain  hybrids  can  repro- 
duce their  kind,  but  that  in  such  cases  there  exists  a 
constant  tendency  in  the  offspring  to  return  again  into 
one  or  other  of  the  original  types  from  which  they  sprang. 
Thus  we  should  never  have  any  strictly  new  type  intro- 
duced, or  any  form  which  differed  very  materially  from 
what  was  already  in  existence,  but  only  a  multitude  of 
minute  shades  of  difference,  in  varieties  which  were  all 
intermediate  between  the  original  species.  In  this  way 
he  proposes  to  account  for  the  endless  varieties  of  some 
of  our  long  cultivated  fruits,  as  apples,  pears,  &c.  The 
subject  is  one  of  great  difficulty,  and  it  will  require 
many  accurate  and  careful  experiments  to  be  made, 
before  we  can  expect  to  ascertain  the  laws  by  which  the 
limitation  of  species  and  the  production  of  hybrids  are 
regulated.  We  are  quite  certain  that  many  forms,  con- 
sidered characteristic  of  particular  species,  have  con- 
tinued unaltered  in  their  minutest  particulars  for  the 
last  3000  years  at  least.  This  is  proved  by  a  careful 
examination  of  the  fragments  of  numerous  plants  found 
in  the  catacombs  of  Egypt.  An  analogous  fact  is  still 
more  strikingly  established  in  the  animal  kingdom,  and 
for  a  much  longer  period ;  since  the  forms  of  certain 
existing  species  of  shells  have  been  found  in  those  ter- 
tiary deposits  of  which  the  geologist  can  say  no  more 
than  that  they  are  comparatively  recent  in  the  history 
v 


290  PHYSIOLOGICAL    BOTANY.  PART  II. 

of  our  globe,  though  incalculably  earlier  than  any  date 
to  which  we  can  refer  by  authentic  records. 

(297.)  Oriyiit  of  I'dricdex. — The  origin  of  varieties 
is  a  phenomenon  in  some  respects  analogous  to  the 
creation  of  hybrids ;  and  it  has  been  even  supposed 
that  all  races,  or  such  varieties  as  are  capable  of  main- 
taining their  peculiarities  by  seed,  must  have  originated  in 
hybridity  between  two  species.  If  such  hybrids  have 
been  fertilised  by  the  parent  species,  and  new  hybrids  of 
the  second  and  third  degree  been  produced,  these  will  so 
closely  resemble  the  parent  plants  that  they  will  appear 
to  be  mere  varieties  of  it. 


CHAP.  VII. 

EPIRRHEOLOGY,  BOTANICAL  GEOGRAPHY,   FOSSIL  BOTANY. 

EFIRRHEOLOCY      (298.).    DIRECTION     OF     ROOTS     AND     STEMS 

(299.) BOTANICAL    GEOGRAPHY   (302.). FOSSIL    BOTANY. 

(315.). 

(298.)  Epir rheology.  —  THIS  term  has  recently  been 
proposed,  to  express  thsft  branch  of  our  science  which 
treats  of  the  effects  produced  by  external  agents  upon 
the  living  plant.  It  can  only  be  considered  as  a  sub- 
ordinate department  of  vegetable  physiology,  and  one 
indeed  whose  limits  are  not  very  strictly  defined.  For 
we  have  seen  that  life  itself  requires  the  stimulus  of 
external  agency,  in  order  that  its  powers  may  be  eli- 
cited, and  produce  the  various  phenomena  of  vege- 
tation included  under  one  or  other  of  the  two  functions 
of  nutrition  and  reproduction.  But  then  these  func- 
tions become  variously  modified,  according  as  the  ex- 
ternal stimuli  by  which  they  are  called  into  action  are 


CHAP.  VII.  EPIRRHEOLOGY.  2§1 

permitted  to  operate  with  greater  or  less  intensity.  In 
all  cases,  there  is  that  happy  mean  which  can  so  regu- 
late the  vital  force  as  to  produce  a  healthy  and  vigorous 
condition  of  existence ;  whilst  every  increase  or  dimi- 
nution in  the  stimulus  applied,  only  tends  to  injure  or 
greatly  to  modify  the  individual  subjected  to  its  long- 
continued  influence.  Physiology  might  be  considered 
as  embracing  the  investigation  only  of  such  phenomena 
as  resulted  from  the  healthy  condition  of  the  vital 
functions ;  whilst  epirrheology  would  take  further  cog- 
nisance of  such  as  resulted  from  an  unhealthy  condi- 
tion of  vegetation.  Hence  this  department  would  lay 
the  foundations  of  another  branch,  termed  the  "  noso- 
logy "  of  plants,  or  that  science  which  treats  of  their 
diseases  ;  and  also  of  the  extensive  subject  of  "  Bota- 
nical Geography,"  which  makes  inquiry  into  those 
causes  which  limit  the  distribution  of  various  species 
to  certain  spots  upon  the  earth's  surface.  But  in  a  trea- 
tise like  the  present  we  have  not  thought  it  necessary 
to  make  any  distinction  between  physiology  and  epir- 
rheology, nor  are  we  prepared  to  allow  that  such  distinc- 
tion is  a  very  judicious  one.  In  order  to  understand 
the  effects  produced  by  the  vital  force,  it  is  necessary  to 
trace  its  operations  under  various  modifications  of  the 
external  stimuli  by  which  it  is  controlled,  and  even  ren- 
dered capable  of  acting  at  all.  These  inquiries  relate  to 
the  results  of  an  action  and  reaction  between  opposing 
forces,  questions  which  cannot  well  be  separated  with- 
out greater  refinement  than  the  subject  seems  to  require. 
There  are,  however,  certain  phenomena,  the  discussion  of 
which  could  not  be  conveniently  introduced  under  either 
of  the  two  functions  into  which  the  vital  properties  were 
arranged.  Of  these  we  may  select  as  an  example  the 
effects  produced  by  the  action  of  gravity  upon  growing 
plants. 

(299.)   Direction  of  Roots  and.  Stems.— That   the 

roots  and  stems  of  most  plants  constantly  develop  in 

opposite  directions,  is  a  fact  too   notorious  to   need  a 

comment ;  and  any  deviation  from  this  general  law  is 

u  2 


292  PHYSIOLOGICAL    BOTANY.  PART  II. 

considered  an  anomalous  circumstance.  It  is  not 
strictly  true  to  say  that  the  tendency  of  all  stems  is 
upwards,  though  it  is  more  nearly  true  that  all  roots 
take  a  direction  downwards.  The  branches  of  the 
weeping  birch,  weeping  willow,  and  some  others  of  this 
character  incline  downwards,  merely  by  the  effect  of 
gravity,  acting  upon  the  long  slender  rods  of  which  they 
are  formed.  But  there  are  some  trees,  as  the  weeping 
ash,  and  weeping  horse-chestnut,  whose  branches  take  a 
decidedly  downward  tendency  from  their  very  origin. 
Many  plants  also  have  underground  stems  (fMoHMff), 
besides  those  which  they  develop  above  ground.  But, 
neglecting  these  anomalies,  it  is  generally  true  that  the- 
stem  has  a  tendency  to  develop  upwards,  and  the  root 
downwards.  There  are  two  causes  to  which  we  may 
ascribe  these  modifications  in  the  directions  of  the 
stems  and  roots.  One  is  "  gravity,"  and  the  other 
«'  light." 

(300.)  Effects  of  Gravity  on  Vi'tjctntinn.  —  That 
gravity  is  an  important  agent  in  determining  the  differ- 
ence between  the  directions  taken  by  the  root  and  stem, 
is  shown  by  an  ingenious  experiment  of  Mr.  Knight. 
He  placed  some  French-beans  on  the  circumference  of 
two  wheels,  and  so  secured  them  that  they  could  not  be 
thrown  off  when  a  rapid  rotatory  motion  was  given  to 
the  wheels.  One  wheel  was  disposed  horizontally,  and 
the  other  vertically,  and  both  were  kept  in  constant 
motion  whilst  the  beans  were  germinating.  The  radi- 
cles of  those  beans  which  germinated  on  the  vertical 
wheel  extended  themselves  outwards  or  from  the  cen- 
tre, and  the  plumules  inwards  or  towards  it.  Those 
which  were  placed  on  the  horizontal  wheel  pushed  their 
radicles  downwards  and  their  plumules  upwards;  but 
the  former  were  also  inclined  from,  and  the  latter  to- 
wards the  axis  of  the  wheel.  This  inclination  was 
found  to  be  greater  in  proportion  as  the  velocity  of  the 
wheel  was  increased.  Now  in  the  vertical  wheel  the 
effects  of  gravity  were  nullified,  since  the  beans  were 
constantly  changing  their  position  with  respect  to  those 


CHAP.  VII.  EPIRRHEOLOGY.  293 

parts  which  were  alternately  uppermost  and  lower- 
most in  each  revolution.  The  only  cause  which 
could  have  produced  the  effects  described  must  be  the 
centrifugal  force,  which  has  here  replaced  the  force  of 
gravity,  compelling  the  root  to  grow  outwards  and  the 
stem  inwards,  instead  of  downwards  and  upwards.  The 
effect  produced  upon  the  horizontal  wheel  is  evidently 
the  result  of  the  combined  action  of  the  two  forces  — 
gravity  inclining  the  root  downwards,  and  the  centri- 
fugal force  propelling  it  outwards ;  and  the  reverse 
with  regard  to  the  stem.  Although  it  is  plain  that 
gravity  is  the  efficient  cause  in  establishing  the  direc- 
tions of  the  stems  and  roots  of  plants,  it  is  not  so  easy 
to  understand  the  manner  in  which  it  produces  opposite 
effects  on  these  two  organs.  Various  theories  have  been 
formed  to  account  for  this,  and  the  most  plausible  is 
that  which  ascribes  it  to  the  different  manners  in 
which  the  newly  developed  tissues  are  added  to  the 
root  and  stem.  In  the  root  the  addition  is  almost 
entirely  confined  to  the  very  extremity,  whilst  the  stem 
continues  to  increase  for  some  time  throughout  its  whole 
length.  Hence  it  is  supposed  that  the  soft  materials 
continually  deposited  at  the  extremity  of  the  root  must 
ever  be  tending  downwards  from  the  mere  effect  of 
gravity  alone.  In  the  stem,  gravity  would  cause  a  sub- 
sidence of  the  denser  and  more  nutritious  materials  to 
the  lower  side,  and  this  side  would  consequently  be 
more  nourished  thart  the  upper,  supposing  the  stem  to 
be  somewhat  inclined  from  the  perpendicular.  The 
consequence  of  one  side  being  better  nourished  than  the 
other,  whilst  the  whole  was  in  a  growing  state,  would 
be  a  greater  extension  of  that  side;  and  thus  a  slight 
curvature  upwards  would  be  given  to  the  stem,  which, 
being  continually  repeated  as  it  develops,  would  always 
tend  to  keep  it  more  or  less  in  a  vertical  position.  Per- 
haps we  want  sufficient  data  to  allow  us  to  lay  any 
great  stress  upon  this  explanation. 

(301.)     Effect  of  Light  on   Vegetation.  —  Light  is 
another  cause  which  produces  a  great  effect  in  modify- 
u  3 


2J)4  PHYSIOLOGICAL    BOTANY.  PABT  II. 

ing  the  directions  of  the  stems  of  plants.  When  grown 
in  a  chamber  which  admits  the  light  on  one  side 
only,  they  constantly  incline  towards  it.  This  has  been 
supposed  to  be  owing  to  a  greater  decomposition  of 
carbonic  acid  on  the  side  which  is  towards  the  light, 
and  a  necessarily  greater  deposition  of  carbon  on  that 
side  than  on  the  other.  This  produces  a  greater  rigidity 
in  those  parts,  and  consequently  a  curvature  on  the  side 
which  is  towards  the  light.  This  effect  is  produced 
only  on  the  young  green  parts  of  plants,  and  does 
not  take  place  in  the  old  woody  portions  ;  nor  is  it 
observed  in  parasitic  species,  which  are  without  the 
means  of  decomposing  carbonic  acid.  The  missletoe 
forms  a  most  remarkable  exception  to  the  usual  laws 
which  regulate  the  direction  of  the  root  and  stem. 
If  a  seed  of  this  plant  be  attached  to  a  piece  of  glass 
placed  over  a  dark  surface,  the  radicle  invariably  ex- 
tends itself  in  a  direction  opposite  to  the  side  in  which 
the  light  shines,  from  whatever  quarter  it  may  come. 
The  branches  of  this  plant  are  also  developed  indiffer- 
ently in  all  directions,  without  any  obvious  tendency 
either  upwards  or  towards  the  side  from  whence  the 
greatest  illumination  may  proceed. 

