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BEGINNERS'    BOTANY 


THE  MACMILLAN  COMPANY 

NEW  YORK   •    BOSTON  •   CHICAGO 
SAN    FRANCISCO 

MACMILLAN  &  CO ,  Limited 

LONDON  •  BOMBAY  •  CALCUTTA 
MELBOURNE 

THE  MACMILLAN  CO.  OF  CANADA,  Ltdw 

TORONTO 


BOUQUET  OF  BEARDED  WHEAT 


BEGINNERS'  BOTANY 


BY 

L.   H.    BAILEY 


AUTHORIZED  BY  THE  MINISTER  OF  EDUCATION 
FOR  ONTARIO 


TORONTO 
THE   MACMILLAN    CO.   OF  CANADA,   LIMITED 

1921 


Copyright,  1921 
By  the  MACMILLAN  CO.  OF  CANADA  LTD. 


PREFACE 

In  ail  teaching  of  plants  and  animals  to  beginners,  the 
plants  themselves  and  the  animals  themselves  should  be 
made  the  theme,  rather  than  any  amount  of  definitions  and 
of  mere  study  in  l)ooks.  Books  will  be  very  useful  m 
guiding  the  way,  in  arranging  the  subjects  systematically, 
and  in  explaining  obscure  points ;  but  if  the  pupil  does  not 
know  the  living  and  growing  plants  when  he  has  completed 
his  course  in  botany,  he  has  not  acquired  very  much  that 
is  worth  the  while. 

It  is  well  to  acquaint  the  beginner  at  first  with  the  main 
features  of  the  entire  plant  rather  than  with  details  of  its 
parts.  He  should  at  once  form  a  mental  picture  of  what 
the  plant  is,  and  what  are  some  of  its  broader  adaptations 
to  the  life  that  it  leads.  In  this  book,  the  pupil  starts  v/ith 
the  entire  branch  or  the  entire  plant.  It  is  sometimes  said 
that  the  pupil  cannot  grasp  the  idea  of  struggle  for  exist- 
ence until  he  knows  the  names  and  the  uses  of  the  different 
parts  of  the  plant.  This  is  an  error,  although  well  estab- 
lished in  present-day  methods  of  teaching. 

Another  very  important  consideration  is  to  adapt  the 
statement  of  any  fact  to  the  understanding  of  a  beginner. 
It  is  easy,  for  example,  to  fall  into  technicalities  when  dis 
cussing  osmosis ;  but  the  minute  explanations  would  mean 
nothing  to  the  beginner  and  their  use  would  tend  to  con- 
fuse the  picture  which  it  is  necessary  to  leave  in  the  pupil's 
mind.  Even  the  use  of  technical  forms  of  expression  would 
probably  not  go  far  enough  to  satisfy  the  trained  physicist. 


Vi  PREFACE 

It  IS  impossible  ever  to  state  the  last  thing  about  any 
proposition.  All  knowledge  is  relative.  What  is  very 
elementary  to  one  mind  may  be  very  technical  and  ad- 
vanced to  another.  It  is  neither  necessary  nor  desirable 
to  safeguard  statements  to  the  beginner  by  such  qualifica- 
tions as  will  make  them  satisfactory  to  the  critical  expert 
in  science.  The  teacher  must  understand  that  while 
accuracy  is  always  essential,  the  degree  of  statement  is 
equally  important  when  teaching  beginners. 

The  value  of  biology  study  lies  in  the  work  with  the 
actual  objects.  It  is  not  possible  to  provide  specimens  for 
every  part  of  the  work,  nor  is  it  always  desirable  to  do  so ; 
for  the  beginning  pupil  may  not  be  able  to  interest  himself 
in  the  objects,  and  he  may  become  immersed  in  details 
before  he  has  arrived  at  any  general  view  or  reason  of  the 
subject.  Great  care  must  be  exercised  that  the  pupil  is 
not  swamped.  Mere  book  work  or  memory  stuffing  is 
useless,  and  it  may  dwarf  or  divert  the  sympathies  of 
active  young  minds. 

The  present  tendency  in  secondary  education  is  away 
from  the  formal  technical  completion  of  separate  subjects 
and  toward  the  developing  of  a  workable  training  in  the 
activities  that  relate  the  pupil  to  his  own  life.  In  the 
natural  science  field,  the  tendency  is  to  attach  less  im- 
portance to  botany  and  zoology  as  such,  and  to  lay  greater 
stress  on  the  processes  and  adaptations  of  life  as  expressed 
in  plants  and  animals.  Education  that  is  not  applicable, 
that  does  not  put  the  pupil  into  touch  with  the  living  know- 
ledge and  the  affairs  of  his  time,  may  be  of  less  educative 
value  than  the  learning  of  a  trade  in  a  shop.  "We  are  begin- 
ning to  learn  that  the  ideals  and  the  abilities  should  he 
developed  out  of  the  common  surroundings  and  affairs  of 


PREFACE 


VII 


life  ratlier  than  imposed  on  the  pupil   as   a  matter  of 
abstract  unrelated  theory 

It  is  much  better  for  the  beginning  pupil  to  acquire  a 
real  conception  of  a  few  central  principles  and  points  of 
view  respecting  common  forms  that  will  enable  him  to  tie 
his  knowledge  together  and  organize  it  and  apply  it,  than 
to  familiarize  himself  with  any  number  of  mere  facts  about 
the  lower  forms  of  life  which,  at  the  best,  he  can  know 
only  indirectly  and  remotely.  If  the  pupil  wishes  to  go 
farther  in  later  years,  he  may  then  take  up  special  groups 
and  phases. 


CONTENTS 


CHAPTER 

I.  No  Two  Plants  or  Parts  are  Alike 

II.  The  Struggle  to  Live 

III.  Survival  of  the  Fit 

IV.  Plant  Societies 
V.  The  Plant  Body 

VI.  Seeds  and  Germination 

VII.  The  Root — The  Forms  of  Roots 

VIII.  The  Root  —  Function  and  Structure 

IX.  The  Stem  —  Kinds  and  Forms  —  Pruning 

X.  The  Stem  —  Its  General  Structure 

XI.  Leaves  —  Form  and  Position    . 

XII.  Leaves — Structure  and  Anatomy 

XIII.  Leaves  —  Function  or  Work 

XIV.  Dependent  Plants     . 
XV.  Winter  and  Dormant  Buds 

XVI.  Bud  Propagation 

XVII.  How  Plants  Climb     . 

XVIII.  The  Flower  —  Its  Parts  and  Forms 

XIX.  The  Flower  —  Fertilization  and  Poll 

XX.  Flower-clusters 

XXI.  Fruits 

XXII,  Dispersal  of  Seeds   . 

XXIII.  Phenogams  and  Cryptogams 

XXIV.  Studifis  in  Cryptogams 
Index  


BEGINNERS'  BOTANY 


CHAPTER  I 
NO  TWO  PLANTS  OR  PARTS  ARE  ALIKE 


Fig.  I.  —  No  Two  Branches  are  Alike. 
(Hemlock.) 

If  one  compares  any  two  plants  of 
the  same  kind  ever  so  closely,  it  will  be 
found  that  they  differ  from  each  other.  The 
;. difference  is  apparent  in  size,  form,  colour,  mode 
of  branching,  number  of  leaves,  number  of  flowers,  vigour, 
season  of  maturity,  and  the  like;  or,  in  other  words,  all 
plants  and  animals  vary  from  an  assumed  or  sta^tdard  type. 
If  one  compares  any  two  brandies  or  twigs  on  a  tree,  it 
will  be  found  that  they  differ  in  size,  age,  form,  vigour,  and 
in  other  ways  (Fig.  i). 

If  one  compares  a7ty  tivo  leaves,  it  will  be  found  that 
they  are  unlike  in  size,  shape,  colour,  yeining,  hairiness, 
markings,  cut  of  the  margins,  or  other  small  features.  In 
some  cases  (as  in  Fig.  2)  the  differences  are  so  great  as  to 
be  readily  seen  in  a  small  black-and-white  drawing. 


BEGINNERS'  BOTANY 


If  the  pupil  extends  his  observation  to  animals,  he 
will  still  find  the  same  truth ;  for  probably  no  two  living 
objects  are  exact  duplicates.  If  any  person  finds  two  objects 
that  he  thinks  to  be  exactly  alike,  let  him  set  to  work  to 


Fig.  2.  — No  Two  Leaves  are  Alike. 

discover   the   differences,   remembering    that   nothing   in 
nature  is  so  small  or  apparently  trivial  as  to  be  overlooked. 

Variation,  or  differences  between  organs  and  also  be- 
tween organisms,  is  one  of  the  most  significant  facts  in 
nature. 

Suggestions. — The  first  fact  that  the  pupil  should  acquire 
about  plants  is  that  no  two  are  alike.  The  way  to  apprehend  this 
great  fact  is  to  see  a  plant  accurately  and  then  to  compare  it  with 


NO    TWO  PLANTS   OR  PARTS  ARE  ALIKE  3 

another  plant  of  the  same  species  or  kind.  In  order  to  direct  and 
concentrate  the  observation,  it  is  well  to  set  a  certain  number  of 
attributes  or  marks  or  qualities  to  be  looked  for.  1.  Suppose 
any  two  or  more  plants  of  corn  are  compared  in  the  following 
points,  the  pupil  endeavouring  to  determine  whether  the 
parts  exactly  agree.  See  that  the  observation  is  close  and 
accurate.  Allow  no  guesswork.  Instruct  the  pupil  to  meas- 
ure the  parts  when  size  is  involved. 

(1)  Height  of  the  plant. 

(2)  Does  it  branch?     How  many  secondary  stems  or  "suckers' 
from  one   root? 

(3)  Shade  or  colour. 

(4)  How   many   leaves. 

(5)  Arrangement  of  leaves  on  stem. 

(6)  Measure  length  and  breadth  of  six  main  leaves. 

(7)  Number  and  position  of  ears;  colour  of  silks. 

(8)  Size  of  tassel,  and  number  and  size  of  its  branches. 

(9)  Stage  of  maturity  or  ripeness  of  plant. 

(10)  Has  the  plant  grown  symmetrically,  or  has  it  been  crowded 
by  other  plants  or  been  obliged  to  struggle  for  light  or  room? 

(11)  Note  all  unusual  or  interesting  marks  or  features. 

(12)  Always  make  note  of  comparative  vigour  of  the  plants. 

Note  to  Teacher. — The  teacher  should  always  insist  on  per- 
sonal work  by  the  pupil.  Every  pupil  should  handle  and  study 
the  object  by  himself.  Books  and  pictures  are  merely  guides  and 
helps.  So  far  as  possible,  study  the  plant  or  animal  just  where  it 
grows  naturally. 

Notebooks. — Insist  that  the  pupils  make  full  notes  and  preserve 
these  notes  in  suitable  books.  Note-taking  is  a  powerful  aid  in 
organizing  the  mental  processes,  and  in  insuring  accuracy  of  obser- 
vation and  record.  The  pupil  should  draw  what  he  sees,  even 
though  he  is  not  expert  with  the  pencil.  The  drawing  should  not 
be  made  for  looks,  but  to  aid  the  pupil  in  his  orderly  study  of  the 
object ;  it  should  be  a  means  of  self-expression. 


CHAPTER   II 
THE  STRUGGLE  TO  LIVE 

Every  plant  and  animal  is  exposed  to  unfavourable  con- 
ditions. It  is  obliged  to  contend  with  these  conditions  in 
order  to  live. 

No  two  plants  or  parts  of  plants  are  identically  exposed 
to  the  conditions  in  which  they  live.     The  large  branches 


Fig.  3.  — a  Battle  for  Life. 

in  Fig.  I  probably  had  more  room  and  a  better  exposure 
to  light  than  the  smaller  ones.  Probably  no  two  of  the 
leaves  in  Fig.  2  are  equally  exposed  to  light,  or  enjoy 
identical  advantages  in  relation  to  the  food  that  they  re- 
ceive from  the  tree. 

Examine  any  tree  to  determine  under  what  advantages 
or  disadvantages  any  of  the  limbs  may  live.  Examine 
similarly  the  different  plants  in  a  garden  row  (Fig.  3);  or 
the  different  bushes  in  a  thicket ;  or  the  different  trees  in 
a  wood. 

4 


THE  STRUGGLE    TO  LIVE 


5 


The  plant  meets  its  conditions  by  succtmibing  to  them 
(that  is,  by  dying),  or  by  adapting  itself  to  them. 

The  tree  meets  the  cold  by  ceasing  its  active  growth, 
hardening  its  tissues,  dropping  its  leaves.  Many  her- 
baceous or  soft-stemmed  plants  meet  the  cold  by  dying 
to  the  ground  and  withdrawing  all  life  into  the  root  parts. 
Some  plants  meet  the  cold  by  dying  outright  and  provid- 
ing abundance  of  seeds  to  perpetuate  the  kind  next  season. 


Fig.  4.  — The  Reach  for  Light  of  a  Tree  on  the  Edge  of  a  Wood. 

Plants  adapt  themselves  to  light  by  growing  toward  it 
(Fig.  4);  or  by  hanging  their  leaves  in  such  position  that 
they  catch  the  light ;  or,  in  less  sunny  places,  by  expand- 
ing their  leaf  surface,  or  by  greatly  lengthening  their 
stems  so  as  to  overtop  their  fellows,  as  do  trees  and  vines. 

The  adaptations  of  plants  will  afford  a  fertile  field  of 
study  as  we  proceed. 


6  BEGINNERS'  BOTANY 

Struggle  for  existence  and  adaptation  to  conditions  are 

among  the  most  significant  facts  in  nature. 

The  sum  of  all  the  conditions  in  which  a  plant  or  an  ani- 
mal is  placed  is  called  its  environment,  that  is,  its  surround- 
ings. The  environment  comprises  the  conditions  of  climate, 
soil,  moisture,  exposure  to  light,  relation  to  food  supply, 
contention  with  other  plants  or  animals.  The  organism 
adapts  itself  to  its  eiivironmcnt,  or  else  it  weakens  or  dies- 
Every  weak  branch  or  plant  has  undergone  some  hardship 
that  it  was  not  wholly  able  to  withstand. 

Suggestions. — The  pupil  should  study  any  plant,  or  branch  of  a 
plant,  with  reference  to  the  position  or  condition  under  -which  it 
grows,  and  compare  one  plant  or  branch  with  another.  With  animals, 
it  is  common  knowledge  that  every  animal  is  alert  to  avoid  or  to 
escape  danger,  or  to  protect  itself.  2.  It  is  well  to  begin  with  a 
branch  of  a  tree,  as  in  Fig.  1.  Note  that  no  two  parts  are  alike  (Chap. 
T).  Note  that  some  are  large  and  strong  and  that  these  stand  far- 
thest toward  light  and  room.  Some  are  very  small  and  weak,  barely 
able  to  live  under  the  competition.  Some  have  died.  The  pupil  can 
easily  determine  which  of  the  dead  branches  perished  first.  He  should 
take  note  of  the  position  or  place  of  the  branch  on  the  tree,  and 
determine  whether  the  greater  part  of  the  dead  twigs  are  toward  the 
centre  of  the  tree  top  or  toward  the  outside  of  it.  Determine  whether 
accident  has  overtaken  any  of  the  parts.  3.  Let  the  pupil  examine 
the  top  of  any  thick  old  apple  tree,  to  see  whether  there  is  any 
struggle  for  existence  and  whether  any  limbs  have  perished.  4.  If 
the  pupil  has  access  to  a  forest,  let  him  determine  why  there  are  no 
branches  on  the  trunks  of  the  old  trees.  Examine  a  tree  of  the 
same  kind  growing  in  an  open  field.  5.  A  row  of  lettuce  or  other 
plants  sown  thick  will  soon  show  the  competition  between  plants. 
Any  fence  row  or  weedy  place  will  also  show  it.  Why  does  the 
farmer  destroy  the  weeds  among  the  corn  or  potatoes?  TIoav  does 
the  florist  reduce  competition  to  its  lowest  terms?  what  is  the  result? 


CHAPTER   III 


THE  SURVIVAL  OF  THE  FIT 


The  plants  that  most  perfectly  meet  their  conditions  are 
able  to  persist.  They  perpetuate  themselves.  Their  off- 
spring are  likely  to  inherit  some  of  the  attributes  that 
enabled  them  successfully  to  meet  the  battle  of  life.  The 
fit  (those  best  adapted  to  their  conditions)  tend  to  survive. 

Adaptation  to  conditions  depends  on  the  fact  of  varia- 
tion; that  is,  if  plants  were  perfectly  rigid  or  invariable 
(all  exactly  aUke)  they  could  not  meet  new  conditions. 
Conditions  are  necessarily  new  for  every  organism.  It  is 
impossible  to  picture  a  perfectly  inflexible  and  stable  succes- 
sion of  plants  or  animals. 

Breeding.  —  Man  is  able  to  modify  plants  and  animals. 
A.11  our  common  domestic  animals  are  very  unlike  their 
original  ancestors.  So  all  our  common  and  long-culti- 
vated plants  have  varied 
from  their  ancestors.  Even 
in  some  plants  that  have 
been  in  cultivation  less  than 
a  century  the  change  is 
marked :  compare  the  com- 
mon black-cap  raspberry 
with  its  common  wild  ances- 
tor, or  the  cultivated  black- 
berry with  the  wild  form. 

By  choosing  seeds  from  a  plant  that  pleases  him,  the 
breeder  may  be  able,  under  given  conditions,  to  produce 

7 


Fig.  5.  — Desirable  and  Undesirable 
Types  of  Cotton  Plants.    Why? 


BEGINNERS'   BOTANY 


Fig.  6,  —  Flax  Breeding. 

A  '.s  a  plant  grown  for  seed  production 

/;  f'i.r  lil.iv  iinMlur.tioii.     Wl'.y? 


Suggestions. 
• — 6.  Every  pu- 
pil should  un- 
dertake at  least 
one  simple  ex- 
periment in  se- 
lection of  s6ed.  He  may  select  kernels  from  the 
best  plant  of  corn  in  the  field,  and  also  from  the 
poorest  plant, — having  reference  not  so  much  to 
mere  incidental  size  and  vigour  of  the  plants  that 
may  be  due  to  accidental  conditions  in  the  field, 
as  to  the  apparently  constitutional  strength  and 
size,  number  of  ears,  size  of  ears,  perfectness  of 
cars  and  kernels,  habit  of  the  plant  as  to  sucker- 
ing,  and  the  like.  The  seeds  may  be  saved  and 
sown  the  next  year.  Every  crop  can  no  doubt 
be  very  greatly  improved  by  a  careful  process 
of  selection  extending  over  a  series  of  years. 
Crops  are  increased  in  yield  or  efficiency  in  three 
ways:  better  general  care;  enriching  the  land  in 
which  they  grow;  attention  to  bre(>dinfT. 


numbers  of  plants  with  more 
or  less  of  the  desired  quali- 
ties; from  the  best  of  these, 
he  may  again  choose  ;  and  so 
on  until  the  race  becomes 
greatly  improved  (Figs.  5,  6, 
7).  This  process  of  continu- 
ously choosing  the  most  suita- 
ble plants  is  known  as  selec- 
tion. A  some- 
what similar 
process  pro- 
ceeds in  wild 
nature,  and  it 
is  then  known 
as  natural  se- 
lection. 


Fig.  7.  — Breed- 
ing. 

A,  effect  from  breed- 
ing from  smallest 
grains  (after  four 
years),  average 
head;  B,  result 
from  breeding  from 
the  plumpest  and 
heaviest  grains 
(after  four  years), 
average  head. 


CHAPTER   IV 
PLANT   SOCIETIES 

In  the  long  course  of  time  in  which  plants  have  been 
accommodating  themselves  to  the  varying  conditions  in 
which  they  are  obHged  to  grow,  tJiey  have  become  adapted 
to  every  different  environment.  Certain  plants,  therefore, 
may  live  together  or  near  each  other,  all  enjoying  the 
same  general  conditions  and  surroundings.  These  aggre- 
gations of  plants  that  are  adapted  to  similar  general  con- 
ditions are  known  as  plant  societies. 

Moisture  and  temperature  are  the  leading  factors  in 
determining  plant  societies.  The  great  geographical 
societies  or  aggregations  of  the  plant  world  may  con- 
veniently be  associated  chiefly  with  the  moisture  supply, 
as :  wet-7'egion  societies^  comprising  aquatic  and  bog 
vegetation  (Fig.  8);  arid-region  societies ^  comprising  desert 
and  most  sand-region  vegetation ;  mid-region  societies^ 
comprising  the  mixed  vegetation  in  intermediate  regions 
(Fig.  9),  this  being  the  commonest  type.  Much  of  the 
characteristic  scenery  of  any  place  is  due  to  its  plant 
societies.  Arid-region  plants  usually  have  small  and  hard 
leaves,  apparently  preventing  too  rapid  loss  of  water. 
Usually,  also,  they  are  characterized  by  stiff  growth,  hairy 
covering,  spines,  or  a  much-contracted  plant-body,  and 
often  by  large  underground  parts  for  the  storage  of  water. 

Plant  societies  may  also  be  distinguished  with  reference 
to  latitude  and  temperature.  There  are  tropical  societies^ 
temperate-region   societies^    boreal  or   cold-region   societies. 

9 


lO 


BEGINNERS'   BOTANY 


With  reference  to  altitude,  societies  might  be  classified 
as  lowland  (which  are  chiefly  wet-region),  intennediaie 
(chiefly  mid-region),  stibalpijie  or  mid-moimtam  (which  are 
chiefly  boreal),  alpine  or  high-moimtain. 

The  above  classifications  have  reference  chiefly  to  great 
geographical  floras  or  societies.  But  there  are  societies 
within  societies.  There  are  small  societies  coming  within 
the  experience  of  every  person  who  has  ever  seen  plants 


Fig.  8.  — a  Wet-region  Society. 

growing  in  natural  conditions.  There  are  roadside,  fence- 
row,  lawn,  thicket,  pasture,  dune,  woods,  cliff,  barn-yard 
societies.  Every  different  place  has  its  characteristic  vegeta- 
tion. Note  the  smaller  societies  in  Figs.  8  and  9.  In  the 
former  is  a  water-lily  society  and  a  cat-tail  society.  In 
the  latter  there  are  grass  and  bush  and  woods  societies. 

Some  Details  of  Plant  Societies.  —  Societies  may  be  com- 
posed of  scattered  and  iiitermingled  plants^  or  of  dense 
chimps  or  groups  of  plants.  Dense  clumps  or  groups  are 
usually  made  up  of  one  kind  of  plant,  and  they  are  then 


PLANT  SOCIETIES 


II 


called  colonies.  Colonies  of  most  plants  are  transient: 
after  a  short  time  other  plants  gain  a  foothold  amongst 
them,  and  an  intermingled  society  is  the  outcome.  Marked 
exceptions  to  this  are  grass  colonies  and  forest  colonies,  in 
which  one  kind  of  plant  may  hold  its  own  for  years  and 
centuries. 

In  a  large  newly  cleared  area,  plants  usually  ^n-/  estab- 
lish themselves  in  dense  colonies.     Note  the  great  patches 


Fig.  9.  — a  Mid-region  Society. 

of  nettles,  jewel-weeds,  smart-weeds,  clot-burs,  fire-weeds 
in  recently  cleared  but  neglected  swales,  also  the  fire-weeds 
in  recently  burned  areas,  the  rank  weeds  in  the  neglected 
garden,  and  the  ragweeds  and  May-weeds  along  the  re- 
cently worked  highway.  The  competition  amongst  them- 
selves and  with  their  neighbours  finally  breaks  up  the 
colonies,  and  a  mixed  and  intei^mingled flora  is  generally 
the  result. 

In  many  parts  of  the  world  the  general  tendency  of  neg- 
lected areas  is  to  run  into  forest.     All  plants  rush  for  the 


12 


BEGINNERS'   BOTANY 


cleared  area.  Here  and  there  bushes  gain  a  foothold. 
Young  trees  come  up  ;  in  time  these  shade  the  bushes  and 
gain  the  mastery.  Sometimes  the  area  grows  to  poplars 
or  birches,  and  people  wonder  why  the  original  forest  trees 
do  not  return  ;  but  these  forest  trees  may  be  growing  unob- 
served here  and  there  in  the  tangle,  and  in  the  slow  pro- 
cesses of  time  the  poplars  perish  —  for  they  are  short-lived 
—  and  the  original  forest  may  be  replaced.  Whether  one 
kind  of  forest  or  another  returns  will  depend  partly  on  the 
kinds  that  are  most  seedful  in  that  vicinity  and  which, 
therefore,  have  sown  themselves  most  profusely.  Much 
depends,  also,  on  the  kind  of  undergrowth  that  first  springs 
up,  for  some  young  trees  can  endure  more  or  less  shade 
than  others. 

Some  plants  associate.  They  grow  together.  This  is 
possible  largely  because  they  diverge  or  differ  in  charac- 
ter. Plants  asso- 
ciate in  two  ways : 
by  grvwing  side  by 
side ;  by  groiving 
above  or  beneath. 
In  sparsely  popu- 
lated societies, 
plants  may  grow 
alongside  each 
other.  In  most 
cases,  however, 
there  is  overgrowth 
and  undergrowth: 
one  kind  grows  beneath  another.  Plants  that  have  be- 
come adapted  to  shade  are  usually  undergrowths.  In  a  cat- 
tail swamp,  grasses  and  other  narrow-leaved  plants  grow 
in  the  bottom,  but  they  are  usually  unseen  by  the  casual 


Fig.  io.  — Overgrowth  and  Undergrowth  in 
Three  Series,  —  trees,  bushes,  grass. 


PLANT  SOCIETIES  1 3 

observer.  Note  the  undergrowth  in  woods  or  under  trees 
(Fig.  10).  Observe  that  in  pine  and  spruce  forests  there 
is  almost  no  undergrowth,  partly  because  there  is  very  little 
light. 

On  the  same  area  the  societies  may  differ  at  different 
times  of  the  year.  There  are  spring,  summer,  and  fall  soci- 
eties. The  knoll  which  is  cool  with  grass  and  strawber- 
ries in  June  may  be  aglow  with  goldenrod  in  September. 
If  the  bank  is  examined  in  May,  look  for  the  young  plants 
that  are  to  cover  it  in  July  and  October;  if  in  Septem- 
ber, find  the  dead  stalks  of  the  flora  of  May.  What  suc- 
ceeds the  skunk  cabbage,  hepaticas,  trilliums,  phlox,  violets, 
buttercups  of  spring }  What  precedes  the  wild  sunflowers, 
ragweed,  asters,  and  goldenrod  of  fall } 

The  Landscape.—  To  a  large  extent  the  colour  of  the  land- 
scape is  determined  by  the  character  of  the  plant  societies. 
Evergreen  societies  remain  green,  but  the  shade  of  green 
varies  from  season  to  season;  it  is  bright  and  soft  in 
spring,  becomes  dull  in  midsummer  and  fall,  and  assumes 
a  dull  yellow-green  or  a  black-green  in  winter.  Deciduous 
societies  vary  remarkably  in  colour — from  the  dull  browns 
and  grays  of  winter  to  the  brown  greens  and  olive-greens 
of  spring,  the  staid  greens  of  summer,  and  the  brilliant 
colours  of  autumn. 

The  autumn  colours  are  due  to  intermingled  shades  of 
green,  yellow  and  red.  The  coloration  varies  with  the  kind 
of  plant,  the  special  location,  and  the  season.  Even  in  the 
same  species  or  kind,  individual  plants  differ  in  colour ;  and 
this  individuality  usually  dstinguishes  the  plant  year  by 
year.  That  is,  an  oak  which  is  maroon  red  this  autumn  is 
likely  to  exhibit  that  range  of  colour  every  year.  The  au- 
tumn colour  is  associated  with  the  natural  maturity  and 
death  of  the  leaf,  but  it  is  most  brilliant  in  long  and  open 


14  BEGTNNEJiS'  BOTANY 

falls  —  largely  because  the  foliage  ripens  more  gradually 
and  persists  longer  in  such  seasons.  It  is  probable  that 
the  autumn  tints  are  of  no  utility  to  the  plant.  Autumn 
colours  are  not  caused  hy  frost.  Because  of  the  long,  dry 
falls  and  the  great  variety  of  plants,  the  autumnal  colour  of 
the  American  landscape  is  phenomenal. 

Ecology. — The  study  of  the  relationships  of  plants  and 
animals  to  each  other  and  to  seasons  and  environments  is 
known  as  ecology  (still  written  cccology  in  the  dictionaries). 
It  considers  the  habits,  habitats,  and  modes  of  life  of  liv- 
ing things  —  the  places  in  which  they  grow,  how  they 
migrate  or  are  disseminated,  means  of  collecting  food, 
their  times  and  seasons  of  flowering,  producing  young, 
and  the  like. 

Suggestions.  —  One  of  the  best  of  all  subjects  for  school  instruc- 
tion in  botany  is  the  study  of  plant  societies.  It  adds  definiteness 
and  zest  to  excursions.  7.  Let  each  excursion  be  confined  to  one 
or  two  societies.  Visit  one  day  a  swamp,  another  day  a  forest, 
another  a  pasture  or  meadow,  another  a  roadside,  another  a  weedy 
field,  another  a  cliff  or  ravine.  Visit  shores  whenever  possible. 
Each  pupil  should  be  assigned  a  bit  of  ground  —  say  lo  or  20  ft. 
square  —  for  special  study.  He  should  make  a  list  showing  (i) 
how  many  kinds  of  plants  it  contains,  (2)  the  relative  abundance 
of  each.  The  lists  secured  in  different  regions  should  be  com- 
pared. It  does  not  matter  greatly  if  the  pupil  does  not  know  all 
the  plants.  He  may  count  the  kinds  without  knowing  the  names. 
It  is  a  good  plan  for  the  pupil  to  make  a  dried  specimen  of  each 
kind  for  reference.  The  pupil  should  endoavour  to  discover  why 
the  plants  grow  as  they  do.  Note  what  kinds  of  plants  grow  next 
each  other ;  and  which  are  undergrowth  and  which  overgrowth ; 
and  which  are  erect  and  which  wide-spreading.  Challenge  every 
plant  society. 


CHAPTER  V 
THE  PLANT   BODY 

The  Parts  of  a  Plant.  —  Our  familiar  plants  are  made  up 
cf  several  distinct  parts.  The  most  prominent  of  these 
parts  are  root,  stem,  leaf,  flower,  fruit,  and  seed.  Familiar 
plants  differ  wonderfully  ift  size  a7td  sJiape,  —  from  fragile 
mushrooms,  delicate  waterweeds  and  pond-scums,  to  float- 
ing leaves,  soft  grasses,  coarse  weeds,  tall  bushes,  slender 
climbers,  gigantic  trees,  and  hanging  moss. 

The  Stem  Part.  —  In  most  plants  there  is  a  main  central 
part  or  shaft  on  which  the  other  or  secondary  parts  are 
borne.  This  main  part  is  the  plant  axis.  Above  ground, 
in  most  plants,  the  main  plant  axis  bears  the  branches ^ 
leaves,  diXidi  flowers ;  below  ground,  it  bears  the  roots. 

The  rigid  part  of  the  plant,  which  persists  over  winter 
and  which  is  left  after  leaves  and  flowers  are  fallen,  is  the 
framework  of  the  plant.  The  framework  is  composed  of 
both  root  and  stem.  When  the  plant  is  dead,  the  frame- 
work remains  for  a  time,  but  it  slowly  decays.  The  dry 
winter  stems  of  weeds  are  the  framework,  or  skeleton  of 
the  plant  (Figs,  ii  and  12).  The  framework  of  trees  is 
the  most  conspicuous  part  of  the  plant. 

The  Root  Part.  —  The  root  bears  the  stem  at  its  apex, 
but  otherwise  it  normally  bears  only  root-branches.  The 
stem,  however,  bears  leaves,  flowers,  and  fruits.  Those 
Hving  surfaces  of  the  plant  which  are  most  exposed  to 
light  are  green  or  highly  coloured.  The  root  tends  to  grow 
downward,  but  the  stem  tends  to  grow  upward  tozvard  light 

lb 


i6 


BEGINNERS'  BOTANY 


and  air.     The  plant  is  anchored  or  fixed  in  the  soil  by  the 
roots.     Plants  have  been  called  "earth  parasites." 

The  Foliage  Part.  —  The  leaves  precede  the  flowers  in 
point  of  time  or  life  of  the  plant.  TJie  flowers  always 
preeede  the  fruits  and  seeds.  Many  plants  die  when  the 
seeds  have  matured.     The  whole  mass  of  leaves  of  any 

plant  or  any  branch  is 
known  as  its  foliage. 
In  some  cases,  as  in 
crocuses,  the  flowers 
seem  to  precede  the 
leaves;  but  the  leaves 
that  made  the  food  for 
these  flowers  grew  the 
preceding  year. 

The  Plant  Generation. 
—  The  course  of  *  a 
plant's  life,  with  all  the 
events  through  which 
the  plant  naturally 
passes,  is  known  as 
the  plant's  life-history. 
The  life-history  em- 
braces various  stages, 
or  epochs,  as  dormant 
seed,  gerin  ination,  grow  thy  flowering,  fruiting.  Some  plan  ts 
run  their  course  in  a  few  weeks  or  months,  and  some  live 
for  centuries. 

The  entire  life-period  of  a  plant  is  called  a  generation. 
It  is  the  whole  period  from  birth  to  normal  death,  without 
reference  to  the  various  stages  or  events  through  which  it 
passes. 

A  generation  begins  with  the  young  seed,  not  with  germi- 


j&R.  vt.  — Plant  of  a 
Vhitib  Sunflower. 


Fig.  12— Frame- 
work OF  Fig.  h. 


THE  PLANT  BODY  1/ 

nation.  //  ends  with  death  —  that  is,  when  no  life  is  left 
in  any  part  of  the  plant,  and  only  the  seed  or  spore 
remains  to  perpetuate  the  kind.  In  a  bulbous  plant,  as  a 
lily  or  an  onion,  the  generation  does  not  end  until  the  bulb 
dies,  even  though  the  top  is  dead. 

When  the  generation  is  of  only  one  season's  duration, 
the  plant  is  said  to  be  annual.  When  it  is  of  two  seasons, 
it  is  biennial.  Biennials  usually  bloom  the  second  year. 
When  of  three  or  more  seasons,  the  plant  is  perennial. 
Examples  of  annuals  are  pigweed,  bean,  pea,  garden  sun- 
flower ;  of  biennials,  evening  primrose,  mullein,  teasel ;  of 
perennials,  dock,  most  meadow  grasses,  cat-tail,  and  all 
shrubs  and  trees. 

Duration  of  the  Plant  Body.  —  Plant  structures  which 
are  more  or  less  soft  and  which  die  at  the  close  of  the 
season  are  said  to  be  herbaceous,  in  contradistinction  to 
being  ligneous  or  woody.  A  plant  which  is  herbaceous  to 
the  ground  is  called  an  herb;  but  an  herb  may  have  a 
woody  or  perennial  root,  in  which  case  it  is  called  an 
herbaceous  perennial.  Annual  plants  are  classed  as  herbs. 
Examples  of  herbaceous  perennials  are  buttercups,  bleed- 
ing heart,  violet,  waterlily,  Bermuda  grass,  horse-radish, 
dock,  dandelion,  goldenrod,  asparagus,  rhubarb,  many 
wild  sunflowers  (Figs.  11,  12). 

Many  herbaceous  perennials  have  short  generations. 
They  become  weak  with  one  or  two  seasons  of  flowering 
and  gradually  die  out.  Thus,  red  clover  usually  begins  to 
fail  after  the  second  year.  Gardeners  know  that  the  best 
bloom  of  hollyhock,  larkspur,  pink,  and  many  other  plants, 
is  secured  when  the  plants  are  only  two  or  three  years 
old. 

Herbaceous  perennials  which  die  away  each  season  to 
bulbs  or  tubers,  are  sometimes  called  pseud-annuals  (that 


I8 


BEGINNERS'   BOTANY 


is,  jalse  annuals).     Of  such  are  lily,  crocus,  onion,  potato, 
and  bull  nettle. 