(302.)  Botanical  Geography.  —  We  cannot  dismiss 
the  physiological  department  of  our  subject,  without 
referring  to  that  branch  of  it  which  treats  of  the 
natural  distribution  of  plants  on  the  earth's  surface  —  in 
other  words,  to  "  Botanical  Geography."  It  is  a  fact 
sufficiently  familiar  to  every  one,  that  different  species 
of  plants  affect  peculiar  situations ;  some  love  an  ex- 
posed aspect,  others  prefer  shady  places ;  some  are 
found  in  mountainous  districts,  others  in  plains,  in 
marshes,  and  even  wholly  submerged  in  lakes,  or  in 
the  sea.  The  various  physical  circumstances  attend- 
ing different  spots  in  the  same  range  of  country 
determine  the  "stations"  in  which  the  different  spe- 
cies of  plants  can  grow.  We  know  that  different 
plants  require  different  degrees  of  temperature  ;  some 
are  calculated  to  live  in  cold  or  temperate  climates, 
whilst  there  are  others  which  belong  to  the  torrid  zone ; 


CHAP.  VII.  BOTANICAL,    GEOGBAPHY.  295 

and  these  last  we  are  obliged  in  our  latitudes  to  preserve 
in  the  stove  or  conservatory.  The  term  "  habitation  " 
has  been  given  to  any  tract  of  country  throughout 
which  each  particular  species  is  found  naturally  distri- 
buted in  stations  adapted  to  its  growth.  The  deter- 
mination of  these  stations  and  habitations  of  plants 
leads  to  an  inquiry  into  the  laws  and  circumstances 
which  regulate  the  distribution  of  species.  We  must 
suppose  that  there  exists  a  mutual  relation  between  the 
external  conditions  under  which  each  species  is  naturally 
disposed,  and  its  own  peculiar  organization ;  and  this 
relation  must  be  sought  for  by  a  patient  comparison  of 
the  various  species,  genera,  and  families  peculiar  to  dif- 
ferent regions,  with  the  precise  conditions  under  which 
they  there  exist.  The  problem  is  one  of  a  most  com- 
plicated description,  and  it  cannot  be  said  that  any  very 
decided  progress  has  hitherto  been  made  towards  its 
solution.  We  shall  mention  some  of  the  more  obvious 
conditions  under  which  all  inquiries  of  this  description 
must  be  regulated,  and  present  the  reader  with  some  of 
the  conclusions  at  which  botanists  have  already  arrived. 

Influence  of  external  Circumstances  on  the  Geographic 
Distribution  of  Plants. 

(303.)  Temperature.  —  The  influence  of  temper- 
ature is  the  most  decided  of  all  the  circumstances  which 
regulate  the  distribution  of  plants  on  the  surface  of  the 
earth.  It  seems  evident,  that  each  species  is  constitu- 
tionally adapted  to  thrive  best  between  certain  limits  of 
temperature,  and  that  every  excess  of  heat  or  cold 
(beyond  these)  is  alike  injurious  to  it.  Hence,  every 
species  must  naturally  be  restricted  within  those  geo- 
graphical boundaries  beyond  which  the  temperature 
either  exceeds  or  falls  short  of  these  limits.  These 
boundaries  will  not  necessarily  coincide  with  any  de- 
finite parallels  of  latitude ;  for  it  is  well  known  that 
the  climate  of  different  places  having  the  same  latitude 
is  very  different.  By  drawing  lines  through  those 
u  4 


29  PHYSIOLOGICAL    BOTANY.  PART  II. 

places  where  the  mean  annual  temperature  is  found  to 
be  the  same,  Humboltlt  established  a  series  of  "  Iso- 
thermal"  lines  intersecting  the  parallels  of  latitude.  But 
these  lines  by  no  means  show  us  what  might  be  the 
probable  range  of  particular  species.  For  an  isothermal 
line  may  intersect  a  range  of  country  where  the  extremes 
of  heat  and  cold  are  very  different ;  and  the  constitution 
of  different  species,  which  may  be  equally  adapted  to  a 
given  mean  temperature,  may  not  be  equally  suited  to 
these  differences  in  the  extremes.  Thus  many  plants 
which  will  live  in  the  open  air  at  Edinburgh,  would 
perish  during  the  severer  winters  of  more  southerly 
regions,  whilst  many  that  can  stand  greater  cold  than 
that  to  which  they  would  he  exposed  at  Edinburgh, 
require  also  greater  heat  in  the  summer  than  they  would 
find  there,  in  order  to  bring  their  fruit  to  perfection,  or 
even  to  ripen  their  wood  sufficiently  to  maintain  them 
in  a  healthy  condition.  In  fact,  the  mean  distribution 
of  temperature  throughout  the  year,  is  a  considera- 
tion of  much  less  importance  than  the  distribution 
per  month,  which  perhaps  most  effectually  regulates 
the  range  of  species.  As  annuals  cannot  maintain 
their  footing  in  any  climate  without  yearly  perfecting 
their  seeds,  they  are  necessarily  limited  to  more  tem- 
perate habitations  than  certain  perennials  ;  it  is  suf- 
ficient for  the  latter,  if  they  occasionally  meet  with 
a  season  in  which  they  may  be  able  to  do  so.  It  has 
been  remarked  that  the  western  parts  of  continents  are 
more  nearly  equable  in  their  temperature  throughout 
the  year  than  the  eastern,  and  the  southern  hemisphere 
than  the  northern  ;  and  that  evergreens  affect  the 
former,  and  deciduous  trees  the  latter  description  of 
climate.  Maritime  districts  have  always  a  more  nearly 
equable  temperature  than  such  as  are  inland. 

Besides  the  physiological  relations  which  plants  pos- 
sess with  regard  to  temperature,  there  are  others  of  a 
physical  character  by  which  their  distribution  is  con- 
siderably affected.  Where  the  temperature  is  so  low 
that  water  exists  only  in  the  form  of  ice,  it  cannot  be 
imbibed  by  the  roots,  and  no  plants  can  live,  there. 


CHAP.  VII.  BOTANICAL    GEOGRAPHY.  297 

When  the  sap  is  frozen,  the  cells  and  vessels  in  which 
it  is  contained  are  ruptured,  and  the  parts  subjected 
to  such  an  accident  die.  But  trees  possess  a  resource 
against  the  effects  of  great  cold,  in  their  roots  pene- 
trating to  a  depth  beyond  that  which  the  frost  has 
reached.  Hence  they  obtain  a  supply  of  caloric,  which 
is  not  readily  carried  off,  because  their  woody  layers  and 
bark  are  bad  conductors  of  heat.  It  has  been  observed 
that  the  internal  parts  of  large  trees  retain  a  temperature 
which  is  about  equal  to  that  of  the  subsoil  at  one  half 
the  depth  of  their  roots. 

The  temperature  of  a  tree,  being  always  influenced  by 
that  of  the  subsoil,  will  be  greater  than  the  surrounding 
atmosphere  during  winter  in  high  latitudes,  and  less 
during  summer  in  low  latitudes.  This  is  even  more 
remarkably  the  case  than  would  at  first  be  imagined,  if 
we  were  to  refer  the  cooling  and  heating  of  the  earth  to 
the  effect  of  radiation  alone.  But  it  has  been  observed 
by  Von  Buch,  that  the  temperature  of  the  subsoil  is 
mainly  regulated  by  that  of  the  surface  waters,  which 
by  infiltrating  into  the  earth  produce  an  effect  far 
greater  than  any  which  may  be  ascribed  to  the  mere 
conducting  power  of  rocks  and  soils.  Now,  in  the 
frigid  zone,  no  infiltration  takes  place  during  the  winter, 
when  every  drop  of  water  is  converted  into  ice  or  snow; 
and  consequently  the  mean  temperature  of  the  subsoil 
in  very  high  latitudes,  will  be  somewhat  higher  than  the 
mean  temperature  of  the  atmosphere  ;  but  this  is  not  so  in 
lower  latitudes,  where  the  infiltration  continues  during 
a  great  portion  of  the  Avinter.  On  the  other  hand,  as 
we  approach  the  torrid  zone,  where  rain  falls  only 
during  the  coolest  season  of  the  year,  the  mean  tem- 
perature of  the  subsoil  will  be  more  cooled  in  propor- 
tion than  in  those  places  where  it  also  falls  during  the 
hottest  weather.  Hence  it  happens  that  the  mean  tem- 
perature of  springs  throughout  the  central  and  northern 
parts  of  Europe,  as  far  as  Edinburgh,  are  much  the 
same  as  the  mean  temperature  of  the  air ;  whilst  from 
the  south  of  Europe  to  the  tropic  of  Cancer,  the  difference 
is  gradually  increasing  in  favour  of  the  atmos  phere 


298  PHYSIOLOGICAL    BOTANY.  PART  II. 

But  from  the  latitude  of  Edinburgh  northwards,  the 
difference  increases  in  favour  of  the  subsoil.  The 
consequence  is  that  certain  plants  which  naturally 
belong  to  the  more  temperate  parts  of  our  zone,  are 
enabled  to  extend  themselves  further  north  and  south 
than  they  could  do  if  the  mean  temperature  of  the  soil 
and  air  were  every  where  the  same. 

(30-t.)  Influence  of  Light.  —  The  influence  of  light 
is  less  essential  than  that  of  temperature  in  fixing  the 
geographical  limits  of  different  species,  though  it  is  cer- 
tainly of  great  importance  in  many  cases.  Light  is,  as 
we  have  seen,  the  chief  agent  in  stimulating  the  vital 
properties,  and  its  effects  are  apparent  in  a  great 
number  of  vital  phenomena,  such  as  the  absorption  of 
the  sap,  the  exhalation  of  moisture,  and  the  decom- 
position of  carbonic  acid.  It  is  probable  that  each 
species  requires  a  peculiar  stimulus  from  different  de- 
grees of  light  as  well  as  of  heat,  and  we  find  that  such 
as  are  succulent,  resinous,  or  oily,  generally  prefer  situ- 
ations where  they  can  obtain  most  light ;  whilst  many 
evergreens  and  others  grow  best  where  they  are  some- 
what shaded.  In  these  respects  alpine  plants  may  be 
contrasted  with  maritime  species,  the  former  receiving 
the  greatest  and  the  latter  the  least  light,  under  the 
same  degree  of  latitude.  Whilst  the  mean  distribution 
of  light  is  more  nearly  equable  for  all  latitudes  than  the 
mean  temperature,  the  variations  in  the  mode  of  its  dis- 
tribution are  much  greater.  Contrast,  for  instance,  the 
alternate  long  continuance  of  light  and  darkness  at  the 
poles  with  their  nearly  equable  daily  distribution  at  the 
equator. 

(305.)  Influence  of  Moisture.  —  The  proportion  in 
which  water  is  supplied,  constitutes  one  of  the  chief 
peculiarities  of  every  "  station  ; "  and  plants  are  very 
differently  constituted  with  respect  to  the  precise  supply 
which  they  require  to  preserve  them  in  a  healthy  con- 
dition. Those  which  require  most,  have  a  loose  and 
spongy  texture,  with  large  and  soft  leaves,  and  little  or 
no  pubescence,  but  many  stomata ;  whilst  such  as  grow 
in  arid  districts  are  frequently  firm  and  succulent,  often 


CHAP.  VII.      BOTANICAL  GEOGRAPHY.  299 

provided  with  long  pubescence,  but  have  few  stomata. 
An  excess  of  water  is  apt  to  corrupt  and  dissolve  the 
outer  texture,  and  hence  we  find  many  aquatics,  as  the 
pondweeds  (Potamogeton),  protected  by  a  superficial 
varnish.  Many  Monocotyledons  are  coated  with  a 
siliceous  pellicle,  and  afford  useful  materials  for  thatch- 
ing, as  the  common  reed. 

(306.)  Influence  of  Soils.  —  Most  soils  are  a  very 
heterogeneous  mixture  of  different  earths  and  other  mat- 
ters ;  and  hence  it  is  not  likely  that  any  very  decided 
feature  will  be  often  impressed  upon  the  flora  of  a  given 
district,  by  any  peculiarity  in  the  purely  chemical 
qualities  which  soils  possess.  That  some  chemical 
action  takes  place  in  certain  soils  cannot  be  positively 
denied,  but  has  probably  been  greatly  exaggerated. 
For  though  certain  plants  seem  to  prefer  particular 
geological  districts  marked  by  the  prevalence  of  pecu- 
liar rocks,  some  especially  abounding  on  limestone 
and  chalk,  others  on  slate-rock ;  yet  it  not  unfre- 
quently  happens  that  many  of  these  plants  also  occur 
in  equal  abundance  in  some  other  localities  where 
the  rocks  possess  a  totally  different  mineralogical  cha- 
racter. It  seems,  therefore,  more  likely  that  such  effects 
may  be  attributed  to  mechanical  rather  than  to  chemical 
causes;  especially  to  the  mode  in  which  different  rocks  dis- 
integrate, and  are  rendered  capable  of  retaining  a  greater 
or  less  abundant  supply  of  moisture.  It  may  indeed  be 
said,  that  these  mechanical  properties  are  generally  the 
direct  result  of  the  peculiar  chemical  qualities  which  the 
rocks  possess,  though  in  some  cases  rocks  of  very  different 
mineralogical  character  certainly  disintegrate  in  much  the 
same  manner.  Hence  we  find  the  same  lichens  and 
some  other  plants  growing  on  schistose  rocks,  whether 
they  happen  to  be  argillaceous  or  cretaceous  in  their 
composition.  Various  soils  may  be  stated  as  generally 
retaining  moisture  in  proportion  to  the  quantity  of  alu- 
mina which  they  contain,  and  parting  with  it  more  rea- 
dily in  proportion  as  they  abound  in  silica.  Siliceous 
tracts  require  most  rain,  and  clay  soils  least,  to  become 


300  PHYSIOLOGICAL    BOTANY.  PART  II. 

proportionably  fertile.  Sandy  districts  support  only 
such  low  or  trailing  plants  as  the  wind  cannot  readily 
root  out,  or  those  which  have  very  deep  and  branching 
roots  ;  whilst  very  tenacious  clays  are  adapted  only  to 
such  species  as  have  small  roots,  and  which  do  not 
require  any  great  depth  of  earth. 

(307.)  Influence  of  the  Atinnx/ilicrr.  —  Although  the 
atmosphere  is  every  where  of  the  same  chemical  com- 
position, its  effects  may  vary  in  proportion  to  the  density 
which  it  possesses  at  different  elevations,  or  according 
to  the  materials  (as  moisture,  gases,  &c.)  which  may 
be  suspended  in  it;  or  lastly  according  to  its  mecha- 
nical action,  in  the  greater  or  less  degree  of  violence 
with  which  it  is  moved  in  different  regions.  It  is  pro- 
bable that  the  difference  in  density  which  the  atmosphere 
possesses  at  different  elevations  above  the  surface  of  the 
earth,  produces  little  or  no  effect  in  comparison  with 
those  which  result  from  the  modifications  which  the 
temperature,  light,  humidity  of  the  air,  &c.  undergo. 
Since  the  mean  temperature  diminishes  in  receding  from 
the  equator  much  in  the  same  proportion  as  in  ascending 
a  mountain,  many  plants  peculiar  to  the  plains  of  higher 
latitudes  are  found  on  the  tops  of  mountains  in  w  armer 
climates.  Hence  a  very,  extensive  range  may  be  given 
artificially  to  some  plants,  by  cultivating  them  at 
different  altitudes  in  different  latitudes.  Humboldt 
has  likened  the  earth  to  two  great  mountains  whose 
bases  meet  at  the  equator,  and  whose  summits  are  the 
poles ;  and,  ceterig  parihus,  we  may  say  that  the 
latitude  at  which  a  plant  thrives  best  will  vary  as  the 
altitude  above  the  sea  at  which  it  also  flourishes  under 
the  tropics.  The  potato  offers  an  interesting  illustra- 
tion of  this  fact  —  growing  in  Chili,  at  an  altitude  of 
eleven  or  twelve  thousand  feet  above  the  level  of  the 
sea,  and  being  well  adapted  to  summer  culture  in  the 
plains  of  the  temperate  zone  as  far  north  as  Scotland. 
The  olive  has  a  much  less  extended  range,  and  can  only 
be  cultivated  as  far  north  as  24°,  and  at  an  altitude  of 
twelve  hundred  feet  in  tropical  climates. 


CHAP.  VII.      BOTANICAL  GEOGRAPHY.  SOI 

(308.)  Botanical  Stations.  —  The  various  peculiari- 
ties which  characterize  different  "stations/'  can  scarcely 
be  appreciated.  Those  which  possess  a  very  general 
resemblance,  may  still  differ  in  some  important  cir- 
cumstance by  which  the  existence,  or  at  least  the  pre- 
valence of  some  peculiar  species  may  be  determined. 
Thus  a  marsh  may  be  formed  by  salt  and  fresh  water 
mixed  in  different  proportions ;  two  tracts  in  other 
respects  alike,  may  be  very  differently  exposed  to  the 
prevalence  of  winds,  or  the  influence  of  sea  breezes, 
&c.  Independently  of  these  modifying  circumstances, 
we  may  enumerate  about  sixteen  tolerably  well  de- 
fined stations,  to  one  or  other  of  which  the  different 
plants  of  every  flora  will  be  found  more  particularly 
attached. 

1.  Maritime.  —  Districts  bordering  on  the  sea  and 
influenced  by  the  spray  and  sea  breezes. 

2.  Marine. — Where  plants    are  growing   beneath 
or  on  the  surface  of  the  sea  itself. 

3.  Aquatic.  —  Freshwater  rivers  and  lakes,  where 
the  plants  are   wholly  immersed  or    floating   on    the 
surface. 

4.  Marsh. — Bogs  and  fens. 

5.  Meadows  and  Pastures. 

6.  Cultivated  Lands. — These  districts    abound    in 
plants  which  have  been  introduced  by  the  agency  of 
man,    and   have  become    completely  or   partially   na- 
turalized. 

7.  Rocks.  —  Lichens,    mosses,    and    other    crypto- 
gamic   tribes    abound    in    rocky    situations,  but  more 
especially  in  the  vicinity  of  springs  and  cascades.     A 
few  phanerogamic  plants  also  affect  such  situations, 
even  where  there  is  little  or  no  soil  to  support  them. 

8.  Sands. 

9.  Barren  Tracts,  by  road  sides,  &c. 

10.  Rubbish.  —  There     are    many    species    which 
seem   to  follow  the  footsteps  of  man,   and  spring  up 
wherever  he  scatters  the  rubbish  and  rejectamenta  of 
his  dwellings. 


302  PHYSIOLOGICAL    BOTANY.  PART  II. 

11.  Forests.  —  These  districts    may   be  'considered 
with  respect  to  the  trees  which  compose  the  forests,  and 
also  with  reference  to  the  humbler  species  which  seek 
their  shade. 

12.  Copses  and  Hedyrx. 

13.  Subterranean  G/IV.V. 

14.  Alpine. 

15.  PARASITIC.  (See  art.  234.) 

16.  PSEUDO-PARASITIC.  (See  art.  234.) 

(SOQ.)  Jiot'iiiii-al  Habitations.— Greater  uncertainty 
prevails  respecting  the  different  habitations  of  plants 
than  their  stations.  If  indeed  the  extent  of  their  ha- 
bitations were  entirely  dependent  upon  their  range  in 
latitude,  the  difficulty  of  determining  them  would  not 
be  so  great ;  but  it  is  a  remarkable  circumstance,  that 
the  vast  majority  of  species  grow  naturally  within  cer- 
tain limits  restricted  in  longitude  as  well  as  in  latitude ; 
that  is  to  say,  the  limits  within  which  they  naturally 
occur,  are  much  more  restricted  than  the  regions  through- 
out which  they  might  readily  grow,  so  far  as  climate  is 
concerned  in  this  question.  There  are  indeed  some 
species  which  have  a  very  extensive  range  in  longitude 
as  well  as  in  latitude,  and  are  even  found  in  both 
hemispheres,  but  several  of  these  have  undoubtedly 
become  thus  generally  dispersed  by  the  agency  of  man. 
Others  we  may  equally  conclude  to  have  been  trans- 
ported by  natural  causes,  from  the  habitations  to  which 
they  were  first  restricted.  But  when  we  have  made  all 
such  allowances,  we  find  the  great  majority  of  species 
so  far  restricted  in  their  range,  as  to  lead  us  to  the  very 
probable  supposition  that  each  was  originally  assigned 
by  the  Creator  to  some  definite  spot  upon  the  surface  of 
the  earth,  from  whence  it  has  wandered  to  a  greater  or 
less  extent  in  all  directions,  until  it  happened  to  meet 
with  such  obstacles  as  were  sufficient  to  check  its  fur- 
ther progress.  It  may  be  worth  while  to  consider  the 
nature  of  those  obstacles  which  afford  the  most  effectual 
barrier  to  the  migration  of  species  from  one  part  of  the 


CHAP.  VII.  BOTANICAL    GEOGRAPHY.  SOS 

earth's  surface  to  another ;  and  also  the  means  by  which 
their  migration  is  most  effectually  provided  for. 
(310.)   Obstacles  to  Migration. — 

1.  Seas.  —  The   salt  of    sea- water  produces  an  in- 
jurious effect  upon  the  seeds  of  plants,  and  completely 
destroys  the  vitality  of  those  which  are  long  subjected 
to  its  influence.     In  proportion  therefore  to  the  extent 
of  sea  which  surrounds  a  tract  of  land,  the  chances  are 
diminished  by  which  the  seeds  of  plants  may  be  wafted 
to  or  from  it  in  a  state  fitted  for  germination.     This 
is  remarkably  exemplified  in  the  flora  of  St.  Helena, 
which  is  so  peculiar,  that  not  more  than  two  or  three 
of  its  indigenous  species  have  been  found  on  the  con- 
tinent of  America,  and  not  one  of  them  on  the  con- 
tinent of  Africa.     Generally  speaking,  the  floras  of  all 
islands  resemble  those  of  the  continents  to  which  they 
are  nearest,  in  proportion  to  their  greater  proximity  to 
those  continents.    England  does  not  possess  fifty  species 
which  have  not  also  been  detected  in  France;   and  pro- 
bably, the  number  peculiar  to  our  flora  is  even  still 
less  than  this.     The  floras  of  the  opposite  shores  of  the 
Mediterranean  are  very  nearly  the  same. 

2.  Deserts.  —  These  are  a  very  effectual  barrier  to 
the  migration  of  species;  and  hence  there  are  scarcely 
any  species  described  in  the  "  Flora  Atlantica"  which 
are  to  be  met  with  in  Senegal ;   the  great  desert  of 
Sahara  completely  intercepting  the  botanical  intercom- 
munication of  the  two  districts. 

3.  Mountain    Chains.  —  Where    mountain    chains 
possess  lofty  summits,  the  cold  of  those  regions  presents 
a  barrier  to  the  migration  of  plants  across  them.      In 
general  however  they  are  not  so  effectual  as  seas  and 
deserts,  on  account  of  their  being  intersected  by  trans- 
verse valleys. 

4.  Partial  Obstacles  are  offered  by  extensive  forests 
and  marshes  ;  for  although  there  are  numerous  species 
which  prefer  such  tracts  as  "  stations, "  to  which  they 
are  best  adapted,  there  are  others  which  cannot  live 


304  PHYSIOLOGICAL    BOTANY.  PART  II. 

under  the  influence  of  the  moisture  and  shade  which 
prevail  there. 