True  annuals  reach  old  age  the  first  year.  Plants  which 
are  normally  perennial  may  become  annual  in  a  shorter- 
season  clhnate  by  being  killed  by  frosty  rather  than  by  dying 
naturally  at  the  end  of  a  season  of  growth.  They  are  cli- 
matic annuals.  Such  plants  are  called  plur-annuals  in  the 
short-season  region.     Many  tropical  perennials  are  plur- 


Fig.  13.  — a  Shrub  or  Bush.    Dogwood  osier. 

annuals  when  grown  in  the  north,  but  they  are  treated  as 
true  annuals  because  they  ripen  sufficient  of  their  crop  the 
same  season  in  which  the  seeds  are  sown  to  make  them 
worth  cultivating,  as  tomato,  red  pepper,  castor  bean, 
cotton.  Name  several  vegetables  that  are  planted  in 
gardens  with  the  expectation  that  they  will  bear  till  frost 
comes. 

Woody    or    ligneous    plants    usually    live    longer    than 
herbs.      Those    that   remain   low    and   produce    several   or 


THE  PLANT  BODY 


19 


many  similar  shoots  from  the 
base  are  called  shrubs,  as  lilac, 
rose,  elder,  osier  (Fig.  13).  Low 
and  thick  shrubs  are  bushes. 
Plants  that  produce  one  main 
trunk  and  a  more  or  less  elevated 
head  are  trees  (Fig.  14).  All 
shrubs  and  trees  are  perennial. 
Every  plant  makes  an  effort 


to  propagate^  or  to  perpetuate  its    :^-^i^'$4 
kind ;   and,  as  far  as  we  can       Biff^f; 
see,  this  is  the  end  for  which 
the  plant  itself  lives.    The  seed 
or  spore  is  the  final  product  of 
the  plaftt. 


Fig.  14.  — a  Tree. 
birch. 


The  weeping 


Suggestions.  —  8.  The  teacher  may  assign  each  pupil  to  one 
plant  in  the  school  yard,  or  field,  or  in  a  pot,  and  ask  him  to  bring 
out  the  points  in  the  lesson.  9.  The  teacher  may  put  on  the 
board  th€  names  of  many  common  plants  and  ask  the  pupils  to 
classify  into  annuals,  pseud-annuals,  plur-annuals  (or  climatic 
annuals),  biennials,  perennials,  herbaceous  perennials,  ligneous 
perennials,  herbs,  bushes,  trees.  Every  plant  grown  on  the  farm 
should  be  so  classified  :  wheat,  oats,  corn,  buckwheat,  timothy, 
strawberry,  raspberry,  currant,  tobacco,  alfalfa,  flax,  crimson  clover, 
hops,  cowpea,  field  bean,  sweet  potato,  peanut,  radish,  sugar-cane, 
barley,  cabbage,  and  others.  Name  all  the  kinds  of  trees  you 
know. 


CHAPTER  VI 

SEEDS  AND   GERMINATION 

The  seed  contains  a  miniature  plant,  or  embryo.     The 
embryo    usually    has    three    parts    that    have    received 
names :  the  stemlet,  or  caulicle ;  the  seed-leaf,  or  cotyledon 
(usually  I  or  2) ;  the   bud,  or  plumule,  lying  between  or 
above  the  cotyledons.    These  parts  are  well 
seen  in  the  common  bean  (Fig.  15),  particu- 
larly when  the  seed  has  been  soaked  for  a 
few  hours.     One  of  the  large  cotyledons  — 
OF  THE  Bean,      comprising  half  of  the  bean  —  is  shown  at 
/?,  cotyledon;  <7,     R.     The  cauliclc  is  at  O,     The  plumule  is 
mutf  i^'fim     shown  at  A,     The  cotyledons  are  attached 
nod*-  to  the  caulicle  at  F:  this  point  may  be  taken 

as  the  first  node  or  joint. 

The  Number  of  Seed-leaves.  —  All  plants  having  two 
seed-leaves  belong  to  the  group  called  dicotyledons.  Such 
seeds  in  many  cases  split  readily  in  halves,  e.g,  a.  bean. 
Some  plants  have  only  one  seed-leaf  in  a  seed.  They 
form  a  group  of  plants  called  monocotyledons.  Indian 
corn  is  an  example  of  a  plant  with  only  one  seed-leaf: 
a  grain  of  corn  does  not  split  into  halves  as  a  bean  does. 
Seeds  of  the  pine  family  contain  more  than  two  cotyledons, 
but  for  our  purposes  they  may  be  associated  with  the  dicoty- 
ledons, although  really  forming  a  different  group. 

These  two  groups — the  dicotyledons  and  the  mono- 
cotyledons —  represent  two  great  natural  divisions  of  the 
vegetable  kingdom.     The  dicotyledons  contain  the  woody 

20 


SEEDS  AXD  GEI:MI NATION  21 

bark-bearing  trees  and  bushes  (except  conifers),  and  most 
of  the  herbs  of  temperate  climates  except  the  grasses, 
sedges,  rushes,  lily  tribes,  and  orchids.  The  flower-parts 
are  usually  in  fives  or  multiples  of  five,  the  leaves  mostly 
netted-veined,  the  bark  or  rind  distinct,  and  the  stem  often 
bearing  a  pith  at  the  centre.  The  monocotyledons  usually 
have  the  flower-parts  in  threes  or  multiples  of  three,  the 
leaves  long  and  parallel-veined,  the  bark  not  separable, 
and  the  stem  without  a  central  pith. 

Every  seed  \^  provided  zvith  food  \o  support  the  germinat- 
ing plant.  Commonly  this  food  is  starch.  The  food  may 
be  stored  in  the  cotyledons^  as  in  bean,  pea,  squash  ;  or  out- 
side the  cotyledojiSf  as  in  castor  bean,  pine,  Indian  corn. 
When  the  food  is  outside  or  around  the  embryo,  it  is 
usually  called  endosperm. 

Seed-coats;  Markings  on  Seed. — The  embryo  and  en- 
dosperm are  inclosed  within  a  covering  made  of  two  or 
more  layers  and  known  as  the  seed-coats. 
Over  the  point  of  the  caulicle  is  a  minute 
hole  or  a  thin  place  in  the  coats  known  as 
the  micropyle.  This  is  the  point  at  which  fig.i6.— exter- 
the  pollen-tube  entered  the  forming  ovule  nal  parts  op 
and  through  which  the  caulicle  breaks  in 
germination.  The  micropyle  is  shown  at  M  in  Fig.  i6. 
The  scar  where  the  seed  broke  from  its  funiculus  (or  stalk 
that  attached  it  to  its  pod)  is  named  the  hilum.  It  occu- 
pies a  third  of  the  length  of  the  bean  in  Fig.  i6.  The 
hilum  and  micropyle  are  always  present  in  seeds,  but  they 
are  not  always  close  together.  In  many  cases  it  is  difficult 
to  identify  the  micropyle  in  the  dormant  seed,  but  its  loca- 
tion is  at  once  shown  by  the  protruding  caulicle  as  germi- 
nation begins.  Opposite  the  micropyle  in  the  bean  (at  the 
other  end  of  the  hilum)  is  an  elevation  known  as  the  raphe. 


22  BEGINNERS'  BOTANY 

This  is  formed  by  a  union  of  the  funiculus,  or  seed-stalk, 
with  the  seed-coats,  and  through  it  food  was  transferred 
for  the  development  of  the  seed,  but  it  is  now  functionless. 

Seeds  differ  wonderfully  in  size,  shape,  colour,  and  other 
characteristics.  They  also  vary  in  longevity.  These 
characteristics  are  peculiar  to  the  species  or  kind.  Some 
seeds  maintain  life  only  a  few  weeks  or  even  days,  whereas 
others  will  "keep"  for  ten  or  twenty  years.  In  special 
cases,  seeds  have  retained  vitality  longer  than  this  limit, 
but  the  stories  that  live  seeds,  several  thousand  years  old, 
have  been  taken  from  the  wrappings  of  mummies  are  un- 
founded. 

Germination. — The  embryo  is  not  dead  ;  it  is  only  dor- 
mant. When  supplied  with  moisture^  warmth^  and  oxygen 
{air\  it  awakes  and  grows :  this  growth  is  germination. 
The  embryo  lives  for  a  time  on  the  stored  food,  but  gradu- 
ally the  plantlet  secures  a  foothold  in  the  soil  and  gathers 
food  for  itself.  When  the  plantlet  is  finally  able  to  shift 
for  its  elf y  germination  is  complete. 

Early  Stages  of  Seedling.  —  The  germinating  seed  first 
absorbs  water ^  and  swells.  The  starchy  matters  gradually 
become  soluble.  The  seed-coats  are  ruptured,  the  caulicle 
and  plumule  emerge.  During  this  process  the  seed 
respires  freely,  throwing  off  carbon  dioxide  (COo). 

The  caulicle  usually  elongates,  and  from  its  lower  end 
roots  are  emitted.  The  elongating  caulicle  is  known  as 
the  hypocotyl  ("below  the  cotyledons").  That  is,  the 
hypocotyl  is  that  part  of  the  stem  of  the  plantlet  lying 
between  the  roots  and  the  cotyledon.  The  general  direc- 
tion of  the  young  hypocotyl^  or  emerging  caulicle,  is  down- 
wards. As  soon  as  roots  form,  it  becomes  fixed  and  its 
subsequent  growth  tends  to  raise  the  cotyledons  above  the 
ground,  as  in  the  bean.     When  cotyledons  rise  into  the 


SEEDS  AND   GERMINATION 


23 


Fig.  17.  —  Pea.  Grotesque  forms  assumed 
when  the  roots  cannot  gain  entrance  to 
the  soil. 


air,  germination  is  said  to  be  epigeal  ("  above  the  earth  "). 
Bean  and  pumpkin  are  examples.  When  the  hypocotyl 
does  not  elongate  greatly 
and  the  cotyledons  remain 
under  ground,  the  germin- 
ation is  hypogeal  (''be- 
neath the  earth").  Pea 
and  scarlet  runner  bean 
are  examples  (Fig.  48). 
When  the  germinating 
seed  lies  on  a  hard  sur- 
face, as  on  closely  com- 
pacted soil,  the  hypocotyl 
and  rootlets  may  not  be  able  to  secure  a  foothold  and  they 
assume  grotesque  forms  (Fig.  17).  Try  this  with  peas  and 
beans. 

The  first  internode  ("  between  nodes  ")  above  the  coty- 
ledons is  the  epicotyl.  It  elevates  the  plumule  into  the 
air,  and  the  plumule- leaves  expand  into  the  first  true  leaves 
of  the  plant.  These  first  true  leaves,  however,  may  be 
very  unlike  the  later  leaves  in  shape. 

Germination  of  Bean.  —  The  common  bean,  as  we  have 
seen  (Fig.  15),  has  cotyledons  that  occupy  all  the  space 
inside  the  seed-coats.  When  the  hy- 
pocotyl, or  elongated  caulicle,  emerges, 
the  plumule-leaves  have  begun  to  en- 
large, and  to  unfold  (Fig.  18).  The 
hypocotyl  elongates  rapidly.  One  end 
of  it  is  held  by  the  roots.  The  other 
is  held  by  the  seed-coats  in  the  soil. 
It  therefore  takes  the  form  of  a  loop, 
and  the  central  part  of  the  loop  "  comes  up  "  first  {a.  Fig. 
19).     Presently  the  cotyledons  come  out  of  the  seed-coats, 


Fig.  18.  —  Cotyledons 
OF  Germinating 
Bean  spread  apart 

TO    SHOW    ELONGAT- 

ING  Caulicle    and 
Plumule. 


M 


BEGINNEKS*   BOTAMY 


and  the  plant  straightens  and  the 
cotyledons  expand.  These  coty- 
ledons, or  "  halves  of  the  bean," 
persist  for  some  time  {by  Fig. 
19).  They  often  become  green 
and  probably  perform  some 
function  of  foliage.  Because  of 
its  large  size,  the  Lima  bean 
shows  all  these  parts  well. 

Germination  of  Castor  Bean.  — 
In  the  castor  bean  the  hilum 
and  micropyle  are  at  the  smaller  end 
(Fig.  20).  The  bean  "  comes  up  "  with  a 
loop,  which  indicates  that  the  hypocotyl 
greatly  elongates.  On  examining  germin- 
ating seed,  however,  it  will  be  found 
that  the  cotyledons  are  contained  inside  a  fleshy  body, 
or  sac  {a,  Fig.  2 1 ).  This  sac  is  the  endosperm.  Against 
its  inner  surface  the  thin,  veiny  coty- 
ledons are  very  closely  pressed,  ab- 


FiG.  19. —  Germination  of 
Bean. 


Fig.  20.  —  Sprout^ 
ING  OF  Castor 
Bean. 


Fig.  21.—  Germina- 
tion OF  Castor  Bean. 

Endosperm  at  a. 


Fig.  22.  —  Castor 
Bean. 

Endosperm  at  a,n\  coty- 
ledons at  b. 


Fig.  23. —  Germination 
Complete  in  Castor 
Bean. 


sorbing  its  substance  (Fig.  22).  The  cotyledons  increase 
in  size  as  they  reach  the  air  (Fig.  23),  and  become  func- 
tional leaves. 


SEEDS  AND   GERMINATION 


25 


Germination  of  Monocotyledons.  —  Thus  far  we  have  stud- 
ied dicotyledonous  seeds  ;  we  may  now  consider  the  mono- 
cotyledonous  group.      Soak  kernels  of  corn.      Note  that 
the  micropyle  and  hilum  are  at  the  smaller  end  (Fig.  24). 
Make  a  longitudinal  section    through   the 
narrow  diameter;    Fig.  25  shows  it.     The 


Fig.  24. — Sprout- 
ing Indian  Corn. 

Hilum  at  h;  micro* 
pyle  at  d. 


Fig.  25.  — Kernel 
OF  Indian  Corn. 

Caulicle  at  b;  cotyle- 
don at  a;  plumule 
at/. 


Fig.  26.— Indian 
Corn. 

Caulicle  at  c,    roots  emerging  at 
ni;  plumule  at/. 


single  cotyledon  is  at  ^,  the  caulicle  at  b,  the  plumule 
at/.  The  cotyledon  remains  in  the  seed.  The  food  is 
stored  both  in  the  cotyledon  and  as  endosperm,  chiefly  the 
latter.  The  emerging  shoot  is  the  plumule,  with  a  sheath- 
ing leaf  (/,  Fig.  26).  The  root  is  emitted  from  the  tip  of 
the  caulicle,  c.  The  caulicle  is  held  in  a  sheath 
(formed  mostly  from  the  seed-coats),  and  some  of 
the  roots  escape  through  the  upper  end 
of  this  sheath  {m,  Fig.  26).  The 
^  yr  epicotyl  elongates,  particularly  if 
'Vfj^  the  seed  is  planted 

deep  or  if  it  is 
kept  for  a  time 
confined.  In  Fig. 
27  the  epicotyl  has 
elongated  from  n  to  p.  The  true  plumule-leaf  is  at  o,  but 
other  leaves  grow  from  its  sheath.  In  Fig.  28  the  roots 
are    seen    emerging   from  the  two  ends  of   the  caulicle- 


Fig.  27.  —  Indian  Corn. 

o,  plumule;  n  to/,  epicotyl. 


26 


BEGINNERS'  BOTANY 


sheath,  r,  m ;  the  epicotyl  has  grown  to  / ;  the  first  plu- 
mule-leaf is  at  o. 

In  studying  corn  or  other  fruits  or  seeds,  the  pupil  should 
note  how  the  seeds  are  arranged,  as  on  the  cob.     Count  the 

rows  on  a  corn  cob.  Odd  or 
even  in  number .-'  Always  the 
same  number.'*  The  silk  is 
the  style:  find  where  it  was 
attached  to  the  kernel.  Did 
the  ear  have  any  coverings } 
Explain.  Describe  colours  and 
markings  of  kernels  of  corn ; 
and  of  peas,  beans,  castor 
bean. 

Gymnosperms.  — The  seeds 
in  the  pine  cone,  not  being 
inclosed  in  a  seed-vessel, 
readily  fall  out  when  the  cone 
dries  and  the  scales  separate. 
Hence  it  is  difficult  to  find 
cones  with  seeds  in  them  after 
autumn  has  passed  (Fig.  29). 
The  cedar  is  also  a  gymno- 
sperm. 

Remove  a  scale  from  a 
pine  cone  and  draw  it  and 
the  seeds  as  they  lie  in  place 
on  the  upper  side  of  the  scale. 
Examine  the  seed,  preferably  with  a  magnifying  glass.  Is 
there  a  hilum }  The  micropyle  is  at  the  bottom  or  little 
end  of  the  seed.  Toss  a  seed  upward  into  the  air.  Why 
does  it  fall  so  slowly  ?  Can  you  explain  the  peculiar  whirl- 
ing motion  by  the  shape  of  the  wing }      Repeat  the  ex- 


FiG.  28.  — Germination  is  Com 

PLETE. 

/,  top  of  epicotyl ;  o,  plumule-leaf; 
m,  roots;  c,  lower  roots. 


SEEDS  AND   GERMINATION' 


n 


periment  in  the  wind.  Remove  the 
wing  from  a  seed  and  toss  it  and  an 
uninjured  seed  into  the  air  together. 
What  do  you  infer  from  these  ex- 
periments "i 

Suggestions.  —  Few  subjects  con- 
nected with  the  study  of  plant-life  are  so 
useful  in  schoolroom  demonstrations  as 
germination.  The  pupil  should  prepare 
the  soil,  plant  the  seeds,  water  them,  and 
care  for  the  plants.  10.  Plant  seeds  in 
pots  or  shallow  boxes.  The  box  should 
not  be  very  wide  or  long,  and  not  over 
four  inches  deep.  Holes  may  be  bored 
in  the  bottom  so  it  will  not  hold  water. 
Plant  a  number  of  squash,  bean,  corn, 
pine,  or  other  seeds  about  an  inch  deep 
in  damp  sand  or  pine  sawdust  in  this 
box.  The  depth  of  planting  should  be 
two  to  four  times  the  diameter  of  the 
seeds.  Keep  the  sand  or  sawdust  moist 
but  not  wet.  If  the  class  is  large,  use 
several  boxes,  that  the  supply  of  speci- 
mens may  be  ample.  Cigar  boxes  and 
chalk  boxes  are  excellent  for  individual 
pupils.  It  is  well  to  begin  the  planting 
of  seeds  at  least  ten  days  in  advance  of 
the  lesson,  and  to  make  four  or  five  differ- 
ent plantings  at  intervals.  A  day  or  two 
before  the  study  is  taken  up,  put  seeds 
to  soak  in  moss  or  cloth.  The  pupil 
then  has  a  series  from  swollen  seeds  to 

complete  germination,  and  all  the  steps  can  be  made  out.  Dry 
seeds  should  be  had  for  comparison.  If  there  is  no  special  room 
for  laboratory,  nor  duplicate  apparatus  for  every  pupil,  each  ex- 
periment may  be  assigned  to  a  committee  of  two  pupils  to  watch 
in  the  schoolroom.  11.  Good  seeds  for  study  are  those  detailed 
in  the  lesson,  and  buckwheat,  pumpkin,  cotton,  morning  glory, 
radish,  four  o'clock,  oats,  wheat.  It  is  best  to  use  familiar  seeds 
of  farm  and  garden.  Make  drawings  and  notes  of  all  the  events 
in  the  germination.  Note  the  effects  of  unusual  conditions,  as 
planting  too  deep  and  too  shallow  and  different  sides  up.  For 
hypogeal  germination,  use  the  garden  pea,  scarlet-runner,  or  Dutch 


Fig.  29. — Cones  of  Hem- 
lock (above),  White 
Pine,  Pitch  Pine. 


28 


BEGINNEL'S'  BOTANV 


case-knife  bean,  acorn,  horse-chestnut.  Squash  seeds  are  excellent 
for  germination  studies,  because  the  cotyledons  become  green  and 
leafy  and  germination  is  rapid.  Onion  is  excellent ,  except  that  it 
germinates  too  slowly.  In  order  to  study  the  root  development  of 
germinating  plantlets,  it  is  well  to  provide  a  deeper  box  with  a  glass 
side  against  which  the  seeds  are  planted.  12-  Observe  the  germina- 
tion of  any  common  seed  about  the  house  premises.  When  elms,  oaks, 
pines,  or  maples  are  abundant,  the  germination  of  their  seeds  may 
be  studied  in  lawns  and  along  fences.  13.  When  studying  germina- 
tion the  pupil  should  note  the  differences  in  shape  and  size  between 
cotyledons  and  plumule  leaves,  and  between  plumule  leaves  and  the 
normal  leaves  (Fig.  30).  Make  drawings.  14.  Make  the  tests  de- 
scribed in  the  introductory  experiments  with  bean,  corn,  the  castor 
bean,  and   other  seed  for  starch  and  proteids.     Test  flour,   oatmeal, 

rice,  sunflower,  four  o'clock, 
various  nuts,  and  any  other 
seeds  obtainable.  "Record  your 
results  by  arranging  the  seeds 
in  three  classes,  1.  Much  starch 
(colour  blackish  or  purple).  2. 
Little  starch  (pale  blue  or 
greenish),  3.  No  starch  (brown 
or  yellow).  15-  Bate  of 
growth  of  seedlings  as  affect- 
ed by  differences  in  tempera- 
ture. Pack  soft  wet  paper  to  the  depth  of  an  inch  in  the  bottom  of 
four  glass  bottles  or  tumblers.  Put  ten  soaked  peas  or  beans  into 
each.  Cover  each  securely  and  set  them  in  places  having  different 
temperatures  that  vary  little.  (A  furnace  room,  a  room  with  a  stove, 
<i  room  without  stove  but  reached  by  sunshine,  an  unheated  room 
not  reached  by  the  sun).  Take  the  temperatures  occasionally , with  the 
thermometer  to  find  difference  in  temperature.  The  tumblers  in 
vrarm  places  should  be  covered  very  tightly  to  prevent  the  germination 
from  being  retarded  by  drying  out.  Record  the  number  of  seeds 
which  sprout  in  each  tumbler  within  1  day,  2  days,  3  days,  4  days, 
etc.  16.  Ifi  oir  necessary  for  tJie  germination  and  grorvth  of  seed- 
lings? Place  damp  blotting  paper  in  the  bottom  of  a  bottle  and 
fill  it  three-fourths  full  of  soaked  seeds,  and  close  it  tightly  with  a 
rubber  stopper  or  oiled  cork.  Prepare  a  ''check  experiment"  by 
having  another  bottle  -v^-ith  all  conditions  the  same  except  that  it 
is  covered  loosely  that  air  may  have  access  to  it,  and  set  the  bottles 
side  by  side  (why  keep  the  bottles  together?).  Record  results  as  in  the 


Fig.  30.  —  MusKMELON  Seedlings,  with 
the  unlike  seed-leaves  and  true  leaves. 


HEEBS  AND  GERMINATION  ^^ 

preceding  experiment.  17-  What  is  the  nature  of  the  gas  given  off 
by  germinating  seeds  F  Fill  a  tin  box  or  large-necked  bottle  with 
dry  beans  or  peas,then  add  water ;  note  how  much  they  swell-  Secure 
two  fruit  jars.  Fill  one  of  them  a  third  full  of  beans  and  keep  them 
moist.  Allow  the  other  to  remain  empty.  In  a  day  or  two  insert 
a  lighted  splinter  or  taper  into  each.  In  the  empty  jar  the  taper 
burns:  it  contains  oxygen.  In  the  seed  jar  the  taper  goes  out:  the 
air  has  been  replaced  by  carbon  dioxide.  The  air  in  the  bottle  may 
be  tested  for  carbon  dioxide  by  removing  some  of  it  with  a  rubber 
bulb  attached  to  a  glass  tube  (or  a  fountain-pen  filler)  and  bubbling 
it  through  lime  water.  18-  Temperature.  Usually  there  is  a  percep- 
tible rise  in  temperature  in  a  mass  of  germinating  seeds.  This  rise 
may  be  tested  with  a  thermometer.  19.  Interior  of  seeds.  Soak 
seeds  for  twenty-four  hours  and  remove  the  coat.  Distinguish  the 
embryo  from  the  endosperm.  Test  with  iodine.  20-  Of  ivhat  utility 
is  the  food  in  seeds?  Soak  some  grains  of  corn  overnight  and  re- 
move the  endosperm,  being  careful  not  to  injure  the  fleshy  cotyledon. 
Plant  the  incomplete  and  also  some  complete  grains  in  moist  sawdust 
and  measure  their  growth  at  intervals.  (Boiling  the  sawdust  will 
destroy  moulds  and  bacteria  which  might  interfere  with  experiment.) 
Peas  or  beans  may  be  sprouted  on  damp  blotting  paper;  the  coty- 
ledons of  one  may  be  removed,  and  this  with  a  normal  seed  equally 
advanced  in  germination  may  be  placed  on  a  perforated  cork  floating 
in  water  in  a  jar  so  that  the  roots  extend  into  the  water.  Their 
growth  may  be  observed  for  several  weeks.  21.  Effect  of  darTcness  on 
seeds  and  seedlings.  A  box  may  be  placed  mouth  downward  over 
a  smaller  box  in  which  seedlings  are  growing.  The  empty  box  should 
rest  on  half-inch  blocks  to  allow  air  to  reach  the  seedlings.  Note 
any  effects  on  the  seedlings  of  this  cutting  off  of  the  light.  An- 
other box  of  seedlings  not  so  covered  may  be  used  as  a  check.  Lay 
a  plank  on  green  grass  and  after  a  week  note  the  c"hange  that  takes 
place  beneath  it.  22.  Seedling  of  jtine-  Plant  pine  seeds.  Notice 
how  they  emerge.  Do  the  cotyledons  stay  in  the  ground?  How  many 
cotyledons  have  they?  When  do  the  cotyledons  get  free  from  the 
seed-coat?  What  is  the  last  part  of  the  cotyledon  to  become  free? 
Where  is  the  growing  point  or  plumule?  How  many  leaves  appear  at 
once?  Does  the  new  pine  cone  grow  on  old  w^ood  or  on  wood  formed 
the  same  spring  with  the  cone?  Can  you  always  find  partly  grown 
cones  on  pine  trees  in  winter?  Are  pine  cones  when  mature  on  two- 
year-old  wood?  How  long  do  cones  stay  on  a  tree  after  the  seeds 
have  fallen  out?  What  is  the  advantage  of  the  seeds  falling  before 
the  cones?    23.  Home  experiments.    If  desired,  nearly  all  of  the  fore- 


30  BEGINNEBS'  BOTANY 

going  experiments  may  be  tried  at  home.  The  pupil  can  thus  make 
the  drawings  for  the  notebook  at  home-  A  daily  record  of  measure- 
ments of  the  change  in  size  of  the  various  parts  of  the  seedliiig 
should  also  be  made.  24.  Seed-testing. — It  is  important  that  one 
know  before  planting  whether  seeds  are  good,  or  able  to  grow.  A 
simple  seed-tester  may  be  made  of  two  plates,  one  inverted  over  the 
other  (Fig.  31).  The  lower  plate  is  nearly  filled  with  clean  sand, 
which  is  covered  with  cheese  cloth  or  blot- 
ting paper  on  which  the  seeds  are  placed. 
Canton  flannel  is  sometimes  used  in  place, 
of  sand  and  blotting  paper.  The  seeds  are 
then  covered  with  another  blotter  or  piece 
of  cloth,  and  water  is  applied  until  the 
sand  and  papers  are  saturated.  Cover  with 
the  second  plate.  Set  the  plates  where  they 
will  have  about  the  temperature  that  the 
Fig.  31.  — a  Home-made  given  seeds  would  require  out  of  doors,  or 
Seed-tester.  perhaps     a    slightly    higher    temperature. 

Place  100  or  more  grains  of  clover,  corn, 
wheat,  oats,  rye,  rice,  buckwheat,  or  other  seeds  in  the  tester,  and 
keep  record  of  the  number  that  sprout.  The  result  will  give  a  per- 
centage measure  of  the  ability  of  the  seeds  to  grow.  Note  whether 
all  the  seeds  sprout  with  equal  vigour  and  rapidity.  Most  seeds 
will  sprout  in  a  week  or  less.  Usually  such  a  tester  must  have  fresh 
sand  and  paper  after  each  test,  for  mould  fungi  are  likely  to  breed 
in  it.  If  canton  flannel  is  used,  it  may  be  boiled.  If  possible,  the 
seeds  should  not  touch  one  another. 

Note    to    Teacher. — With   the    study    of    germination,    the   pupil 
will   need  to   begin   dissecting. 

For  dissecting,  one  needs  a  lens  for  the  examination  of  the 
smaller  parts  of  plants  and  animals.  It  is  best  to  have  the  lens- 
mounted  on  a  frame,  so  that  the  pupil  has  both  hands  free  for 
pulling  the  part  in  pieces.  An  ordinary  pocket  lens  may  be  mount- 
ed on  a  wire  in  a  block  as  in  Fig.  A.  A  cork  is  slipped  on  the 
top  of  the  wire  to  avoid  injury  to  the  face.  The  pupil  should  be 
provided  with  two  dissecting  needles  (Fig.  B),  made  by  securing 
an  ordinary  needle  in  a  pencil-like  stick.  Another  convenient  ar- 
rangement is  shown  in  Fig.  C.  A  small  tin  dish  is  used  for  the 
base.  Into  this  a  stiff  wire  standard  is  soldered.  The  dish  is  filled 
with  solder  to  make  it  heavy  and  firm.  Into  a  cork  slipped  on  the 
standard,  a  cross  wire  is  inserted,  holding  on  the  end  a  jeweller's 


SEEDS  AND  GERMINATION 


31 


glass.*  The  lens  can  be  moved  up  and  down  and  sidewise.  This 
outfit  can  be  made  for  about  seventy-five  cents.  Fig.  D  shows 
a  convenient  hand-rest  or  uissecting-stand  to  be  used  under  this 
lens.     It  may  be  16  in.  long,  4  in.  high,  and  4  or  5  in.  broad. 

Various  kinds  of  dissecting  microscopes  are  on  the  market,  and 
these  are  to  be  recommended  when  they  can  be  afforded. 


A— Dissecting  Stand. 


5.  — Dis- 
secting 
Needle 
%  natural 
si2e. 


C  — Dissecting  Glass. 


^.  —  Improvised 
Stand  for  Lens, 


Instructions  for  the  use  of  the  compound  microscope,  with 
which  some  schools  may  be  equipped,  cannot  be  given  in  a  brief 
space;  the  technique  requires  careful  training.  Such  microscopes 
are  not  needed  unless  the  pupil  studies  cells  and  tissues. 


CHAPTER  VII 

THE  ROOT  — THE  FORMS  OF  ROOTS 

The  Root  System.  —  The  offices  of  the  root  are  to  hold 
the  plant  in  place,  and  to  gather  food.  Not  all  the  food 
materials,  however,  are  gathered  by  the  roots. 


Fig.  32. —  Tap-root 
System  of  Alfalfa. 


Tap-root  of  the  Dandelion. 


Fig.  33. 

The  entire  mass  of  roots  of  any  plant  is  called  its  root 
system.  The  root  system  may  be  annual,  biennial  or  peren- 
nial, herbaceous  or  woody,  deep  or  shallow,  large  or  small. 

Kinds  of  Roots.  —  A  strong  leading  central  root,  which 
runs  directly  downwards,  is  a  tap-root    The  tap-root  forms 


THE  ROOT—  THE  FORMS  OF  ROOTS 


33 


an  axis  from  which  the  side  roots  may  branch.  The  side 
or  spreading  roots  are  usually  smaller.  Plants  that  have 
such  a  root  system  are  said  to  be  tap-rooted.  Examples 
are  red  clover,  alfalfa,  beet,  turnip, 
radish,  burdock,  dandelion,  hickory 
(Figs.  32,  33). 

A  fibrous  root  system  is  one  that 
is  composed  of  many  nearly  equal 
slender  branches.  The  greater 
number  of  plants  have  fibrous  roots. 
Examples  are  many  common 
grasses,  wheat,  oats,  corn.  The 
buttercup  in  Fig.  34  has  a  fibrous 
root  system.  Many  trees  have  a 
strong  tap-root  when  very  young, 
but  after  a  while  it  ceases  to  ex- 
tend strongly  and  the  side  roots 
develop  until  finally  the  tap-root 
character  disappears. 

Shape  and  Extent  of  the  Root  Sys- 
tem. —  The  depth  to  which  roots 
extend  depends  on  the  kind  of  plant,  and  the  natJire  of  the 
soil.  Of  most  plants  the  roots  extend  far  in  all-directions 
and  lie  comparatively  near  the  surface.  The  roots  usually 
radiate  from  a  common  point  just  beneath  the  surface  of 
the  ground. 

The  roots  grow  here  and  there  in  search  of  foody  often 
extending  much  farther  in  all  directions  than  the  spread 
of  the  top  of  the  plant.  Roots  tend  to  spread  farther  in 
poor  soil  than  in  rich  soil,  for  the  same  size  of  plant. 
The  root  has  no  such  defi^iite  form  as  the  stem  has.  Roots 
are  usually  very  crooked,  because  they  are  constantly 
turned  aside  by  obstacles.     Examine  roots  in  stony  soil. 


Fig.  34.  — a  Buttercup 
Plant,  with  fibrous  roots. 


34 


BEGINNERS*  BOTANY 


The  extent  of  root  surface  is  usually  very  large,  for  the 
feeding  roots  are  fine  and  very  numerous.  An  ordinary 
plant  of  Indian  corn  may  have  a  total  length  of  root 
(measured  as  if  the  roots  were  placed  end  to  end)  of  several 
hundred  feet. 

The  fine  feeding  roots  are  most  abundant  in  the  richest 
part  of  the  soil.  They  are  attracted  by  the  food  materials. 
Roots  often  will  completely  surround  a  bone  or  other 
morsel.  When  roots  of  trees  are  exposed,  observe  that 
most  of  them  are  horizontal  and  lie  near  the  top  of  the 
ground.  Some  roots,  as  of  willows,  extend  far  in  search 
of  water.  They  often  run  into  wells  and  drains,  and  into 
the  margins  of  creeks  and  ponds.  Grow  plants  in  a  long 
narrow  box,  in  one  end  of  which  the  soil  is  kept  very  dry 
and  in  the  other  moist :  observe  where  the  roots  grow. 

Buttresses.  —  With  the  increase  in  diameter,  the  upper 
roots  often  protrude  above  the  ground  and  become  bracing 
buttresses.     These  buttresses  are  usually  largest  in  trees 

which  always  have  been 
exposed  to  strong  winds 
(Fig.  35).  Because  of 
growth  and  thickening, 
the  roots  elevate  part  of 
their  diameter,  and  the 
washing  away  of  the  soil 
makes  them  to  appear  as 
if  having  risen  out  of 
the  ground. 

Aerial  Roots. — Although  roots  usually  grow  underground, 
there  are  some  that  naturally  grow  above  ground.  These 
usually  occur  on  climbing  plants,  the  roots  becoming  stip- 
ports  or  fulfilling  the  office  of  tendrils.  These  aerial  roots 
usually  turn  away  from  the  light,  and  therefore  enter  the 


^a5s^^ 


Fig.  35.  —  The  Bracing  Base  of  a 
Field  Pine. 


THE  ROOT—  THE  EORMS   OF  ROOTS 


35 


crevices  and  dark  places  of  the  wall  or  tree  over  which  the 


plant 


climbs. 


The  trumpet  creeper  (Fig.  36),  true  or 
English  ivy,  and  poison  ivy  climb  by 
means  of  roots. 


Fig.  37.  —  Aerial  Roots  of  an  Orchid. 

In  some  plants  all  the  roots  are 
aerial ;  that  is,  the  plant  grows  above 
ground^  and  the  roots  gather  food 
from  the  air.  Such  plants  usually 
grow  on  trees.  They  are  known  as 
epiphytes  or  air-plants.  The  most  fam- 
iliar examples  are  some  of  the  tropi- 
cal orchids  which  are  grown  in  glass- 
houses (Fig.  37).  Rootlike  organs  of  dodder  and  other 
parasites  are  discussed  in  a  future  chapter. 


Fig.  36.  — Aerial  Roots 
OF  Trumpet  Creeper 
OR  Tecoma. 