(311.)  Means  of  Transport.  — 

1 .  Currents.  —  Rivers  and  other  currents  of  fresh 
water  are  among  the  most  effectual  means  of  dispersing 
the  seeds   of   plants:    even  the  sea  may   occasionally 
serve  a  like  purpose  where  the  seed  is  protected  from 
its  influence  by  some  accidental  circumstance. 

2.  Atmosphere.  —  Many    seeds    are   provided  with 
downy  and  winglike  appendages,  by  which  their  dis- 
persion is  secured  ;  but  more  especially  the  minute  im- 
palpable sporules  of  cryptogamic  plants  appear  capable 
of  being  wafted  to  very  considerable  distances  by  this 
means.     It  has  been  supposed  that  two  species  of  lichen 
found   on   the  coasts  of  Bretagne,   have  been  brought 
thither  from  Jamaica  by  the  prevalence  of  the  south- 
west winds. 

3.  Animals.  —  Seeds  often  become  entangled   in  the 
hair  and  wool  of  many  animals,  and  may  thus  be  carried 
by  them  to  considerable  distances  from   the  spot  where 
they  grew  ;    but  more  especially  such  as  are  furnished 
witli  hard  pericarps,   or  bony  coverings   to  the  kernel 
(as  in  stone-fruits)  are  capable  of  resisting  the  digestive1 
powers  of  the  stomach,  and  are  thus  conveyed  by  birds 
from  one  region  to  another  in  a  state  fitted  for  germin- 
ation.    But  man  is  most  instrumental  in   the  disper- 
sion  of  different  kinds  of  plants.      The  seeds  of  some 
he  has   carried   intentionally  from  one   quarter  of  the 
globe  to  another ;    and  others   have  been  accidentally 
transported  by  him    in    a   thousand   ways,  and  follow 
his  footsteps  wherever  he  has  penetrated. 

(312.)  Botanical  Rpyirmf*.  —  It  seems  to  tea  natural 
consequence  of  our  considering  the  geographical  distri- 
bution of  every  species  to  have  taken  place  by  its  gradual 
dispersion  from  one  definite  spot  on  the  earth's  surface, 
that  some  would  be  found  only  in  one  district,  and 
others  in  another,  provided  these  were  separated  by 
some  great  physical  feature,  such  as  a  chain  of  moun- 
tains or  a  wide  sea ;  and  that  two  such  districts,  though 


CHAP.   VII.  BOTANICAL    GEOGRAPHY.  305 

they  might  lie  under  the  same  parallel  of  latitude,  would 
contain  few  species  common  to  both.  Such  districts  are 
termed  " botanical  regions."  These  are  spaces  enclosing 
particular  species,  distributed  through  them  in  the  sta- 
tions adapted  to  their  growth ;  but  so  encompassed  by 
physical  obstructions,  that  the  great  majority  of  species 
found  within  their  limits  are  not  to  be  met  with  else- 
where. We  do  not  as  yet  possess  any  very  accurate 
information  respecting  the  number  and  exact  extent  of 
the  well-defined  botanical  regions  into  which  the  surface 
of  the  earth  may  be  mapped  out.  There  are  about 
fifty  whose  floras  have  been  partially  examined,  and  of 
which  the  following  list  has  been  given: — 

1.  Arctic.  —  Includes   the  northern  parts   of  Asia, 
Europe,  and  America.     This  region  is  not  well  defined 
towards  the  south  ;  but  may  be  considered  as  termin- 
ating in  that  direction  between  lat.  62°  and  66°. 

2.  European.  —  Included  within  a  line  drawn  from 
the  north  of  Scotland,  through  St.  Petersburg,  the  Ural 
Mountains,  to  the  north  of  the  coasts  of  the  Mediterranean 
up  to  the  Pyrenees. 

3.  Mediterranean.  • —  Coasts  all    round    the    Medi- 
terranean,  with    Italy,    Dalmatia,   Greece,   Syria,   and 
Spain. 

4.  Red  Sea. —  Includes  Egypt,  Abyssinia,  and  part 
of  Arabia. 

5.  Persian.  —  Includes    countries   round    the    Per- 
sian Gulf. 

6.  Caucasian.  —  Caucasian     chain     and     countries 
between  the  Euxine  and  Caspian. 

7.  Tartarian.  —  About  Lake  Aral. 

8.  Siberian.  —  Between  the    Northern    Ocean    and 
the  Ural  Mountains.     Bounded  towards  the  south  by 
the  Altaic  Mountains. 

9.  Nepaul.  —  The  chain  of  the  Himalaya. 

10.  Bengal.  —  The  plains  through  which  the  Ganges 
flows. 

1 1 .  Indian The  Peninsula  and  Ceylon. 


306  PHYSIOLOGICAL    BOTANY.  PART  II. 

12.  Birman  empire. 

13.  Cochin-Chin  a. 

14.  Indian  Archipelago. 

15.  New  Holland,  with  Van  Diemen,  New  Zealand, 
New  Caledonia,  Norfolk  Island. 

16.  Fri<  Hilly  mid  Swift y  Islands,  with  those  adjacent. 
17-   Sandn-irh  Islands. 

18.  Mulgrave,  Carolines,  Marian,  &c. 

19.  Philippine  Ixlnnnx. 

20.  China,  with  Corea  and  Japan.     Too  little  known 
to  be  subdivided. 

21.  Alfiitinn  Iitlanilx,  and  the  north-west  of  America. 

22.  North-east  of  America.  —  Canada  and  the  United 
States. 

23.  Mexico.  —  From   California  and  Texas   to  the 
Isthmus  of  Panama. 

'J  k  Antilles. 

25.  J'f  iii-zii  f  fa,  Carthagena,  and  the  Oronoco. 

26.  New  Grenada  and  Quito. — Includes  every  variety 
of  climate,  from  the  sea-shore  to  the  summits  of  the 
highest  Andes. 

27-  Guyana.  —  Cayenne,  Surinam. 

28.  Peru. 

29.  Bolivia. 

30.  The  Basin  of  the  Amazon. 

31.  Arorth-east  of  Brazil. 

32.  South-east  of  Brazil. 

33.  West  of  Brazil. 

34.  Argentine    Region.  —  Between    the    Andes    of 
Chili,  Paraguay,  Brazil,  and  Patagonia. 

35.  Chili,  with  the  Island  of  Chiloe. 

36.  Patagonia. 

37-  Ascension,  and  St.  Hflfnn. 

38.  Tristan  d'  Acunha,  and  Diego  d'Alvares. 

39.  Prince  Edward's,  Marion,  Kerguekn,  and  St. 
Paul. 

40.  Cape   of  Good   Hope,    with    all    extra-tropical 
Southern  Africa. 


CHAP.  VII.  BOTANICAL    GEOGRAPHY.  307 

41.  Madagascar,  with   the    Mauritius  and    Isle  of 
Bourbon. 

42.  Congo. 

43.  Guinea. 

44.  Senegambia. 

45.  Canaries,  Madeira  and  Azores. 

The  centres  of  Africa,  Asia,  and  other  unexplored 
districts  probably  afford  several  more  regions. 

Twelve  of  the  regions  enumerated  belong  to  the 
northern  hemisphere,  between  the  pole  and  tropic  of 
Cancer ;  twenty-six  are  intra-tropical ;  and  seven  are 
extra-tropical,  in  the  southern  hemisphere.  The  first 
are  the  largest,  and  approach  each  other  the  nearest ; 
the  second  are  less  extended,  and  more  frequently  se- 
parated by  the  ocean  and  deserts  ;  the  last  are  very  un- 
equal in  extent,  and  above  all  more  dispersed,  many  of 
them  being  small  islands  in  the  midst  of  an  immense 
ocean. 

(313.)  Relative  Number  of  Individuals  and  Groups 
in  each  Region.  —  In  contrasting  one  botanical  region 
with  another,  inquiry  may  be  made  as  to  the  number 
of  individuals  which  each  may  be  supposed  to  contain, 
and  also  as  to  the  number  of  species,  genera,  and  fami- 
lies. The  result  of  the  first  of  these  inquiries  must 
depend  upon  the  actual  extent  of  country  included  in 
the  region,  and  upon  the  character  of  its  climate.  The 
nature  of  the  plants  which  grow  in  the  region  will  also 
form  an  important  element  in  this  inquiry,  since  a  space 
occupied  by  a  single  tree  may  contain  many  hundreds 
of  smaller  plants,  and  those  regions  in  which  large 
species  prevail  will  not  contain  so  many  individuals  as 
those  which  abound  in  small  ones.  The  greater  or  less 
prevalence  of  particular  species  in  a  given  region,  may 
be  observed  by  noting  the  number  of  places  in  which  they 
occur  ;  and  then  representing  by  ciphers  the  relative 
abundance  in  which  they  appear  to  exist  in  each  spot, 
the  sums  of  these  ciphers  will  afford  some  approximation 
to  the  relative  abundance  of  each  species.  Those  regions 
x  2 


308  PHYSIOLOGICAL    BOTANY.  PART  If. 

which  embrace  a  greater  diversity  of  stations  will,  ceteris 
paribus,  also  contain  a  greater  number  of  species.  Those 
which  are  more  strictly  isolated  from  each  other  are 
not  so  likely  to  interchange  their  species  ;  and  hence  it 
is  observed,  that  a  given  space  on  a  continent  generally 
contains  a  far  greater  number  of  species  than  an  equal 
space  in  an  island.  An  elevation  of  temperature  is 
favourable  to  the  greater  number  of  species,  as  we  find  by 
the  fact  that  the  number  at  different  latitudes  increases 
as  we  approach  the  equator.  The  genera  and  families 
also  seem  to  obey  a  similar  law;  but  we  scarcely  possess 
sufficient  information  to  speak  positively  as  to  the  pro- 
portion in  which  the  relative  rate  of  their  increase  takes 
place.  It  does  not  appear  that  the  same  proportion  of 
genera  to  species  is  maintained  in  different  latitudes  : 
for  instance,  the  species  in  Sweden  are  to  those  in 
France  as  one  to  three;  whilst  the  genera  are  as  one  to 
two. 

(3 14-.)  Proportion  of  Species  in  each  Class,  in  dif- 
ferent Regions.  —  If  a  botanist  collect  indiscriminately 
all  the  plants  he  meets  with,  in  any  region  he  may  be 
examining,  he  will  most  probably  be  soon  able  to  obtain 
a  very  close  approximation  to  the  relative  proportion 
which  the  species  of  each  of  the  three  classes,  and 
many  of  the  orders  bear  to  each  other,  long  before  he 
has  obtained  an  accurate  notion  of  the  whole  number  of 
species  which  the  region  possesses.  So  far  as  calcu- 
lations have  hiterto  been  made,  the  following  general 
laws  appear  to  be  correct ;  and  it  is  not  likely  that  they 
will  be  modified  by  any  additional  information  which 
future  researches  may  procure. 

1.  The  proportion  of  cryptogamic  to  phanerogamic 
species  increases  as  we  recede  from  the  equator. 

2.  The  proportion  of   Dicotyledones  to  Monocotyle- 
dones  increases  as  we  approach  the  equator. 

3.  The    absolute  number    of  species,  and  also  the 
proportion  of  woody  species  to  the  herbaceous,  increases 
as  we  approach  the  equator. 

4.  The  number  of  species  either  annual  or  biennial 


CHAP.  VII.  BOTANICAL    GEOGRAPHY.  309 

(monocarpeans')  is  greatest  in  temperate  regions,  and 
diminishes  both  towards  the  equator  and  poles. 

Many  local  circumstances  produce  remarkable  mo- 
difications in  the  relative  proportions  between  the 
species  of  different  classes  and  orders,  in  regions  under 
the  same  parallels  of  latitude.  Thus  for  instance,  ceteris 
paribus,  the  cryptogamic  tribes  flourish  most  in  moist 
regions.  The  places  best  adapted  to  the  growth  of 
ferns  are  the  (islands  in  tropical  climates,  in  some  of 
which,  as  in  St.  Helena,  one  half  the  flora  is  composed 
of  them.  It  is  remarkable  that  in  this  respect,  and  as 
regards  the  existence  of  arborescent  species  in  this 
order,  the  ancient  flora  of  our  coal-fields,  appears  to 
approximate  very  closely  to  that  of  islands  situate  in 
the  midst  of  an  extended  ocean  and  in  low  latitudes. 
The  same  causes  which  appear  favourable  to  the  in- 
crease of  cryptogamic  species,  seem  also  to  produce 
a  diminution  in  the  proportions  which  dicotyledons 
bear  to  monocotyledons.  Other  relations  of  consi- 
derable interest  have  been  pointed  out  between  the 
species  of  different  orders,  occurring  in  different  re- 
gions ;  but  we  cannot  enter  into  the  minutiae  of  their 
details,  our  object  being  rather  to  present  the  reader 
with  the  principles  on  which  such  investigations  depend, 
than  to  acquaint  him  with  the  partial  results  which 
have  hitherto  been  deduced  from  them ;  several  of 
which  must  doubtless  be  greatly  modified  hereafter, 
considering  the  little  knowledge  we  at  present  possess 
of  the  floras  of  many  parts  of  the  world. 

Th,e  following  table  exhibits  a  few  of  those  results 
which  appear  to  have  been  most  satisfactorily  esta- 
blished. It  gives  the  relative  proportion  which  ten 
well-defined  orders,  or  families  of  plants,  bear  to  the 
whole  of  the  phanerogamic  tribes  in  the  torrid,  tem- 
perate, and  frigid  zones  respectively,  and  shows  us  in 
which  they  occur  in  the  greatest  relative  abundance, 
decreasing  as  we  recede  from  that  zone  towards  the 
others. 


x  3 


310 


PHYSIOLOGICAL    BOTANV. 


PART  II. 


Orders. 

Equatorial 
Lat.    O-lOf 

Temperate. 

450—520 

Frigid. 

67°—  79° 

Maximum 
ratio  in 

Junceae     -~l 

(Rushes)       \ 

?fe 

*1 

1 

Frigid. 

Cyperaceae  "1 
(Sedges)         \ 

,1,  Old  World 
s'fl  New  World 

}ij 

J 

Frigid. 

Gramineae  \ 

(Greases]     J 

A 

TJ 

T5 

Frigid. 

Compositae  i 

^  Old  World 
^  New  World 

i 

T3 

Temperate. 

LeguminosfD 

2 

33 

Equatorial. 

Rubiaceae   -j 

y,  Old  World 
,'.N?ew  World 

Jsb 

yy 

Equatorial. 

Euphorbiacea? 

SI 

4 

1(53 

Equatorial. 

Malvaceae   - 

JJ 

M 

Equatorial. 

Umbelliferae 

1 

I 

S'u 

Temperate. 

Crucifera?   - 

S      { 

T'g  Europe 
g'j  Amer. 

Temperate. 

(315.)  Fossil  Botany. —  The  history  of  vegetation 
could  not  be  completed  without  some  inquiry  respecting 
those  plants  which  existed  on  the  earth  in  its  primaeval 
state,  during  the  extended  geological  epochs  which 
elapsed  before  the  establishment  of  the  present  order  of 
things.  Traces  of  this  .ancient  vegetation  are  very 
abundant  in  certain  strata,  but  more  especially  in  the 
"  coal-measures,"  the  important  mineral  combustible 
obtained  from  them  being  nothing  else  than  vegetable 
matter  in  an  altered  and  fossilized  state.  In  general,  we 
do  not  find  the  remains  of  plants  so  perfectly  preserved 
as  the  skeletons  of  vertebrate  animals,  or  the  testaceous 
coverings  of  mollusca.  It  is  also  rare  to  meet  with 
those  parts  (the  flower  and  seeds)  upon  which  the  dis- 
tinction of  species  and  their  classification  chiefly  depend  : 
but  still  the  fragments  which  remain  often  possess  very 
great  beauty ;  and  many  specimens  of  wood  are  so  exactly 
preserved,  that  their  tissue  may  be  distinguished  under  a 
microscope  as  completely  as  in  recent  species.  As  it  is 
principally  from  these  fragments  of  stems,  and  the  im- 
pressions of  leaves,  that  any  comparison  between  the 


CHAP.  VII.  FOSSIL    BOTANY.  311 

ancient  and  present  flora  of  our  planet  must  be  insti- 
tuted, it  will  be  evident  that  such  data  must  generally 
be  far  too  imperfect  to  admit  of  any  accurate  deter- 
mination of  specific  differences,  though  they  may  afford 
us  sufficient  materials  for  ascertaining  several  truths  of 
high  interest.  The  class,  order,  sometimes  the  precise 
genus,  may  be  ascertained  to  which  a  fossil  vegetable 
belongs,  even  though  we  posses  only  a  small  fragment 
of  the  plant.  More  frequently,  these  fossils  bear  an 
analogy  to  some  recent  genera,  which  they  closely  re- 
semble, but  to  which  they  cannot  be  accurately  referred. 
In  such  cases  this  resemblance  is  indicated  by  referring 
them  provisionally  to  a  genus  whose  name  is  a  modifi- 
cation of  the  recent  genus :  thus  "  Lycopodites"  is  a 
genus  of  fossil  plants  allied  to  "  Lycopodium,"  but  too 
imperfectly  known  to  have  its  characters  fully  pointed 
out. 

(316.)  Botanical  Epochs.  —  It  was  soon  remarked, 
when  the  study  of  fossil  vegetables  began  to  attract  the 
attention  of  botanists,  that  those  from  the  coal-measures 
were  distinct  from  the  plants  now  existing  on  the  sur- 
face of  the  earth,  and  that  they  more  nearly  resembled 
the  species  of  tropical  climates  than  such  as  grew  in 
the  temperate  zones.  Subsequent  researches  have  shown 
that  the  species  embedded  in  different  strata  likewise 
differ  from  each  other,  and  that  on  the  whole  there  are 
about  fourteen  distinct  gealogical  formations  in  which 
traces  of  vegetables  occur.  According  to  Mons.  Bron- 
gniart  they  first  appear  in  the  schists  and  limestones 
below  the  coal.  These  contain  a  few  cryptogamic 
species  (about  thirteen),  of  which  four  are  marine 
AlgiE,  and  the  rest  ferns,  or  the  allied  orders.  In  the 
coal  itself  above  300  distinct  species  have  been  re- 
cognised, among  which  those  of  the  higher  tribes  of 
cryptogamic  plants  are  the  most  abundant,  amounting 
to  about  two  thirds  of  the  whole.  Many  of  them  are 
arborescent,  and  parts  of  their  trunks  are  found  stand- 
ing vertically  in  the  spots  where  they  grew.  There  are 
no  marine  plants  in  the  formation.  A  few  palms  and 
x  4 


312  PHYSIOLOGICAL    BOTANY.  PART  II. 

Graminese  are  the  chief  Monocotyledones ;  and  there  are 
several  Dicotyledones  which  have  been  considered  analo- 
gous to  Apocynete,  Euphorbiacete,  Cacteae,  Coniferae, 
&c.  No  great  stress  need  be  laid  at  present  upon  the 
several  proportions  which  species  of  these  classes  bear 
to  each  other ;  as  it  is  probable  that  subsequent  re- 
searches will  considerably  modify  them.  The  great  pre- 
dominance and  size  of  arborescent  ferns  and  other  tribes  of 
Ductulosa?  constitute  the  main  feature  of  the  formation. 

Above  the  coal  we  arrive  at  the  new  red  sandstone ; 
in  some  of  the  formations  subordinate  to  this  series  a 
few  species  of  fossil  plants  occur.  In  the  oolitic  series 
they  become  more  abundant,  and  some  beds  are  re- 
markably characterized  by  the  prevalence  of  the  genus 
Zamia,  together  with  some  Conifera?,  Liliacea?,  and 
many  ferns,  the  latter  being  very  distinct  from  those  in 
the  former  formations.  In  the  green  sandstone  and 
chalk  few  species  have  been  hitherto  found,  and  these 
are  almost  all  marine.  Among  the  tertiary  strata  (or 
those  above  the  chalk)  the  Dicotyledones  begin  to  pre- 
vail to  a  far  greater  extent  than  they  did  before,  and 
the  plants  are  entirely  different,  including,  terrestrial, 
lacustrine,  and  marine  species.  Several  fruits  are 
referable  to  existing  genera,  as  Acer,  Juglans,  Salix, 
Ulmus,  Cocos,  Pinus,  &c. 

It  is  remarkable  that  scarcely  any  species  has  been 
found  in  more  than  one  distinct  formation,  and  none 
have  occurred  in  any  two  which  are  separated  by  a  long 
epoch.  Hence  it  appears  to  be  a  natural  conclusion,  that 
there  have  been  successive  destructions  and  creations  of 
distinct  species.  Mons.  Brongniart  has  grouped  the 
several  formations  in  which  vegetable  remains  are 
found,  under  four  great  epochs,  during  each  of  which 
no  very  marked  transitions  occur  in  the  general  cha- 
racter of  the  vegetation  ;  but  between  any  two  of  these 
epochs,  a  striking  and  decided  change  takes  place : 
even  most  of  the  genera  are  different,  and  none  of  the 
species  are  alike.  These  epochs  include  the  periods 
during  which  the  following  strata  were  deposited :  — 


CHAP.  VII.  FOSSIL    BOTANY.  313 

1.  From  the  earliest  secondary  rocks  to  the  upper- 
most beds  of  the  coal-measures. 

2.  The  new  red  sandstone  series. 

3.  From  the  lowest  beds  of  the  oolitic  series  to  the 
chalk  inclusive. 

4.  The  beds  above  the  chalk. 

Judging  from  analogy,  from  the  characters  and  rela- 
tive proportions  of  the  species  in  different  classes,  the  tem- 
perature of  those  parts  in  which  the  plants  of  the  first 
period  were  growing  must  have  been  both  hotter  and 
moister  than  the  climates  in  any  part  of  the  earth  at 
present.  It  has  been  plausibly  conjectured  that  the  at- 
mosphere was  more  charged  with  carbonic  acid  at  those 
early  periods  of  our  planet's  history,  when  gigantic 
species  of  cryptogamic  plants  formed  the  main  feature 
of  its  vegetation.  The  abundance  of  reptiles,  also, 
without  any  Mammalia  during  the  same  epoch,  appears 
favourable  to  this  supposition.  Since  the  fossil  plants, 
which  have  been  found  in  the  arctic  regions,  are 
analogous  to  those  which  now  grow  in  tropical  islands, 
it  seems  likely,  that  not  only  must  they  have  enjoyed  a 
higher  temperature,  but  also  a  more  equable  diffusion 
of  light  than  those  regions  now  possess.  Speculations 
of  this  description,  imperfect  as  they  confessedly  are  at 
present,  may  one  day  lead  to  the  most  important  re- 
sults, and  may  teach  us  many  truths  respecting  the 
earliest  conditions  of  our  planet,  which  the  science  of 
astronomy  could  never  have  suggested.  And  surely  no 
one  ought  to  consider  such  inquiries  too  bold  for  our 
limited  faculties,  needless  for  our  present,  or  dangerous 
for  our  future  welfare.  No  naturalist,  desirous  of  know- 
ing the  truth,  can  be  so  weak  as  to  fancy  that  any 
search  into  the  works  of  God,  or  any  contemplation 
of  the  wonders  of  his  creation,  can  interfere  with  the 
lessons  he  has  taught  us  in  his  revealed  and  written  word. 
The  commentator  who  wishes  us  to  pay  attention  to 
his  interpretations  of  the  sacred  text,  must  not  pro- 
ceed upon  the  supposition  that  there  has  been  any  thing 
written  in  the  Bible  for  our  learning,  which  can  possibly 


314  PHYSIOLOGICAL    BOTANY.  PART  II. 

be  at  variance  with  the  clear  and  undeniable  conclusions 
deducible  from  other  and  independent  sources.  If  the 
letter  does  not  announce  a  particular  fact  revealed  in 
the  works  of  the  creation,  a  true  believer  will  imme- 
diately infer  that  the  letter  (though  it  have  the  au- 
thority of  inspiration)  was  not  intended  to  teach  that 
fact.  When  the  philologist  has  ably  interpreted  the 
letter,  the  aid  of  the  natural  historian  may  still  be 
needed  before  the  divine  can  safely  pronounce  upon 
the  exact  scope  and  meaning  of  the  instruction  which 
it  was  intended  to  convey. 