36 


BEGINNERS'  BOTANY 


Some  plants  bear  aerial  roots,  that  may  propagate  the 
plant  or  may  act  as  braces.  They  are  often  called  prop-roots. 
The  roots  of  Indian  corn  are  familiar  (Fig.  38).  Many 
ficus  trees,  as  the  banyan  of  India,  send  out  roots  from 
their  branches ;  when  these  roots  reach  the  ground  they 
take  hold  and  become  great  trunks,  thus  spreading  the 
top  of  the  parent  tree  over  large 
areas.  The  mangrove  tree  of  the 
tropics  grows  along  seashores  and 
sends  down  roots  from  the  over- 
hanging branches  (and  from  the 
fruits)  into  the  shallow  water,  and 
thereby  gradually  marches  into  the 
sea.  The  tangled  mass  behind  catch- 
es the  drift,  and  soil  is  formed. 

Adventitious  Roots. —  Sometimes 
roots  grow  from  the  stem  or  other 
unusual  places  as  the  result  of  some 
accident  to  the  plant,  being  located 
without  known  method  or  law.  They 
are  called  adventitious  (chance) 
roots.  Cuttir!igs  of  the  stems  of 
roses,  figs,  geraniums,  and  other 
plants,  when  planted,  send  out  ad- 
ventitious roots  and  form  new 
plants.  The  ordinary  roots,  or  soil  roots,  are  of  course  not 
classed  as  adventitious  roots.  The  adventitious  roots  arise 
on  occasion,  and  not  as  a  normal  or  regular  course  in  the 
growth  of  the  plant. 

No  two  roots  are  alike;  that  is,  they  vary  among  them- 
selves as  stems  and  leaves  do.     Eacli  JHnd  of  plant  has  its 


Fig.  38.  —  Indian  Corn, 
showing  the  brace  roots 
at  00. 


THE  ROOT—  THE   FORMS   OF  ROOTS 


37 


own  form  or  habit  of  root  (Fig.  39).  Carefully  wash  awa^ 
the  soil  from  the  roots  of  any  two  related  plants,  as  oats 
and  wheat,  and  note  the  differences  in  size,  depth,  direc- 
tion, mode  of  branching,  num- 
ber of  fibrils,  colour,  and  other 


Fig.  39.  — Roots  of  Bari.ey  at  A  and  Corn  at  B. 
Carefully  trace  the  differences. 

features.  The  character  of  the  root  system  often  governs 
the  treatment  that  the  farmer  should  give  the  soil  in  which 
the  plant  or  crop  grows. 

Roots  differ  not  only  in  their  form  and  habit,  but  also  in 
colour  of  tissue,  character  of  bark  or  rind,  and  other  fea- 
tures. It  is  excellent  practice  to  fry  to  identify  different 
plants  by  means  of  their  roots.  Let  each  pupil  bring  to 
school  two  plants  with  the  roots  very  carefully  dug  up,  as 
cotton,  corn,  potato,  bean,  wheat,  rye,  timothy,  pumpkin, 
clover,  sweet  pea,  raspberry,  strawberry,  or  other  common 
plants. 

Root  Systems  of  Weeds.  —  Some  weeds  are  pestiferous 
because  they  seed  abundantly,  and  others  because  their 
underground  parts  run  deep  or  far  and  are  persistent. 
Make  out  the  root  systems  in  the  six  worst  weeds  in  your 
locality. 


CHAPTER   VIII 


THE  ROOT.  —  FUNCTION  AND  STRUCTURE 


The  function  of  roots  is  twofold,  —  to  provide  support  or 
anchorage  for  the  plant,  and  to  collect  and  convey  food  ma- 
terials. The  first  function  is  considered  in  Chapter  VII; 
we  may  now  give  attention  in  more  detail  to  the  second. 

The  feeding  surface  of  the  roots 
is  near  their  ends.  As  the  roots 
become  old  and  hard,  they  serve 
only  as  channels  through  which 
food  passes  and  as  holdfasts  or 
supports  for  the  plant.  The  root- 
hold  of  a  plant  is  very  strong. 
Slowly  pull  upwards  on  some  plant, 
and  note  how  firmly  it  is  anchored 
in  the  soil. 

Roots  have  power  to  choose  their 
food;  that  is,  they  do  not  absorb 
all  substances  with  which  they 
come  in  contact.  They  do  not  take 
up  great  quantities  of  useless  or 
harmful  materials,  even  though 
these  materials  may  be  abundant  in  the  soil ;  but  they 
may  take  up  a  greater  quantity  of  some  of  the  plant-foods 
than  the  plant  can  use  to  advantage.  Plants  respond  very 
quickly  to  liberal  feeding, — that  is,  to  the  application  of 
plant-food  to  the  soil  (Fig  40).  The  poorer  the  soil,  the 
more  marked  are  the  results,  as  a  rule,  of  the  application 

38 


Fig.  40.-— Wheat  growing 
under  diffkkent  soil 
Treatments.  Soil  defi- 
cient in  nitrogen;  com- 
mercial nitrogen  applied 
to  pot  3  (on  right). 


THE  ROOT— FUNCTION  AND  STRUCTURE  39 

of  fertilizers.    Certain  substances,  as  common  salt,  will  kill 
the  roots. 

Roots  absorb  Substances  only  in  Solution.  —  Substances 
cannot  be  taken  in  solid  particles.  These  materials  are 
in  solution  in  the  soil  water,  and  the  roots  themselves 
also  have  the  power  to  dissolve  the  soil  materials  to  some 
extent  by  means  of  substances  that 
they  excrete.  The  materials  that 
come  into  the  plant  through  the 
roots  are  water  and  mostly  the  min- 
eral substances^  as  compounds  of  po- 
tassium, iron,  phosphorus;  calcium, 
magnesium,  sulphur,  and  chlorine. 
These  mineral  substances  compose 
the  ash  when  the  plant  is  burned. 
The  carbon  is  derived  from  the  air 
through  the  green  parts.  Oxygen 
is  derived  from  the  air  and  the  soil 
water. 

Nitrogen  enters  through  the  Roots. 

—  All  plants  must  have  nitrogen; 

yet,  although  about  four-fifths  of  F1G.41.  — Nodules  on  roots 
.,         .     .        .^  ,      ^  ^  OF  Red /Clover. 

the  air  is  nitrogen,  plants  are  not 

able,  so  far  as  we  know,  to  take  it  in  through  their  leaves. 
It  enters  through  the  roots  in  combination  with  other  ele- 
ments, chiefly  in  the  form  of  nitrates  (certain  combinations 
with  oxygen  and  a  mineral  base).  The  great  family  of 
leguminous  plants,  however  (as  peas,  beans,  cowpea, 
clover,  alfalfa,  vetch),  use  the  nitrogen  contained  in  the  air 
in  the  soil.  They  are  able  to  utilize  it  through  the  agency 
of  nodules  on  their  roots  (Figs.  41,  42).  These  nodules 
contain  bacteria,  which  appropriate  the  free  or  uncom- 
bined  nitrogen  and  pass  it  on  to  the  plant.     The  nitrogen 


40 


BEGIJVNEKS'   BOTANY 


Fig.  42.— Nodules  on  Vetch. 


becomes  incorporated  in  the  plant  tissue,   so  that  these 
crops  are  high  in  their  nitrogen  content.     Inasmuch  as 

nitrogen  in  any  form  is 
expensive  to  purchase  in 
fertiUzers,  the  use  of  legu- 
minous crops  to  plough  un- 
der is  a  very  important  ag- 
ricultural practice  in  pre- 
paring the  land  for  other 
crops.  In  order  that  legum- 
inous crops  ma}'  acquire  at- 
mospheric nitrogen  more 
freely  and  thereby  thrive 
better,  ihe  land  is  sometimes 
soivn  or  inoculated  icith  the 
nodule-forming   hacteria. 

Roots  require  moisture  in  order  to  serve  the  plant.  The 
soil  water  that  is  valu- 
able to  the  plant  is  not 
the  free  water,  but  the 
t/iin  film  of  moisture 
which  adheres  to  each 
little  particle  of  soil.  The 
finer  the  soil,  the  greater 
the  number  of  particles, 
and  therefore  the  greater 
is  the  quantity  of  film 
moisture  that  it  can  hold. 
This  moisture  surround- 
ing the  grains  may  not 
be  perceptible,  yet  the 
plant  can  use  it.  Root  absorption  may  continue  in  a  soil 
which  seems  to  be  dust  dry.     Soils  that  are  very  hard  and 


Fig.  43.  —  Two  Kinds  of  Soil  that  have 
BEEN  Wet  and  then  Dried.  The 
loamy  soil  above  remains  loose  and  capa- 
ble of  growing  plants;  the  clay  soil  below 
has  baked  and  cracked. 


THE  ROOT— FUNCTION  AND  STRUCTURE 


41 


"baked"  (Fig.  43)  contain  very  little  moisture  or  air, — 
not  so  much  as  similar  soils  that  are  granular  or  mellow. 

Proper  Temperature  for  Root  Action.  —  The  root  must  be 
warm  in  order  to  perform  its  functions.  Should  the  soil  of 
fields  or  greenhouses  be  much  colder  than  the  air,  the 
plant  suffers.  When  in  a  warm  atmosphere,  or  in  a  dry- 
atmosphere,  plants  need  to  absorb  much  water  from  the 
soil,  and  the  roots  must  be  warm  if  the  root-hairs  are  to 
supply  the  water  as  rapidly  as  it  is  needed.  If  the  roots  are 
chilled^  the  plant  may  wilt  or  die. 

Roots  need  Air.  —  Corn  on  land  that  has  been  flooded  by 
heavy  rains  loses  its  green  colour  and  turns  yellow.  Besides 
diluting  plant-food^  the  water  drives  the  air  from  the  soily  and 
this  suffocation  of  the  roots  is  very  soon  ap- 
parent in  the  general  ill  health  of  the  plant. 
Stirring  or  tilling  the  soil  aerates  it.  Water 
plants  and  bog  plants  have  adapted  them- 
selves to  their  particular  conditions.  They 
get  their  air  either  by  special  surface  roots, 
or  from  the  water  through  stems  and  leaves. 

Rootlets.  —  Roots  divide  into  the  thinnest 
and  finest  fibrils  :  there  are  roots  and  there 
are  rootlets.  The  smallest  rootlets  are  so 
slender  and  delicate  that  they  break  off 
even  when  the  plant  is  very  carefully  lifted 
from  the  soil. 

The  rootlets^  or  fi7te  divisions^  ai^e  clothed  with  the  root- 
hairs  (Figs.  44,  45,  46).  These  root-hairs  attach  to  the 
soil  particles y  and  a  great  amount  of  soil  is  thus  brought 
into  actual  contact  with  the  plant.  These  are  very  deli- 
cate prolonged  surface  cells  of  the  roots.  They  are  borne 
for  a  short  distance  just  back  of  the  tip  of  the  root. 

Rootlet  and  root-hair  differ.      The  rootlet  is  a  compact 


Fig.  44.  —  Root- 
hairs  OF  THE 
Radish. 


42 


1, 


y 


BEGINNERS'  BOTANY 


Fig.  45,  —  Cross-section  of  Root, 
enlarged,  showing  root-hairs. 


cellular  structure.       The    root-hair   is   a    delicate    tub7ilaf 
cell  (Fig.  45),   within    which    is   contained  livifig-  matter 

(protoplasm) ;  and  the  protoplasmic  lining  niembrane  of  the 

wall  governs  the  entrance  of 
water  and  substances  in  solu- 
tion. Being  long  and  tube- 
like,  these  root-hairs  are 
especially  adapted  for  tak- 
ing in  the  largest  quantity 
of  solutions;  and  they  are 
the  principal  means  by  which 
plant-food  is  absorbed  from 
the  soil,  although  the  sur- 
faces of  the  rootlets  them- 
selves do  their  part.  Water 
plants   do    not    produce    an 

abundant  system  of  root-hairs,  and    such    plants   depend 

largely  on  their  rootlets. 

The  root-hairs  are  very  small,  often  invisible.      They, 

with  the  young  roots,  are  usually  broken  off  when  the 

plant  is  pulled  up.      They  are 

best  seen  when  seeds  are  germin- 
ated   between    layers    of    dark 

blotting  paper  or  flannel.       On 

the   young   roots   they   will   be 

seen  as  a  mould-like  or  gossamer- 
like   covering.     Root-hairs  soon 

die  :  they  do  not  grow  into  roots. 

New  ones  form  as  the  root  grows. 
Osmosis. — The  water  with  its 

nourishment    goes    through  the 

thin  walls  of  the  root-hairs  and  rootlets  by  the  process 

of  osmosis.     If  there  are  two  liquids  of  different  density 


Fig.  46.  —  RooT-HAiR,  much  en- 
larged, in  contact  with  the  soil 
particles  (j)  .  Air-spaces  at  a  \ 
water-films  on  the  particles,  as 
at  w. 


THE  ROOT— FUNCTION  AND  STRUCTURE  43 

on  the  inside  and  outside  of  an  organic  (either  vegetable 
or  animal)  membrane,  the  liquids  tend  to  mix  through  the 
membrane.  The  law  of  osmosis  is  that  the  most  rapid 
flow  is  toward  the  denser  solution.  The  protoplasmic  lin- 
ing of  the  cell  wall  is  such  a  membrane.  The  soil  water 
being  a  weaker  solution  than  the  sap  in  the  roots,  the 
flow  is  into  the  root.  A  strong  fertilizer  sometimes  causes 
a  plant  to  wither,  or  "burns  it."     Explain. 

Structure  of  Roots.  — The  root  that  grows  from  the  lower 
end  of  the  caulicle  is  the  first  or  primary  root.  Secondary 
roots  branch  from  the  primary  root.  Branches  of  second- 
ary roots  are  sometimes  called  tertiary  roots.  Do  the  sec- 
ondary roots  grow  from  the  cortex,  or  from  the  central 
cylinder  of  the  primary  root.^  Trim  or  peel  the  cortex 
from  a  root  and  its  branches  and  determine  whether  the 
branches  still  hold  to  the  central  cylinder  of  the  main  root. 

Internal  Structure  of  Roots.  —  A  section  of  a  root  shows 
that  it  consists  of  a  central  cylinder  (see  Fig.  45)  sur- 
rounded by  a  layer.  This  layer  is  called  the  cortex.  The 
outer  layer  of  cells  in  the  cortex  is  called  the  epidermis, 
and  some  of  the  cells  of  the  epidermis  are  prolonged 
and  form  the  delicate  root-hairs.  The  cortex  resembles 
the  bark  of  the  stem  in  its  nature.  The  central  cylinder 
contains  many  tube-Hke  canals,  or  "  vessels  "  that  convey 
water  and  food  (Fig.  45).  Cut  a  sweet  potato  across  (also 
a  radish  and  a  turnip)  and  distinguish  the  central  cylin- 
der, cortex,  and  epidermis.  Notice  the  hard  cap  on  the  tip 
of  roots.     Roots  differ  from  stems  in  having  no  real  pith. 

Microscopic  Structure  of  Roots.  — Near  the  end  of  any 
young  root  or  shoot  the  cells  are  found  to  differ  from  one  an- 
other more  or  less,  according  to  the  distance  from  the 
point.  This  diffei'entiation  takes  place  in  the  region  just 
back  of  the  growing  point.     To  study  growing  points,  use 


44 


BEGINNERS*  BOTANY 


the  hypocotyl  of  Indian  corn  which  has  grown  about  one- 
half  inch.  Make  a  longitudinal  section.  Note  these  points 
(Fig.  47):  {a)  the  tapering  root-cap  beyond  the  growing 
point ;  {b)  the  blunt  end  of  the  root  proper  and  the  rec- 
tangular shape  of  the  cells  found  there;  {c)  the  group 
of  cells  in  the  middle  of  the  first  layers  beneath  the  root- 
cap, —  this  group  is  the  growing 
point;  {d)  study  the  sUght  differ- 
ences in  the  tissues  a  short  dis- 
tance back  of  the  growing  point. 
There  are  four  regions  :  the  central 
cylinder,  made  up  of  several  rows 
of  cells  in  the  centre  (//);  the  en- 
dodermis,  (e)  composed  of  a  single 
layer  on  each  side  which  separates 
the  central  cylinder  from  the  bark ; 
the  cortex,  or  inner  bark,  {e)  of  sev- 
eral layers  outside  the  endodermis ; 
and  the  epidermis,  or  outer  layer  of 
bark  on  the  outer  edges  {d).  Make 
a  drawing  of  the  section.  If  a 
series  of  the  cross-sections  of  the 
hypocotyl  should  be  made  and  stud- 
ied by  the  pupil  beginning  near 
the  growing  point  and  going  up- 
ward, it  would  be  found  that  these  four  tissues  become  more 
distinctly  marked,  for  at  the  tip  the  tissues  have  not  yet 
assumed  their  characteristic  form.  The  central  cylinder 
contains  the  ducts  and  vessels  which  convey  the  sap. 

The  Root-cap.  —  Note  the  form  of  the  root-cap  shown  in 
the  microscopic  section  drawn  in  Fig.  47.  Growing  cells, 
and  especially  those  which  are  forming  tissue  by  sub- 
dividing, are  very  deHcate  and  are  easily  injured.     The 


Fig.  47.  —  Growing  Point 
OF  Root  of  Indian  Corn. 

d,  d,  cells  which  will  form  the 
epidermis;  /,  /,  cells  that 
will  form  bark;  <»,  ^,  endoder- 
mis; //,  cells  which  will  form 
the  axis  cylinder;  /,  initial 
group  of  cells,  or  growing 
point  proper;  c,  root-cap. 


THE  ROOT-- FUNCTION  AND  STRUCTURE 


45 


cells  forming  the  root-cap  are  older  and 
tougher  and  are  suited  for  pushing 
aside  the  soil  that  the  root  may  pene- 
trate it. 

Region  of  most  Rapid  Growth. — The 
roots  of  a  seedling  bean  may  be  marked 
at  equal  distances  by  waterproof  ink  or 
by  bits  of  black  thread  tied  moderately 
tight.  The  seedling  is  then  replanted 
and  left  undisturbed  for  two  days. 
When  it  is  dug  up,  the  region  of  most 
rapid  growth  in  the 


Fig.  48.  —The  Mark- 
ing OF  THE  Stem 
AND  Root. 


Fig.  49.— The  Result 


root  can  be  deter- 
mined.    Give   a  reason   why  a   root 
cannot  elongate  thfoiighoiit  its  length, 
—  whether  there  is  anything  to  pre- 
vent a  young  root  from  doing  so. 

In  Fig.  48  is  shown  a  germinating 
scarlet  runner  bean  with  a  short  root 
upon   which    are    marks   made   with 
waterproof  ink;   and  the   same  root 
(Fig.  49)  is  shown  after  it  has 
grown  longer.     Which  part  of  it 
did  not  lengthen  at  all }   Which 
part  lengthened  slightly .?  Where 
is  the  region  of  most  rapid  growth.!* 
Geotropism.  —  Roots   turn    to- 
ward the  earth,  even  if  the  seed 
is  planted  with  the  micropyle  up. 
This  phenomenon  is  called  posi- 
tive geotropism.   Stems  grow  away 
from  the  earth.     This  is  negative 
geotropism. 


46 


BEGINNERS'  BOTANY 


Suggestions  (Chaps.  VII  and  VIII). — 25.  Tests  for  food.  Ex- 
amine a  number  of  roots,  including  several  fleshy  roots,  for  the 
presence  of  food  material,  making  the  tests  used  on  seeds.  26. 
Study  of  root-hairs.  Carefully  germinate  radish,  turnip,  cabbage, 
or  other  seed,  so  that  no  delicate  parts  of  the  root  will  be  injured. 
For  this  purpose,  place  a  few  seeds  in  packing-moss  or  in  the  folds 
of  thick  cloth  or  of  blotting  paper,  being  careful  to  keep  them  moist 
and  warm.  In  a  few  days  the  seed  has  germinated,  and  the  root 
has  grown  an  inch  or  two  long.  Notice  that,  except  at  a  dis- 
tance of  about  a  quarter  of  an  inch  behind  the  tip,  the  root  is 
covered  with  minute  hairs  (Fig.  44).  They  are  actually  hairs; 
that  is,  root-hairs.  Touch  them  and  they  collapse,  they  are  so 
delicate.  Dip  one  of  the  plants  in  water,  and  when  removed  the 
hairs  are  not  to  be  seen.  The  water  mats  them  together  along 
the  root  and  they  are  no  longer  evident.  Root-hairs  are  usually 
destroyed  when  a  plant  is  pulled  out  of  the  soil,  be  it  done 
ever  so  carefully.  They  cling  to  the  minute  particles  of  soil 
(Fig.  46).  The  hairs  show  best  against  a  dark  background. 
27.  On  some  of  the  blotting  papers,  sprinkle  sand ;  observe  how 
the  root-hairs  cling  to  the  grains.  Observe  how  they  are  flat- 
tened when  they  come  in  contact  with  grains  of  sand.     28.  Root 

hold  of  plant.  The 
pupil  should  also 
study  the  root  hold. 
Let  him  carefully  pull 
up  a  plant.  If  a  plant 
grow  alongside  a 
fence  or  other  rigid 
object,  he  may  test 
the  root  hold  by  se- 
curing a  string  to 
the  plant,  letting  the 
string  hang  over  the 
fence,  and  then  add- 
ing weights  to  the 
string.  Will  a  stake 
of  similar  size  to  the 
plant  and  extending 
no  deeper  in  the 
ground  have  such 
firm  hold  on  the  soil? 
What  holds  the  ball 
of  earth  in  Fig.  50? 
29.  Roots  exert  pressure.  Place  a  strong  bulb  of  hyacinth  or 
daffodil  on  firm-packed  earth  in  a  pot ;  cover  the  bulb  nearly  to 
the  top  with  loose  earth  j  place  in  a  cool  cellar ;  after  some  days 


Fig,  50.— Th^  Grasp  of  a  Plant  on  the  Parti- 
cles OF  Earth.  A  grass  plant  pulled  in  a  garden. 


THE  ROOT-^ FUNCTION  AND  STRUCTURE 


47 


Fig.  51.— 
Plant  grow- 
ing IN  In- 
verted Pot. 


or  weeks,  note  that  the  bulb  has  been  raised  out  of  the  earth  by 
the  forming  roots.   All  roots  exert  pressure  on  the  soil  as  they  grow. 
Explain.     30.   Response  of  roots  and  stems  to  the  force  of  gravity^ 
or  geotropism.     Plant  a  fast-growing  seedling  in  a 
pot  so  that  the  plumule  extends  through  the  drain 
hole  and  suspend  the  pot  with  mouth  up  {i.e.  in 
the  usual  position).    Or  use  a  pot  in  which  a  plant 
is  already  growing,  cover  with  cloth  or  wire  gauze 
to  prevent  the  soil  from  falling,  and  suspend  the 
pot  in  an  inverted  position  (Fig.  51).     Notice  the 
behaviour  of  the  stem,  and  after  a  few  days  remove 
the  soil  and  observe  the  position  of  the  root.    31.  If 
a  pot  is  laid  on  one  side,  and  changed  every  two 
days  and  laid  on  its  opposite  side,  the  effect  on  the 
root  and  stem  will  be  interesting.     32.  If  a  fleshy 
root  is  planted  wrong  end  up,  what  is  the  result  ? 
Try  it  with  pieces  of  horse-radish  root.     33.  By 
planting  radishes  on  a  slowly  revolving  wheel  the 
effectofgravity  may  be  neutralized.     34.  Region  of 
root  most  sensitive  to  gravity.    Lay  on  its  side  a  pot  containing  a 
growing  plant.     After  it  has  grown  a  few  days,  wash  away  the  earth 
surrounding  the  roots.     Which  turned  downward  most  decidedly, 
the  tip  of  root  or  the  upper  part?     25.  Soil  texture.    Carefully  turn 
up  soil  in  a  rich  garden  or  field  so  that  you  have  unbroken  lumps 
as  large  as  a  hen's  tgg.     Then  break  these  lumps  apart  carefully 
^^^^^^^^^__^^____^^^_^_^______^_^^^^       with  the  fingers  and 

/^^IS^^^^Sc^^lt^^^^^^l^'^r^^TT^      determine  whether 

there  are  any  traces 
or  remains  of  roots 
(Fig.  52).  Are  there 
any  pores,  holes,  or 
channels  made  by 
roots  ?  Are  the  roots 
in  them  still  living? 
36.  Compare  an- 
other lump  from  a 
clay  bank  or  pile 
where  no  plants 
have  been  growing. 
Is  there  any  differ- 
ence in  texture  ?  37.  Grind  up  this  clay  lump  very  fine,  put  it  in 
a  saucer,  cover  with  water,  and  set  in  the  sun.  After  a  time  it 
will  have  the  appearance  shown  in  the  lower  saucer  in  Fig.  43. 
Compare  this  with  mellow  garden  soil.  In  which  will  plants  grow 
best,  even  if  the  plant- food  were  the  same  in  both  ?  Why  ?  38.  To 
test  the  effect  of  moisture  on  the  plant,  let  a  plant  in  a  pot  or  box  dry 


Fig.  52.  —  Holes  in  Soil  made  by  Roots,  now 
decayed.    Somewhat  magnified. 


48  BEGINNERS*  BOTANY 

out  till  it  wilts  ;  then  add  water  and  note  the  rapidity  with  which 
it  recovers.  Vary  the  experiment  in  quantity  of  water  appUed. 
Does  the  plant  call  for  water  sooner  when  it  stands  in  a  sunny  win- 
dow than  when  in  a  cool  shady  place?  Prove  it.  39.  Immerse 
a  potted  plant  above  the  rim  of  the  pot  in  a  pail  of  water  and  let 
it  remain  there.  What  is  the  consequence  ?  Why  ?  40.  To  test 
the  effect  of  temperature  on  roots.  Put  one  pot  in  a  dish  of  ice 
water,  and  another  in  a  dish  of  warm  water,  and  keep  them  in  a 
warm  room.  In  a  short  time  notice  how  stiff  and  vigorous  is  the 
one  whose  roots  are  warm,  whereas  the  other  may  show  signs  of 
wilting.  41.  The  process  of  osmosis.  Chip  away  the  shell  from 
the  large  end  of  an  egg  so  as  to  expose  the  uninjured  membrane 
beneath  for  an  area  about  as  large  as  a  ten-cent  piece.  With  sealingr- 
wax,  chewing-gum,  or  paste,  stick  a  quill  about  three  inches  long  to 
the  smaller  end  of  the  ^^g.  After  the  tube  is  in  place,  run  a 
hat  pin  into  it  so  as  to  pierce  both  shell  and  membrane ;  or  use 
a  short  glass  tube,  first  scraping  the  shell  thin  with  a  knife  and 
then  boring  through  it  with  the  tube.  Now  set  the  egg  upon  the 
mouth  of  a  pickle  jar  nearly  full  of  water,  so  that  the  large  end 
with  the  exposed  membrane  is  beneath  the  water.  After  several 
hours,  observe  the  tube  on  top  of  the  egg  to  see  whether  the  water 
has  forced  its  way  into  the  egg  and  increased  its  volume  so  that 
part  of  its  contents  are  forced  up  into  the  tube.  If  no  tube  is  at 
hand,  see  whether  the  contents  are  forced  through  the  hole  which 
has  been  made  in  the  small  end  of  the  egg.  Explain  how  the  law 
of  osmosis  is  verified  by  your  result.  If  the  eggshell  contained 
only  the  membrane,  would  water  rise  into  it?  If  there  were  no 
water  in  the  bottle,  would  the  egg-white  pass  down  into  the  bot- 
tle? 42.  The  region  of  most  rapid  growth.  The  pupil  should 
make  marks  with  waterproof  ink  (as  Higgins'  ink  or  indelible 
marking  ink)  on  any  soft  growing  roots.  Place  seeds  of  bean, 
radish,  or  cabbage  between  layers  of  blotting  paper  or  thick  cloth. 
Keep  them  damp  and  warm.  When  stem  and  root  have  grown 
an  inch  and  a  half  long  each,  with  waterproof  ink  mark  spaces 
exactly  one-quarter  inch  apart  (Figs.  48,  49).  Keep  the  plantlets 
moist  for  a  day  or  two,  and  it  will  be  found  that  on  the  stem  some 
or  all  of  the  marks  are  more  than  one-quarter  inch  apart;  on  the 
root  the  marks  have  not  separated.  The  root  has  grown  beyond 
the  last  mark. 


CHAPTER   IX 
THE   STEM  — KINDS   AND  FORMS;   PRUNING 

The  Stem  System.  —  The  stem  of  a  plant  is  the  part 
that  bears  the  btids^  leaves^  flowers^  and  fruits.  Its  office 
is  io  hold  these  parts  up  to  the  light  and  the  air;  and 
through  its  tissues  the  various  food-materials  and  the  life- 
giving  fluids  are  distributed  to  the  growing  and  working 
parts. 

The  entire  mass  or  fabric  of  stems  of  any  plant  is  called 
its  stem  system.  It  comprises  the  trunk,  branches,  and 
twigs,  but  not  the  stalks  of  leaves  and  flowers  that  die  and 
fall  away.  The  stem  system  may  be  herbaceous  or  woody, 
annual,  biennial,  or  perennial ;  and  it  may  assume  many 
sizes  and  shapes. 

Stems  are  of  Many  Forms. — The  general  way  in  which 
a  plant  grows  is  called  its  habit.  The  habit  is  the  appear- 
ance or  general  form.  Its  habit  may  be  open  or  loose, 
dense,  straight,  crooked,  compact,  straggling,  climbing, 
erect,  weak,  strong,  and  the  like.  The  roots  and  the  leaves 
are  the  important  functional  or  ivoi'king  parts ;  the  stem 
merely  connects  them,  and  its  form  is  exceedingly  variable. 

Kinds  of  Stems. —  The  stem  may  be  so  short  as  io  be 
scarcely  distinguishable.  In  such  cases  the  crown  of  the 
plant  —  that  part  just  at  the  surface  of  the  ground  —  bears 
the  leaves  and  the  flowers ;  hut  this  crown  is  really  a  very 
short  stem.  The  dandelion,  Fig.  33,  is  an  example.  Such 
plants  are  often  said  to  be  stemless,  however,  in  order  to 
distinguish  them  from  plants  that  have  long  or  conspic- 
E  49 


so 


BEGINNERS'  BOTANY 


uous   Stems.      These   so^alled  stemless  plants   die  to   the 
ground  every  year. 

Stems  are  erect  when  they  grow  straight  up  (Figs.  53, 
54).     They  are  trailing  when  they  run  along  on  the  ground, 


Fig.  53.  —  Strict  Simple 
Stem  of  Mullein. 


Fig.  54.  —  Strict  Upright  Stem 
OF  Narrow-leaved  Dock. 


as  melon,  wild  morning-glory  (Fig.  55).     They  are  creep- 
ing when  they  run  on  the  ground  and  take  root  at  places, 


Fig.  55.— Trailing  Stem  of  Wild  Morning  Glory  {Convolvulus  arvensis). 


as  the  strawberry.  They  are  decumbent  when  they  lop 
over  to  the  ground.  They  are  ascending  when  they  lie 
mostly  or  in  part  on  the  ground  but  stand  more  or  less 
upright   at   their   ends;    example,   a   tomato.     They   are 


THE   STEMS— KINDS  AND  FORMS;    PRUNING 


51 


climbiiig  when  they  cling  to  other  objects 
for  support  (Figs.  36,  56). 

Trees  in  which  the  main  trunk  or  the 
** leader'*  continues  to  grow  from  its  tip 
are  said  to  be  excurrent  in  growth.  The 
branches  are  borne  along  the  sides  of  the 
trunk,  as  in  common  pines  (Fig.  57)  and 
spruces.  Excurrent  means  running  out  or 
running  up. 

Trees  in  which  the  main  trunk  does 
not  continue  are  said  to  be  deliques- 
cent.      The  brandies  arise  from   07ie 
common  point  or  from  each  other.    The 
stem  is  lost  in  the  branches.     The  apple 
tree,  plum  (Fig.  58),  maple,  elm,  oak,  China 
tree,  are  familiar  examples.     Deliquescent 
means  dissolving  or  melting  away. 

Each  kind  of  plant  has  its  own  peculiar 

habit  or  direction  of  growth.    Spruces  al- 

'ways  grow  to  a  single  stem  or  trunk,  pear 


Fig.  56.  — a 

Climbing  Plant 

(a  twiner). 


Fig.  57.  —  Excurrent 
Trunk.    A  pine. 


Fig.  58.  — Deliquescent  Trunk 
OF  Plum  Tree. 


52  BEGINNERS'   BOTANY 

trees  are  always  deliquescent,  morning-glories  are  always 
trailing  or  climbing,  strawberries  are  always  creeping. 
We  do  not  know  why  each  plant  has  its  own  habit,  but 
the  habit  is  in  some  way  associated  with  the  plant's  gene- 
alogy or  with  the  way  in  which  it  has  been  obliged  to  live. 

The  stem  may  be  simple  or  branched.  A  simple  stem 
usually  grows  from  the  terminal  bud,  and  side  branches 
either  do  not  start,  or,  if  they  start,  they  soon  perish. 
Mulleins  (Fig.  53)  are  usually  simple.     So  are  palms. 

Branched  stems  may  be  of  very  different  habit  and  shape. 
Some  stem  systems  are  narrow  and  erect ;  these  are  said 
to  be  strict  (Fig.  54).  Others  are  diffuse,  open,  branchy, 
twiggy. 

Nodes  and  Internodes. — The  parts  of  the  stem  at  which 
buds  grow  are  called  nodes  or  joints  and  the  spaces  be- 
tween the  buds  are  internodes.  The  stem  at  nodes  is 
usually  enlarged,  and  the  pith  is  usually  interrupted.  The 
distance  between  the  nodes  is  influenced  by  the  vigour  of 
the  plant :   how } 


Fig.  59.— Rhizome  or  Rootstock. 

Stems  vs.  Roots.  —  Roots  sometimes  grow  above  ground 
(Chap.  VII);  so,  also,  stems  sometimes  gtoiv  underground, 
and  they  are  then  known  as  subterranean  stems,  rhizomes, 
or  rootstocks  (Fig.  59). 

Stems  normally  bear  leaves  and  buds,  and  thereby  are 
they  distinguished  from  roots;  usually,  also,  they  contain 
a  pith.  The  leaves,  however,  may  be  reduced  to  mere 
scales,  and  the  buds  beneath  them  may  be  scarcely  visible. 


THE   STEMS— KINDS  AND  FORMS;    PRUNING  53 

Thus  the  "  eyes "  on  a  white  potato  are  cavities  with  a 
bud  or  buds  at  the  bottom  (Fig.  60).  Sweet  potatoes  have 
no  evident  "  eyes  "  when  first  dug,  (but  they  may  develop 
adventitious  buds  before  the  next  grow- 
ing-season). The  white  potato  is  a  stem : 
the  sweet  potato  is  probably  a  root. 

How  Stems  elongate.  —  Roots  elongate 
by  growing  near  the  tip.  Stems  elon- 
gate by  growijtg  more  or  less  throusrh-     ^^^"'     ^-  ~  Sprouts 

^  -^     <^  ^  o  ARISING  FROM  THE 

out  the  young  or  soft  part  or  "  between  buds,  or  eyes,  of  a 
joints "  (Figs.  48,  49).  But  any  part  P°'^'°  '"^^'■• 
of  the  stem  soon  reaches  a  limit  beyond  which  it  cannot 
grow,  or  becomes  "fixed";  and  the  new  parts  beyond 
elongate  until  they,  too,  become  rigid.  When  a  part  of 
the  stem  once  becomes  fixed  or  hard,  it  never  increases  in 
length  :  that  is,  tJie  trunk  or  woody  parts  never  grow  longer 
or  higher ;  branches  do  not  become  farther  apart  or  higher 
from  the  ground. 

Stems  are  modified  in  form  by  the  particular  or  incidental 
conditions  under  which  they  grow.  The  struggle  for  light 
is  the  chief  factor  in  determining  the  shape  and  the  direc- 
tion of  any  limb  (Chap.  II).  This  is  well  illustrated  in  any 
tree  or  bush  that  grows  against  a  building  or  on  the  mar- 
gin of  a  forest  (Fig.  4).  In  a  very  dense  thicket  the 
innermost  trees  shoot  up  over  the  others  or  they  perish. 
Examine  any  stem  and  endeavour  to  determine  why  it  took 
its  particular  form. 