INDEX    AND   GLOSSARY. 


The  language  of  the  botanist  comprises  many  words  adopted,  or  rather 
compounded,  from  Greek  and  Latin,  which  are  seldom  applied  in  their 
strictly  classical  signification  ;  and  some  English  terms  are  also  employed  in  a 
peculiar  and  technical  sense.  Thederivation  of  many  of  these  is  here  given, 
that  the  reader  may  be  the  better  able  to  remember  them  ;  but  further  refer- 
ence is  made  to  the  article  and  page,  where  the  fullest  explanation  of  their 
meaning  occurs,  in  the  body  of  the  work. 


A. 

ABORTION  (115.),  118. 
Absorption  (160.),  176. 
Acotyledones  («,  not ;  x.vrvX-/3uv,  a 

seed  leaf  ,  (36.),  35. 
Adfluxion  (167 .),  182. 
Adventitious  buds  (57.),  51. 
Aerial-stem  (45.),  43. 
./Estivation  (restiva,  summer  quar- 
ters), (104.),  101. 
Age  of  trees  (240.),  243. 
Air-cells  (21.),  19. 
Air-cells  (174.),  188. 
Akenium  (a,  not ;  va/vai,  to  open), 

(108.  6.  Jig.  117.),  109. 
Albumen  (albumen,    the  white  of 

an  egg),  (34.  1.),  32. 
Albumen,  formation  of  (269.),  271. 
Alburnum  (alburnum,   sap-wood), 

(50.),  45. 

Alternate  (82.),  75. 
Amnios  (269.),  271. 
Amylaceous  (amylon,  wheaten 

foodi,  iike  flour. 
Anastomose,  (a.va.fn.u.aKTi;,  passing 

of  one  vein  into  another). 
Anatropous  («»«,  over;  TSVTU,  to 

turn),  (267.),  271. 
Angulinerved  (72.),  62. 
Annular  (annulus,  a  ring),  ringed. 
Anther  («»#•<£»?,  flowery),  (97.  and 

98.  Jig.  98.),  96. 

Apex  (aper,  the  summit,  pi.  apices). 
Apocarpous    (axe,    apart ;    XK^TO;, 

fruit),  where  the  carpels  are  not 

united  into  a  compound   pistil, 
103. 


Arillus  (109.),  111. 

Articulation  (69),  60. 

Ascent  of  sap  (163.),  178. 

Assimilation  (223.),  227. 

Atmosphere,  influence  of  (307.), 
300. 

Awn  (96.),  96. 

Axil  (axilla,  the  arm-pit).  The 
angle  at  which  a  leaf  or  branch 
unites  with  the  stem. 

Axis,  imaginary  line,  drawn  lon- 
gitudinally through  the  middle 
of  an  organ. 


B. 

Bell-shaped,  or  campanulate  (95.  1. 
fig.  92.  a),  94. 

Berry  (108.  10.  .fig.  120.),  109. 
*rBiennial,  lasting  two  years. 

Bladders  (42.),  41. 

Botanical  geography  (302.),  294. 

Botanical  habitations  (309.),  302. 

Botanical  regions  (312.),  304. 

Botanical  stations  iSOS.),  301. 

Bractea  (bractea,  a  thin  leaf  of  me- 
tal), (91.),  89. 

Branches  (59.),  51. 

Budding  (228.  3.),  233. 

Buds  (57.),  50. 

Buds,  on  leaves  (293.  fig.  168.1,  286. 

Buds  and  embryos,  connection  of, 
(291.!,  285. 

Bulb  (65.),  57. 


316 


INDEX    AND    GLOSSARY. 


Caloric,  development  of  (254.), 
858. 

Calyciflone  (102.),  101. 

Calyx  (caJyi,  the-  cup  of  a  flower), 

(92.  and  94.),  Si- 
Cambium  (34.  2.),  32. 

Camphor  (208.),  21& 

Campulitropous  (««j*r^X»t,  curv- 
ed ;  TUTU,  to  turn),  (i'67.>,  270. 

Capital  inn  .ca/n'tuJum,  a  little  head), 
SO.  fig.  87  , 

Capsule  (captula,  a  cheat),  (108.  8.), 

CariopMi    (»««,  the  head  ;  v^if, 

l.Tin  ,  (108.  3.),  108. 
Carpel*    (««<*•,,  fruit),  (92.),  91. 

(101).),  98. 

Catkin,  (.89.  fig.  82.),  86. 
Caudex  (cawier,  a  stem),  (99.),  38. 
Caudex  (S4.1.  77. 
Caulinar  'rauJii,  a  ttem},  attached 

to  the  (tern. 
Cellulare*  (36.  £),  36. 
Cellular  tiuue  (Id),  14. 
Centrifugal  inflorescence  (88.),  84. 
Centripetal  inflorescence  (89.),  86. 
Chalaze  (r«i«£«,  tubercle  in  the 

»kin),  (286.),  270. 
Chara  (194.  fig.  158.),  207. 
Character  (13i),  138. 
Chromatometer     {^•HUM,   colour ; 
>   AUTfo.,  measure),  1186.',  200." 
Cili«  (ciitum,  hair  of  the  eyelids), 

fringes  of  hair  or  bristle*,  167. 
it  i?       rircinatui,    rounded), 

Circulation  (195.),  208. 

Classes  (33.),  30. 

Closten  (16.),  (»>*rrii{,  a  spindle], 

elongated  vesicle*  of  the  cellular 

tissue,  .15. 

Cluster.    See  Raceme. 
Cohorts  (13t),  137. 
Colour  (181.),  1<»4. 
Colour  of  fruit  (474.),  275. 
Complex  organs  (32.  \  29. 
Compound  organs  (28.),  24. 
Com-   \>\.Ji)!.  1:37.),  89. 
Comluplicate  (104.),  102. 
Coniferous,  bearing  cones,  as  the 

fir  tribes. 

Connate  (83.  fig.  73.  a),  75. 
Connective  (connccto,   to  join  to- 
gether), (98.),  97. 
Conservative  organs  (10.),  10. 
Contorted     (contortus.      twisted), 

(104.),  102. 
Cormus  (66.),  58. 
Corolla  (corolla,  a  little  crown),  (92. 

and  95.),  91. 
Corolliflora?  (102.),  101. 
Corymb  (x.trunZ«,  a  summit,  or  a 

branch),  (90.  fig.  85.),  87. 


Cotyledons  (xmXrjtn,  a  hollow 
vessel)  ;  used  in  botany  to  signify 
the  seed-leaves  (34.  1.  ',  '.\. 

Cow-rree  (203.  a),  216. 

C'ronate,  cut  into  ruiiiuli-.l  teeth. 

Cr>|itot?amic  (xfu-rrte,  concealed  ; 
X«u«f,  marriage;,  (;>S.  l.;,A>. 

Culms  (culmus,  a  stem),  the  stem 
ofKra-vs  H  ,  D& 

Curvinerved  (7i),  66. 

Cuticle  (cuticnlii,  the  outermost 
>kinv, 

Cutn-ular,  belonging  to  the  skin  or 

CUtH'If. 

Cyma  (cyma,  a  branch  or  sprout), 

(61.  , 
Cyme  (88.),  84. 


D. 

Deciduous  (decitiuus,  liable  to  fall), 

opposed  to  persistent 
Decurrent  (rfecurro,  to  run  down), 


.       ..,. 
Degeneration  (116.\  118. 
Dehiscencc     (dehiicent,     gaping), 

(107.),  MS. 
Depressed        (ilcprcstus,      pressed 

ilown),  where  the  transverse  sec- 

tion of  an  organ  is  larger  than 

the  longitudinal. 
Descent  of  sap  (190  ),  204. 
Deomodium     gyrans     (149.  2.  fig. 

150.),  166. 

Development   'iJ<O,  234. 
Diadolphous  .  ««•  ,  twice  ;  xfaljH,  a 

brother),  (97.),  91. 
Dichotomous  ^hyunfitt.  divided  in 

two),  (tiS.flg.ft).  a],  ^l. 
Dicotyledoncs  (tif,  twice  ;  **rv/fj- 

ttn,  a  se«fl-li 

Diffusion  of  proper  juice;  1W'.),  20.3. 
Dionaea  muscipula  .H'.i.  4.  fe  151.), 

167. 

Disk  (101.),  99. 
Dissemination  (27S.\  276. 
Dissemination,  modes  of  .  279.\  278. 
inent  (distepto,  to  separate}, 

(H6.),  104. 

Divergent,  separating  asunder. 
Divided.   See  Incised. 
Divisions  (131.),  137. 
Drupe  (druptF,  unripe  olives),  (108.) 

3.),  108. 

Drupel  (108.  3.),  108. 
Ducts  (ilnctus,  a  pipe   for    water), 

(24.\  22. 

DuctnloHi  (.To.  2.),  36. 
Duramen  (duramen,  a  hardening), 

(50.',  44. 
Duration  (235.),  238. 


INDEX    AND    GLOSSARY. 


317 


E. 

Earths  (220.),  224. 
Eductulosa?  (36.  2.),  36. 
Elasticity  of  tissue  (142.),  158. 
Electricity  (156.),  172. 
Elementary  textures  (13.),  13. 
Embryo  (ipZfuor,  the  foetus),  (34. 1.), 

31. 

Embryo  (111.),  112. 
Embryo,  formation  of  (268.),  271. 
Embryo,  vitality  of  (290),  285. 
Embryonic  sack  (266.),  2ti9. 
Endocarp    (mdov,  within  ;    xttero;, 

fruit),  (106.1, 105. 
Endogena?  (ltd™,  within  ;  ytwefuu, 

to  beget),  (35.),  33. 
Endosmometer  (144.  J?£.  148.),  160. 
Endosmose  (svSov,  within ;  anrfji.o{, 

impulsion),  (144.),  159. 
Ephemeral  flowers  (250.),  255. 
Epicarp  (uri,  upon  ;  xacrxos,  fruit), 

(106.),  105. 
Epidermis    (aridiewf,     the   skin). 

(29.),  25. 

Epigynous  (in,  upon  j  yutri,  a  wo- 
man), (101.),  100. 
Epirrheology   (ixiffovi,  an    influx1!. 

(298.),  290. 

Equinoctial  plants  (250.),  258. 
Equitant   (equito,    to    ride),    (Jig. 

72.  4),  74. 

Erect  (III.  fig.  126.  i),  113. 
Etiolation  (178.  \  192. 
Excitability  (146.),  161. 
Excretions  (212.),  220. 
Exfoliate,  to  scale  off. 
Exhalation  (168.),  185. 
Exogena?  (<J*i,  without ;  -yuta/Ma, 

to  beget),  (34.),  31. 
Expansion,    stimulants   to    (251.), 

256. 
Extraneous  matters  (219.),  224. 


F. 

Farinaceous  (farina,  meal),  formed 

of  ineil.like  powder. 
Fasciculate  (fasciculus,  a  bundle), 

in  bundles,  (fig.  30.  c),  41. 
Fecula  (197.),  2fl. 
Fertilization  (255.),  259. 
Fibre  (13.1,  13. 
Fibrils  (39.1,  38. 
Filament  (97.  \  96. 
Filamentous     (filum,    a    thread), 

threadlike. 

Fixation  of  carbon  (175.),  189. 
Flavour  (273.),  274. 
Flocculent  (floccus,  a  lock  of  wool), 

wool-like. 

Floral  whorls  (9?.),  90. 
Flower-buds  (85.),  7a 


Flower-buds  (245.),  250. 
Flowering  (246.),  251. 
Foliaceous  branches  (76.),  69. 
Follicle  (folliculvs,    a   little  bag). 

(108.  1.  Jfc.114.),  107. 
Foramen  (foramen,  a  hole),  (111.), 

113. 

Foramen,  (266.),  269. 
Fossil  Botany  (315.),  310. 
Fovilla  (262.),  266. 
Fraxinella  (213.1,  221. 
Frond  (frons,  a  leaf),  (84.),  77. 
Fruit  (105.),  102. 
Fugacious   (fugax,  fleet),   lasting 

for  a  very  short  time. 
Functions    of    vegetation    (152.), 

170. 

Fundamental  organs  (38.),  37. 
Funicular  chord  (funiculus,  a  little 

rope),  (109.),  111. 
Funnel-shaped,     or     infundibuli- 

form,  (95.  1  fig.  92.  6),  94. 
Fusiform  (fustis,  a  spindle),  spin. 

die-shaped  (fig.  3.  c),  15. 


G. 

Gatnosepalous  (-ya,u.o; ,  marriage  ; 
sepalum,  a  sepal),  where  the  se. 
pals  are  united  together. 

Gemmule  gemma,  a  young  bud), 
(111.),  113. 

Genus  (33.),  30. 

Germen  {germen,  a  bud).  See  Ova- 
rium  (1(;0.),  98. 

Germination-  (283.),  282 

Germination,  stimulants  to  (284.). 
283. 

Glans  (g/ans,  an  acorn).  (108.  7 
fig.  118.),  109. 

Glue  (215.),  221. 

Glossology  (•yKu/nra.,  the  tongue; 
\oy/>f,  a  discourse).  The  depart- 
ment of  Botany  which  contains 
an  explanation  of  the  technical 
terms  used  in  the  science  (3.),  3. 

Glumaceous  (96.  fig.  95.),  having 
the  character  of  a  glume,  95. 

Glume  (gluma,  a  husk  of  corn), 
(96 ),  95. 

Gluten,  a  tenacious  substance  ex- 
tracted from  flour. 

Gourd  (108.  9.  fix.  119.),  109. 

Grafts  (227.),  231. 

Granulated,  having  the  appearance 
of  being  composed  of  grains. 

Granules  of  the  pollen  (99.),  93. 

Granules  (263.),  267. 

Gravity,  effects  of  (300.),  292. 

Growth  (224.),  227. 

Gurn  (177.),  191. 


318 


INDEX    AND    GLOSSARY. 


H. 


Habitation*  (302.),  £95- 
Habitations  (909.),  302. 
Hair  i31.  fig.  19.),  27. 
Heart-wood  (50.),  4i. 
Heat,  action  of  (287.),  285. 
Herbaceous,  of  a  soft  and  succulent 

nature  —  opposed  to   the  woody 

structure  of  trees. 
Hiluin     (/iilum,   the   black    on    a 

bean),  (109.:,  111. 
Hilum  ,266  , 

Horary  expansion  (250.),  255. 
Hybrid!      hybri'la,    a    mongrel), 

(295.),  287. 
Hygroscopicity    of    tissue    (143), 

159. 
Hypocarpogean     (ur»,    beneath  ; 

*«/T«,    fruit  ;  yr.,   the   earth), 

(2*.),  27a 
Hypogynous   (uv»,  beneath  ;   yvtit, 

a  woman),  (101.)  10U 

I.  &J. 

Incised  (incittu,  cut),  (fig.  63.  A), 

67. 

Indefinite  inflorescence  (89.),  85. 
Indehixrcnt      in,    nut;    rlf/iiiccTU, 

cleaving  "pen),  where  there  is  no 

natural  line  of  suture. 
Individuality  (23rt,  237,  238.),  239. 
Inferior  (101.),  100. 
Inflorescence  (86.),  80. 
Inflorescence,  stimulants  to  (247.), 

ML 

Intercellular  (17.),  17. 
Intcrnodium    (56.),  the  space  be-. 

tween  two  knots,  .50. 
Inverse  embryo  (111.,  fig.  126.  a), 

113. 
Involute  inrulutus,  folded  in),  (fig. 

•  ,  74. 

Irritability  (148.),  163. 
Joints  (56.),  50. 


Kernel  (109.),  111. 
Knot,  (J.. 


Labiate  (la'jium,  a  lip),  (95.  2.  fig. 

93.),  9*. 
Lacuna?  (lacuna,  a  hollow  place), 

(21.),  1!'. 

Lamina,  a  thin  pl.ite  of  any  thing. 
Latex  (later,  )U\re),  (I95.)i 
Leaflets  (70.)    The  subdivisions  of 

a  compound  leaf,  61. 


Left-handed  spiral  (55.  fig.  41.  a), 

49. 
legume  CiMMMKj  pulse),  (108.  2. 

fig.  115.),  107. 
Lenticella?  k4;i.),  42. 
Lenticular,  shaped  like  a  lens. 
Light  (154.),  171. 
Light,  action  of  ,'JSS    , 
Light,  ef fee t!>  of  ^>il.\  293. 
Light,  influence  of  ,:'*H.\  298. 
Lignine    (lignum,    wood),    ^200.), 

Limb  of  a  leaf  ((59.),  fiO. 

Lime  (220.),  224. 

Linear,  equally  straight  through, 
out,  the  edges  parallel  to  each 
other. 

Linna-an  system  (137.\  145. 

Lipped.    .V<v  Labiate. 

Lobe,  the  separate  divisions  of  a 
leaf  or  other  organ,  between  the 
indentations  on  it-  margin. 

Lorulicidal  (luculus,  a  little  |K>uch), 
(107.  ftq.  111.6),  where  the  open- 
ing is  in  the  middle  of  the  cell, 
105. 

Longevity  of  trees  (241.),  244. 

Lomentaceous  (108.  2.  jig.  115.  rf), 
where  an  organ,  as  the  seed  ves- 
sel, or  a  leaf,  H  nun  h  contracted 
at  intervals,  108. 

Lunate  (tuna,  moon),  crescent. 
sha|>ed. 

Lymph    (lympha,    water),    (163.), 


M. 

Macerate,  to  decompose  by  the  ac- 
tion of  water. 

Maturation  (265.),  2(>8. 

Maturation  (271 

Maturation,  stimulants  to  (272.), 
274. 

Medullary  r.iys  (:J4.  2.),  33. 

Medullary  rays  \~>i.  . 

Medullary  sheath    :U.  2.),  32. 

Meilullary  sheath  (49.),  44. 

Membrane    1 

Meteoric  plants  (250.),  256. 

Migration,  obstacles  to  (310.),  303. 

Milk    ,'i i. 5.),  215 

Moi.ture,  action  of  (285.),  284. 

Moisture,  influence  of  (;i05.),  298. 

Molecules  i5.),  the  smallot  par- 
ticles (simple  or  compound)  of 
which  simple  minerals  are  com- 
!>osed,  6. 

Monailcljihniis  (/juiti,  alone ;  «JiA- 
*«,  a  brother),  (97.  Jig.  97.  a), 
97. 

MonocarjK-an  (itmei,  alone;  *«*T»f, 
fruit  ,  236.  ',  238. 

Mnuochlainydeie  (fiuttf,  alone  ; 
y_\<tfj.'jt,  a  coat),  101. 


INDEX    AND    GLOSSARY. 


Monocotyledones    (ptvos,   alone  ; 

Korvl.r$m,  a  seed-leaf),  (35.),  33. 
Monocotyledonous  stems  (53.),  46. 
Monophyllous  (potes, alone:  qvXKov, 

a  leaf). 
Monosepalous  (JMIOS,  alone ;  sepa. 

lum,  a  sepal). 
Monstrosity  (85.),  79. 
Morphology    (p^ifr,  form  ;    >.oyo(, 

a  discourse),  (114.),  116. 


N. 

Nectary  (103.). 

Nectary,  functions  of  (253.).  258. 

Nervation  (71.),  61. 

Nerves  (69.),  59. 

Nodosities,  knotted  appearances. 

Normal    (norma/is,    right   by   the 

rule),  (115.),  118. 
Nosology  (totrof,  a  disease:  Asysj ,  a 

discourse),  (298.),  291. 
Nucleus  (266.),  267. 
Nut  (108.  4.. /fe.  116.),  108. 
Nutrition  (159.),  175. 


O. 


.),  74. 

Oil  (206.),  218. 

Opposite  (82.),  75. 

Order  (33.),  30. 

Organizable  products  (176.),  190 

Organized  bodies  (6.),  6. 

Organs  (8.),  9. 

Organography  (o»y«v8y,  an  organ  ; 
•y^oufu,  to  write),  (3.),  the  depart- 
ment of  Botany  which  contains 
a  description  of  the  organs  of 
plants,  3. 

Orthotropous  (OP  Bos,  straight  ; 
TJS™,  to  turn),  (267.),  270. 

Ovarium  and  Ovary  (ovum,  an 
egg\  (100.),  the  part  of  the  pistil 
containing  the  seeds,  98. 

Ovate  (ovum,  egg),  egg-shaped. 
(fig.  30.  a). 

Ovule  (ovum,  an  egg),  (100.),  the 
young  seed,  98. 

Ovule,  development  of  (270.),  272 

Ovule,  modifications  of  (267  ),  270 

Ovule,  origin  of  (266.),  2fi8. 

Oxygen  (180.),  193. 

Oxygen,  action  of  (286.),  284. 


P. 

Palmate  (palrna,  the  hand),  hand- 
shaped,  (fig.  30.  b,  and  fig.  38.) 
Palminerved"  (72.  b ),  64 
Panicle  (90.  fig.  84.),  87. 


319 


Papilionaceous  (papilio,  a  butter- 
fly), (95.  3.  fig.  94.),  95. 
Parasites  (234.),  235. 
Parenchyma  (69.),  59. 
Paries  [paries,  the  wall  of  a  house) 

(parietes,  pi.). 
Parietal,  belonging  to  the  paries  — 

attached  to  the  paries. 
Partite   (partitus,    divided),    (fie 

63.  c),  67. 

Patent,  spreading  open  widely. 
Pedalinerved  (72.  d.),  65. 
Pedate  (pes.  pi.  pedes,  a  foot),  (fig. 

60.),  a  shape   somewhat  like  a 

foot,  65. 

Pedicel  (86.),  80 
Peduncle  (86.),  80. 
Pellicle  (pellis,  the  skin),  a   thin 

skin. 
Peltate  (velta,  a  shield),  (fig.  59.), 

65. 

Peltinerved  (72.  c.),  65. 
Penninerved    (pennatus,   winged). 

(72.  a.),   63. 

Perennial,  lasting  many  years. 
Perfoliate  (per,  through  ;  folium,  a 

leaf),  (83.  fig.  7J.  a,  b),  76. 
Perianth    (««j,  around;   «>#«?     a 

flower),  (92,  93.),  90. 
Perianth,  functions  of  (252.),  257. 
Pericarp    (3-65;,    around  :    Kxc-ra, 

fruit),  (106.),  103. 
Perigynous  («{/,  around;   yu«j,  a 

woman),  (101.),  100. 
Periodic  influences  (249.),  254. 
Periodicity  (151.),  169. 
Perisperm   (««,  around;  mie/Mc,, 

seed),  (269.),  271. 
Permanence  of  species  (296.),  288. 
Persistent,  remaining  when   other 

parts  fall  off 
Personate  (persona,  a  mask,  (95.  2. 

fig.  131.  a),  94. 
Petals  (xvru.\<n,  a  leaf),   (92.),  the 

subordinate  parts  of  the  corolla, 

91. 
Petiole  (petiolus,  the  stalk  of  fruits), 

(69.),  used  in  botany  for  the  stalk 

of  leaves,  60. 
Phanerogamic    (tfuttfa;,    evident ; 

y«^«,  marriage),  (36.  1.),  35. 
Phyllodium  (ifu^^ov,  a  leaf;  iTSot, 

form),  (75.),  68. 
Phytography  (tfunii,  a  plant ;  yjapa, 

to  write),  (3.),  the  department  of 

Botany  which  contains  a  descrip- 
tion of  the  entire  plant,  3. 
Pinnate       (pinnntus,       feathered, 

winged),  (/2.  a.),  63. 
Pinnatifid  (72.  a.),  cut  in  a  pinnate 

manner,  63. 
Pistil  (pistillum,  a  pestle),  (92. 100.), 

92. 