The  stem  is  cylindrical,  the  outer  part  being  bark  and 
the  inner  part  being  wood  or  woody  tissue.  In  the  dicoty- 
ledonous plants,  the  bark  is  usually  easily  separated  from 
the  remainder  of  the  cyHnder  at  some  time  of  the  year ;  in 
monocotyledonous  plants  the  bark  is  not  free.  Growth  in 
thickness  takes  place  inside  the  covering  and  not  on  the  very 


54 


BE G INNER S'  BOTANY 


outside  of  the  plant  cylinder.  It  is  evident,  then,  that  the 
covering  of  bark  must  expandin  order  to  allow  of  the  expan- 
sion of  the  woody  cylinder  within  it.  The  tis- 
sues, therefore,  must  be  under  constant  pressure 
or  tension.  It  has  been  determined  that  the 
pressure  within  a  growing  trunk  is  often  as 
much  as  fifty  pounds  to  the  square  inch.  The 
lower  part  of  the  limb  in  Fig.  6i  shows  that 
the  outer  layers  of  bark  (which  are  long  since 
dead,  and  serve  only  as  protective  tissue)  have 
reached  the  Hmit  of  their  expanding  capacity 
and  have  begun  to  split.  The  pupil  will  now 
be  interested  in  the  bark  on  the  body  of  an  old 
elm  tree  (Fig.  62);  and  he  should  be  able  to 
suggest  one  reason  why  stems  remain  cylindri- 
cal, and  why  the  old  bark  becomes  marked 
with  furrows,  scales,  and  plates. 

Most  woody  plants  increase  in  diameter  by  the 
addition  of  an  annual  layer  or  *'ring''  on  the 
Branch.  outside  of  the  woody  cylinder, 
underneath  the  bark.  The  monocotyledo- 
nous  plants  comprise  very  few  trees  and 
shrubs  in  temperate  climates  (the  palms, 
yuccas,  and  other  tree-like  plants  are  of 
this  class),  and  they  do  not  increase 
greatly  in  diameter  and  they  rarely  branch 
to  any  extent. 

Bark-bound  Trees. — If,  for  any  rea- 
son, the  bark  should  become  so  dense 
and  strong  that  the  trunk  cannot  ex- 
pand, the  tree  is  said  to  be  ' 'bark-bound." 
Such  condition  is  not  rare  in  orchard  trees  tliat  have  been 
neglected.     When  good  tillage  is  given  tc  such  trees,  they 


Fig.  62.  —  Piece  of 
Bark  from  an 
Old  Elm  Trunk. 


THE   STEMS— KINDS  AND  FORMS;    TRUNIN G 


55 


may  not  be  able  to  overcome  the  rigidity  of  the  old  bark, 
and,  therefore,  do  not  respond  to  the  treatment.  Sometimes 
the  parts  with  thinner  bark  may  outgrow  in  diameter  the 
trunk  or  the  old  branches  below  them.  The  remedy  is 
to  release  the  tension.  This  may  be  done  either  by  soften- 
ing the  bark  (by  washes  of  soap  or  lye),  or  by  separating 
it.  The  latter  is  done  by  slitting  the  bark-bound  part 
(in  spring),  thrusting  the  point  of  a  knife  through  the 
bark  to  the  wood,  and  then  drawing  the  blade  down  the 
entire  length  of  the  bark- 
bound  part.  The  slit  is 
scarcely  discernible  at  first, 
but  it  opens  with  the  growth 
of  the  tree,  filHng  up  with 
new  tissue  beneath.  Let  the 
pupil  consider  the  ridges 
which  he  now  and  then  finds 
on  trees,  and  determine 
whether  they  have  any  sig- 
nificance—  whether  the  tree 
has  ever  been  released,  or  in- 
jured by  natural  agencies. 

The  Tissue  covers  the 
Wounds  and  "heals"  them. 
—  This  is  seen  in  Fig.  63,  in  which  a  ring  of  tissue  rolls  out 
over  the  wound.  This  ring  of  healing  tissue  forms  most 
rapidly  and  uniformly  when  the  wound  is  smooth  and  regu- 
lar. Observe  the  healing  on  broken  and  splintered  limbs; 
also  the  difference  in  rapidity  of  healing  between  wounds 
on  strong  and  weak  limbs.  There  is  a  diflPerence  in  the 
rapidity  of  the  healing  process  in  different  kinds  of  trees. 
Compare  the  apple  tree  and  the  peach.    This  tissue  may  in 


Fig.  63. —  Proper  Cuthng  of  a 
Branch.  The  wound  will  soon  be 
"healed." 


56 


BE GINNKRS '  BOTANY 


Fig.  64.  —  Erroneous 
Pruning. 


turn  become  bark-bound,  and  the  healing  may  stop.     On 
large  wounds  it  progresses  more  rapidly  the  first  few  years 

than  it  does  later.     This  roll  or 
ring  of  tissue  is  called  a  callus. 

The  callus  grows  from  the  liv- 
ing tissue  of  the  stem  just  about 
the  wound.  It  cannot  cover  long 
dead  stubs  or  very  rough  broken 
branches  (Fig.  64).  Therefore, 
in  pruning  the  brandies  should  be 
cut  close  to  the  trunk  and  made 
even  and  smooth  ;  all  long  stubs 
must  be  avoided.  The  seat  of 
the  wound  should  be  close  to  the 
living  part  of  the  trunk,  for  the 
stub  of  the  limb  that  is  severed 
has  no  further  power  in  itself 
of  making  heaUng  tissue.  The 
end  of  the  remaining  stub  is 
merely  covered  over  by  the 
callus,  and  usually  remains  a 
dead  piece  of  wood  sealed  in- 
side the  trunk  (Fig.  65).  If 
wounds  do  not  heal  over  speed- 
ily, germs  and  fungi  obtain 
foothold  in  the  dying  wood 
and  rot  sets  in.  Hollow  trees 
are  those  in  which  the  decay- 
fungi  have  progressed  into  the 
inner  wood  of  the  trunk ;  they 
have  been  infected  {¥\g.  66). 

Large  wounds  should  be  protected  with  a  covering   of 
paint,  melted  wax,  or  other  adhesive  and  lasting  material, 


Fig.  65.  — Knot  in  a  Hemlock 
Log. 


THE  STEMS— KINDS  AND  FORMS;    PRUNING 


57 


Fig.  66.— a  Knot  Hole, 
and  the  beginning  of  a 
hollow  trunk. 


to  keep  out  the  germs  and  fungi. 
A  covering  of  sheet  iron  or  tin  may- 
keep  out  the  rain,  but  it  will  not  ex- 
clude the  germs  of  decay ;  in  fact, 
it  may  provide  tlie  very  moist  con- 
ditions that  such  germs  need  for 
their  growth.  Deep  holes  in  trees 
should  be.  treated  by  having  all  the 
decayed  parts  removed  down  to  the 
clean  wood,  the  surfaces  painted  or 
otherwise  sterilized,  and  the  hole 
filled  with  wax  or  cement. 
Stems  and  roots  are  living,  and 

they   should   not   be   wounded    or 

mutilated    unnecessarily.      Horses 

should  never  be  hitched  to  trees. 

Supervision    should    be    exercised 

over  persons  who   run  telephone, 

telegraph,  and  electric  light  wires, 

to   see  that   they  do  not  mutilate 

trees.  Electric  light  wires  and  trol- 
ley wires,  when  carelessly  strung 

or  improperly  insulated,  may  kill 

trees  (Fig.  6'j). 

Suggestions.  —  Forms  of  stems. 

43.  Are  the  trunks  of  trees  ever  per- 
fectly cylindrical?  If  not,  what  may 
cause  the  irregularities  ?  Do  trunks  often 
grow  more  on  one  side  than  the  other? 

44.  SHt  a  rapidly  growing  limb,  in  spring, 


with  a  knife  blade,  and  watch  the  result 
during  the  season.  45.  Examine  the 
w«odpile,  and  observe  the  variations  in 
thickness  of  the  annual  rings,  and  especi- 
ally of  the  same  ring  at  different  places 
in  the  circumference.     Cross-sections  of 


\  \ 

XA/^ 

^V*Pt/v  /^ 

\k      Jr 

r^^^    f 

V  L- 

\  n      /" 

-i/ 

^^ 

vll^^^^^ 

^ir- — 

13 

l^fl 

,^hh 

lifll^^p 

^^SHWB 

w^^^^^. 

"  '.^0^\L-'^ 

^^&*" 

Fig.  67.  —  Elm  Tree  killed 
BY  A  Direct  Current 
FROM  AN  Electric 
Railroad  System. 


58 


BEG/NNEKS'  BOTANY 


horizontal  branches  are  interesting  in  this  connection.  46.  Note 
the  enlargement  at  the  base  of  a  branch,  and  determine  whether 
this  enlargement  or  bulge  is  larger  on  long,  horizontal  limbs  than 
on  upright  ones.  Why  does  this  bulge  develop?  Does  it  serve 
as  a  brace  to  the  limb,  and  is  it  developed  as  the  result  of  constant 
strain?  47.  Strength  of  stems.  The  pupil  should  observe  the 
fact  that  a  stem  has  wonderful  strength.  Compare  the  propor- 
tionate height,  diameter,  and  weight  of  a  grass  stem  with  those  of 
the  slenderest  tower  or  steeple.  Which  has  the  greater  strength? 
Which  the  greater  height?  Which  will  withstand  the  most  wind? 
Note  that  the  grass  stem  will  regain  its  position  even  if  its  top  is 
bent  to  the  ground.  Note  how  plants  are  weighted  down  after  a 
heavy  rain  and  how  they  recover  themselves.  48.  Split  a  corn- 
stalk and  observe  how  the  joints  are  tied  together  and  braced  with 
fibres.  Are  there  similar  fibres  in  steins  of  pigweed,  cotton,  sun- 
flower, hollyhock? 


Fig.  68.  —  Potato.     What  are  roots,  and  what  stems  ?     Has  tlie  plant  more  than 
one  kind  of  stem  ?  more  than  two  kinds  ?     Explain. 


CHAPTER   X 


THE  STEM  — ITS   GENERAL   STRUCTURE 


There  are  two  main  types  of  stem  structure  in  flowering 
plants,  the  differences  being  based  on  the  arrangement  ot 
bundles  or  strands  of  tissue.  These  types  are  endogenous 
and  exogenous  (page  20).  It  will  require  patient  laboratory 
work  to  understand  what  these  types  and  structures  are. 

Endogenous,  or  Monocotyledonous  Stems.  —  Examples  of 
endogenous  stems  are  all  the  grasses,  cane-brake,  sugar- 
cane, smilax  or  green-brier, 
palms,  banana,  canna,  bam- 
boo, lilies,  yucca,  aspara- 
gus, all  the  cereal  grains. 
For  our  study,  a  cornstalk 
may  be  used  as  a  type. 

A  piece  of  cornstalk^ 
either  green  or  dead,  should 
be  in  the  hand  of  each 
pupil  while  studying  this 
lesson.  Fig.  69  will  also 
be  of  use.  Is  there  a  swelling  at  the  nodes.!*  Which 
part  of  the  internode  comes  nearest  to  being  perfectly 
round }  There  is  a  grooved  channel  running  along  one 
side  of  the  internode :  how  is  it  placed  with  reference  to 
the  leaf  ?  with  reference  to  the  groove  in  the  internode 
below  it  ?  What  do  you  find  in  each  groove  at  its  lower 
end?  (In  a  dried  stalk  only  traces  of  this  are  usually 
seen.)     Does  any  bud  on  a  cornstalk  besides  the  one  at 

59 


Fig.  69.  —  Cross-section  of  Corn- 
stalk, showing  the  scattered  fibro- 
vascular  bundles.     Slightly  enlarged. 


6o 


BEGINNERS'  BOTANY 


the  top  ever  develop  ?     Where   do  suckers   come   from  ? 
Where  does  the  ear  grow  ? 

Cut  a  cross-section  of  the  stalk  between  the  nodes  (Fig. 
69).  Does  it  have  a  distinct  bark  ?  The  interior  consists 
of  soft  **pith"  and  tough  woody  parts.  The  wood  is  found 
in  strands  or  fibres.  Which  is  more  abundant?  Do  the 
fibres  have  any  definite  arrangement  ?  Which  strands  are 
largest.?  Smallest."*  The  firm  smooth  rind  {which  cannot 
properly  be  called  a  bark)  consists  of  small  wood  strands 
packed  closely  together.  Grass  stems  are  hollow  cylinders ; 
and  the  cornstalk,  because  of  the  lightness  of  its  contents, 
is  also  practically  a  cylinder.  Stems  of  this  kind  are  ad- 
mirably adapted  for  providing  a  strong  support  to  leaves 
and  fruit.  This  is  in  accordance  with  the  well-known  law 
that  a  hollow  cylinder  is  much  stronger  than  a  solid 
cylinder  of  the  same  weight  of  material. 
Cut  a  thin  slice  of  the  inner  soft  part  and 
hold  it  up  to  the  light.  Can  you  make  out 
a  number  of  tiny  compartments  or  cells.? 
These  cells  consist  of  a  tissue  called  paren- 
chyma^ the  tissue  from  which  when  young  all 
the  other  tissues  arise  and  differentiate.  The 
numerous  walls  of  these  cells  may  serve  to 
brace  the  outer  wall  of  the  cylinder ;  but  their 
chief  function  in  the  young  stalk  is  to  give 
origin  to  other  cells.  When  alive  they  are 
filled  with  cell  sap  and  protoplasm. 

Trace  the  woody  strands  through  the  nodes. 
Do  they  ascend  vertically }  Do  they  curve 
toward  the  rind  at  certain  places  ?  Compare 
their  course  with  the  strands  shown  in  Fig.  70.  The  woody 
strands  consist  chiefly  of  tough  fibrous  cells  that  give  rigidity 


Fig.  70.  —  Dia- 
gram TO  SHOW 
THE  Course  of 

FiBRO- VASCU- 
LAR Bundles 
IN  Monocoty- 
ledons. 


THE  STEM— ITS    GENERAL   STRUCTURE 


6l 


Fig.  71.— Diagram  of 
Wood  Strands  or 

FiBRO-VASCULAR 

Bundles  in  a 
Root,  showing  the 
wood  (jr)  and  bast 
(/)  separated. 


and  strength  to  the  plant,  and  of  long  tubular  interrupted 

canals  that  serve  to  convey  sap  upward  from  the  root  and  to 

convey  food  downward  from  the  leaves  to  the  stem  and  the 

roots. 

Monocotyledons,    as   shown    by    fossils,    existed  before 

dicotyledons  appeared,  and  it  is  thought  that  the  latter 

were  developed  from  ancestors  of  the 

former.     It  will  be  interesting  to  trace 

the  relationship  in  stem  structure.     It 

will  first  be  necessary  to  learn  something 

of  the  structure  of  the  wood  strand. 
Wood  Strand  in  Monocotyledons  and 

Dicotyledons.  —  Each   wood   strand  (or 

fibro-vascular   bundle)   consists   of   two 

parts  —  the  bast  and  the  wood  proper. 

The  wood  is  on  the  side  of  the  strand 

toward  the  centre  of  the  stem  and  con- 
tains large  tubular  canals  that  take  the  watery  sap  upward 

from  the  roots.     The  bast  is  on  the  side  toward  the  bark, 

and  contains  fine  tubes 
through  which  diffuses 
the  dense  sap  contain- 
ing digested  food  from 
the  leaves.  In  the  root 
(Fig.  71)  the  bast  and 
the  wood  are  separate, 
so  that  there  are  two 
kinds  of  strands. 

In  monocotyledons, 
as  already  said,  the 
strands  (or  bundles)  are 
usually  scattered  in  the 

stem    with   no   definite   arrangement  (Figs.   72,    73).      In 

dicotyledons  the  strands,   or  bundles,  are  arranged  in  a 


Fig.  72.  —  Part  of  Cross-section  of  Root- 
stock  OF  Asparagus,  showing  a  few  fibro- 
vascular  bundles.    An  endogenous  stem. 


62 


BRCrNNERS*  BOTANY 


Scattered 
Bundles  or 
Strands,  in 
monocotyledons 
at  a,  and  the  bun- 
dles in  a  circle  in 
dicotyledons  at  b. 


Fio.  74.  —Dicotyledonous  Stem  of  One  Year  at  Left 

WITH  Five  Bundles,  and  a  two-year  stem  at  right. 
<7,  the  pith;   c,  the  wood  part ;    ^,  the  bast  part;    a,  one  year's  growth. 

ring.      As  the  dicotyledonous  seed  germi- 
Fio.  73.  —  The     nates,   five  bundles  are  usually  formed  in 

its  hypocotyl  (Fig.  74);  soon  five  more  are 

interposed 

between 

them,  and 

the  multi- 
plication continues,  in 
tough  plants,  until  the 
bundles  touch  (Fig.  74, 
right).  The  inner  parts 
thus  form  a  ring  of  wood 
and  the  outer  parts  form 
the  inner  bark  or  bast.  A 
new  ring  of  wood  or  bast 
is  formed  on  stems  of  di- 
cotyledons each  year,  and 

the  age  of  a  cut  stem  is 

„  .,     J   .         .      J  Fig.  75.  — Fibro-vascular  Bundle  of 

easily  determmed.  i.,^,^^,  corn,  much  magnified. 

When  cross-sections   of     ^,  annular  vessel  ;    ^',  annular  or  spiral  vessel ; 
♦^^^^^^4.    1    J  IT  ^^»  thick-walled  vessels;      W,  tracheids  or 

mOnOCOtyledonOUS  and  dl-  ^^ody  tissue  ;    F,  sheath  of  fibrous  tissue  sur- 

rounding  the  bundle  ;  FT,  fundamental  tissue 
or  pith  ;  S,  sieve  tissue  ;  P,  sieve  plate  ;  C, 
companion  cell  ;  /,  intercellular  space,  formed 
by  tearing  down  of  adjacent  cells  ;  VV ,  wood 
parenchyma. 


cotyledonous  bundles  are 
examined  under  the  mi- 
croscope, it  is  readily  seen 


THE  STEM— ITS  GENERAL  STRUCTURE 


63 


why  dicotyledonous  bundles  form  rings  of  wood  and  mono- 
cotyledonous  cannot  (Figs.  75  and  'j^).  The  dicotyledon- 
ous bundle  (Fig.  ^6)  has,  running  across  it,  a  layer  of  brick- 
shaped  cells  called  cambium,  which  cells  are  a  specialized 
form  of  the  parenchyma  cells  and  retain  the  power  of 


Fig.  76.  — The  Dicotyledonous  Bundle  or  Wood  Strand.    Upper  figure 
is  of  moonseed  : 

r,  cambium  ;  </,  ducts  ;  i,  end  of  first  year's  growth  ;  2,  end  of  second  year's  growth  ;  bast 
part  at  left  and  wood  part  at  right.  Lower  figure  (from  Wettstein)  is  sunflower:  h,  wood- 
cells;  ^.vessels;  <:,  cambium;  /.fundamental  tissue  or  parenchyma;  ^,  bast;  ^/,  bast 
parenchyma;  s,  sieve-tubes. 

growing  and  multiplying.  The  bundles  containing  cam- 
bium are  called  open  bundles.  There  is  no  cambium  in 
monocotyledonous  bundles  (Fig.  75)  and  the  bundles  are 
called  closed  bundles.  Monocotyledonous  stems  soon  cease 
to  grow  in  diameter.     The  stem  of  a  palm  tree  is  almost 


64  BEGINNERS'  BOTANY 

as  large  at  the  top  as  at  the  base.  As  dicotyledonous 
plants  grow,  the  sterns  become  thicker  each  year,  for  the 
delicate  active  cambium  layer  forms  new  cells  from  early 
spring  until  midsummer  or  autumn,  adding  to  the  wood 
within  and  to  the  bark  without.  As  the  growth  in  spring 
is  very  rapid,  the  first  wood-cells  formed  are  much  larger 
than  the  last  wood-cells  formed  by  the  slow  growth  of  the 


Fig.  77.  —-White  Pine  Stem,  s  years  old.    The  outermost  layer  is  bark. 

late  season,  and  the  spring  wood  is  less  dense  and  of  a 
lighter  colour  than  the  summer  wood;  hence  the  time 
between  two  years'  growth  is  readily  made  out  (Figs.  77 
and  78).  Because  of  the  rapid  growth  of  the  cambium  in 
spring  and  its  consequent  soft  walls  and  fluid  contents,  the 
bark  of  trees  ''peels"  readily  at  that  season. 

Medullary  Rays.  —  The  first  year's  growth  in  dicotyle- 
dons forms  a  woody  ring  which  almost  incloses  the  pith, 
and  this  is  left  as  a  small  cylinder  which  does  not  grow 


THE  STEM— ITS   GENERAL   STRUCTURE 


65 


larger,  even  if  the  tree  should  Hve  a  century.  It  is  not 
quite  inclosed,  however,  for  the  narrow  layers  of  soft  cells 
separating  the  bundles  remain  be- 
tween them  (Fig.  78),  forming  ra- 
diating lines  called  medullary  rays 
or  pith  rays. 

The  Several  Plant  Cells  and  their 
Functions* —  In  the  wood  there  are 
some  parenchyma  cells  that  have 
thin  walls  still,  but  have  lost 
the  power  of  di- 
vision. They  are 
now  storage  cells. 
Therie     are     also 

wood  fibres  which  /,  pith;  /,  parenchyma 

are     thick-walled 


AIX 

^ 

s 

^ 

^ 

V^ 

^ 

S 

H 

SO 


Fig.  78.  — Arrangement  of 
Tissues  in  Two  -  yea r- 
OLD  Stem  of  Moonseed. 


The  fibro- 
vascular    bundles,    or    wood 
strands,  are  very  prominent,  with 
Fig.  79.  — Markings    and  rigid   (h,  Fig.  thin  medullary  rays  between. 

IN    Cell  Walls  rr/^N  i  .  .    xi  i 

OF  Wood  Fibre     '^h  ^nd  servc  to  support  the  sap-canals 


j/,  spiral ;  an,  annular 
sc,  scalariform. 


or    wood   vessels    (or   tracheids)    that   are 
formed    by    the    absorption    of    the    end 

walls  of  upright  rows  of  cells ;  the  canals 

pass  from  the  roots  to  the  twigs  and  even 

to  ribs  of  the  leaves  and  serve  to  transport 

the  root  water.    They  are  recognized  (Fig. 

79)  by  the  pecuHar  thickening  of  the  wall 

on  the  inner  surface  of  the  tubes,  occur- 
ring in  the  form  of  spirals.     Sometimes  the 

whole   wall  is  thickened  except  in  spots 

called  pits  (,^,  Fig.  76).     These  thin  spots 

(Fig.  80)  allow  the  sap  to  pass  to  other   p^^  g^ 

cells  or  to  neighbouring  vessels. 
The  cambium,  as  we  have  seen,  consists  '^t^ttThtlt 

of  cells  whose  function  is  growth.     These       pit  borders  at  o,  *, 


Pits  in 
THE  Cell  Wall. 


66 


BEGINNERS*  BOTANY 


cells  are  thin-walled  and  filled  with  protoplasm.     During 

the  growing  season  they  are  continually  adding  to  the 

wood  within  and  the  bark  with- 
out ;  hence  the  layer  moves  out- 
ward as  it  deposits  the  new 
woody  layer  within. 

The  bark  consists  of  inner  or 
fibrous  bark  or  new  bast  (these 
fibres  in  flax  become  linen),  the 
green  or  middle  bark  which  func- 
tions somewhat  as  the  leaves, 
and  the  corky  or  outer  bark. 
The  common  word  "  bark "  is 
seen,  therefore,  not  to  represent 
a  homogeneous  or  simple  struc- 
ture, but  rather  a  collection  of 
several  kinds  of  tissue,  all  sepa- 
rating from  the  wood  beneath 
by  means  of  cambium.  The  new 
bast  contains  (i)  the  sieve-tubes 
(Fig.  8i)   which   transport   the 

sap  containing  organic  substances,  as  sugar 

and  proteids,  from  the  leaves  to  the  parts 

needing  it  {s,  Fig.  j6\     These  tubes  have 

been   formed   like   the   wood   vessels,  but 

they  have  sieve-plates  to  allow  the  dense 

organic-laden   sap  to  pass  with   sufficient 

readiness   for  purposes   of   rapid  distribu- 
tion.    (2)  There  are  also  thick-walled  bast 

fibres    (Fig.    82)    in   the   bast   that   serve 

for    support.       (3)      Tlioro    is    also    some 

parenchyma     in     the   new      l;ast;      it      is      Fig.  82.— thick- 

,  ,  ,  .  ei  WALLED  BaST 

now    m    part    a    storage    tissue.        borne-  cells. 


Fig.  81.  — Sieve-tubes,  j,  j; 

/  shows  a  top  view  of  a  sieve-plate, 
with  a  companion  cell,  c,  at  the 
side;  o  shows  sieve-plates  in  the 
side  of  the  cell.  In  s,  s  the  proto- 
plasm is  shrunken  from  the  walls 
by  reagents. 


THE  STEM— ITS   GENERAL   STRUCTURE  6/ 

times  the  walls  of  parenchyma  cells  in  the  cortex  thicken 
at  the  corners  and  form  brace  cells  (Fig.  83)  (collenchyma) 
for  support ;  sometimes  the  whole  wall  is  thickened,  form- 
ing  grit  cells   or  stone  cells  (Fig. 

84 ;  examples  in 

tough    parts    of 

pear,  or  in  stone 

of  fruits).  Some 

parts   serve   for 
FIG.  83.  -  COLL  EN-     secretions  (milk, 
CHYMA  IN  Wild     rosin,  etc.)    and 

TEWELWEED        or  11       1       r 

TOUCH-ME-NOT  (IM-        ^^^     Callcd     lutCX 

PATIENS).  tubes.  ^'''-  ^'*-  -^^'"^  ^'^''^'• 

The  outer  bark  of  old  shoots  consists  of  corky  cells  that 
protect  from  mechanical  injury,  and  that  contain  a  fatty  sub- 
stance (suberin)  impermeable  to  water  and  of  service  to 
keep  m  moisture.  There  is  sometimes  a  cork  cambium  (or 
phellogen)  in  the  bark  that  serves  to  extend  the  bark  and 
keep  it  from  splitting,  thus  increasing  its  power  to  protect. 

Transport  of  the  <*Sap." — We  shall  soon  learn  that  the 
common  word  "  sap  "  does  not  represent  a  single  or  simple 
substance.  We  may  roughly  distinguish  two  kinds  of  more 
or  less  fluid  contents:  (i)  the  root  zvater,  sometimes  called 
mineral  sap,  that  is  taken  in  by  the  root,  containing  its 
freight  of  such  inorganic  substances  as  potassium,  calcium, 
iron,  and  the  rest ;  this  root  water  rises,  we  have  found,  ifi 
the  ivood  vessels,  —  that  is,  in  the  young  or  "sapwood  "  (p. 
96);  (2)  Xho,  elaborated  or  oi'gani:;ed  materials  Y^^iSsmghdick 
and  forth,  especially  from  the  leaves,  to  build  up  tissues 
in  all  parts  of  the  plant,  some  of  it  going  down  to  the  roots 
and  root-hairs ;  this  organic  material  is  transported,  as  we 
have  learned,  in  the  sieve-tubes  of  the  inner  bast,  —  that  is, 
in  the  **  inner  bark."     Removing  the  bark  from  a  trunk  in 


6S 


BEGINNERS'  BOTANY 


a  girdle  will  not  stop  the  upward  rise  of  the  root  water  so 
long  as  the  wood  remains  alive ;  but  it  will  stop  the  passage 
of  the  elaborated  or  food-stored  materials  to  parts  below 
and  thus  starve  those  parts ;  and  if  the  girdle  does  not 
heal  over  by  the  deposit  of  new  bark,  the  tree  will  in  time 
starve  to  death.  It  will  now  be  seen  that  the  common 
practice  of  placing  wires  or  hoops  about  trees  to  hold 
them  in  position  or  to  prevent  branches  from  falling  is 
irrational,  because  such  wires  interpose  barriers  over  which 

the  fluids  cannot  pass ;  in 
time,  as  the  trunk  increases 
in  diameter,  the  wire  girdles 
the  tree.  It  is  much  better 
to  bolt  the  parts  together  by 
rods  extending  through  the 
branches  (Fig.  85).  These 
bolts  should  fit  very  tight  in 
their  holes.     Why? 

Wood.  —  The  main  stem 
or  trunk,  and  sometimes 
the  larger  branches,  are  the 
sources  of  lumber  and  tim- 
ber. Different  kinds  of  wood  have  value  for  their  special 
qualities.  The  business  of  raising  wood,  for  all  purposes, 
is  known  as  forestry.  The  forest  is  to  be  considered  as  a 
crop,  and  the  crop  must  be  harvested,  as  much  as  corn  or 
rice  is  harvested.  Man  is  often  able  to  grow  a  more  pro- 
ductive forest  than  nature  does. 

Resistance  to  decay  gives  value  to  wood  used  for  shingles 
{cypress^  heart  of  yellow  pine)  and  for  fence  posts  (mul- 
berry^ cedar^  post  oak^  bois  d'arCy  mesqtiite). 

Hardness  and  strength  are  qualities  of  great  value  in 
building.     Live  oak  is  used  in  ships.     Red  oaky  rock  maple^ 


Fig.    85.— The    Wrong    Way    to 
BRACE   A   Tree.     (See  Fig.    iiS;. 


THE  STEM— ITS   GENERAL   STRUCTURE  69 

and  yellow  pine  are  used  for  floors.  The  best  flooring  is 
sawn  with  the  straight  edges  of  the  annual  rings  upward ; 
tangential  sawn  flooring  may  splinter.  Chestnut  is  common 
in  some  parts  of  the  country,  being  used  for  ceiling  and 
inexpensive  finishing  and  furniture.  Locust  and  bois  d'arc 
(osage  orange)  are  used  for  hubs  of  wheels;  bois  d'arc 
makes  a  remarkably  durable  pavement  for  streets.  Ebony 
is  a  tropical  wood  used  for  flutes,  black  piano  keys,  and 
fancy  articles.  Ash  is  straight  and  elastic ;  it  is  used 
for  handles  for  Hght  implements.  Hickory  is  very  strong 
as  well  as  elastic,  and  is  superior  to  ash  for  handles,  spokes, 
and  other  uses  where  strength  is  wanted.  Hickory  is 
never  sawn  into  lumber,  but  is  split  or  turned.  The 
"second  growth,"  which  sprouts  from  stumps,  is  most 
useful,  as  it  splits  readily.  Fast-growing  hickory  in  rich 
land  is  most  valuable.  The  supply  of  useful  hickory  is 
being  rapidly  exhausted. 

Softness  is  oftejz  important.  White  pine  and  sweet  gum 
because  of  their  softness  and  lightness  are  useful  in  box- 
making.  "  Georgia  "  or  southern  pine  is  harder  and  stronger 
than  white  pine ;  it  is  much  used  for  floors,  ceilings,  and 
some  kinds  of  cabinet  work,  y^laiie  pine  is  used  for  window- 
sash,  doors,  and  moulding,  and  cheaper  grades  are  used  for 
flooring.  Hemlock  is  the  prevailing  lumber  in  the  east  for 
the  framework  and  clapboarding  of  buildings.  Redwood 
and  Douglas  spruce  are  common  building  materials  on  the 
Pacific  coast.  Cypress  is  soft  and  resists  decay  and  is 
superior  to  white  pine  for  sash,  doors,  and  posts  on  the 
outside  of  houses.  Cedar  is  readily  carved  and  has  a 
unique  use  in  the  making  of  chests  for  clothes,  as  its  odour 
repels  moths  and  other  insects.  Willow  is  useful  for  bas- 
kets and  light  furniture.  Basswood  or  linden  is  used  for 
light  ceiling  and  sometimes  for  cheap  floors.      Whitewood 


70 


BEGINNERS'   BOTANY 


(incorrectly  called  poplar)  is  employed  for  wagon  bodies 
and  often  for  house  finishing.  It  often  resembles  curly 
maple. 

Beauty  of  grain  and  polish  gives  wood  value  for  furni- 
ture,- pianos,  and  the  like.  Mahogany  and  white  oak  are 
most  beautiful,  although  red  oak  is  also  used.  Oak  logs 
which  are  first  quartered  and  then  sawn  radially  expose  the 
beautiful  silver  grain  (medullary  rays).     Fig.  Z6  shows  one 

mode  of  quartering. 
The  log  is  quartered 
on  the  lines  a,  a,  byb  \ 
then  succeeding 
boards  are  cut  from 
each"  quarter  at  i, 
2,  3,  etc.  The  nearer 
the  heart  the  better 
the  "grain"  :  why? 
Ordinary  boards  are 
sawn  tangentially, 
as  c^  c.  Curly  pine, 
curly  walnut,  and 
bird's-eye  maple  are 
woods  that  owe  their 
beauty  of  grain  to  wavy  lines  or  buried  knots.  A  mere 
stump  of  curly  walnut  is  worth  several  hundred  dollars. 
Such  wood  is  sliced  very  thin  for  veneering  and  glued 
over  oilier  woods  in  luakiiijj^  pianos  and  furniture.  If 
the  cause  of  wavy  grain  could  be  found  out  and  such  wood 
grown  at  will,  the  discovery  would  be  very  useful.  Maple  is 
much  used  for  furniture.  Birch  may  be  coloured  so  as  very 
closely  to  represent  mahogany,  and  it  is  useful  for  desks. 

Special  Products  of  Trees. — Cork  from  llic  hark  of  tJic 
cork  oak  in  Spain,  latex  from  the  rubber,  and  sap  from  the 


Fig.  86.  — The  Making  of  Ordinary  Boards, 
AND  One  V^ay  of  Making  "  Quartered  " 
Boards. 


THE   STEM— ITS   GENERAL   STRUCTURE  *J\ 

sugar-maple   trees,  turpentine  from  pine,  tannin  from  oak 
bark,  Peruvian  bark  from  cinchona,  are  all  useful  products. 

Suggestions.  —  Parts  of  a  root  and  stem  through  which  liquids 
rise.  49.  Pull  up  a  small  plant  with  abundant  leaves,  cut  off  the 
root  so  as  to  leave  two  inches  or  more  on  the  plant  (or  cut  a  leafy 
shoot  of  squash  or  other  strong-growing  coarse  plant),  and  stand  it 
in  a  bottle  with  a  little  water  at  the  bottom  which  has  been  coloured 
with  red  ink  (eosine).  After  three  hours  examine  the  root;  make 
cross  sections  at  several  places.  Has  the  water  coloured  the  axis 
cylinder?  The  cortex?  What  is  your  conclusion?  Stand  some 
cut  flowers  or  a  leafy  plant  with  cut  stem  in  the  same  solution  and 
examine  as  before  :  conclusion  ?  50.  Girdle  a  twig  of  a  rapidly 
growing  bush  (as  willow)  in  early  spring  when  growth  begins  {a) 
by  very  carefully  removing  only  the  bark,  and  {U)  by  cutting  away 
also  the  sapwood.  Under  which  condition  do  the  leaves  wilt? 
Why  ?  51.  Stand  twigs  of  willow  in  water ;  after  roots  have  formed 
under  the  water,  girdle  the  twig  (in  the  two  ways)  above  the  roots. 
What  happens  to  the  roots,  and  why?  52.  Observe  the  swellings 
on  trees  that  have  been  girdled  or  very  badly  injured  by  wires  or 
otherwise  :  where  are  these  swellings,  and  why  ?  53.  Kinds  of 
wood.  Let  each  pupil  determine  the  kind  of  wood  in  the  desk, 
the  floor,  the  door  and  window  casings,  the  doors  themselves,  the 
sash,  the  shingles,  the  fence,  and  in  the  small  implements  and 
furniture  in  the  room ;  also  what  is  the  cheapest  and  the  most 
expensive  lumber  in  the  community.  54.  How  many  kinds  of 
wood  does  the  pupil  know,  and  what  are  their  chief  uses? 