Pitcher  (80.),  73. 
Pith  (34.  2.;,  32. 


890 


INDEX    AND    GLOSSARY. 


Pith  (48.),  44. 

Placenta  (100.),  99. 

Placenta  (105.),  100. 

Plumule  plumiHa,  a  little  feather  , 

(34.  1.),  31. 
Plumule    1  111,  II .!. 
Pollen    poUfn,  tine  flower),  (97.  99. 

fie.  99.),  96. 

Pollen,  <ii.per«ion  of  258.),  882. 
Pollen,  formation  or  /.V.l.j  i»5. 
Pollen  tube  (2»K.\  266. 
Polyadelphous  (nAvr,  many ;  «iU- 

*«,  a  l>rother),  (97.),  97. 
Polycarpean  (*«Xi*,  many ;  ***rw, 

fruit  ,(235.),  238. 
Polygonal  (vtAi* ,  many ;  j-or,  an 

angle),  having  many  angles  and 

MM, 

Pomum  (108. 11.  fig.  106.  121.1, 110. 
Preservation  of  teed  (287.),  27a 
Prickle  (62.),  53. 
Primary  groups  (33.),  29. 
Primine  (2ti6.), 269. 
Progression  of  «ap  (191),  205. 
1'n il i I'.TOUS  ( prolet, the  young ;  fero, 

to  bear),  (292.),  286. 
I'ropvati.Mi    .+  >.),  248. 

i'r:.|'  .    -'15. 

1'ropulsion  (166.),  18L 
PrututiK  (225.),  229. 
Pseudcwpcrtnic  (^U/JK  ,  a  falsehood ; 

m;u«,  teed),  (276.),  277. 
Pubescence      (atbetcent,     downy), 

(31.),  27. 
Pyxidiurn  brvfctW,  a    little  box), 

(107.  fig.  112.),  105. 


Race  (131.),  137. 

Raceme  (racrmui,  a  bunch), 


fig.  81.  a),  85. 
Rachis  <««r'f, 
(96.),  96. 


fpine  of  the  back), 


Radical,  proceeding  from  the  mm- 

mit  of  ihe  root. 
Radical  excretions  (217.).  222. 
Radicle     ratlicula,  a    little   root), 

(34.  1 

Radicle  (1 11.  \m. 
Kaphe   ,/>*?/;,   a   joint  or  suture), 

(266.1,  ITU. 
Raphide*  (tufit,  a  needle),  (20.), 

19. 

Receptacle*  (21. \  19. 
Rece|>tacle  to  the  flower  (86.),  80. 
Regions,  botanical  (312.),  304. 
Repnxhictioi) 
Reproduction,  certainty  of  (260.), 

M, 

Reproductive  organs  (11.),  10. 
Resin  (205.),  218. 


Respiration  (172.),  186. 

Revolute  (n-mlutus,  turned  "back), 

Hlnzoinji  (;(J»/i*«,  a   root\   (44.), 

Rhiinma  it;;   . 

Rhiioma  ((H.),  77. 

Rhomboidal  dodecahedron  (fig.  5. 
b),  a  regular  geometric  figure, 
whose  side*  are  twelve  similar' 
and  equal  rhombs,  or  plane  t'mir- 
tided  figures,  having  their  tides 
equal,  but  their  angles  not  right 
angles,  16. 

Rice-paper  (50.  fig.  36.),  45. 

Right-handed  spiral  (55.  fig.  41.  b\ 
49. 

Root  (99.),  38. 

Roots,  direction  of  (2!>> 

Rotate    (rota,    a    wheel),    wheel- 
shaped,  (fti.  1.  fig.  W.  i/.,  !>l. 

Hutation  of  cro|»  (218 ),  223. 
Runners  (62.J,  54. 


Salts  (221.),  225. 

Salver-shaped  (or  hypocrateriform), 

(95.  1.  fig  92.  c),  94. 
Samara  (U)8.  12  fig.  122.),  110. 
Sarcocarp    (r*»l,    flesh  ;     *m*-e»t, 

Iruit'..  .1C«.:,  105. 
Scar  (69.),  60. 
Scent  (210.),  219. 
Scorpioidal   (rxttriK,  a  scorpimi  ; 

ultt,  form  ,  (88.  fig.  80.  b),  85. 
Secretion  (196.),  211. 
Sections  (131.1,  137. 
Secundine  (266.),  269. 
Seed  (109.),  .110. 
Seed-cover  (34.  1.),  31. 
Sensibility  (150.),  168. 
Sensitive  plant  (149.  l.fif.  14R  ,  \C,\. 
Sepals  (92.),  the  subordinate  parts 

of  the  calyx,  !>1. 
Scptirulal  '5rfVur»,.ihe<lRe  or  fence), 

i>l>cning  along  the  division*  be- 
tween the  cells  (107.  Jig.  111.  a), 

105 
Scrrature  (terra,  a  saw),  having  the 

edge   jagged  or    toothed    like  a 

saw. 
Sessile  (letiilit,  dwarfish),  without 

a  stalk. 

Sexes  (257.),  260. 
Shoots  (58.),  51. 
Silica  (220..,  an  earth  ;  the  basis  of 

flints,  quartz,  Sec.,  225. 
Siliqua  tiliiiua,  a  husk  or  pod),  (108. 

13. fig.  Hi),  lid. 
Silver  grain  (51.),  45. 
Simple  mineral  (5.),  6. 


INDEX    AND    GLOSSARY. 


321 


Sinus  (sinus,  a  bay),  the  indenta- 
tions on  the  edge  of  a  leaf. 
Sleep  (155.\  171. 
Snag  (225.),  229. 
Soil,  action  of  (289.),  285. 
Soils,  influence  of  (306.),  299. 
Spadix  (89.  fig-  8S.  6),  86. 
Spathe  (ffvA,  a.  ladle),  (91.  Jig.  88.), 

90. 

Species  (33.),  29. 
Spermoderm  (trxiefMt,,  seed  ;  Ssj/t**, 

skin),  (109.),  lit 

Spicula?   (spiculum,  a   dart),  small 
thread-like     and     sharp-pointed 
bristles. 
Spike  (spica.  an  ear  of  corn),  (89.), 

85. 
Spikelet,  a  little  spike  (89.  fig.  95. 

c),  86. 

Spine  (spina,  a  thorn),  (78.),  71. 
Spiral-vessels  (23.),  38. 
Spongioles     (ipongia,     a    sponge), 

(39.),  38. 

Sporules   («ro»«,  a  seed),   (36.   1.), 

the  reproductive  organs  of  the 

cryptogamic  tribes,  analogous  to 

the  seeds  of  flowering  plants,  35. 

Spur,   the  prolongation  backwards 

of  a  sepal,  petal,  &c., 
Stamen  (stamen,  the  chive  of  the 

flower).  (92.  97.),  91. 
Stations,  botanical  '(302.),  294. 
Stations,  botanical  (308.),  301. 
Stellate  (stella,  a  star),  star-shaped, 

(fit.  21.  a). 
Stem  (44.),  42. 

Stems,  direction  of  (299.',  291. 
Stigma  (100.),  98. 
Stigma,  action  of  (264.),  267. 
Stings  (31.  fig.  20.  a),  28. 
Stings  (214.),  221. 
Stipes  (stipes,  trunk  of  a  tree),  (84.), 

77. 
Stipules  (stipula,  husk  round  straw), 

(77.),  70. 
Stomata  (frtfut,  the  mouth),  (30.), 

26 

Stock  (227.),  238. 
Striated,  marked  with  stripes. 
Style  (<rn/Xo?,  a  style),  (100.),  98. 
Suckers  (62.),  54. 
Sugar  (199.),  213. 
Superior  ilOl.),  100. 
Suture  (sulura,  a  seam),  where  a 
division  takes  place  naturally  in 
the  fruit. 
Syncarpous  (o-vv,  together  ;  xcte'ro;, 

'fruit),  (fig.  106),  103. 
Syngenesious  (rut,  together ;  y£vs<r;j, 
generation),  (138.),  149. 


T. 

Tap  (39.),  38. 

Taste  (2 10.),  219. 

Taxonomy  (™J<;,  order;  vo^tf,  a 
law),  (130.),  the  same  as  sys- 
tematic Botany.  —  The  Depart- 
ment of  the  science  in  which 
plants  are  arranged  and  classified, 
135. 

Tegmen  (legmen,  a  covering), 
(266 ),  269. 

Temperature  (157.),  172. 

Temperature,  effects  of  (303.),  295. 

Tendril  (79.),  71. 

Terminal  inflorescence  (88.),  83. 

Testa  (testa,  an  earthen  pot),  (266.), 
269. 

Thalamiflora  (&aX«,u.»?,  a  bed- 
chamber), (102.),  101. 

Thallus  (84.),  78. 

Theca  (.S-jjzsj,  a  sheath  or  case), 
(113.),  115. 

Thecaphore  (S-yxri,  a  case ;  <? e»a/,  to 
bear),  (100.),  99. 

Thorns  (62.),  53. 

Toothed  (fig.  63.  a),  67. 

Torus  (torus,  a  bed),  (92.),  90. 

Trachea?  (23.),  21. 

Transport,  means  of  (311.),  304. 

Transverse,  embryo  (111.  fig.  126. 
c),  113. 

Tribes  (131.),  137. 

Tuber     ( tuber,    an    excrescence), 

(64.),  56. 

Turio  (turio,  a  young  branch), 
(58.),  51. 


Valve,  a  part  which  becomes  de- 
tached by  means  of  a  natural 
rupture  along  a  line  of  suture,  as 
in  seed-vessels. 

Valvular  (104.),  102. 

Variation  (131.),  137. 

Varieties  (33.),  30. 

Varieties  (131.),  137. 

Varieties,  origin  of  (297.),  290. 

Vasa  propria  (21.),  19. 

Vasculares  (36.  2.),  36. 

Vascular  tissue  (22.),  20. 

Veins  (69.),  59. 

Venation  (71.),  61. 

Vernation  (vernus,  belonging  to 
spring-time),  (81.),  74. 

Verticillate  (verticulum,  a  whirl 
for  a  spindle),  (82.),  75. 

Vesicles  (vesicula,  a  little  bladder), 
(16.),  14. 

Viscous  (vt'scus,  glue),  clammy  and 
glutinous. 

Vital  vessels  (27.),  24. 


322  INDEX    AND    GLOSSARY. 


r 


w. 


Wax  (216.).  224. 
Winged  (83.  fig.  7*.),  76. 


Umbel  (90.  fig.  86.),  87. 

Umbellate,  in  the  form  of  an  urn-         \von3TsuT~ii" 
Umbilical  chord.    See  Funicular.        '     Woody  Bbref  (2i),  2S. 
l'ndcr-«hrub  (45.),  4A 
Unorganized  bodies  (5.),  the  object* 
of  the  mineral  kingdom,  5. 


THE    END. 


LONDON : 

Printed  by  A.  SPOTTISWOOPE, 
Scw.'Street-Square. 


CABINET 

OF 

NATURAL    HISTORY. 

CONDUCTED   BY    THE 

REV.  DIONYSIUS  LARDNER,  LL.D.  F.R.S.  L.&  E. 

M.R.I.A.   F.R.A.S.   F.L.S.   F.Z.S.   Hon.  F.C.P.S.  &c.  &c. 

ASSISTED    BY 

EMINENT  SCIENTIFIC  MEN. 


DESCRIPTIVE  AND  PHYSIOLOGICAL 

BOTANY. 

BY    THE 

REV.  J.  S.  HENSLOW,   M.  A. 

PROFESSOR  OP  BOTANY   IN  THE  UNIVERSITY   OP  CAMBRIDGE. 


LONDON: 

PRINTED  FOB 

LONGMAN,   REES,   ORME,  BROWN,   GREEN,  &   LONGMAN, 

PATERNOSTER-ROW  ; 

AND    JOHN    TAYLOR, 

UPPER  GOWER  STREET. 

1836. 


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