Note  to  Teacher.  —  The  work  in  this  chapter  is  intended  to  be 
mainly  descriptive,  for  the  purpose  of  giving  the  pupil  a  rational 
conception  of  the  main  vital  processes  associated  with  the  stem, 
in  such  a  way  that  he  may  translate  it  into  his  daily  thought.  It 
is  not  intended  to  give  advice  for  the  use  of  the  compound  micro- 
scope. If  the  pupil  is  led  to  make  a  careful  study  of  the  text,  draw- 
ings, and  photographs  on  the  preceding  and  the  following  pages, 
he  will  obtain  some  of  the  benefit  of  studying  microscope  sections 
without  being  forced  to  spend  time  in  mastering  microscope 
technique.  If  the  school  is  equipped  with  compound  microscopes, 
a  teacher  is  probably  chosen  who  has  the  necessary  skill  to 
manipulate  them  and  the  knowledge  of  anatomy  and  physiology 
that  goes  naturally  with  such  work ;  and  it  would  be  useless  to 
give  instruction  in  such  work  in  a  text  of  this  kind.  The  writer  is 
of  the  opinion  that  the  introduction  of  the  compound  microscope 
into  first  courses  in  botany  has  been  productive  of  harm.  Good 
and  vital  teaching  demands  first  that  the  pupil  have  a  normal, 


72 


BEGINNERS*  BOTANY 


direct,  and  natural  relation  to  his  subject,  as  he  commonly  meets 
it,  that  the  obvious  and  significant  features  of  the  plant  world  be 
explained  to  him  and  be  made  a  means  of  training  him.  The 
beginning  pupil  cannot  be  expected  to  know  the  fundamental 
physiological  processes,  nor  is  it  necessary  that  these  processes 
should  be  known  in  order  to  have  a  point  of  view  and  trained 
intelligence  on  the  things  that  one  customarily  sees.  Many  a 
pupil  has  had  a  so-called  laboratory  course  in  botany  without 
having  arrived  at  any  real  conception  of  what  plants  mean,  or 
without  having  had  his  mind  opened  to  any  real  sympathetic 
touch  with  his  environment.  Even  if  one's  knowledge  be  not 
deep  or  extensive,  it  may  still  be  accurate  as  far  as  it  goes,  and 
his  outlook  on  the  subject  may  be  rational. 


Fig.  87.  — The  Many-stemmed  Thickets  of  Mangrove  of  Southern- 
most Seacoasts,  many  of  the  trunks  being  formed  of  aerial  roots. 


CHAPTER   XI 

LEAVES  — FORM  AND  POSITION 

Leaves  may  be  studied  from  four  points  of  view,  — with 
reference  to  (1)  their  kinds  and  shapes;  {2)  their  position,  or 
arrangemefit  on  the  plant;  (3)  their  anatomy ,  or  structure ; 


Fig.  88.  — a  Simple  Netted-veined  Leaf. 

(4)  their  functiouy  or  the  work  they 
perform.  This  chapter  is  concerned 
with  the  first     ,4t  two  categories. 


Fig.  90. — Compound  or  Branched  Leaf 
OF  Brake  (a  common  fern). 


Fig.  89.  — a  Simple  Par- 
allel-veined Leaf. 

Kinds.  —  Leaves 
are  simple  or  un- 
branchcd  (Figs.  ^Z, 
89),  and  compound  or 
branched  (Fig.  90), 


73 


H 


BEGINNERS*  BOTANY 


The  method  of  compounding  or  branching  follows  the 
mode  of  veining.  The  veining,  or  venation,  is  of  two  gen- 
eral kinds.  In  some  plants  the  main  veins 
diverge,  and  there  is  a  conspicuous  net- 
work of  smaller  veins ;  such  leaves  are 
netted-veined.  They  are  characteristic  of 
the  dicotyledons.  In  other  plants  the 
main  veins  are  parallel,  or  nearly  so,  and 
there  is  no  conspicuous  network ;  these 
are  parallel-veined  leaves  (Figs.  89,  102). 
These  leaves  are  the  rule  in  monocoty- 
ledonous  plants.  The  venation  of  netted- 
veined  leaves  is  pinnate  or  feather-like 
when  the  veins  arise  from  the  side  of  a 
continuous  midrib  (Fig.  91);  palmate  or 
digitate  (hand-like)  when  the  veins  arise 
from  the  apex  of  the  petiole  (Figs.  Z^,  92).  If  leaves  were 
divided  between  the  main  veins,  the  former  would  be 
pinnately  arid  the  latter  digitately  compound. 

It   is  customary  to  speak  of  a  leaf  as  compound  only 
when  the  parts  or  branches  are  completely  separate  blades, 


Fig.  91.  —  Com- 
plete Leaves  of 
Willow. 


Fig.  92.  — Digitate-veined  Pel- 
tate Leaf  of  Nasturtium. 


Fig.  93.  — Pinnately  Compound 
Leaf  of  Ash. 


as  when  the  division  extends  to  the  midrib  (Figs.  90,  93, 
94,95).     The  parts  or   branches   are   known   as   leaflets. 


LEAVES— FORM  AND   POSITION 


n 


Sometimes  the  leaflets  themselves  are  compound,  and  the 
whole  leaf  is  then  said  to  be  bi-compound  or  twice-com- 


FlG.  94,  — DlGI- 

TATELY  Compound 
Leaf  of  Rasp- 
berry. 


Fig.  95.  — Poison  Ivy.     Leaf  and  Fruit. 

pound  (Fig.  90).  Some  leaves  are  three-compound,  four- 
compound,  or  five-compound.  Decompound  is  a  general 
term  to  express  any  degree  of 
compounding  beyond  twice-com- 
pound. 

Leaves  that  are  not  divided  as 
far  as  to  the  midrib  are  said  to 
be: 

lobed,  if  the  openings  or  sinuses 
are  not  more  than  half  the  depth 
of  the  blade  (Fig.  96); 

cleft,  if  the  sinuses  are  deeper      pio.  96.  -  Lobed  leaf  of 
than  the  middle  ;  Sugar  Maple. 


76 


BEGINNERS*  BOTANY 


Fig.  97.  — Digitately  Parted  Leaves 
OF  Begonia. 


parted,  if  the  sinuses 
reach  two  thirds  or  more 
to  the  midrib  (Fig.  97); 

divided,  if  the  sinuses 
reach  nearly  or  quite  to 
the  midrib. 

The  parts  are  called 
lobes,  divisions,  or  seg- 
ments, rather  than  leaf- 
lets. The  leaf  may  be 
pinnately  or  digitately 
A   pinnately   parted   or 


lobed,  parted,  cleft,  or  divided. 

cleft  leaf  is  sometimes  said  to  be  pinnatifid. 

Leaves  may  have 
one  or  all  of  three 
parts  —  blade,     or 
expanded  part ;  pe- 
tiole, or  stalk ;  stip- 
ules, or 
appendages 
at  the  base  of  the 
petiole.  A  leaf  that 
has  all  three  of  these 
parts  is  said  to  be 
complete  (Figs.  91, 
106).    The  stipules 
are  often  green  and 
leaflike     and    per- 
form the  function    fig.  98 
of    foliage   as   in   the 
pea  and  the  Japanese  quince  (the  latter  common  in  yards). 

Leaves  and  leaflets  that  have  no  stalks  are  said  to  be 
sessile  (Figs.  98,  103),  i,e.  sitting.     Find  several  examples. 


Oblong 


ovate  Sessile  Leaves  of 
Tea. 


LEAVES'- FORM  AND  POSITION 


77 


Fig.  99.—  Clasp- 
ing Leaf  of  a 
"Wild  Aster. 


The  same  is  said  of  flowers  and  fruits. 
The  blade  of  a  sessile  leaf  may  partly  or 
wholly  surround  the  stem,  when  it  is  said 
to  be  clasping.  Examples  :  aster  (Fig.  99), 
corn.  In  some  cases  the  leaf  runs  down 
the  stem,  forming  a  wing ;  such  leaves  are 
said  to  be  decurrent  (Fig.  100).  When 
opposite  sessile  leaves  are  joined  by  their 
bases,  they  are  said  to  be  connate  (Fig.  loi). 
Leaflets  may  have  one  or  all  of  these 

three  parts,  but  the  stalks  of 
leaflets  are  called  petiolules 
and  the  stipules  of  leaflets  are 
called  stipels.  The  leaf  of  the 
garden  bean  has  leaflets,  peti- 
olules, and  stipels. 

The  blade  is  usually  attached 
to  the  petiole  by  its  lower  edge. 
In  pinnate-veined  leaves,  the  petiole  seems  to 
continue  through  the  leaf  as  a  midrib  (Fig.  91). 
In  some  plants,  however,  the  petiole  joins 
the  blade  inside  or  beyond  the  margin  (Fig.  92).  Such 
leaves  are  said  to  be  pel- 
tate or  shield-shaped.  This 
mode  of  attachment  is  par- 
ticularly common  in  float- 
ing leaves  {e.g.  the  water 
lilies).  Peltate  leaves  are 
usuafly  digitate-veined. 

How  to  Tell  a  Leaf.— It 
is  often  difficult  to  distin- 

guishcompound  leaves  from       ^^^   ,01. -Two  Pairs  of  Connate 
leafy  branches,  and  leaflets  Leaves  of  Honeysuckle. 


Fig.  100.  —  De- 
current 
Leaves  of 
Mullein. 


78 


BEGINNERS'  BOTANY 


from  leaves.  As  a  rule  leaves  can  be  distinguished  by 
the  following  tests :  ( i  )  Leaves  are  temporary  strjictures^ 
sooner  or  later  falling.  (2)  Usually  buds  are  borne  in  their 
axils,  (3)  Leaves  are  usually  borne  at  joints  or 
nodes.  (4)  They  arise  on  wood  of  the  curre7it 
year's  growth.  (5)  They  have  a  more  or  less 
defiiiite  arrangement.  When  leaves  fall,  the  twig 
that  bore  them  remains;  when  leaflets  fall,  the 
main  petiole  or  stalk  that  bore  them  also  falls. 

Shapes.  —  Leaves  and  leaflets  are  infinitely 
variable  in  shape.  Names  have  been  given  to 
some  of  the  more  definite  or  regular  shapes. 
These  names  are  a  part  of  the  language  of  bot- 
any. The  names  represent  ideal  or 
typical  shapes ;  there  are  no  two 
leaves  alike  and  very 
few  that  perfectly  con- 
form to  the  definitions. 
The  shapes  are  likened 
to  those  of  famihar  ob- 
jects or  of  geometrical 
figures.  Some  of  the 
commoner  shapes  are  as 
follows  (name  original 
examples  in  each  class): 
Linear,   several  times  longer  than  broad,  with  the   sides 

\      nearly  or  quite  parallel.     Spruces  and  most  grasses 
are  examples  (Fig.  102).     In  linear  leaves,  the  main 
veins  are  usually  parallel  to  the  midrib. 
Oblong,  twice  or  thrice  as  long  as  broad,  with  the  sides 

\  parallel  for  most  of  their  length.  Fig.  103  shows  the 
short-oblong  leaves  of  the  box,  a  plant  that  is  used 
for  permanent  edgings  in  gardens. 


Fig.  102.— 
Linear- 
acuminate 
Leaf  of 
Grass. 


Fig.  103.  —  Short-oblong 
Leaves  of  Box. 


LEAVES— FORM  AND  POSITION 


79 


Elliptic  differs  from  the  oblong  in  having  the  sides  gradu- 
ally tapering  to  either  end  from  the  middle.     The 

^k     European  beech  (Fig.  104)  has  elliptic 

^^  leaves.     (This  tree  is  often  planted  in 
this  country.) 

Lanceolate,   four  to   six   times   longer   than 
broad,  widest  below   the  middle,  and 

V   tapering  to  either  end.     Some  of  the 
narrow-leaved    willows  are   examples. 
Most  of   the  willows  and  the   peach 
have  oblong-lanceolate  leaves. 
Spatulate,   a   narrow   leaf  that   is  broadest 

\      toward  the  apex.     The  top  is  usually 
rounded. 


104.  — 


Elliptic  Leaf 

OF  Purple 

Beech. 


Fig.  105. —  Ovate 
Serrate  Leaf  of 
Hibiscus. 


Fig.  106. — Leaf  of  Apple,  showing  blade, 
petiole,  and  small  narrow  stipules. 

Ovate,  shaped  somewhat  like  the  longitudinal  section  of  an 
^  Q^gg\  about  twice  as  long  as  broad,  tapering  from  near 
^  the  base  to  the  apex.  This  is  one  of  the  commonest 
^    leaf  forms  (Figs.  105,  106). 


8o 


BEGINNERS'  BOTANY 


Obovate,  ovate  inverted,  —  the  wide  part  towards  the  apex. 

Leaves  of  mullein  and  leaflets  of  horse-chestnut  and 
S     false  indigo  are  obovate.     This  form  is  commonest 

in  leaflets  of  digitate  leaves  :  why  ? 
Reniform,  kidney-shaped.     This  form  is  sometimes  seen  in 
^^   wild  plants,  particularly  in  root-leaves.     Leaves  of 
^^     wild  ginger  are  nearly  reniform. 
Orbicular,  circular  in  general  outline.     Very  few  leaves  are 

#    perfectly  circular,   but  there    are    many    that    are 
nearer  circular  than  of  any  other  shape.  (Fig.  107). 


Fig.  107.  —  Orbicular 
LoBED  Leaves. 


Fig.  108.— Truncate 
Leaf  of  Tulip  Tree. 


The  shape  of  many  leaves  is  described  in  combinations 
of  these  terms  :  as  ovate-lanceolate,  lanceolate-oblong. 

The  shape  of  the  base  and  the  apex  of  the  leaf  or  leaflet 
is  often  characteristic.  The  base  may  be  rounded  (Fig. 
104),  tapering  (Fig.  93),  cordate  or  heart-shaped  (Fig.  105), 
truncate  or  squared  as  if  cut  off.  The  apex  may  be  blunt 
or  obtuse,  acute  or  sharp,  acuminate  or  long-pointed,  trun- 
cate (Fig.  108).     Name  examples. 

The  shape  of  the  margin  is  also  characteristic  of  each 
kind  of  leaf.  The  margin  is  entire  when  it  is  not  in- 
dented or  cut  in   any  way  (Figs.  99,    103).      When  not 


LEAVES  — FORM  AND  POSITION 


8i 


entire,  it  may  be  undulate  or  wavy  (Fig.  92),  serrate  or 
saw-toothed  (Fig.  105),  dentate  or  more  coarsely  notched 
(Fig.  95),  crenate  or  round-toothed,  lobed,  and  the  like. 
Give  examples. 

Leaves  on  the  same  plant  often  differ  greatly  in  form. 
Observe  the  different  shapes  of  leaves  on  the  young 
growths  of  mulberries  (Fig.  2)  and  wild  grapes ;  also 
on  vigorous  squash  and  pumpkin  vines.  In  some  cases 
there  may  be  simple  and 
compound  leaves  on  the 
same  plant.  This  is 
marked  in  the  so-called 
Boston  ivy  or  ampelop- 
5is  (Fig.  109),  a  vine 
ihat  is  used  to  cover 
brick  and  stone  build- 
ings. Different  degrees 
of  compounding,  even 
in  the  same  leaf,  may 
often  be  found  in  honey 
locust.  Remarkable  dif- 
ferences in  forms  are 
seen  by  comparing  seed-leaves  with  mature  leaves  of  any 
plant   (Fig.  30). 

The  Leaf  and  its  Environment.  —  The  form  and  shape 
of  the  leaf  often  have  direct  relation  to  the  place  in  which 
the  leaf  grozvs.  Floati7tg  leaves  are  usually  expanded  and 
flaty  and  the  petiole  varies  in  length  with  the  depth  of 
the  water.  Submerged  leaves  are  usually  linear  or  thread- 
likCf  or  are  cut  into  very  narrow  divisions:  thereby 
more  surface  is  exposed,  and  possibly  the  leaves  are  less 
injured  by  moving  water.  Compare  the  sizes  of  the  leaves 
on  the  ends  of   branches  with  those  at  the  base  of   the 


Fig.  109.  —  Different  Forms  of  Leaves 
FROM  one  Plant  of  Ampelopsis. 


82  BEGINNERS*  BOTANY 

branches  or  in  the  interior  of  the  tree  top.  In  dense 
foliage  masses,  the  petioles  of  the  lowermost  or  under- 
most leaves  tend  to  elongate — to  push  the  leaf  to  the  light. 

On  the  approach  of  winter  the  leaf  usually  ceases  to 
work,  and  dies.  It  may  drop,  when  it  is  said  to  be  decidu- 
ous; or  it  may  remain  on  the  plant,  when  it  is  said  to  be 
persistent.  If  persistent  leaves  remain  green  during  the 
winter,  the  plant  is  said  to  be  evergreen.  Give  examples 
in  each  class.  Most  leaves  fall  by  breaking  off  at  the 
lower  end  of  the  petiole  with  a  distinct  joint  or  articula- 
tion.  There  are  many  leaves,  however,  that  wither  and 
hang  on  the  plant  until  torn  off  by  the  wind;  of  such 
are  the  leaves  of  grasses,  sedges,  lilies,  orchids,  and  other 
plants  of  the  monocotyledons.  Most  leaves  of  this  char- 
acter are  parallel-veined. 

Leaves  also  die  and  fall  from  lack  of  light.  Observe  the 
yellow  and  weak  leaves  in  a  dense  tree  top  or  in  any 
thicket.  Why  do  the  lower  leaves  die  on  house  plants } 
Note  the  carpet  of  needles  under  the  pines.  All  ever- 
greens shed  their  leaves  after  a  time.  Counting  back  from 
the  tip  of  a  pine  or  spruce  shoot,  determine  how  many 
years  the  leaves  persist.  In  some  spruces  a  few  leaves 
may  be  found  on  branches  ten  or  more  years  old. 

Arrangement  of  Leaves.  —  Most  leaves  have  a  regular 
position  or  arrangement  on  the  stem.  TJiis  position  or 
directio7t  is  determined  largely  by  exposure  to  sunlight.  In 
temperate  chmates  they  usually  hang  in  such  a  way  that 
they  receive  the  greatest  amount  of  light.  One  leaf  shades 
another  to  the  least  possible  degree.  If  the  plant  were 
placed  in  a  new  position  with  reference  to  light,  the  leaves 
would  make  an  effort  to  turn  their  blades. 

When  leaves  are  opposite  the  pairs  usually  alternate. 
That  is,  if  one  pair  stands  north  and  south,  the  next  pair 


LEAVES— FORM  AND  POSITION 


83 


stands  east  and  west.  See  the  box-elder  shoot,  on  the 
left  in  Fig.  1 10.  O^te  pair  does  not  shade  the  pair  beneath. 
The  leaves  are  in  four  vertical  ranks. 

There  are  several  kinds  of  alternate  arrangement.  In  the 
elm  shoot,  in  Fig.  no,  the  third  bud  is  vertically  above  the 
first.  This  is  true  no 
matter  which  bud  is  taken 
as  the  starting  point. 
Draw  a  thread  around 
the  stem  until  the  two 
buds  are  joined.  Set  a 
pin  at  each  bud.  Ob- 
serve that  two  buds  are 
passed  (not  counting  the 
last)  and  that  the  thread 
makes  one  circuit  of  the 
stem.  Representing  the 
number  of  buds  by  a  de- 
nominator, and  the  num- 
ber of  circuits  by  a 
numerator,  we  have  the 
fraction  \y  which  expresses 
the  part  of  the  circle  that  lies  between  any  two  buds. 
That  is,  the  buds  are  one  half  of  360  degrees  apart,  or 
180  degrees.  Looking  endwise  at  the  stem,  the  leaves 
are  seen  to  be  2-ranked.  Note  that  in  the  apple  shoot 
(Fig.  1 10,  right)  the  thread  makes  two  circuits  and  five 
buds  are  passed :  two  fifths  represents  the  divergence 
between  the  buds.     The  leaves  are  5-ranked. 

Every  plant  has  its  own  arrangement  of  leaves.  For 
opposite  leaves,  see  maple,  box  elder,  ash,  lilac,  honey- 
suckle, mint,  fuchsia.  For  2-ranked  arrangement,  see 
all  grasses,   Indian   corn,  basswood,  elm.     For  3-ranked 


Fig,  iio.  —  Phyij.otaxy  of  Box  Elder, 
EiM.  Apple. 


84 


BEGINNERS*  BOTANY 


arrangement,  see  all  sedges.  For  5-ranked  (which  is  one 
of  the  commonest),  see  apple,  cherry,  pear,  peach,  plum, 
poplar,  willow.  For  8-ranked,  see  holly,  osage  orange, 
some  willows.  More  complicated  arrangements  occur  in 
bulbs,  house  leeks,  and  other  condensed  plants.  The  buds 
or  "eyes"  on  a  potato  tuber,  which  is  an  underground  stem 
(why  .?),  show  a  spiral  arrangement  (Fig.  1 1 1). 
The  arrange^nent  of  leaves  on  the  stem  is 
known  as  phyllotaxy  (literally,  '*  leaf  arrange- 
ment ").  Make  out  the  phyllotaxy  on  six 
different  plants  nearest  the  schoolhouse  door. 
In  some  plants,  several  leaves  occur  at  one 
level,  being  arranged  in  a  circle  around  the 
stem.  Such  leaves  are  said  to  be  verticillate, 
or  whorled.  Leaves  arranged  in  this  way  are 
usually  narrow :  why  } 

Although  a  definite  arrangement  of  leaves 

is  the  rule  in  most  plants,   it   is  subject  to 

modification.     On    shoots    that    receive    the 

Fig.  III.  —       light  only  from  one  side  or  that  grow  in  dif- 

^Tthe^po^     ficult  positions,  the  arrangement  may  not  be 

TATo  Tuber,     definite,     Examine  shoots  that  grow  on  the 

w^ork  It  out       under  side  of  dense  tree  tops  or  in  other  par- 

on  a  fresh  *^  * 

long  tuber.        tially  lighted  positions. 


Suggestions.  —  55.  The  pupil  should  match  leaves  to  determine 
whether  any  two  are  alike.  Why  ?  Compare  leaves  from  the 
same  plant  in  size,  shape,  colour,  form  of  margin,  length  of  petiole, 
venation,  texture  (as  to  thickness  or  thinness),  stage  of  maturity, 
smoothness  or  hairiness.  56.  Let  the  pupil  take  an  average 
leaf  from  each  of  the  first  ten  different  kinds  of  plants  that 
he  meets  and  compare  them  as  to  the  above  points  (in  Exer- 
cise 55),  and  also  name  the  shapes.  Determine  how  the  various 
leaves  resemble  and  differ.  57.  Describe  the  stipules  of  rose, 
apple,  fig,  willow,  violet,  pea,  or  others.  58.  In  what  part  of 
the  world  are  parallel- veined  leaves  the  more  common  ?    59.   Do 


LEAVES— FORM  AND  POSITION  8$ 

you  know  of  parallel-veined  leaves  that  have  lobed  or  dentate  mar- 
gins ?  60.  What  becomes  of  dead  leaves  ?  61.  Why  is  there 
no  grass  or  other  undergrowth  under  pine  and  spruce  trees  ? 
62.  Name  several  leaves  that  are  useful  for  decorations.  Why 
are  they  useful  ?  63.  What  trees  in  your  vicinity  are  most 
esteemed  as  shade  trees  ?    What  is  the  character  of  their  foliage  ? 

64.  Why  are  the  internodes  so  long  in  water- sprouts  and  suckers  ? 

65.  How  do  foliage  characters  in  corn  or  sorghum  differ  when  the 
plants  are  grown  in  rows  or  broadcast  ?  Why  ?  66.  Why  may 
removal  of  half  the  plants  increase  the  yield  of  cotton  or  sugar- 
beets  or  lettuce  ?  67.  How  do  leaves  curl  when  they  wither  ? 
Do  different  leaves  behave  differently  in  this  respect?  68.  What 
kinds  of  leaves  do  you  know  to  be  eaten  by  insects  ?  By  cattle  ? 
By  horses  ?  What  kinds  are  used  for  human  food  ?  69.  How 
would  you  describe  the  shape  of  leaf  of  peach?  apple?  elm? 
hackberry?  maple?  sweet-gum?  corn?  wheat?  cotton?  hickory? 
cowpea?  strawberry?  chrysanthemum?  rose?  carnation?  70.  Are 
any  of  the  foregoing  leaves  compound  ?  How  do  you  describe  the 
shape  of  a  compound  leaf  ?  71.  How  many  sizes  of  leaves  do  you 
find  on  the  bush  or  tree  nearest  the  schoolroom  door  ?  72.  How 
many  colours  or  shades?  73.  How  many  lengths  of  petioles? 
74.   Bring  in  all  the  shapes  of  leaves  that  you  can  find. 


CHAPTER   XII 


LEAVES  — STRUCTURE  OR  ANATOMY 

Besides  the  framework,  or  system  of  veins  found  in 
blades  of  all  leaves,  there  is  a  soft  cellular  tissue  called 
mesophyll,  or  leaf  parenchyma,  and  an  epidermis  or  skin 
that  covers  the  entire  outside  part. 

Mesophyll.  —  The  mesophyll  is  not  all  alike  or  homoge- 
neous. The  upper  layer  is  composed  of  elongated  cells 
placed  perpendicular  to  the  surface  of  the  leaf.  These 
are  called  palisade  cells.     These  cells  are  usually  filled 

with  green  bod- 
ies called  chlo- 
rophyll grains. 
The  grain  con- 
tains a  great 
number  of  chlo- 
rophyll drops 
imbedded  in 
the  protoplasm. 
Below  the  pali- 
sade cells  is  the 


Fig.  113.  — Section  of  a  Leaf, showing  the  airspaces. 

Breathing- pore  or  stoma  at  a.    The  palisade  cells  which  chiefly 
conuin  the  chlorophyll  are  at  b.    Epidermal  cells  at  c. 


spongy  parenchyma,  composed  of  cells  more  or  less  spher- 
cal  in  shape,  irregularly  arranged,  and  provided  with  many 
intercellular  air  cavities  (Fig.  113).  In  leaves  of  some 
plants  exposed  to  strong  light  there  may  be  more  than  one 
layer  of  palisade  cells,  as  in  the  India-rubber  plant  and 
the  oleander.  Ivy  when  grown  in  bright  light  will  develop 
two  such  layers  of  cells,  but  in  shaded  places  it  may  be 

S6 


LEAVES—  STRUCTURE   OR  ANATOMY  8/ 

found  with  only  one.  Such  plants  as  iris  and  compass 
plant,  which  have  both  surfaces  of  the  leaf  equally  exposed 
to  sunlight,  usually  have  a  palisade  layer  beneath  each 
epidermis. 

Epidermis.  —  The  outer  or  epidermal  cells  of  leaves  do 
not  bear  chlorophyll,  but  are  usually  so  transparent  that 
the  green  mesophyll  can  be  seen  through  them.  They 
often  become  very  thick-walled,  and  are  in  most  plants 
devoid  of  all  protoplasm  except  a  thin  layer  lining  the 
walls,  the  cavities  being  filled  with  cell  sap.  This  sap  is 
sometimes  coloured,  as  in  the  under  epidermis  of  begonia 
leaves.  It  is  not  common  to  find  more  than  one  layer  of 
epidermal  cells  forming  each  surface  of  a  leaf.  The  epi- 
dermis serves  to  retain  moisture  in  the  leaf  and  as  a  general 
protective  covering.  In  desert  plants  the  epidermis,  as  a 
rule,  is  very  thick  and  has  a  dense  cuticle,  thereby  pre- 
venting loss  of  water. 

There  are  various  outgrowths  of  the  epidermis.  Hairs 
are  the  chief  of  these.  They  may  be  (i)  simple,  as  on 
primula,  geranium,  naegelia;  (2)  once  branched,  as  on  wall- 
flower; (3)  compound,  as  on  verbascum  or  mullein;  (4) 
disk-like,  as  on  shepherdia;  (5)  stellate,  or  star-shaped,  as 
in  certain  crucifers.  In  some  cases  the  hairs  are  glandular, 
as  in  Chinese  primrose  of  the  greenhouses  {^Primula 
Sinensis)  and  certain  hairs  of  pumpkin  flowers.  The  hairs 
often  protect  the  breathing  pores,  or  stomates,  from  dust 
and  water. 

Stomates  (sometimes  called  breathing -pores)  are  small 
openiftgs  or  pores  in  the  epidermis  of  leaves  and  soft  stems 
that  allow  the  passage  of  air  and  other  gases  and  vapourr, 
{stomate  or  stoma,  singular ;  stomates  or  stomata,  plural). 
They  are  placed  7iear  the  large  intercellular  spaces  of  the 
mesophyll,  usually  in  positions  least  affected   by   direct 


SS  BEGINNERS'  BOTANY 

sunlight.  Fig.  114  shows  the  structure.  There  are  two 
guard-cells  at  the  mouth  of  each  stomate,  which  may  in 
most  cases  open  or  close  the  passage  as  the  conditions 
of  the  atmosphere  may  require.     The  guard-cells  contain 

Fig.  114.  — Diagram  OF  Stomate  Fig.  115.  —  Stomate    of    Ivy, 

OF  Iris  (Oslerhout).  showing  compound  guard-cells. 

chlorophyll.  In  Fig.  1 1 5  is  shown  a  case  in  which  there 
are  compound  guard-cells,  that  of  ivy.  On  the  margins 
of  certain  leaves,  as  of  fuchsia,  impatiens,  cabbage,  are 
openings  known  as  water-pores. 

Stomates  are  very  numerous ^  as  will  be  seen  from  the  num- 
bers showing  the  pores  to  each  square  inch  of  leaf  surface : 

Lower  surface        Upper  surface 

Peony I3j790  None 

Holly 63,600  None 

Lilac 160,000  None 

Mistletoe 200  200 

Tradescantia 2,000  2,000 

Garden  Flag  (iris) iIjS72  ii>572 

The  arrangement  of  stomates  on  the  leaf  differs  with 

each  kind  of  plant.     Fig,  116  shows  stomates  and  also  the 

outlines  of  contiguous  epidermal  cells. 

The  function  or  work  of  the  stomates 

is  to  regulate  the  passage  of  gases  into 

and  out  of   the   plant.     The  directly 

active  organs  or  parts  are  guard-cells, 

^        ,      ^  on    either    side    the    opening.       One 

Fig.  116. —  Stomates  ^         ^ 

OF  GERANIUM  LEAF,      mcthod  of  Opening  is  as  follows :  The 


LEAVES—  STKUCTURE   OR  ANATOMY 


89 


P 


% 


thicker  walls  of  the  guard-cells  (Fig.  114)  absorb  water 
from  adjacent  cells,  these  thick  walls  buckle  or  bend  and 
part  from  one  another  at  their  middles  on  either  side  the 
opening,  causing  the  stomate  to  open,  when  the  air  gases 
may  be  taken  in  and  the  leaf  gases  may  pass  out.  When 
moisture  is  reduced  in  the  leaf  tissue,  the  guard-cells  part 
with  some  of  their  contents,  the  thick  walls 
straighten,  and  the  faces  of  the  two  opposite 
ones  come  together,  thus  closing  the  stomate 
and  preventing  any  water  vapour  from  pass- 
ing out.  When  a  leaf  is  actively  at  work 
making  new  organic  compounds,  the  stomates 
are  usually  open;  when  unfavourable  condi- 
tions arise,  they  are  usually  closed.  They 
also  commonly  close  at  night,  when  growth 
(or  the  utilizing  of  the  new  materials)  is  most 
likely  to  be  active.  It  is  sometimes  safer  to 
fumigate  greenhouses  and  window  gardens 
at  night,  for  the  noxious  vapours  are  less 
likely  to  enter  the  leaf.  Dust  may  clog  or 
cover  the  stomates.  Rains  benefit  plants 
by  washing  the  leaves  as  well  as  by  provid- 
ing moisture  to  the  roots. 

Lenticels.  —  On  the  young  woody  twigs 
of  many  plants  (marked  in  osiers,  cherry, 
birch)  there  are  small  corky  spots  or  eleva- 
tions known  as  lenticels  ( Fig.  117).  They  mark  the  loca- 
tion of  some  loose  cork  cells  that  function  as  stomates, 
for  greeji  shoots,  as  well  as  leaves,  take  in  and  discharge 
gases;  that  is,  soft  green  twigs  function  as  leaves.  Under 
some  of  these  twig  stomates,  corky  material  may  form 
and  the  opening  is  torn  and  enlarged:  the  lenticels  are 
successors  to  the  stomates.       The  stomates  lie  in  the  epi- 


FiG.  117.  —  Len- 
ticels  on 
Young  Shoot 
OF  Red  Osier 

(CORNUS). 


$6  BEClNNEJiS*  BOTANY 

dermis,  but  as  the  twig  ages  the  epidermis  perishes  and 
the  bark  becomes  the  external  layer.  Gases  continue  to 
pass  in  and  out  through  the  lenticels,  until  the  branch  be- 
comes heavily  covered  with  thick,  corky  bark.  With  the 
growth  of  the  twig,  the  lenticel  scars  enlarge  lengthwise 
or  crosswise  or  assume  other  shapes,  often  becoming  char- 
acteristic markings. 

Fibro-vascular  Bundles.  —  We  have  studied  the  fibro- 
vascular  bundles  of  stems  (Chap.  X).  These  stem  bun- 
dles continue  into  the  leaves^  ramifying  into  the  veins, 
carrying  the  soil  water  inwards  and  bringing,  by  diffusion, 
the  elaborated  food  out  through  the  sieve-cells.  Cut 
across  a  petiole  and  notice  the  hard  spots  or  areas  in  it ; 
strip  these  parts  lengthwise  of  the  petiole.    What  are  they } 

Fall  of  the  Leaf.  —  In  most  common  deciduous  plants, 
when  the  season's  work  for  the  leaf  is  ended,  the  nutritious 
matter  may  be  withdrawn,  and  a  layer  of  corky  cells  is  com- 
pleted over  the  surface  of  the  stem  where  the  leaf  is  attached. 
The  leaf  soon  falls.  It  often  falls  even  before  it  is  killed 
by  frost.  Deciduous  leaves  begin  to  show  the  surface  line 
of  articulation  in  the  early  growing  season.  This  articula- 
tion may  be  observed  at  any  time  during  the  summer.  The 
area  of  the  twig  once;  covered  by  the  petioles  is  called  the 
leaf-scar  after  the  leaf  has  fallen.  In  Chap.  XV  are  shown 
a  number  of  leaf-scars.  In  the  plane  tree  (sycamore  or 
buttonwood),  the  leaf-scar  is  in  the  form  of  a  ring  surround- 
ing the  bud,  for  the  bud  is  covered  by  the  hollowed  end  of. 
the  petiole ;  the  leaf  of  sumac  is  similar.  Examine  with  a 
hand  lens  leaf-scars  of  several  woody  plants.  Note  the 
number  of  bundle-scars  in  each  leaf-scar.  Sections  may 
be  cut  through  a  leaf-scar  and  examined  with  the  micro- 
scope. Note  the  character  of  cells  that  cover  the  leaf- 
scar  surface. 


LEAVES--- STRUCTURE    OR  ANATOMY  9I 

Suggestions.  —  To  study  epidermal  hairs :  75.  For  this  study, 
use  the  leaves  of  any  hairy  or  woolly  plant.  A  good  hand  lens  will 
reveal  the  identity  of  many  of  the  coarser  hairs.  A  dissecting  micro- 
scope will  show  them  still  better.  For  the  study  of  the  cell  structure, 
a  compound  microscope  is  necessary.  Cross-sections  may  be  made 
so  as  to  bring  hairs  on  the  edge  of  the  sections;  or  in  some 
cases  the  hairs  may  be  peeled  or  scraped  from  the  epidermis  and 
placed  in  water  on  a  slide.  Make  sketches  of  the  different  kinds  of 
hairs.  76.  It  is  good  practice  for  the  pupil  to  describe  leaves  in 
respect  to  their  covering  :  Are  they  smooth  on  both  surfaces  ?  Or 
hairy?  Woolly?  Thickly  or  thinly  hairy?  Hairs  long  or  short? 
Standing  straight  out  or  lying  close  to  the  surface  of  the  leaf? 
Simple  or  branched?  Attached  to  the  veins  or  to  the  plane  surface? 
Colour?  Most  abundant  on  young  leaves  or  old?  77-  Place  a 
hairy  or  woolly  leaf  under  water.  Does  the  hairy  surface  appear 
silvery  ?  Why  ?  Other  questions :  78.  Why  is  it  good  practice 
to  wash  the  leaves  of  house  plants?  79.  Describe  the  leaf-scars 
on  six  kinds  of  plants  :  size,  shape,  colour,  position  with  reference 
to  the  bud,  bundle-scars.  80.  Do  you  find  leaf-scars  on  mono- 
cotyledonous  plants  —  corn,  cereal  grains,  lilies,  canna,  banana, 
palm,  bamboo,  green  brier?  81.  Note  the  table  on  page  88. 
Can  you  suggest  a  reason  why  there  are  equal  numbers  of  stomates 
on  both  surfaces  of  leaves  of  tradescantia  and  flag,  and  none  on 
upper  surface  of  other  leaves  ?  Suppose  you  pick  a  leaf  of  lilac 
(or  some  larger  leaf),  seal  the  petiole  with  wax  and  then  rub 
the  under  surface  with  vaseline  ;  on  another  leaf  apply  the  vaseline 
to  the  upper  surface  ;  which  leaf  withers  first,  and  why?  Make  a 
similar  experiment  with  iris  or  blue  flag.  82.  Why  do  leaves  and 
shoots  of  house  plants  turn  towards  the  light?  What  happens 
when  the  plants  are  turned  around  ?  83.  Note  position  of  leaves 
of  beans,  clover,  oxalis,  alfalfa,  locust,  at  night 


CHAPTER   XIII 
LEAVES  — FUNCTION  OR  WORK 

We  have  discussed  (in  Chap.  VIII)  the  work  or  function 
of  roots  and  also  (in  Chap.  X)  the  function  of  stems. 
We  are  now  ready  to  complete  the  view  of  the  main  vital 
activities  of  plants  by  considering  the  function  of  the 
green  parts  (leaves  and  young  shoots). 

Sources  of  Food.  —  The  ordinary  green  plant  has  but  two 
sources  from  which  to  secure  food,  *—  the  air  and  the  soil. 
When  a  plant  is  thoroughly  dried  in  an  oven,  the  water 
passes  off ;  this  water  came  from  the  soil.  The  remaining 
part  is  called  the  dry  substance  or  dry  matter.  If  the  dry 
matter  is  burned  in  an  ordinary  fire,  only  the  ash  remains; 
this  ash  came  from  the  soil.  The  part  that  passed  off  as 
gas  in  the  burning  cojttained  the  elements  that  came  from 
the  air ;  it  also  contained  some  of  those  that  came  from 
the  soil  —  all  those  (as  nitrogen,  hydrogen,  chlorine)  that 
are  transformed  into  gases  by  the  heat  of  a  common  fire. 
The  part  that  comes  from  the  soil  (the  ash)  is  small  in 
amount,  being  considerably  less  than  lo  per  cent  and 
sometimes  less  than  i  per  cent.  Water  is  the  most 
abundant  single  constituent  or  substance  of  plants.  In  a 
corn  plant  of  the  roasting-ear  stage,  about  80  per  cent  of 
the  substance  is  water.  A  fresh  turnip  is  over  90  per 
cent  water.  Fresh  wood  of  the  apple  tree  contains  about 
45  per  cent  of  water. 

Carbon.  —  Carbon  enters  abundantly  into  the  composition 
of  all  plants.     Note  what  happens  when  a  plant  is  burned 

92 


LEAVES— FUNCTION  OR    WORK  93 

without  free  access  of  air,  or  smothered,  as  in  a  charcoal 
pit.  A  mass  of  charcoal  remains,  almost  as  large  as  the 
body  of  the  plant.  Charcoal  is  almost  pure  carbon,  the  ash 
present  being  so  small  in  proportion  to  the  large  amount 
of  carbon  that  we  look  on  the  ash  as  an  impurity.  Nearly 
half  of  the  dry  substance  of  a  tree  is  carbon.  Carbon 
goes  off  as  a  gas  when  the  plant  is  bii7'ned  in  air.  It  does 
not  go  off  alone,  but  in  combination  with  oxygen  in  the 
form  of  carbon  dioxide  gas,  COo. 

The  green  plant  secures  its  carbon  from  the  air.  In 
other  words,  much  of  the  solid  ynatter  of  the  plant  comes 
from  one  of  the  gases  of  the  air.  By  volume,  carbon  dioxide 
forms  only  a  small  fraction  of  1  per  cent,  of  the  air. 
It  would  be  very  disastrous  to  animal  life,  however,  if  this 
percentage  were  much  increased,  for  it  excludes  the  life- 
giving  oxygen.  Carbon  dioxide  is  often  called  ''foul  gas." 
It  may  accumulate  in  old  wells,  and  an  experienced  person 
will  not  descend  into  such  wells  until  they  have  been  tested 
with  a  torch.  If  the  air  in  the  well  will  not  support  com- 
bustion,— that  is,  if  the  torch  is  extinguished, — it  usually 
means  that  carbon  dioxide  has  drained  into  the  place.  The 
air  of  a  closed  schoolroom  often  contains  far  too  much  of 
this  gas,  along  with  little  solid  particles  of  waste  matters. 
Carbon  dioxide  is  often  known  as  carbonic  acid  gas. 

Appropriation  of  the  Carbon. — The  carbon  dioxide  of  the 
air  readily  diffuses  itself  into  the  leaves  and  other  green 
parts  of  the  plant.  The  leaf  is  delicate  in  texture,  and  when 
very  young  the  air  can  diffuse  directly  into  the  tissues. 
The  stomates,  however,  are  the  special  inlets  adapted  for 
the  admission  of  gases  into  the  leaves  and  other  green 
parts.  Through  these  stomates,  or  diffusion-pores,  the  out- 
side air  enters  into  the  air-spaces  of  the  plant,  and  is  finally 
absorbed  by  the  little  cells  containing  the  Hving  matter. 


94 


BEGINNERS ' .  BOTA  NY 


Chlorohyll  ("leaf  green")  is  the  agent  that  secures 
the  energy  by  means  of  which  carbon  dioxide  is  utilized. 
This  material  is  contained  in  the  leaf  cells  in  the  form  of 
grains  (p.  86)  ;  the  grains  themselves  are  protoplasm,  only 
the  colouring  matter  being  chlorophyll.  The  chlorophyll 
bodies  or  grains  are  often  most  abundant  near  the  upper 
surface  of  the  leaf,  where  they  can  secure  the  greatest 
amount  of  light.  Without  this  green  colouring  matter, 
there  would  be  no  reason  for  the  large  flat  surfaces  which 
the  leaves  possess,  and  no  reason  for  the  fact  that  the 
leaves  are  borne  most  abundantly  at  the  ends  of  branches, 
where  the  light  is  most  available.  Plants  with  coloured 
leaves  as  coleus,  have  chlorophyll,  but  it  is  masked  by 
other  colouring  matter.  This  other  colouring  matter  is 
usually  soluble  in  hot  water:  boil  a  coleus  leaf  and  notice 
that  it  becomes  green  and  the  water  becomes  coloured. 

Plants  groivn  in  darkness  are  yellow  and  slender,  and 
do  not  reach  maturity.  Compare  the  potato  sprouts  that 
have  grown  from  a  tuber  lying  in  a  dark  cellar  with 
those  that  have  grown  normally  in  the  bright  light. 
The  shoots  have  become  slender,  and  are  devoid  of  chloro- 
phyll; and  when  the  food  that  is  stored  in  the  tuber  is 
exhausted  these  shoots  will  have  lived  useless  lives.  A 
plant  that  has  been  grown  in  darkness  from  the  seed  will 
soon  die,  although  for  a  time  the  little  seedling  will  grow 
very  tall  and  slender.  Why  ?  Light  favours  the  production 
of  chlorophyll,  and  the  chlorophyll  is  the  agent  in  the  mak- 
ing of  the  organic  carbon  compounds.  Sometimes  chloro- 
phyll is  found  in  buds  and  seeds,  but  in  most  cases  these 
places  are  not  perfectly  dark.  Notice  how  potato  tubers  de- 
velop chlorophyll,  or  become  green,  when  exposed  to  light. 

Photosynthesis. — Carbon  dioxide  diffuses  into  the  leaf; 
during  sunlight  it  is  used,  and  oxygen  is  given  off.     How 


LEAVES-^FUNCTION   OB    WOBK  95 

the  carbon  dioxide  which  is  thus  absorbed  may  be  used  in 
making  an  organic  food  is  a  complex  question,  and  need  not 
be  studied  here;  but  it  may  be  stated  that  carbon  dioxide 
and  water  are  the  constituents.  Complex  compounds  are 
built  up  out  of  simpler  ones. 

Chlorophyll  absorbs  certain  light  rays,  and  the  energy 
thus  directly  or  indirectly  obtained  is  used  by  the  living 
matter  in  uniting  the  carbon  dioxide  absorbed  from  the  air 
with  some  of  the  water  brought  up  from  the  roots.  The 
idtimate  result  usually  is  starch.  The  process  is  obscure, 
but  sugar  is  generally  one  step;  and  our  first  definite 
knowledge  of  the  product  begins  when  starch  is  deposited 
in  the  leaves.  The  process  of  using  the  carbon  dioxide  of 
the  air  has  been  known  as  carbon  assimilation,  but  the 
term  now  most  used  is  photosynthesis  (from  two  Greek 
words  meaning  light  and  placing  together.) 

Starch  and  Sugar. — All  starch  is  composed  of  carbon, 
hydrogen,  and  oxygen  {CqH.iqOq)„.  The  sugars  and  the 
substance  of  cell  walls  are  very  similar  to  it  in  composition. 
All  these  substances  are  called  carbohydrates.  In  making 
fruit  sugar  from  the  carbon  and  oxygen  of  carbon  dioxide 
and  from  the  hydrogen  and  oxygen  of  the  water,  there 
is  a  surplus  of  oxygen  (6  parts  COg  +  6  parts  H.O 
==  CeH^g^e  +  6  Oo).  It  is  this  oxygen  that  is  given  off 
into  the  air  during  sunlight. 

Digestion. — Starch  is  in  the  form  of  insoluble  granules. 
When  such  food  material  is  carried  from  one  part  of  the 
plant  to  another  for  purposes  of  growth  or  storage,  it  is 
made  soluble  before  it  can  be  transported.  "When  this 
starchy  material  is  transferred  from  place  to  place,  it  is 
usually  changed  into  sugar  by  the  action  of  a  diastase. 
This  is  a  process  of  digestion.  It  is  much  like  the  change 
of  starchy  foodstuffs  to  sugary  foods  effected  by  the  saliva. 


96 


BEGINNERS'  BOTANY 


Distribution  of  the  Digested  Food.  —  After  being  changed 
to  the  sohible  form,  tJiis  luatcrial  is  ready  to  be  used  in 
growth,  either  in  tlie  leaf,  in  the  stem,  or  in  the  roots. 
With  other  more  complex  products  it  is  then  distributed 
throughojit    all   the  growing  parts 
.  of  the  plant ;   and   when    passing 

'  ;  down  to  the  root,  it  seems  to  pass 

more  readily  through  the  inner 
bark,  in  plants  which  have  a  defi- 
nite bark.  This  gradual  down- 
ward diffusion  through  the  inner 
bark  of  materials  suitable  for 
growth  is  the  process  referred  to 
when  the  **  descent  of  sap  "  is  men- 
tioned. Starch  and  other  products 
are  often  stored  in  one  grozving 
season  to  be  nsed  in  the  next  sea- 
son. If  a  tree  is  constricted  or 
strangled  by  a  wire  around  its 
trunk  (Fig.  ii8),  the  digested  food 
cannot  readily  pass  down  and  it  is  stored  above  the  girdle, 
causing  an  enlargement. 

Assimilation. —  TJie  food  from  the  air  and  that  from  the 
soil  unite  in  the  living  tissues.  The  *'sap"  that  passes 
upwards  from  the  roots  in  the  growing  season  is  made  up 
largely  of  the  soil  water  and  the  salts  which  have  been 
absorbed  in  the  diluted  solutions  (p.  ^'jy  This  upward- 
moving  water  is  conducted  largely  through  certain  tubular 
canals  of  the  young  luood.  These  cells  are  never  continu- 
ous tubes  from  root  to  leaf;  but  the  water  passes  readily 
from  one  cell  or  canal  to  another  in  its  upward  course. 

The  upward-moving  water  gradually  passes  to  the  grow- 
ing parts,  and  everywhere  in  the  living  tissues,  it  is,  of 


Fig,  I i8.  — Trunk  Girdled 
BY  A  Wire.    See  Fig.  85. 


LEAVES—  FUNCTION  OR   WORK  97 

course,  in  the  most  intimate  contact  with  the  soluble  carbo- 
hydrates and  products  of  photosynthesis.  In  the  build- 
ing up  or  reconstructive  and  other  processes  it  is  therefore 
available.  We  may  properly  conceive  of  certain  of  the 
simpler  organic  molecules  as  passing  through  a  series  of 
changes,  gradually  increasing  in  complexity.  There  will 
be  formed  substances  containing  nitrogen  in  addition  to 
carbon,  hydrogen,  and  oxygen.  Others  will  contain  also 
sulphur  and  phosphorus,  and  the  various  processes  may 
be  thought  of  as  culminating  in  protoplasm.  Protoplasm 
is  the  living  matter  in  pla7its.  It  is  in  the  cells,  and  is 
usually  semifluid.  Starch  is  not  living  matter.  The" 
complex  process  of  building  up  the  protoplasm  is  called 
assimilation. 

Respiration.  —  Plants  need  oxygen  for  respiration^  as 
anifnals  do.  We  have  seen  that  plants  need  the  carbon 
dioxide  of  the  air.  To  most  plants  the  nitrogen  of  the  air 
is  inert,  and  serves  only  to  dilute  the  other  elements ;  but 
the  oxygen  is  necessary  for  all  life.  We  know  that  all 
animals  need  this  oxygen  in  order  to  breathe  or  respire. 
In  fact,  they  have  become  accustomed  to  it  in  just  the 
proportions  found  in  the  air;  and  this  is  now  best  for 
them.  When  animals  breathe  the  air  once,  they  make  it 
foul,  because  they  use  some  of  the  oxygen  and  give  off 
carbon  dioxide.  Likewise,  all  living  parts  of  the  plant  must 
have  a  constant  supply  of  oxygen.  Roots  also  need  it,  for 
they  respire.  Air  goes  in  and  out  of  the  soil  by  diffusion, 
and  as  the  soil  is  heated  and  cooled,  causing  the  air  to 
expand  and  contract. 

The  oxygen  passes  into  the  air-spaces  and  is  absorbed 
by  the  moist  cell  membranes.  In  the  living  cells  it  makes 
possible  the  formation  of  simpler  compounds  by  which 
energy  is  released.      This  energy   enables   the   plant  to 


98  BEGINNERS'  BOTANY 

work  and  grow,  and  the  final  products  of  this  action  are 
carbon  dioxide  and  water.  As  a  result  of  the  use  of  this 
oxygen  by  night  and  by  day,  plants  give  off  carbon  dioxide. 
Plants  respire;  hut  since  they  are  stationary,  and  more  or 
less  inactive,  they  do  not  need  so  much  oxygen  as  animals  do, 
and  they  do  not  give  off  so  much  carbon  dioxide.  A  few 
plants  in  a  sleeping  room  need  not  disturb  one  more  than  a 
family  of  mice.  It  should  be  noted,  however,  that  germina- 
ting seeds  respire  vigorously,  hence  they  consume  much  oxy- 
gen; and  opening  buds  and  flowers  are  likewise  active. 

Transpiration.  —  Much  more  water  is  absorbed  by  the 
roots  than  is  used  in  growth,  attd  this  surplus  water  passes 
from  the  leaves  into  the  atmosphere  by  an  evaporation  process 
known  as  transpiration.  Transpiration  takes  place  more 
abundantly  from  the  under  surfaces  of  leaves,  and  through 
the  pores  or  stomates.  A  sunflower  plant  of  the  height 
of  a  man,  during  an  active  period  of  growth,  gives  off  a 
quart  of  water  per  day.  A  large  oak  tree  may  transpire 
150  gallons  per  day  during  the  summer.  For  every  ounce 
of  dry  matter  produced,  it  is  estimated  that  15  to  25  pounds 
of  water  usually  passes  through  the  plant. 

When  the  roots  fail  to  supply  to  the  plant  sttfficient  water 
to  equalize  that  transpired  by  the  leaves,  the  plant  wilts. 
Transpiration  from  the  leaves  and  delicate  shoots  is  in- 
creased by  all  the  conditions  which  increase  evapora- 
tion, such  as  higher  temperature,  dry  air,  or  wind.  The 
stomata  open  and  close,  tending  to  regulate  transpiration 
as  the  varying  conditions  of  the  atmosphere  affect  the 
moisture  content  of  the  plant.  However,  in  periods  of 
drought  or  of  very  hot  weather,  and  especially  during  a 
hot  wind,  the  closing  of  these  stomates  cannot  sufficiently 
prevent  evaporation.  The  roots  may  be  very  active  and 
yet  fail  to  absorb  sufficient  moisture  to  equalize  that  given 


LEAVES -- FUNCTION  OR    WORK  99 

off  by  the  leaves.  The  plant  shows  the  effect  (how  ?). 
On  a  hot  dry  day,  note  how  the  leaves  of  corn  '*  roll "  tow- 
ards afternoon.  Note  how  fresh  and  vigorous  the  same 
leaves  appear  early  the  following  morning.  Any  injury  to 
the  roots,  such  as  a  bruise,  or  exposure  to  heat,  drought,  or 
cold  may  cause  the  plant  to  wilt. 

Water  is  forced  up  by  root  pressure  or  sap  pressure. 
(Exercise  99.)  Some  of  the  dew  on  the  grass  in  the  morn- 
ing may  be  the  water  forced  up  by  the  roots ;  some  of  it  is 
the  condensed  vapour  of  the  air. 

The  wilting  of  a  plant  is  due  to  the  loss  of  water  from 
the  cells.  The  cell  walls  are  soft,  and  collapse.  A  toy 
balloon  will  not  stand  alone  until  it  is  inflated  with  air 
or  liquid.  In  the  woody  parts  of  the  plant  the  cell  walls 
may  be  stiff  enough  to  support  themselves,  even  though 
the  cell  is  empty.  Measure  the  contraction  due  to  wilt- 
ing and  drying  by  tracing  a  fresh  leaf  on  page  of  note- 
book, and  then  tracing  the  same  leaf  after  it  has  been 
dried  between  papers.  The  softer  the  leaf,  the  greater 
will  be  the  contraction. 

Storage.  —  We  have  said  that  starch  may  be  stored  in 
tv/igs  to  be  used  the  following  year.  The  very  early  flowers 
on  fruit  trees,  especially  those  that  come  before  the  leaves, 
and  those  that  come  from  bulbs,  as  crocuses  and  tulips, 
are  supported  by  the  starch  or  other  food  that  was  organ- 
ized the  year  before.  Some  plants  have  very  special  stor- 
age reservoirs,  as  the  potato,  in  this  case  being  a  thickened 
stem  although  growing  underground.  (Why  a  thickened 
stem.!*  p.  84.)  It  is  well  to  make  the  starch  test  on  winter 
twigs  and  on  all  kinds  of  thickened  parts,  as  tubers  and  bulbs. 

Carnivorous  Plants.  — Certain  plants  capture  insects  and 
other  very  small  animals  and  utilize  them  to  some  extent 
as  food.     Such  are  the  sundew,  which  has  on  the  leaves 


lOO 


BE  GINNEKS'   B  O  TAN  Y 


sticky  hairs  that  close  over  :he  insect;  the  Venus 's  fly-trap 
of  the  Southern  States,  in  which  the  halves  of  the  leaves 

close  over  the  prey  like  the  jaws 
of  a  steel  trap ;  and  the  various 
kinds  of  pitcher  plants  that  col- 
lect insects  and  other  organic 
matter  in  deep,  water-filled,  flask- 
like leaf  pouches  (Fig.  1 19). 

The  sundew  and  the  Venus 's 
fly-trap  are  sensitive  to  contact. 
Other  plants  are  sensitive  to  the 
touch  without  being  insectivo- 
rous. The  common  cultivated 
sensitive  plant  is  an  example. 
This  is  readily  grown  from  seeds 
(sold  by  seedsmen)  in  a  warm 
place.  Related  wild  plants  in 
the  south  are  sensitive.  The 
utility  of  this  sensitiveness  is  not  understood. 

Parts  that  Simulate  Leaves.  —  We  have  learned  that 
leaves  are  endlessly  modified  to  suit  the  conditions  in  which 
the  plant  is  placed.  The  most  marked  modifications  are  in 
adaptation  to  light.  On  the  other  hand,  other  organs  often 
perform  the  fmtctions  of  leaves.  Green  shoots  function  as 
leaves.  These  shoots  may  look  like  leaves,  in  which  case 
they  are  called  cladophylla.  The  foliage  of  common 
asparagus  is  made  up  of  fine  branches :  the  real  morpho- 
logical leaves  are  the  minute  dry  functionless  scales  at  the 
bases  of  these  branchlets.  (What  reason  is  there  for  calling 
them  leaves!*)  The  broad  **  leaves"  of  the  florist's  smilax 
are  cladophylla.  Where  are  the  leaves  on  this  plant }  In 
most  of  the  cacti,  the  entire  plant  body  performs  the  func- 
tions of  leaves  until  the  parts  become  cork-bound. 


Fig.   119. —The    Common 
Pitcher  Plant  {Sarracenia 

purpurea)  showingr  the  tubular 
leaves  and  the  odd,  longp-stalked 
flowers. 


LEAVES—  FUNCTION  OR    WORK 


lOI 


Leaves  are  sometimes  modified  to  perform  other  functions 
than  the  vital  processes:  they  may  be  tendrils,  as  the 
terminal  leaflets  of  pea  and  sweet  pea;  or  spines,  as  in 
barberry.  Not  all  spines  and  thorns,  however,  represent 
modified  leaves:  some  of  them  (as  of  hawthorns,  osage 
orange,  honey  locust)  are  branches. 

Suggestions. — To  test  for  chlorophyll.  84.  Purchase  about  a 
gill  of  wood  alcohol.  Secure  a  leaf  of  geranium,  clover,  or  other 
plant  that  has  been  exposed  to  sunlight  for  a  few  hours,  and,  after 
dipping  it  for  a  minute  in  boiling  water,  put  it  in  a  white  cup  with 
sufficient  alcohol  to  cover.  Place  the  cup  in  a  shallow  pan  of 
hot  water  on  the  stove  where  it  is  not  hot  enough  for  the  alcohol 
to  take  fire.  After  a  time  the  chlorophyll  is  dissolved  by  the 
alcohol  which  has  become  an  intense  green.  Save  this  leaf  for 
the  starch  experiment  (Exercise  85).  Without  chlorophyll,  the 
plant  cannot  appropriate  the  carbon  dioxide  of  the  air.  Starch 
and  photosynthesis.  85-  Starch  is  present  in  the  green  leaves 
which  have  been  exposed  to  sunlight;  but  in  the  dark  no  starch 
can  be  formed  from  carbon  dioxide.  Apply  iodine  to  the  leaf  from 
which  the  chlorophyll  was  dissolved  in  the  previous  experiment. 
Note  that  the  leaf  is  coloured  purplish-brown  throughout.  The  leaf 
contains  starch.  86-  Se- 
cure a  leaf  from  a  plant 
which  has  been  in  the 
dark  for  about  two  days. 
Dissolve  the  chlorophyll  as 
before,  and  attempt  to  stain 
this  leaf  with  iodine.  No 
purplish-brown  colour  is  pro- 
duced. This  shows  that 
the  starch  manufactured  in 
the  leaf  may  be  entirely 
removed  during  darkness. 
87.  Secure  a  plant  which 
has  been  kept  in  darkness 
for  twenty-four  hours  or 
more.  Split  a  small  cork 
and  pin  the  two  halves  on  opposite  sides  of  one  of  the  leaves,  as 
shown  in  Fig.  120.  Place  the  plant  in  the  sunlight  again.  After 
a  morning  of  bright  sunshine  dissolve  the  chlorophyll  in  this  leaf 
with  alcohol;  then  stain  the  leaf  with  the  iodine.  Notice  that  the 
leaf  is  stained  deeply  except  where  the  cork  was;  there  sunlight  and 
carbon  dioxide  were  excluded,  Fig.  121.     There  is  no  starch  in  the 


Fig.  I20.  — Exclud- 
ing Light  and 
CO2  FROM  Part 
OF  A  Leaf. 


Fig.  121.— The 
Result. 


I02 


BEGINNERS'  BOTANY 


covered  area.  88.  Plants  or  parts  of  plants  that  have  developed 
no  chlorophyll  can  form  no  starch.  Secure  a  variegated  leaf  of 
coleus,  ribbon  grass,  geranium,  or  of  any  plant  showing  both  white 
and  green  areas.  On  a  day  of  bright  sunshine,  test  one  of  these 
leaves  by  the  alcohol  and  iodine  method  for  the  presence  of  starch. 
Observe  that  the  parts  devoid  of  green  colour  have  formed  no 
starch.     However,  after  starch  has  once  been  formed  in  the  leaves, 


it  may  be 
to  be  again 
the    living 


changed  into  soluble  substances  and  removed, 
converted  into  starch  in  certain  other  parts  of 
tissues.  To  test  the  gnmig  off  of  oxygen  by  day. 
89.  Make  the  experiment  illus- 
trated in  Fig.  12  2.  Under  a  fun- 
nel in  a  deep  glass  jar  containing 
fresh  spring  or  stream  water  place 
fresh  pieces  of  the  common 
waterweed  elodea  (or  anacharis). 
Have  the  funnel  considerably 
smaller  than  the  vessel,  and  sup- 
port the  funnel  well  up  from  the 
bottom  so  that  the  plant  can  more 
readily  get  all  the  carbon  dioxide 
available  in  the  water.  Why  would 
boiled  water  be  undesirable  in  this 
experiment?  For  a  home-made 
glass  funnel,  crack  the  bottom  off 
a  narrow-necked  bottle  by  press- 
ing a  red-hot  poker  or  iron  rod 
against  it  and  leading  the  crack 
around  the  bottle.  Invert  a  test- 
tube  over  the  stem  of  the  fun- 
nel. In  sunlight  bubbles  of 
oxygen  will  arise  and  collect  in 
the  test-tube.  If  a  sufficient 
quantity  of  oxygen  has  collected, 
a  lighted  taper  inserted  in  the 
tube  will  glow  with  a  brighter  flame,  showing  the  presence  of 
oxygen  in  greater  quantity  than  in  the  air.  Shade  the  vessel. 
Are  bubbles  given  off?  For  many  reasons  it  is  impracticable 
to  continue  this  experiment  longer  than  a  few  hours.  90.  A 
simpler  experiment  may  be  made  if  one  of  the  waterweeds 
Cabomba  (water-lily  family)  is  available.  Tie  a  imniber  of  branches 
together  so  that  the  basal  ends  shall  make  a  smdll  bundle.  Place 
these  in  a  large  vessel  of  spring  water,  and  insert  a  test-tube  of 
water  as  before  over  the  bundle.  The  bubbles  will  arise  from  the 
cut  surfaces.  Observe  the  bubbles  on  pond  scum  and  water- 
weeds  on  a  bright  day.      To  illustrate  the  results  of  respiration 


Fig.  122.  — To  show  the  Escape 
OF  Oxygen. 


LEAVES— FUNCTION  OR    WORK 


103 


Fig.  123.  —  To  ILLUS- 
TRATE A  Product 
OF  Respiration. 


Fig.  124.  —  Respira- 
tion OF  Thick 
Roots. 


(CO2).    91.  In  a  jar  of  germinating  seeds  (Fig.  123)  place  carefully 
a  small  dish  of  limewater  and  cover  tightly.     Put  a  similar  dish  in 

another  jar  of  about   the 

same  air  space.    After  a  few 

hours  compare  the  cloudi- 
ness or  precipitate  in  the 

two  vessels  of  limewater. 

92.    Or,   place    a  growing 

plant   in  a   deep   covered 

jar   away   from   the   Hght, 

and. after  a  few  hours  in- 
sert a   lighted   candle   or 

splinter.     93.  Or,  perform 

a  similar  experiment  with 

fresh    roots    of   beets    or 

turnips    (Fig.     124)    from 

which  the  leaves  are  mostly 

removed.  In  this  case, 
the  jar  need  not  be  kept  dark ;  why  ? 
To  test  transpiration.  94.  Cut  a  succulent 
shoot  of  any  plant,  thrust  the  end  of  it  through  a  hole  in  a  cork, 
and  stand  it  in  a  small  bottle  of  water.  Invert  over  this  a  fruit 
jar,  and  observe 
that  a  mist  soon 
accumulates  on 
the  inside  of  the 
glass.  In  time 
drops  of  water 
form.  95.  The  ex- 
periment may  be 
varied  as  shown  in 
Fig.  125.  96.  Or, 
invert  the  fruit 
jar  over  an  entire 
plant,  as  shown  in 
Fig.  126,  taking 
care  to  cover  the 
soil  with  oiled 
paper  or  rubber 
cloth  to  prevent 
evaporation  from 
the  soil.  97.  The 
test  may  also  be 
made  by  placing 
the  pot,  properly 
protected,  on  bal-  Fig.  121;. —To  illusprate  Transpiration, 


I04 


BEGINNERS'  BOTANY 


ances,  and  the  loss  of  weight  will  be  noticed  (Fig.  127).  98.  Cut 
a  winter  twig,  seal  the  severed  end  with  wax,  and  allow  the  twig 
to  lie  several  days.  It  shrivels.  There  must  be  some  upward 
movement  of  water  even  in  winter,  else  plants  would  shrivel 
and  die.  99.  To  illustrate  sap  pressure. 
The  upward  movement  of  sap  water  often 
takes  place  under  considerable  force.  The 
cause  of  this  force,  known  as  root  pressure^ 
is  not  well  understood.  The  pressure  varies 
with  different  plants  and  under  different 
conditions.  To  illustrate : 
cut  off  a  strong-growing  ^:;^^ 

small  plant  near 
the  ground.  By 
means  of  a  bit  of 
rubber  tube  attach 
a  glass  tube  with 
a  bore  of  approxi- 
mately the  diame- 
ter of  the  stem. 
Pour  in  a  little 
water.  Observe 
the  rise  of  the 
water  due  to  the 
pressure  from  be- 
low (Fig  128).  Some  plants  yield  a  large 
amount  of  water  under  a  pressure  sufficient 
to  raise  a  column  several  feet ;  others  force 
out  Httle,  but  under  consider- 
able pressure  (less  easily  de- 
monstrated). The  vital  pro- 
cesses {i.e.,  the  life  processes). 
100.  The  pupil 
having  studied 
roots,  stems, 
and  leaves, 
should  now 
be  able  to  de- 
scribe the  main 
vital  functions 
of  plants  :  what 
is  the  root  func- 
tion? stem  function?  leaf  function?  101.  What 
is  meant  by  the  "sap"?  102.  Where  and  how 
does  the  plant  secure  its  water?  oxygen?  car-  yig.  128.  —To  snov; 
bonf    hydrogen i    nitrogcMi  ?    sulpWur  .^    potassium^  Sap  PREiJSURE. 


Fig.  126.  —  To  illustrate 
Transpiration. 


ITG.  127  —  Loss  OF  Water. 


LEAVES— FUNCTION  OR    WORK 


los 


.alcium?  iron?  phosphorus?  103.  Where  is  all  the  starch  in  the 
world  made?  What  does  a  starch-factory  establishment  do? 
Where  are  the  real  starch  factories  ?  104.  In 
what  part  of  the  twenty-four  hours  do 
plants  grow  most  rapidly  in  length?  When 
is  food  formed  and  stored  most  rapidly? 
105.  Why  does  corn  or  cotton  turn  yellow 
in  a  long  rainy  spell?  106.  If  stubble, 
corn  stalks,  or  cotton  stalks  are  burned 
in  the  field,  is  as  much  plant-food  returned 
to  the  soil  as  when  they  are  ploughed 
under?  107.  What  process  of  plants  is 
roughly  analogous  to  perspiration  of  ani- 
mals? 108.  What  part  of  the  organic 
world  uses  raw  mineral  for  food  ?  109.  Why 
is  earth  banked  over  celery  to  blanch  it? 
110.  Is  the  amount  of  water  transpired 
equal  to  the  amount  absorbed?  HI.  Give 
some  reasons  why  plants  very  close  to  a 
house  may  not  thrive  or  may  even  die. 
112.  Why  are  fruit-trees  pruned  or  thinned 
out  as  in  Fig.  129?  Proper  balance  be- 
tween fop  and  roof,  113.  We  have  learned 
that  the  leaf  parts  and  the  root  parts  work 
together.  They  may  be  said  to  balance 
each  other  in  activities,  the  root  supplying  pjQ^  ^^^  _  p^^  Apple 
the  top  and  the  top  supplying  the  root  tree,  with  suggestions 
(how?).  If  half  the  roots  were  cut  from  as  to  pruning  when  it 
a  tree,  we  should  expect  to  reduce  the  top  is  set  in  the  orchard.  At 
also,  particularly  if  the  tree  is  being  trans-  ''J^  "^^°^^  *  P'^""^'^ 
planted.  How  would  you  prune  a  tree  or  °^* 
bush  that  is  being  transplanted?     Fig.  130  may  be  suggestive. 


Fig.  129.  —  Before  and  after  Pruning. 


CHAPTER   XIV 

DEPENDENT   PLANTS 

Thus  far  we  have  spoken  of  plants  that  have  roots  and 
foliage  and  that  depend  on  themselves.     They  collect  the 
raw  materials  and  make  them  over  into  assimilable  food. 
They  are  independent.     Plants  without  green  foliage  can- 
not  make   food ;    they 
must  have  it  made  for 
them     or     they     die. 
They  are  dependent.  A 
sprout   from   a   potato 
tuber  in  a  dark  cellar 
cannot  collect  and  elab- 
orate carbon  dioxide.  It 
lives  on  the  food  stored 
.  ,,  ,    r  in  the  tuber. 

Fig.  131.  —  A  Mush  ROOM,  example  of  a  sapro- 
phytic plant.     This  is  the  edible  cultivated  All plmits  witJl  fiatU- 

"^"'^'^°°"^-  rally  white  or  blanched 

parts  are  dependent.  Their  leaves  do  not  develop.  They 
live  on  organic  matter  —  that  which  has  been  made  by  a 
plant  or  elaborated  by  an  animal.  The  dodder,  Indian 
pipe,  beech  drop,  coral  root  among  flower-bearing  plants, 
also  mushrooms  and  other  fungi  (Figs.  131,  132)  are  exam- 
ples. The  dodder  is  common  in  swales,  being  conspicuous 
late  in  the  season  from  its  thread-Uke  yellow  or  orange 
stems  spreading  over  the  herbage  of  other  plants.  One 
kind  attacks  alfalfa  and  is  a  bad  pest.  The  seeds  germin- 
ate  in   the   spring,  but   as  soon   as  the   twining  stem  a:- 

106 


DEPENDENT  PLANTS 


107 


Fig.  132.— a  Parasitic 
Fungus,  magnified. 
The  mycelium,  or 
vegetative  part,  is 
shown  by  the  dotted- 
shaded  parts  ramify- 
ing in  the  leaf  tissue. 
The  rounded  haus- 
toria  projecting  into 
the  cells  are  also 
shown.  The  long 
fruiting  parts  of  the 
fungus  hang  from  the 
under  surface  of  the 
leaf. 


taches  itself  to  another  plant,  the  dod- 
der dies  away  at  the  base  and  becomes 
wholly  dependent.  It  produces  flowers 
in  clusters  and  seeds  itself  freely 
(Fig.  133). 

Parasites  and  Saprophytes.  —  A  plant 
that  is  dependent  on  a  living  plant  or 
animal  is  a  parasite,  and  the  plant  or 
animal  on  which  it  lives  is  the  host. 
The  dodder  is  a  true  parasite ;  so  are 
the  rusts,  mildews,  and  other  fungi  that 
attack  leaves  and  shoots  and  injure 
them. 

The  threads  of  a  parasitic  fungus 
usually  creep  through  the  intercellular 
spaces  in  the  leaf  or  the  stem  and  send 
suckers  (or  haustoria)  into  the  cells 
(Fig.  132).  The  threads  (or  the  hy- 
phae)  clog  the  air-spaces  of  the  leaf 
and  often  plug  the  stomates, 
and  they  also  appropriate  and 
disorganize  the  cell  fluids ;  thus 


they  injure  or  kill  their  host.     The  mass  of  hyphae 
of   a  fungus   is   called   mycelium.     Some   of   the 
hyphae  finally  grow  out  of  the  leaf  and  produce 
spores   or  reproductive  cells  that  an- 
swer the  purpose  of  seeds  in  distrib- 
uting the  plant  (b,  Fig.  132). 

A  plant  that  lives  on  dead  or  de- 
caying matter  is  a  saprophyte.     Mush- 
rooms (Fig.  131)  are  examples;  they 
live  on    the  decaying   matter   in   the       dodder  in 
soil.    Mould  on  bread  and  cheese  is  an  Fruit. 


io8 


BEGINNERS'  BOTANY 


example.  Lay  a  piece  of  moist  bread  on  a  plate  and 
invert  a  tumbler  over  it.  In  a  few  days  it  will  be  mouldy. 
The  spores  were  in  the  air,  or  perhaps  they  had  already 
fallen  on  the  bread  but  had  not  had  opportunity  to  grow. 
Most  green  plants  are  unable  to  make  any  direct  use  of 
the  humus  or  vegetable  mould  in  the  soil,  for  they  are  not 

saprophytic.  The  shelf- 
fungi  (Fig.  134)  are  sap- 
rophytes. They  are  com- 
mon on  logs  and  trees. 
Some  of  them  are  perhaps 
partially  parasitic,  extend- 
ing the  mycelium  into  the 
wood  of  the  living  tree 
and  causing  it  to  become 
black-hearted  (Fig.  134). 
Some  parasites  spring 
from  the  ground,  as  other 
plants  do,  but  they  are 
parasitic  on  the  roots  of 
their  hosts.  Some  para- 
sites may  be  partially 
parasitic  and  partially 
sap7'opJiytic.  Many  (per- 
haps most)  of  these 
ground  saprophytes  are 
aided  in  securing  their 
food  by  soil  fungi,  which  spread  their  delicate  threads  over 
the  root-like  branches  of  the  plant  and  act  as  intermedi- 
aries between  the  food  and  the  saprophyte.  These  fungus- 
covered  roots  are  known  as  mycorrhizas  (meaning  "  fungus 
root").  Mycorrhizas  are  not  peculiar  to  saprophytes. 
They  are  found  on  many  wholly  independent  plants,  as, 


Fig.  134.  — Tinder  Fungus  {Pofyporus 
igniarius)  on  beech  log.  The  external 
part  of  the  fungus  is  shown  below ;  the 
heart-rot  injury  above. 


DEPENDENT  PLANTS 


109 


Fig.  135.  —  Bacteria  of  Several 
Forms,  much  magnified. 


for  example,  the  heaths,  oaks,  apples,  and  pines.  It  is 
probable  that  the  fungous  threads  perform  some  of  the 
offices  of  root-hairs  to  the 
host.  On  the  other  hand, 
the  fungus  obtains  some 
nourishment  from  the 
host.  The  association 
seems  to  be  mutual. 

Saprophytes  break 
down  or  decompose  or- 
ganic substances.  Chief 
of  these  saprophytes  are 
many  microscopic  organ- 
isms known  as  bacteria  (Fig.  135).  These  innumerable 
organisms  are  immersed  in  water  or  in  dead  animals  and 

plants,  and  in  all  manner  of 
moist  organic  products.  By 
breaking  down  organic 
combinations,  they  produce 
decay.  Largely  through 
their  agency,  and  that  of 
many  true  but  microscopic 
fungi,  all  things  pass  i?ito 
soil  and  gas.  Thus  are  the 
bodies  of  plants  and  animals 
removed  and  the  continuing 
round  of  life  is  maintained. 
Some  parasites  are  green- 
leaved.  Such  is  the  mistle- 
toe (Fig.  136).  They  anchor 
themselves  on  the  host  and 
absorb  its  juices,  but  they 
also    appropriate    and     use 


Fig.  136.  — American  Mistletoe 
growing  on  a  Walnut  Branch. 


no  BEGINNERS'  BOTANY 

the  carbon  dioxide  of  the  air.  In  some  small  groups  of 
bacteria  a  process  of  organic  synthesis  has  been  shown  to 
take  place. 

Epiphytes.  —  To  be  distinguished  from  the  dependent 
plants  are  those  that  grow  on  other  plants  without  taking 
food  from  them.  These  are  green-leaved  plants  whose 
roots  burrow  in  the  bark  of  the  host  plant  and  perhaps 
derive  some  food  from  it,  but  which  subsist  chiefly  on 
materials  that  they  secure  from  air  dust,  rain  water,  and 
the  air.  These  plants  are  epiphytes  (meaning  "upon 
plants")  or  air  plants. 

Epiphytes  abound  in  the  tropics.  Certain  orchids  are 
among  the  best  known  examples  (Fig.  37).  The  Spanish 
moss  or  tillandsia  of  the  South  is  another.  Mosses  and 
lichens  that  grow  6n  trees  and  fences  may  also  be  called 
epiphytes.  In  the  struggle  for  existence,  the  plants 
probably  have  been  driven  to  these  special  places  in  which 
to  find  opportunity  to  grow.  Plants  grow  where  they 
must,  not  where  they  will. 

Suggestions.  — 114.  Is  a  puffball  a  plant  ?  Why  do  you 
think  so?  115.  Are  mushrooms  ever  cultivated,  and  where 
and  how?  116.  In  what  locations  are  mushrooms  and  toadstools 
usually  found?  (There  is  really  no  distinction  between  mush- 
rooms and  toadstools.  They  are  all  mushrooms.)  117.  What 
kinds  of  mildew,  blight,  and  rust  do  you  know?  118.  How  do 
farmers  overcome  potato  blight?  Apple  scab?  Or  any  other 
fungous  "plant  disease"?  119.  How  do  these  things  injure 
plants?  120.  What  is  a  plant  disease?  121.  The  pupil  should 
know  that  every  spot  or  injury  on  a  leaf  or  stem  is  caused  by 
something,  —  as  an  insect,  a  fungus,  wind,  hail,  drought,  or  other 
agency.  How  many  uninjured  or  perfect  leaves  are  there  on 
the  plant  growing  nearest  the  schoolhouse  steps?  122.  Give 
formula  for  Bordeaux  mixture  and  tell  how  and  for  what  it  is  used. 


CHAPTER   XV 


WINTER  AND  DORMANT  BUDS 


A  bud  is  a  growing  point,  terminating  an  axis  either  long 
or  short,  or  being  the  starting  point  of  an  axis.  All 
branches  spring  from  buds.  In  the  growing  season  the 
bud  is  active ;  later  in  the  season  it  ceases  to  increase  the 
axis  in  length,  and  as  winter  approaches  the  growing 
point  becomes  more  or  less  thickened  and  covered  by  pro- 
tecting scales,  in  preparation  for  the  long  resting  season. 
This  resting,  dormant,  or  winter  body  is  what  is  commonly 
spoken  of  as  a  "bud."  A  winter  bud  may  be  defined 
as  an  inactive  covered  growing  pointy  waiting  for  spring. 

Structurally,  a  dormant  bud  is  a  shortened  axis  or  branch, 
bearing  miniature  leaves  or  flowei's  or  bothy  and  protected 
by  a  covering.  Cut  in  two,  lengthwise,  a 
bud  of  the  horse-chestnut  or  other  plant 
that  has  large  buds.     With  a  pin  separate 

the  tiny  leaves.    Count  them. 

Examine  the  big  bud  of  the 

rhubarb  as  it  Hes  under  the 

ground  in  late  winter  or  early 

spring ;  or  the  crown  buds  of 

asparagus,  hepatica,  or  other 

early    spring    plants.      Dis- 
sect large  buds  of  the  apple 

and  pear  (Figs.  137,  138). 
The  bud  is  protected  by  firm   and  dry  scales.     These 
scales  are  modified  leaves.     The  scales  fit  close.     Often 


Fig.  137.  —  Bud 
OF  Apricot, 
showing  the 
miniature 
leaves. 


Fig.  138.-  Bud  OF 
Pear,  showing 
both  leaves  and 
flowers.  The 
latter  are  the  lit- 
tle knobs  in  the 
centre. 


Ill 


112 


BEGINNERS*  BOTANY 


the  bud  is  protected  by  varnish  (see  horse-chestnut  and 
the  balsam  poplars).  Most  winter  buds  are  more  or  less 
woolly.  Examine  some  of  them  under  a  lens.  As  we  might 
expect,  bud  coverings  are  most  prominent  in  cold  and  dry 
cHmates.  Sprinkle  water  on  velvet  or  flannel,  and  note 
the  result  and  give  a  reason. 

All  winter  buds  give  rise  to  branches,  not  to  leaves  alone; 
that  is,  the  leaves  are  borne  on  the  lengthening  axis. 
Sometimes  the  axis,  or  branch,  remains  very  short, — so 
short  that  it  may  not  be  noticed.  Sometimes  it  grows 
several  feet  long. 

Whether  the  bra7ich  grows  large  or  not  depends  on  the 
chance  it  has, — position  on  the  plant,  soil,  rainfall,  and 
many  other  factors.  The  new  shoot  is  the 
unfolding  and  enlarging  of  the  tiny  axis 
and  leaves  that  we  saw  in  the  bud.  If  the 
conditions  are  congenial,  the  shoot  may 
form  more  leaves  than  were  tucked  away 
in  the  bud.  The  length  of  the  shoot  usu- 
ally depends  more  on  the  length  of  the 
internodes  than  on  the  number  of  leaves. 

Where  Buds  are.  —  Buds  are  borne  in  the 
axils  of  the  leaves,  —  in  the  acute  angle 
that  the  leaf  makes  with  the  stem.  When 
the  leaf  is  growing  in  the  summer,  a  bud 
is  forming  above  it.  When  the  leaf  falls, 
the  bud  remains,  and  a  scar  marks  the 
place  of  the  leaf.  Fig.  139  shows  the  large  leaf-scars  of 
ailanthus.  Observe  those  on  the  horse-chestnut,  maple, 
apple,  pear,  basswood,  or  any  other  tree  or  bush. 

Sometimes  two  or  more  buds  are  borne  in  one  axil ;  the 
extra  ones  are  accessory  or  supernumerary  buds.  Observe 
them   in   the   Tartarian  honeysuckle  (common  in  yards), 


Fig.  139.  — Leaf- 
scars.  —  Ailanthus 


WINTER  AND  DORMANT  BUDS 


113 


walnut,  butternut,  red  maple,  honey  locust,  and  sometimes 
in  the  apricot  and  peach. 

If  the  bud  is  at  the  end  of  a  shoot,  however  short  the 
shoot,  it  is  called  a  terminal  bud.  It  continues  the  growth 
of  the  axis  in  a  direct  line.  Very  often 
three  or  more  buds  are  clustered  at  the  tip 
(Fig.  140);  and  in  this  case  there  may  be 
more  buds  than  leaf  scars.  Only  one  of 
them,  however,  is  strictly  terminal. 

A  bud  in  the  axil  of  a  leaf  is  an  axillary 
or  lateral  bud.  Note  that  there  is  normally 
at  least  one  bud  in  the  axil  of  every  leaf  on 
a  tree  or  shrub  in  late  summer  and  fall.  The 
axillary  buds,  if  they  grow,  are  the  starting 
points  of  new  shoots  the  following  season.  If 
a  leaf  is  pulled  off  early  in  summer,  what 
will  become  of  the  young  bud  in  its  axil.? 
Try  this. 

Bulbs  and  cabbage  heads  may  be  likened  to  buds  ;  that  is, 
they  are  condensed  stems,  with  scales  or  modified  leaves 

densely  overlapping 
and  forming  a 
rounded  body  (Fig. 
141).  They  differ 
from  true  buds,  how- 
ever, in  the  fact 
that  they  are  con- 
densations of  whole 
main    stems   rather 

than  embryo  stems 
Fig.  141.  — a  Gigantic  Bud.  —  Cabbage.  .  Mr 

borne  m  the  axils  of 

leaves.    But  bulblets  (as  of  tiger  lily)  may  be  scarcely  dis- 
tinguishable from  buds  on  the  one  hand  and  from  bulbs 


Fig.  140.  —  TER- 
MINAL Bud 
BETWEEN  TWO 

OTHER  Buds. 
—  Currant. 


114 


BEGINNERS'  BOTANY 


on  the  other.     Cut  a  cabbage  head  in  two,  lengthwise, 
and  see  what  it  is  like. 

The  buds  that  appear  on  roots  are  unusual  or  abnormal, 

— they  occur  only  occasionally  and  in  no  definite  order. 

Buds  appearing  in  unusual  places  on  any  part  of  the  plant 

are  called  adventitious  buds.     Such  usually  are  the  buds 

that  arise  when  a  large  limb  is  cut   off,   and 

from  which  suckers 

or    water    sprouts 

arise. 

How  Buds  Open. 
—  When  the  bud 
swells,  the  scales 
are  pushed  apart, 
the  little  axis  elon- 
gates and  pushes 
out.  In  most  plants 
the  outside  scales 
fall  very  soon,  leaving  a  little  ring  of  scars. 
With  terminal  buds,  this  ring  marks  the  end 
of  the  year's  growth.  How? 
Notice  peach,  apple,  plum, 
willow,  and  other  plants.  In 
some  others,  all  the  scales  grow  for  a  time, 
as  in  the  pear  (Figs.  142,  143,  144).  In 
other  plants  the  inner  bud  scales  become 
green  and  almost  leaf-like.  See  the  maple 
and  hickory. 

Sometimes  Flowers  come  out  of  the 
Buds.  —  Leaves  may  or  may  not  accompany 
the  flowers.  We  saw  the  embryo  flowers  in 
Fig.  138.  The  bud  is  shown  again  in  Fig. 
142.     In  Fig.  143  it  is  opening.    In  Fig.  145 


Fig.  142.  — 
Fruit-bud 
OF  Pear. 


Fig.  143.  — The 
opening  of 
THE  Pear 
Fruit-bud. 


Fig.  144.— Open- 
ing Pear 
Leaf-bud. 


Fig.  145.  — Open- 
ing   OF     THE 

Pear-bud. 


WINTER  AND  DORMANT  BUDS 


115 


it  is  more  advanced,  and  the  woolly  unformed  flowers  are 
appearing.     In  Fig.  146  the  growth  is  more  advanced. 


Fig.  146.— a  sin- 
gle Flower 
IN  THE  Pear 

CLUSTER,  as 
seen  at  7  A.M. 
on  the  day  of 
its  opening.  At 
10  o'clock  it 
will  be  fully  ex- 
panded. 


Fig.  147.  — The 
opening  of 
THE  Flower- 
bud  OF 
Apricot. 


Fig.  /i4^  ^  Apricot 
FLOwfelf-BUD,  enlarged. 


leaf-buds. 


Buds  that  contain  or 
produce  only  leaves  are 
Those  which  contain  only  flowers  are  flower 


buds  or  fruit-buds.     The  latter  occur  on 
peach,  almond,  apricot,  and  many  very 
early  spring-flowering  plants.    The 
single  flower  is  emerging  from  the 
apricot  bud  in  Fig.  147.     A  longi- 
tudinal section  of  this  bud,  enlarged,  is 
shown  in  Fig.  148.     Those  that  contain 
both  leaves  and  flowers  are  mixed  buds, 
as  in  pear,  apple,  and  most  late  spring- 
flowering  plants. 

Fruit  buds  are  usually  thicker  or 
stouter  than  leaf-buds.  They  are  borne 
in  different  positions  on  different  plants. 
In  some  plants  (apple,  pear)  they  are 
on  the  ends  of  short  branches  or  spurs; 
in  others  (peach,  red  maple)  they  are 

along   the  sides  of   the  last   year's 

°  ^  Fig.  149. —Fruit-buds 

growths.       In   Fig.  149    are   shown      and  Leaf-buds  of  pear. 


Ii6 


BEGINNERS'  BOTANY 


three  fruit-buds  and  one  leaf-bud  on  E,  and  leaf-buds  on 
A,     See  also  Figs.  150,  151,  152,  153,  and  explain. 


Fig.  150.  —  Fruit-buds  of  Apple 
ON  Spurs:  a  dormant  bud  at 
the  top. 


Fig.  151.  — Clus- 
ter OF  Fruit- 
buds  OF  SWEET 

Cherry,  with 
one  pointed 
leaf-bud  in  cen- 
tre. 


Fig.  152.  —  Two 
Fruit-buds 
OF  Peach 
with  a  leaf- 
bud  between. 


Fig.  153.  — Opening  of  Leaf-buds  and  Flower-buds  of  Apple. 

^^The  burst  of  spring''  means  in  large  part  the  opening  of 
the  buds.  Everything  was  made  ready  the  fall  before.  The 
embryo  shoots  and  flowers  were  tucked  aivay,  and  the  food 
was  stored.  The  warm  rain  falls,  and  the  shutters  open 
and  the  sleepers  wake. 

Arrangement  of  Buds. — We  have  found  that  leaves  are 
usually  arranged  in  a  definite  order ;  buds  are  borne  in  the 
axils  of   leaves :   therefore  buds  miist  exhibit  phyllotaxy. 


WINTER  AND  DORMANT  BUDS  WJ 

Moreover,  branches  grow  from  buds:  branches,  therefore, 
should  show  a  definite  arrangement.  Usually,  however,  they 
do  not  show  this  arrangement  because  not  all  the  buds  grow 
and  not  all  the  branches  live.  (See  Chaps.  II  and  III.) 
It  is  apparent,  however,  that  the  mode  of  arrangement  of 
buds  determines  to  some  extent  the  form  of  the  tree.  Com- 
pare bud  arrangement  in  pine  or  fir  with  that  in  maple  or 
apple. 


Fig.  154,  —  Oak  Spray.      How  are  the  leaves  borne  with  reference  to 
the  annual  growths  ? 

The  uppermost  buds  on  any  twig,  if  they  are  well 
matured,  are  usually  the  larger  and  stronger  and  they  are 
the  most  likely  to  grow  the  next  spring;  therefore,  branches 
tend  to  be  arranged  in  tiers  (particularly  well  marked  in 
spruces  and  firs).     See  Fig.  154  and  explain  it. 

Winter  Buds  show  what  has  been  the  Effect  of  Sunlight. — 
Buds  are  borne  in  the  axils  of  the  leaves,  and  ihe  si&e  or  the 
vigour  df  the  leaf  determines  to  a  large  extent  the  size  of  the 
hud.  Notice  that,  in  most  instances,  the  largest  buds  are 
nearest  the  tip  (Fig.  157).  If •  the  largest  buds  are  not 
near  the  tip,  there  is  some  special  reason  for  it.  Can  you 
state  it  ?     Examine  the  shoots  on  trees  and  bushes. 


Il8  BEGINNERS'  BOTANY 

Suggestions.  —  Some  of  the  best  of  all  observation  lessons  are 
those  made  on  dormant  twigs.  There  are  many  things  to  be 
learned,  the  eyes  are  trained,  and  the  specimens  are  everywhere 
accessible.  123.  At  whatever  time  of  year  the  pupil  takes  up  the 
study  of  branches,  he  should  look  for  three  things :  the  ages  of 
the  various  parts,  the  relative  positions  of  the  buds  and  the  leaves,  the 
different  sizes  of  similar  or  comparable  buds.  If  it  is  late  in 
spring  or  early  in  summer,  he  should  watch  the  development  of 
the  buds  in  the  axils,  and  he  should  determine  whether  the 
strength  or  size  of  the  bud  is  in  any  way  related  to  the  size  and 
the  vigour  of  the  subtending  (or  supporting)  leaf.  The  sizes  of  buds 
should  also  be  noted  on  leafless  twigs,  and  the  sizes  of  the  former 
leaves  may  be  inferred  from  the  size  of  the  leaf-scar  below  the 
bud.  The  pupil  should  keep  in  mind  the  fact  of  the  struggle 
for  food  and  light,  and  its  effects  on  the  developing  buds. 
124.  The  bud  and  the  branch.  A  twig  cut  from  an  apple  tree 
in  early  spring  is  shown  in  Fig.  155.  The  most  hasty  obser- 
vation shows  that  it  has  various  parts,  or  members.  It  seems  to 
be  divided  at  the  point  /  into  two  parts.  It  is  evident  that  the 
part  from/  to  h  grew  last  year,  and  that  the  part  below/  grew 
two  years  ago.  The  buds  on  the  two  parts  are  very  unlike, 
and  these  differences  challenge  investigation.  —  In  order  to  under- 
stand this  seemingly  lifeless  twig,  it  will  be  necessary  to  see  it  as 
it  looked  late  last  summer  (and  this  condition  is  shown  in  Fig. 
156).  The  part  from  /  to  h,  —  which  has  just  completed  its 
growth,  —  is  seen  to  have  its  leaves  growing  singly.  In  every  axil 
(or  angle  which  the  leaf  makes  when  it  joins  the  shoot)  is  a  bud. 
The  leaf  starts  first,  and  as  the  season  advances  the  bud  forms  in 
its  axil.  When  the  leaves  have  fallen,  at  the  approach  of  winter, 
the  buds  remain,  as  seen  in  Fig.  155.  Every  bud  on  the  last 
year's  growth  of  a  winter  twig,  therefore,  marks  the  position 
occupied  by  a  leaf  when  the  shoot  was  growing.  —  The  part  below 
/,  in  Fig.  156,  shows  a  wholly  different  arrangement.  The  leaves 
are  two  or  more  together  {aaaa)y  and  there  are  buds  without 
leaves  {bbbb) .  A  year  ago  this  part  looked  like  the  present  shoot 
from  f  to  hy  —  that  is,  the  leaves  were  single,  with  a  bud  in  the 
axil  of  each.  It  is  now  seen  that  some  of  these  bud-like  parts 
are  longer  than  others,  and  that  the  longest  ones  are  those  which 
have  leaves.  It  must  be  because  of  the  leaves  that  they  have 
increased  in  length.  The  body  c  has  lost  its  leaves  through  some 
accident,  and  its  growth  has  ceased.  In  other  words,  the  parts 
at  aaaa  are  like  the  shoot  ///,  except  that  they  are  shorter,  and 
they  are  of  the  same  age.  One  grew  from  the  end  or  terminal 
bud  of  the  main  branch,  and  the  others  from  the  side  or  lateral 
buds.  Parts  or  bodies  that  bear  leaves  are,  therefore,  branches. 
«—  Tb^  buds  at  bbbb  have  no  leaves,  and  they  remain  the  same 


WINTER  AND  DORMANT  BUDS 


119 


size  that  they  were  a  year  ago.    They  are  dormant.    The  only  way 
for  a  mature  bud  to  grow  is  by  making  leaves  for  itself,  for  a  leaf 


Fig.  155.  — An 
Apple  Twig. 


Fig.  156.— -  Same  twig  before  leaves  fell. 


will  never  stand  below  it  again.     The  twig,  therefore,  has  buds  of 
two  ages,  —  those  at  M^  s^re  two  seasons  old,  and  those  on  th^ 


120  BEGINNERS'  BOTANY 

tips,  of  all  the  branches  {aaaa,  h),  and  in  the  axil  of  every  leaf, 
are  one  season  old.  It  is  only  the  terminal  buds  that  are  not 
axillary.  When  the  bud  begins  to  grow  and  to  put  forth  leaves, 
it  gives  rise  to  a  branch,  which,  in  its  turn,  bears  buds.  —  It  will 
now  be  interesting  to  determine  why  certain  buds  gave  rise  to 
branches  and  why  others  remained  dormant.  The  strongest 
shoot  or  branch  of  the  year  is  the  terminal  one  {fh).  The 
next  in  strength  is  the  uppermost  lateral  one,  and  the  weakest 
shoot  is  at  the  base  of  the  twig.  The  dormant  buds  are  on  the 
under  side  (for  the  twig  grew  in  a  horizontal  position).  All  this 
suggests  that  those  buds  grew  which  had  the  best  chance,  —  the 
most  sunlight  and  room.  There  were  too  many  buds  for  the  space, 
and  in  the  struggle  for  existence  those  that  had  the  best  oppor- 
tunities made  the  largest  growth.  This  struggle  for  existence 
began  a  year  ago,  however,  when  the  buds  on  the  shoot  below/ 
were  forming  in  the  axils  of  the  leaves,  for  the  buds  near  the  tip 
of  the  shoot  grew  larger  and  stronger  than  those  near  its  base. 
The  growth  of  one  year,  therefore,  is  very  largely  determined  by 
the  conditions  under  which  the  buds  were  formed  the  previous 
year.  Other  dud  characters.  125.  It  is  easy  to  see  the  swelling 
of  the  budr  in  a  room  in  winter.  Secure  branches  of  trees  and 
shrubs,  two  to  three  feet  long,  and  stand  them  in  vases  or  jars, 
as  you  would  flowers.  Renew  the  water  frequently  and  cut  off 
the  lower  ends  of  the  shoots  occasionally.  In  a  week  or  two  the 
buds  will  begin  to  swell.  Of  red  maple,  peach,  apricot,  and  other 
very  early-flowering  things,  flowers  may  be  obtained  in  ten  to 
twenty  days.  126.  The  shape,  size,  and  colour  of  the  winter  buds 
are  different  in  every  kind  of  plant.  By  the  buds  alone  botanists 
are  often  able  to  distinguish  the  kinds  of  plants.  Even  such 
similar  plants  as  the  different  kinds  of  willows  have  good  bud 
characters.  127.  Distinguish  and  draw  fruit-buds  of  apple,  pear, 
peach,  plum,  and  other  trees.  If  different  kinds  of  maples  grow 
in  the  vicinity,  secure  twigs  of  the  red  or  swamp  maple,  and  the 
soft  or  silver  maple,  and  compare  the  buds  with  those  of  the  sugar 
maple  and  the  Norway  maple.       What  do  you  learn? 


Fig.  157.  —  Buds  of  the  Hickory, 


CHAPTER  XVI 
BUD  PROPAGATION 

We  have  learned  (in  Chap.  VI)  that  plants  propagate 
by  means  of  seeds.  They  also  propagate  by  means  of  bud 
parts  ^ — as  roots  toe  ks  {rhizomes)y  roots  y  runners  ^  layers  ^  bulbs. 
The  pupil  should  determine  how  any  plant  in  which  he  is 
interested  naturally  propagates  itself  (or  spreads  its  kind). 
Determine  this  for  raspberry,  blackberry,  strawberry,  June- 
grass  or  other  grass,  nut-grass,  water  hly,  May  apple  or 
mandrake,  burdock,  Irish  potato,  sweet  potato,  buckwheat, 
cotton,  pea,  corn,  sugar-cane,  wheat,  rice. 

Plants  may  be  artificially  propagated  by  similar  means, 
as  by  layerSy  cuttingSy  and  grafts.  The  last  two  we  may 
discuss  here. 

Cuttings  in  General.  — A  bit  of  a  plant  stuck  into  the 
grotmd  stands  a  cJiance  of  growing ;  and  this  bit  is  a  cutting. 
Plants  have  preferences,  however,  as  to  the  kind  of  bit 
which  shall  be  used,  but  tJicre  is  no  way  of  telling  what  this 
preference  is  except  by  trying.  In  some  instances  this  prefer- 
ence has  not  been  discovered,  and  we  say  that  the  plant 
cannot  be  propagated  by  cuttings. 

Most  plants  prefer  that  the  cutting  be  made  of  the  soft 
or  growing  parts  (called  "wood"  by  gardeners),  of  which 
the  "slips"  of  geranium  and  coleus  are  examples.  Others 
grow  equally  well  from  cuttings  of  the  hard  or  mature  parts 
or  wood,  as  currant  and  grape;  and  in  some  instances  this 
mature  wood  may  be  of  roots,  as  in  the  blackberry.  In 
some  cases  cuttings  are  made  of   tubers,  as  in  the  Irish 

121 


122 


BEGINNERS'  BOTANY 


potato  (Fig.  60).  Pupils  should  make  cuttings  now  and 
then.  If  they  can  do  nothing  more,  they  can  make  cut 
tings  of  potato,  as  the  farmer  does;  and  they  can  plant 
them  in  a  box  in  the  window. 

The  Softwood  Cutting. — The  softwood  cutting  is  made 
from  tissue  that  is  still  growing,  or  at  least  from  that 
which  is  not  dormant.     It  comprises  one  or  two  joints ^  with 


Fig.  158.  — Geranium  Cutting. 


Fig.  159.  —  Rose  Cutting. 


a  leaf  attached  (Figs.  158,  159).  It  must  not  be  allowed 
to  wilt.  Therefore,  it  must  be  protected  fro^n  direct  sun- 
light and  dry  air  until  it  is  ivell  established ;  and  if  it  has 
many  leaves ^  some  of  them  shotdd  be  removed,  or  at  least  cut 
in  twOy  in  order  to  reduce  the  evaporating  sjcrface.  The 
soil  should  be  uniformly  moist.  The  pictures  show  the 
depth  to  which  the  cuttings  are  planted. 

For  most  plants,  the  proper  age  or  maturity  of  wood  for 
the  making  of  cuttings  may  be  determined  by  giving  the 
twig  a  quick  bend:  if  it  snaps  and  hangs  by  the  bark,  it  is  in 
proper  condition;  if  it  bends  without  breaking,  it  is  too 
young  and  soft  or  too  old ;  if  it  splinters,  it  is  too  old  and 
woody.  The  tips  of  strong  upright  shoots  usually  make 
the  best  cuttings.  Preferably,  each  cutting  should  have  a 
joint  or  node  near  its  base;  and  if  the  internodes  are  very 
short  it  may  comprise  two  or  three  joints. 


BUD  PROPAGATION 


123 


Fig.  160.  —  Cutting-box. 


Tlie  st£m  of  the  cutting  is  inserted  one  third  or  more  of  its 
lengtJi  in  clean  sand  or  gravel,  and  the  earth  is  pressed  firmly 
about  it.  A  newspaper  may  be  laid  over  the  bed  to  ex- 
clude the  light  —  if  the  sun  strikes  it — and  to  prevent  too 
rapid  evaporation.  The  soil  should  be  moist  clear  through, 
not  on  top  only. 

Loose  sandy  or  gravelly  soil  is  nsed.  Sand  used  by 
masons  is  good  material  in  which  to  start  most  cuttings;  or 
fine  gravel  —  sifted  of  most 
of  its  earthy  matter — may 
be  used.  Soils  are  avoided 
which  contain  much  decay- 
ing organic  matter,  for  these 
soils  are  breeding  places  of 
fungi,  which  attack  the  soft 
cutting  and  cause  it  to  "  damp 
off,"  or  to  die  at  or  near  the  surface  of  the  ground.  If  the 
cuttings  are  to  be  grown  in  a  window,  put  three  or  four 
inches  of  the  earth  in  a  shallow  box  or  a  pan.  A  soap 
box  cut  in  two  lengthwise,  so  that  it  makes  a  box  four  or 
five  inches  deep  —  as  a  gardener's  fiat — is  excellent  (Fig. 
160).     Cuttings  of  common  plants,  as  geranium,  coleus, 

fuchsia,  carnation,  are  kept  at  a 
living-room  temperature.  As  long 
as  the  cuttings  look  bright  and 
green,  they  are  in  good  condition. 
It  may  be  a  month  before  roots 
form.  When  roots  have  formed, 
the  plants  begin  to  make  new 
leaves  at  the  tip.  Then  they  may 
be  transplanted  into  other  boxes 
or  into  pots.  The  verbena  in  Fig,  161  is  just  ready  for 
transplanting. 


Fig.  161.  — Verhena  Cutting 
ready  for  transplanting. 


124 


BEGINNERS*  BOTANY 


Fig.  162.— Old  Geranium  Plant 
cut  back  to  make  it  throw  out 
Shoots  from  which  Cuttings 
can  be  made. 

dow  plants  are  those  which 
old.  The  geranium 
aiid  fuchsia  cut- 
tings which  are 
made  in  Januaryy 
February y  or  MarcJi 
will  give  compact 
blooming  plants  for 
the  7text  winter; 
and  thereafter  7iew 
ones  should  take 
their  places   (Fig. 

163). 

The  Hardwood 
Cutting.  —  Best  re- 
sults with  cuttings 
of  mature  wood  are 


It  is  not  always  easy  to 
find  growing  shoots  from 
which  to  make  the  cut- 
tings. The  best  practice, 
in  that  case,  is  to  cut  back 
an  old  pi  ant y  then  keep  it 
wann  and  well  watered^ 
and  thereby  force  it  to  throw 
out  new  shoots.  The  old 
geranium  plant  from  the 
window  garden,  or  the  one 
taken  up  from  the  lawn 
bed,  may  be  treated  this 
way  (see  Fig.  162).  The 
best  plants  of  geranium 
and  coleus  and  most  win- 
are  not  more  than  one  year 


Fig.  163.- 


Early  Winter  Geranium,  from 
a  spring  cutting. 


BUD  PROPAGATION 


125 


secured  when  the  cuttings  are  made  in  the  fall  and  then 
buried  until  spring  in  sand  ift  the  cellar.  These  cuttings 
are  usually  six  to  ten  inches  long.  They  are  not  idle  while 
they  rest.  The  lower  end  calluses  or  heals,  and  the  roots 
form  more  readily  when  the  cutting  is  planted  in  the 
spring.  But  if  the  proper  season  has  passed,  take  cuttings 
at  any  time  in  winter,  plant  them  in  a  deep 
box  in  the  window,  and  watch.  They  will 
need  no  shading  or  special  care.  Grape, 
currant,  gooseberry,  willow,  and  poplar 
readily  take  root  from  the  hardwood. 
Fig.  164  shows  a  currant  cutting.  It  has 
only  one  bud  above  the  ground. 

The  Graft.  —  When  the  cutting  is  inserted 
in  a  plant  rather  than  in  the  soil,  it  is  a 
graft ;  and  the  graft  may  grow.  In  this 
case  the  cutting  grows  fast  to  the  other 
plant,  and  the  two  become  one.  When 
the  cutting  is  inserted  in  a  plant,  it  is  no 
longer  called  a  cutting  but  a  scion ;  and  the 
plant  in  which  it  is  inserted  is  called  the 
stock.  Fruit  trees  are  grafted  in  order 
that  a  ce7'tain  variety  or  kind  may  be  per- 
petuated, as  a  Baldwin  or  Ben  Davis  vari- 
ety of  apple,  Seckel  or  Bartlett  pear,  Navel 
or  St.  Michael  orange. 

Plants  have  preferences  as  to  the  stocks  on  which  they 
will  grow  ;  but  zve  can  find  out  ivJiat  their  choice  is  only 
by  making  the  experiment.  The  pear  grows  well  on  the 
quince,  but  the  quince  does  not  thrive  on  the  pear. 
The  pear  grows  on  some  of  the  hawthorns,  but  it  is  an 
unwilling  subject  on  the  apple.  Tomato  plants  will  grow 
on   potato   plants   and   potato   plants   on   tomato   plants. 


I 


I 


Fig.  164.  — Cur- 
rant CUTIING. 


126  BEGINNERS*  BOTANY 

When  the  potato  is  the  root,  both  tomatoes  and  potatoes 
may  be  produced,  although  the  crop  will  be  very  small; 
when  the  tomato  is  the  root,  neither  potatoes  nor  tomatoes 
will  be  produced.  Chestnut  will  grow  on  some  kinds  of 
oak.  In  general,  one  species  or  kind  is  grafted  on  the 
same  species,  as  apple  on  apple,  pear  on  pear,  orange  on 
orange. 

The  forming,  growing  tissue  of  the  stem  (on  the  plants 
we  have  been  discussing)  is  the  cambium  (Chap.  X),  lying 
on  the  ontside  of  the  woody  cy Haider  beneath  the  bark.  In 
order  that  union  may  take  place,  the  camhium  of  the  scion 
and  of  the  stock  must  come  together.  Therefore  the  scion 
is  set  in  the  side  of  the  stock.  There  are  many  ways  of 
shaping  the  scion  and  of  preparing  the  stock  to  receive  it. 
These  ways  are  dictated  largely  by  the  relative  sizes  of 
scion  and  stock,  although  many  of  them  are  matters  of 
personal  preference.  The  underlying  principles  are  two: 
securing  close  contact  between  the  cambiums  of  scion  and 
stock;  covering  the  ivounded  surfaces  to  prevent  evapora- 
tion and  to  protect  the  parts  from  disease. 

On  large  stocks  the  commonest  form  of  grafting  is  the 
cleft-graft.  The  stock  is  cut  off  and  split;  and  in  one  or 
both  sides  a  wedge-shaped  scion  is  firmly  inserted.  Fig. 
165  shows  the  scion;  Fig.  166,  the  scions  set  in  the  stock; 
Fig.  167^  the  stock  waxed.  It  wall  be  seen  that  the  lower 
bud — that  lying  in  the  wedge — is  covered  by  the  wax; 
but  being  nearest  the  food  supply  and  least  exposed  to 
weather,  it  is  the  most  likely  to  grow :  it  will  push  through 
the  wax. 

Cleft-grafting  is  practised  in  spring,  as  growth  begins. 
The  scions  are  cut  previously,  when  perfectly  dormant,  and 
from  the  tree  which  it  is  desired  to  propagate.  The  scions 
are  kept  in  sand  or  moss  in  the  cellar.     Limbs  of  various 


BUD  PROPAGATION 


127 


sizes  may  be  cleft-grafted, — from  a  half  inch  up  to  four 
inches  in  diameter;  but  a  diameter  of  one  to  one  and  a 
half  inches  is  the  most  convenient  size.  All  the  leading 
or  main  branches  of  a  tree  top  may  be  grafted.  If  the 
remaining  parts  of  the  top  are  gradually  cut  away  and 
the  scions  grow  well,  the  entire  top  will  be  changed  over  to 
the  new  variety. 


Fig.  165.— 

SciOIsf  OF 

Apple. 


Fig.  166.— The 
Scion  Inserted. 


Fig.  167.— The 
Paris  Waxed. 


Another  form  of  grafting  is  known  as  budding.  In  this 
case  a  single  bud  is  used,  and  it  is  sHpped  underneath  the 
bark  of  the  stock  and  securely  tied  (not  waxed)  with  soft 
material,  as  bass  bark,  corn  shuck,  yarn,  or  raffia  (the  last 
a  commercial  palm  fibre).  Budding  is  performed  when  the 
bark  of  the  stock  will  slip  or  peel  (so  that  the  bud  can  be 
inserted),  and  when  the  bud  is  mature  ejiougJi  to  grow. 
Usually  budding  is  performed  in  late  summer  or  early 
fall,  when  the  winter  buds  are  well  formed ;  or  it  may  be 
practised  in  spring  with  buds  cut  in  winter.  In  ordinary 
summer  budding  (which  is  the  usual  mode)  the  *'bud"  or 
scion  forms  a  union  with  the  stock,  and  then  lies  dormant 
till  the  following  spring,  as  if  it  were  still  on  its  own  twig. 


128 


BEGINNERS'  BOTANY 


Budding  is  mostly  restricted  to  young  trees  in  the  nursery. 
In  the  spring  following  the  budding,  the  stock  is  cut  off 
just  above  the  bud,  so  that  only  the  shoot  from  the  bud 
grows  to  make  the  future  tree.  This  prevailing  form  of 
J  budding  (shield-budding)  is  shown  in  Fig. 

\i  168. 

^  t  Suggestions.  — 128.    Name  the  plants  that  the 

■  I  gardener    propagates     by    means     of    cuttings. 

I  129.   By  means  of  grafts.     130.   The  cutting-box 

I  may  be  set  in  the  window.     If  the  box  does  not 

'  receive  direct  sunlight,  it  may  be  covered  with  a 

pane  of  glass  to  prevent  evaporation.  Take  care 
that  the  air  is  not  kept  too  close,  else  the  daraping- 
off  fungi  may  attack  the  cuttings,  and  they  will 
rot  at  the  surface  of  the  ground.  See  that  the 
pane  is  raised  a  little  at  one  end  to  afford  ventila- 
tion ;  and  if  the  water  collects  in  drops  on  the 
under  side  of  the  glass,  remove  the  pane  for  a 
time.  131.  Grafting  wax  is  made  of  beeswax, 
resin,  and  tallow.  A  good  recipe  is  one  part  (as 
one  pound)  of  rendered  tallow,  two  parts  of  bees- 
wax, four  parts  of  resin;  melt  together  in  a  kettle ; 
pour  the  liquid  into  a  pail  or  tub  of  water  to  so- 
lidify it;  work  with  the  hands  until  it  has  the 
colour  and  "  grain"  of  taffy  candy,  the  hands  being 
greased  when  necessary.  The  wax  will  keep  any 
length  of  time.  For  the  little  grafting  that  any 
pupil  would  do,  it  is  better  to  buy  the  wax  of  a 
seedsman.  132.  Grafting  is  hardly  to  be  recom- 
mended as  a  general  school  diversion,  as  the  mak- 
ing of  cuttings  is ;  and  the  account  of  it  in  this 
chapter  is  inserted  chiefly  to  satisfy  the  general 
curiosity  on  the  subject.  133.  In  Chap.  V  we  had 
a  definition  of  a  plant  generation  :  what  is  "  one 
generation  '*  of  a  grafted  fruit  tree,  as  Le  Conte 
pear,  Baldwin,  or  Ben  Davis  apple?  134.  The 
Elberta  peach  originated  about  i88o  :  what  is 
meant  by  "  originated  "  ?  135.  How  is  the  grape 
propagated  so  as  to  come  true  to  name  (explain 
what  is  meant  by  "coming  true")?  currant? 
strawberry?  raspberry?  blackberry?  peach? 
pear?  orange?  fig?  plum?  cherry?  apple?  chest- 
nut? pecan? 


rrC.  l68.  — BUD- 
DING. The 
"bud";  the 
opening  to  re- 
ceive it ;  the 
bud  tied. 


CHAPTER   XVII 
HOW  PLANTS   CLIMB 

We  have  found  that  plants  struggle  or  contend  for  a 
place  in  which  to  live.  Some  of  them  become  adapted  to 
grow  in  the  forest  shade,  others  to  grow  on  other  plants, 
as  epiphytes,  others  to  climb  to  the  light.  Observe  how 
woods  grapes,  and  other  forest  climbers,  spread  their  foli- 
age on  the  very  top  of  the  forest  tree,  while  their  long 
flexile  trunks  may  be  bare. 

There  are  several  ways  by  which  plants  climb,  but  most 
climbers  may  be  classified  into  four  groups  :  ( i )  scramblers, 
(2)  root  climbers,  (3)  tendril  climbers,  (4)  twiners. 

Scramblers.  —  Some  plants  rise  to  light  and  air  by  rest- 
ing their  long  and  weak  stems  on  the  tops  of  bushes  and 
quick-growing  herbs.  Their  stems  may  be  elevated  in  part 
by  the  growing  twigs  of  the  plants  on  which  they  recline. 
Such  plants  are  scramblers.  Usually  they  are  provided 
with  prickles  or  bristles.  In  most  weedy  swamp  thickets, 
scrambling  plants  may  be  found.  Briers,  some  roses,  bed- 
straw  or  galium,  bittersweet  {Solanum  Dulcamara^  not  the 
Celastrus\  the  tear-thumb  polygonums,  and  other  plants  are 
familiar  examples  of  scramblers. 

Root  Climbers.  —  Some  plants  climb  by  means  of  true 
roots.  These  roots  seek  the  dark  places  and  therefore 
enter  the  chinks  in  walls  and  bark.  The  trumpet  creeper 
is  a  famiHar  example  (Fig.  36).  The  true  or  English 
ivy,  which  is  often  grown  to  cover  buildings,  is  another 
instance.  Still  another  is  the  poison  ivy.  Roots  are 
K  129 


I30 


BEGINNERS'  BOTANY 


J'^\y\^^  The  fr< 

'%  ^vl  until  it 

'  *-k  //  it  attac 

1    ■ 


distinguished    from    stem   tendrils   by   their   irregular  of 
indefinite  positio7t  as  well  as  by  their  mode  of  growth. 

Tendril  climbers.  —  A  slender  coiling  part  that  serves  to 
hold  a  climbing  plant  to  a  support  is  known  as  a  tendril. 

The  free  end  swings  or  curves 
strikes  some  object,  when 
attaches  itself  and  then  coils 
and  draws  the  plant  close  to  the 
support.     The  spring  of  the  coil 
Fig.  169.  —  Tendril,  to  show       also  allows  the  plant  to  move  in 
where  the  coil  is  changed.  ^j^^  ^^y^^^  thereby  enabUng  the 

plant  to  maintain  its  hold.  Slowly  pull  a  well-matured 
tendril  from  its  support,  and  note  how  strongly  it  holds 
on.  Watch  the  tendrils  in  a  wind-storm.  Uisually  the  ten- 
dril attaches  to  the  support  by  coiling  about  it,  but  the  Vir- 
ginia creeper  and  the  Boston  ivy  (Fig.  170)  attach  to  walls 
by  means  of  disks 
on  the  ends  of  the 
tendrils. 

Since  both  ends 
of  the  tendril  are 
fixed,  when  it  finds 
a  support,  the  coil- 
ing would  tend  to 
twist  it  in  two.  It 
will  be  found,  how- 
ever, that  the  tendril 
coils  in  different  di- 
rections in  different  parts  of  its  length.  In  Fig.  169,  show- 
ing an  old  and  stretched-out  tendril,  the  change  of  direction 
in  the  coil  occurred  at  a.  In  long  tendrils  of  cucumbers 
and  melons  there  may  be  several  changes  of  direction. 

Tendrils  may  represent  either  branches  or  leaves.    In  the 


70.— Tendril 
Boston  Ivy. 


HOW  PLANTS  CLIMB 


131 


Virginia  creeper  and  the  grape  they  are  branches;  they 
stand  opposite  the  leaves  in  the  position  of  fruit  clusters, 
and  sometimes  one  branch  of  a  fruit  cluster  is  a  tendril. 
These  tendrils  are  therefore  homologous  with  fruit-clusters, 
and  fruit  clusters  are  branches. 

In  some  plants  tendrils  are  leaflets  (Chap.  XI).  Ex- 
amples are  the  sweet  pea  and  the  common  garden  pea.  In 
Fig.  171,  observe  the  leaf  with  its  two  great 
stipules,  petiole,  six  normal  leaflets,  and  two 
or  three  pairs  of  leaflet  tendrils  and  a  termin- 
al leaflet  tendril.  The  cobea,  a  common 
garden  climber,  has  a  similar  arrangement. 
In  some  cases  tendrils  are  stipules^  as  prob- 
ably in  the  green  briers 
(smilax). 

The  petiole  or  midrib 
may  act  as  a  tendril,  as 
in  various  kinds  of  clem- 
atis. In  Fig.  172,  the 
common  wild  clematis 
or  *'  old  man  vine,"  this 
mode  is  seen. 

Twiners.  —  The  entire 
plant  or  shoot  may  wind  about  a  support.  Such  a  plant  is 
a  twiner.  Examples  are  bean,  hop,  morning-glory,  moon- 
flower,  false  bittersweet  or  waxwork  {Celastriis),  some 
honeysuckles,  wistaria,  Dutchman's  pipe,  dodder.  The 
free  tip  of  the  twining  branch  sweeps  about  in  curves,  much 
as  the  tendril  does,  until  it  finds  support  or  becomes  old 
and  rigid. 

Each  kind  of  plant  usually  coils  in  only  one  direction. 
Most  plants  coil  against  the  sun,  or  from  the  observer's 
left  across  his  front  to  his  right  as  he  faces  the  plant. 


w"^ 

&(>. 


Fig.  171.  —  Leaves  of  Pea, 
—  very  large  stipules,  op- 
posite leaflets,  and  leaflets 
represented  by  tendrils. 


132 


BEGINNERS'  BOTANY 


Examples  are  bean,  morning-glory.     The  hop  twines  from 
the  observer's  right  to  his     l\     left,  or  with  the  sun. 


Fig.  172.  -  Clematis  climbing  by  Leaf-tendril. 

Suggestions. — 136.  Set  the  pupil  to  watch  the  behaviour  of  any 
plant  that  has  tendrils  at  different  stages  of  maturity.  A  vigorous 
cucumber  plant  is  one  of  the  best.  Just  beyond  the  point  of  a  young 
straight  tendril  set  a  stake  to  compare  the  position  of  it.  Note 
whether  the  tendril  changes  position  from  hour  to  hour  or  day 
to  day.  137.  Is  the  tip  of  the  tendril  perfectly  straight?  Why? 
Set  a  small  stake  at  the  end  of  a  strong  straight  tendril,  so  that  the 
tendril  will  just  reach  it.  Watch  and  make  drawing.  138-  If  a 
tendril  does  not  find  a  support  what  does  it  do?  139.  To  test  the 
movement  of  a  free  tendril  draw  an  ink  line  lengthwise  of  it,  and 
note  whether  the  line  remains  always  on  the  concave  side  or  the 
convex  side.  140-  Name  the  tendril-bearing  plants  that  you  know. 
141.  Make  similar  observations  and  experiments  on  the  tips  of 
twining  stems.  142.  What  twining  plants  do  you  know,  and  which 
way  do  they  twine?  143.  How  does  any  plant  that  you  know 
shoot  up?  144.  Does  the  stem  of  a  climbing  plant  contain  more 
or  less  substance  (weight)  than  an  erect  self-supporting  stem  of 
the  same  height?      Explain. 


CHAPTER   XVIII 
THE  FLOWER  — ITS   PARTS  AND  FORMS 

The  function  of  the  flower  is  to  produce  seed.  It  is 
probable  that  all  its  varied  forms  and  colours  contribute 
to  this  supreme  end.  These  forms  and  colours  please  the 
human  fancy  and  add  to  the  joy  of  living,  but  the  flower 
exists  for  the  good  of  the  plant,  not  for  the  good  of  man. 
The  parts  of  the  flower  are  of  two  general  kinds  —  those 
that  are  directly  concerned  in  the  production  of  seedSy  and 
those  that  act  as  covering  atid  protecting  organs.  The 
former  parts  are  known  as  the  essential  organs ;  the  latter 
as  the  floral  envelopes. 

Envelopes.  —  The  floral  envelopes  usually  bear  a  close 
resemblance  to  leaves.  These  envelopes  are  very  com- 
monly of  two  series  or  kinds  —  the 
outer  and  the  inner.  The  outer  series, 
known  as  the  calyx,  is  usually  smaller 
and  green.  It  usually  comprises  the 
outer  cover  of  the  flower  bud.  The 
calyx  is  the  lowest  whorl  in  Fig.  173.       f^^  173. -flower  of 

The    inner    series,    known    as    the       a  buttercup  in  sec- 
corolla,  is   usually  coloured  and  more 
special  or  irregular  in  shape  than  the  calyx.     It  is  the 
showy  part  of  the  flower,  as  a  rule.     The  corolla  is  the 
second  or  large  whorl  in  Fig.  173. 

The  calyx  may  be  composed  of  several  leaves.  .  Each 
leaf  is  a  sepal.  If  it  is  of  one  piece,  it  may  be  lobed  or 
divided,  in  which  case  the  divisions  are  called  calyx -lobes. 


134 


BEGINNERS'  BOTANY 


In  like  manner,  the  corolla  may  be  composed  of  petals,  or 
it  may  be  of  one  piece  and  variously  lobed.  A  calyx  of 
one  piece,  no  matter  how  deeply  lobed,  is  gamosepalous. 
A  corolla  of  one  piece  is  gamopetalous.  When  these 
series  are  of  separate  pieces,  as  in  Fig.  173,  the  flower  is 
said  to  be  polysepalous  and  polypetalous.     Sometimes  both 

series  are  of  separate  parts,  and 
sometimes  only  one  of  them  is  so 
formed. 

The  floral  envelopes  are  ho- 
mologous  with  leaves.  Sepals  and 
petals,  at  least  when  more  than 
three  or  five,  are  in  more  than 
one  whorl,  and  on^  whorl  stands 
below  another  so  that  the  parts 
overlap.  They  are  borne  on  the 
expanded  or  thickened  end  of  the 
flower  stalk ;  this  end  is  the  torus. 
In  Fig.  173  all  the  parts  are  seen 
as  attached  to  the  torus.  This 
part  is  sometimes  called  the  re- 
ceptacle, but  this  word  is  a  common-language  term  of 
several  meanings,  whereas  torus  has  no  other  meaning. 
Sometimes  one  part  is  attached  to  another  part,  as  in  the 
fuchsia  (Fig.  174),  in  which  the  petals  are  borne  on  the 
calyx-tube. 

Subtending  Parts.  —  Sometimes  there  are  leaf-like  parts 
jusf  below  the  calyx,  looking  like  a  second  calyx.  Such 
parts  accompany  the  carnation  flower.  These  parts  are 
bracts  (bracts  are  small  specialized  leaves);  and  they  form 
an  involucre.  We  must  be  careful  that  we  do  not  mistake 
them  for  true  flower  parts.  Sometimes  the  bracts  are 
large  and  petal-like,  as  in  the  great  white  blooms  of  the 


Fig.  174.  —  Flower  of 
Fuchsia  in  Section. 


THE  FLOWER  — ITS  PARTS  AND  FORMS 


135 


flowering   dogwood :    here   the   real   flowers   are   several, 
small  and  greenish,  forming  a  small  cluster  in  the  centre. 

Essential  Organs.  —  The  essential  organs  are  of  two 
series.  The  outer  series  is  composed  of  the  stamens.  The 
inner  series  is  composed  of  the  pistils. 

Stamens  bear  the  pollen,  which  is  made  up  of  grains  or 
spores,  each  spore  usually  being  a  single  plant  cell.  The 
stamen  is  of  two  parts,  as  is  readily  seen  in  Figs.  173, 
174, — the  enlarged  terminal  part  or  anther,  and  the  stalk 
or  filament.  The  filament  is  often  so  short  as  to  seem  to 
be  absent,  and  the  anther  is  then  said  to  be  sessile.  The 
anther  bears  the  pollen  spores.  It  is  made  up  of  two  or 
four  parts  (known  as  sporangia  or  spore-cases),  which 
burst  and  discharge  the 
pollen.  When  the  pollen  is 
shedy  the  stamen  dies. 

The    pistil     has     three 


parts :  the  lowest,  or  seed- 
bearing  part,  which  is  the 
ovary;  the  stigma  at  the 
upper  extremity,  which  is 
a  flattened  or  expanded 
surface,  and  usually  rough- 
ened or  sticky;  the  stalk- 
like part  or  style,  connect- 
ing the  ovary  and  the  stig- 
ma. Sometimes  the  style  is  apparently  wanting,  and  the 
stigma  is  said  to  be  sessile  on  the  ovary.  These  parts  are 
shown  in  the  fuchsia  (Fig.  174).  The  ovary  or  seed  vessel 
is  at  a.  A  long  style,  bearing  a  large  stigma,  projects  from 
the  flower.    See  also  Figs.  175  and  176. 

Stamens  and  pistils  probably  are  homologous  with  leaves. 
A  pistil  is  sometimes  conceived  to  represent  anciently  a 


Fig.  175.— The  Structure  of  a 
Plum  Blossom. 

j«,  sepals;  f>,  petals;  sta,  stamens;  o,  ovary; 
s,  style;  5^,  tig^ma.  The  pistil  consists  of 
the  ovary,  the  styl«  and  the  stigma.  It 
contains  the  seed  part.  The  stamens  are 
tipped  with  anthers,  in  which  the  pollen  is 
borne.    The  ovary,  o,  rip*ns  into  the  fruit. 


136 


BEGINNERS'  BOTANY 


Fig.  176.  — Simple 
Pistils  of  But- 
tercup, one  in 
longitudinal  sec- 
tion. 


leaf  as  if  rolled  into  a  tube ;  and  an  anther,  a  leaf  of  which 
the  edges  may  have  been  turned  in  on  the  midrib. 

The  pistil  may  be  of  one  part  or  com- 
partment^ or  of  many  parts.  The  different 
units  or  parts  of  which  it  is  composed  are 
carpels.  Each  carpel  is  homologous  with 
a  leaf.  Each  carpel  bears  one  or  more 
seeds.  A  pistil  of  one  carpel  is  simple; 
of  two  or  more  carpels,  compound.  Usu- 
ally the  structure  of  the  pistil  may  be  de- 
termined by  cutting  horizontally  across  the  lower  or  seed- 
bearing  part,  as  Figs.  177,  178  explain.  A  flower  may 
contain  a  simple  pistil  (one  carpel),  as 

the  pea  (Fig.  177);  several  simple  pis-  .     ^ 

tils  (several  separate  carpels),  as  the       ^^^^^       If 
buttercup  (Fig.  176);  or  a  componnd  "^      ^ 

pistil  with  carpels  united,  as  the  Saint 

John's  wort  (Fig.  1 78)  and  apple.    How    fig.   177.  -  Pistil   of 
-     .  1    •>       A  1    ■»  Garden     Pea,    the 

many  carpels  m  an  apple .''     A  peach  t 

An   okra  pod  ?     A   bean   pod }     The 

seed  cavity  in  each  carpel  is  called  a 

locule  (Latin  locus,  a  place).     In  these 

l6cules  the  seeds  are  boi-ne. 

Conformation  of  the  Flower.  —  A 
flower  that  has  calyx,  corolla,  stamens, 
and  pistils  is  said  to  be  complete  (Fig. 
173);  all  others  are  incomplete.  In 
some  flowers  both  the  floral  envelopes 
are  wanting :  such  are  naked.  When 
one   of  the   floral   envelope   series  is 

Fig.  178.— Compound     wanting,  the  remaining  series  is  said 
joHiI.^  wort.  ^li     to  be  calyx,  and  the  flower  is  therefore 

has  5  carpels.  apCtalOUS  (without  petals).      The  knot- 


stamens  being  pulled 
down  in  order  to  dis- 
close it ;  also  a  section 
showing  the  single 
compartment  (com- 
pare Fig.  188). 


THE  FLOWER  — ITS  PARTS  AND  FORMS 


n? 


weed  (Fig.  179),  smartweed,  buckwheat^  elm  are 
examples. 

Some  flowers  lack  the  pistils :  these  are  stami- 
nate,  whether  the  envelopes  are  missing  or  not. 
Others  lack  the  stamens :  these  are  pistillate. 
Others  have  neither  stamens  nor  pistils:  these 
are  sterile  (snowball  and  hydrangea).    Those 
that  have  both  stamens  and  pistils  are  per- 
fect, whether  or  not  the  envelopes  are  missing. 

Those  that  lack 
either  stamens  or 
pistils  are  imper- 
fect or  diclinous. 
Staminate  and 
pistillate  flowers 
are  imperfect  or 
diclinous. 

When  staminate  and  pistillate  flowers  are  borne  on  the 
same  plant,  e.g.  oak  (Fig.   180),  corn, 
beech,  chestnut,  hazel,  walnut,  hickory, 
pine,  begonia  (Fig.   181),  watermelon, 


Fig.  179.  —  Knotweed,  a  very  common  but  inconspicu- 
ous plant  along  hard  walks  and  roads.  Two  flowers, 
enlarged,  are  shown  at  the  right.  These  flowers  are 
very  small  and  borne  in  the  axils  of  the  leaves. 


Fig,  180.  — Staminate  Catkins  of 
Oak.  The  pistillate  flowers  are  in  the 
leaf  axils,  and  not  shown  in  this  pic- 
ture. 


Fig.  181.— Begonia 
Flowers. 

Staminate  at  A ;  pistil- 
late below,  with  the 
winged  ovary  at  B. 


138 


BEGINNERS'  BOTANY 


gourd,  pumpkin,  the  plant  is  monoecious  ("  in  one  house  ") 
When  they  are  on  different  plants,  e.g.  poplar,  cottonwood, 

bois  d'arc,  willow  (Fig.  182), 
the  plant  is  dioecious  (**  in  two 
houses  ").  Some  varieties  of 
strawberry,  grape,  and  mul- 
berry are  partly  dioecious.  Is 
the  rose  either  monoecious 
or  dioecious } 

Flowers  in  which  the  parts 
of  each  series  are  alike  are 
said  to  be  regular  (as  in  Figs. 
173,  174,  175).  Those  in 
which  some  parts  are  unlike 
other  parts  of  the  same  series 
are  irregular.  Their  regularity  may  be  in  calyx,  as  in 
nasturtium  (Fig.  183);  in  corolla  (Figs.  184,  185);  in  the 
Q^  i|  stamens  (compare  nasturtium,  catnip, 

Fig.  185,  sage);  in  the  pistils.    Irregu- 
larity is  most  frequent  in  the  corolla. 


s 
Fig.  182.  — Catkins  of  a  Willow. 

A  staminate  flower  is  shown  at  s,  and  a 
pistillate  flower  at  /.  The  staminate 
and  pistillate  are  on  different  plants. 


Fig.  183.  —  Flower  of 
Garden  Nasturtium. 

Separate  petal  at  a.  The 
calyx  is  produced  into  a 
spur. 


Fig.  185.— 

Flower  of 

Catnip. 


Fig.  184.  — The  Five  Pktals 
of  the  Pansy,  detached  to 
show  the  form. 


THE  FLOWER  — ITS  PARTS  AND  FORMS  1 39 

Various  Forms  of  Corolla.  —  The  corolla  often  assumes 
very  definite  or  distinct  forms,  especially  when  gamopet- 
alous.  It  may  have  a  long  tube  with  a  wide-flaring  limb, 
when  it  is  said  to  be  funnelform,  as  in  morning-glory 
and  pumpkin.  If  the  tube  is  very  narrow  and  the  limb 
stands  at  right  angles  to  it,  the  corolla  is  salverform,  as 
in  phlox.  If  the  tube  is  very  short  and  the  limb  wide- 
spreading  and  nearly  circular  in  outline,  the  corolla  is 
rotate  or  wheel-shaped,  as  in  potato. 

A  gamopetalous  corolla  or  gamosepalous  calyx  is  often 
cleft  in  such  way  as  to  make  two  prominent  parts.  Such 
parts  are  said  to  be  lipped  or  labiate.  Each  of  the  lips  or 
lobes  may  be  notched  or  toothed.  In  5-membered  flowers, 
the  lower  lip  is  usually  3-lobed  and  the  upper  one  2-lobed. 
Labiate  flowers  are  characteristic  of  the  mint  family  (Fig. 
185),  and  the  family  therefore  is  called  the  Labiatae.  (Lit- 
erally, labiate  means  merely  "hpped,"  without  specifying  the 
number  of  lips  or  lobes ;  but  it  is  commonly  used  to  desig- 
nate 2-lipped  flowers.)  Strongly  2-parted  polypetalous 
flowers  may  be  said  to  be  labiate ;  but  the  term  is  of ten- 
est  used  for  gamopetalous  co- 
rollas. 

Labiate  gamopetalous  flowers 
that  are  closed  in  the  throat  (or 
entrance  to  the  tube)  are  said  to 
be  grinning  or  personate  (per- 
sonate means  masked).     Snap-      fig.  186. -personate flower 

.  y  f  QP  Toadflax. 

dragon    is    a    typical    example; 

also  toadflax  or  butter-and-eggs  (Fig.  186),  and  many 
related  plants.  Personate  flowers  usually  have  defin- 
ite relations  to  insect  pollination.  Observe  how  an 
insect  forces  his  head  into  the  closed  throat  of  the  toad- 
flax. 


140 


BEGINNERS'  BOTANY 


The  peculiar  flowers  of  the  pea  tribes  are  explained  in 
Figs.  187,  188. 

Spathe  Flowers.  —  In  many  plants,  very  simple  (often 
naked)  flowers  are  borne  in  dense,  more  or  less  fleshy 
spikes,  and  the  spike  is  niclosed  in  or  attended  by  a  leaf, 
sometimes  corolla-like,  known  as  a  spathe.  The  spike  of 
flowers  is  technically  known  as  a  spadix.  This  type  of 
flower  is  characteristic  of  the  great  arum  family,  which  is 


Fig.  187.  —  Flowers  of  the 
Common  Bean,  with  one 
flower  opened  (a)  xo  show 
the  structure. 


Fig.  188.  — Diagram  of  Alfalfa  Flower 
IN  Section: 

C,  calyx,  Z),  standard;  W,  wing;  K,  keel;  T,  sta- 
men-tube; F,  filament  of  tenth  stamen;  X^ 
stigma;  K,  style;  <9,  ovary;  the  dotted  lines  at 
E  show  position  of  stamen-tube,  when  pushed 
upward  by  insects.     Enlarged. 


chiefly  tropical.  The  commonest  wild  representatives  are 
Jack-in-the-pulpit,  or  Indian  turnip,  and  skunk  cabbage.  In 
the  former  the  flowers  are  all  diclinous  and  naked.  In  the 
skunk  cabbage  all  the  flowers  are  perfect  and  have  four  se- 
pals. The  common  calla  is  a  good  example  of  this  type  of 
inflorescence. 

Composite  Flowers. — The  head  (anthodium)  or  so- 
called  "flower"  of  sunflower  (Fig.  189),  thistle,  aster, 
dandelion,  daisy,  chrysanthemum,  goldenrod,  is  com- 
posed of  several  or  many  little  flowers^  or  florets.     These 


THE  FLOWER  —  ITS  PARTS  AND  FORMS 


141 


Fig.  189.  — Head  of  Sunflower, 


florets  are  inclosed  in  a  more  or  less  dense  and  usually 
green  involucre.  In  the  thistle  (Fig.  1 90)  this  involucre  is 
prickly.  A  longitudinal 
section  discloses  the  flo- 
rets, all  attached  at  bot- 
tom to  a  common  torus, 
and  densely  packed  in 
the  involucre.  The  pink 
tips  of  these  florets  con- 
stitute the  showy  part  of 
the  head. 

Each  floret  of  the  this- 
tle (Fig.  190)  is  a  com- 
plete flower.  At  a  is  the  ovary.  At  ^  is  a  much-divided 
plumy  calyx,  known  as  the  pappus.  The  corolla  is  long- 
tubed,  rising  above  the  pappus,  and  is  enlarged  and  5-lobed 

at  the  top,  c.  The  style  pro- 
jects at  e.  The  five  anthers 
are  united  about  the  style  in 
a  ring  at  d.  Such  anthers 
are  said  to  be  syngenesious. 
These  are  the  various  parts 
of  the  florets  of  the  Com- 
positae.  In  some  cases  the 
pappus  is  in  the  form  of 
barbs,  bristles,  or  scales,  and 
sometimes  it  is  wanting. 
The  pappus,  as  we  shall  see 
later,  assists  in  distributing 
the  seed.  Often  the  florets 
are  not  all  alike.  The  corolla 
of  those  in  the  outer  circles  may  be  developed  into  a  long, 
straplike,  or  tubular  part,  and  the  head  then  has  the  ap- 


FiG,  190.  —  Longitudinal  Section 
OF  Thistle  Head;  also  a  Floret 
OF  Thistle. 


142 


BEGINNERS'  BOTANY 


pearance  of  being  one  flower  with  a  border  of  petals.  Of 
such  is  the  sunflower  (Fig.  189),  aster,  bachelor's  button  or 
cornflower,  and  field  daisy  (Fig.  211).  These  long  corolla- 
limbs  are  called  rays.  In  some  cultivated  composites,  all 
the  florets  may  develop  rays,  as  in  the  dahlia  and  the  chry- 
santhemum. In  some  species,  as  dandelion,  all  the  florets 
naturally  have  rays.  Syngenesious  arrangement  of  an- 
thers is  the  most  characteristic  single  feature  of  the 
composites. 

Double  Flowers.  — Under  the  stimulus  of  cultivation  and 
increased    food   supply,  flowers  tend   to   become   double. 

True  doubling  arises 
in  two  ways,  mor- 
phologically:  (i)j/'<2- 
mcjis  or  pistils  may 
produce  petals  (Fig.  ■ 
191)  ;  (2)  adventi- 
tious or  accessory 
petals  may  arise  in 
the  circle  of  petals. 
Both  these  cate- 
gories may  be  pres- 
ent in  the  same 
flower.  In  the  full 
double  hollyhock  the  petals  derived  from  the  staminal  col- 
umn are  shorter  and  make  a  rosette  in  the  centre  of  the 
flower.  In  Fig.  192  is  shown  the  doubling  of  a  daffodil 
by  the  modification  of  stamens.  Other  modifications  of 
flowers  are  sometimes  known  as  doubling.  For  example, 
double  dahlias,  chrysanthemums,  and  sunflowers  are  forms 
in  which  the  disk  flowers  have  developed  rays.  The  snow- 
ball is  another  case.  In  the  wild  snowball  the  external 
flowers  of  the  cluster  are  large  and  sterile.     In  the  culti- 


FiG.  191.  — Petals  arising  from  the  Stami- 
nal Column  of  Hollyhock,  and  accessory 
petals  in  the  corolla-whorl. 


THE  FLOWER  — ITS  PARTS  AND  FORMS  1 43 

vated  plant  all  the  flowers  have  become  large  and  sterile^ 
Hydrangea  is  a  similar  case. 


Fig.  192.  —  Narcissus  or  Daffodil.    Single  flower  at  the  right. 

Suggestions. — 14S.  If  the  pupil  has  been  skilfully  conckieted 
through  this  chapter  by  jneans  of  careful  study  of  specimens  rather 
than  as  a  mere  memorizing  process,  he  will  be  in  mood  to  chal- 
lenge any  flower  that  he  sees  and  to  make  an  effort  to  understand 
it.  Flowers  are  endlessly  modified  in  form;  but  they  can  be 
understood  if  the  pupil  looks  first  for  the  anthers  and  ovaries. 
How  may  anthers  and  ovaries  always  be  distinguished?  146.  It  is 
excellent  practice  to  find  the  flowers  in  plants  that  are  commonly 
known  by  name,  and  to  determine  the  main  points  in  their  struc- 
ture. What  are  the  flowers  in  Indian  corn?  pumpkin  or  squash? 
celery?  cabbage?  potato?  pea?  tomato?  okra?  cotton?  rhubarb? 
chestnut?  wheat?  oats?  147.  Do  all  forest  trees  have  flowers? 
Explain.  148.  Name  all  the  monoecious  plants  you  know. 
Dioecious.  149.  What  plants  do  you  know  that  bloom  before 
the  leaves  appear?  Do  any  bloom  after  the  leaves  fall?  150.  Ex- 
plain the  flowers  of  marigold,  hyacinth,  lettuce,  clover,  asparagus, 
garden  calla,  aster,  locust,  onion,  burdock,  lily-of-the-valley,  crocus. 
Golden  Glow,  rudbeckia,  cowpea.     151.    Define  a  flower. 

Note  to  the  Teacher.  —  It  cannot  be  urged  too  often  that 
the  specifnens  thefnselves  be  studied.  If  this  chapter  becomes  a 
mere  recitation  on  names  and  definitions,  the  exercise  will  be 
worse  than  useless.  Properly  taught  by  means  of  the  flowers 
themselves,  the  names  become  merely  incidental  and  a  part  of 
the  pupil's  language,  and  the  subject  has  living  interest. 


CHAPTER   XIX 


THE  FLOWER  — FERTILIZATION  AND  POLLINATION 


Fertilization.  —  Seeds  result  from  the  union  of  two  ele- 
ments or  parts.  One  of  these  elements  is  a  cell-nucleus 
of  the  pollen-grain.  The  other  ele- 
ment is  the  cell-nucleus  of  an  egg- 
cell,  borne  in  the  ovary.  The 
pollen-grain  falls  on  the  stigma 
(Fig.  193).  It  absorbs  the  juices 
exuded  by  the  stigma,  and  grows 
by  sending  out  a  tube  (Fig.  194). 
This  tube  grows  downward  through 
the  style,  absorbing  food  as  it  goes, 
and  finally  reaches  the  egg-cell  in 
the  interior  of  an  ovule  in  the 
ovary  (Fig.  195),  and  fertilization, 
or  union  of  a  nucleus  of  the  pollen  and  the 
nucleus  of  the  egg-cell  in  the  ovule,  takes  place. 
The  ovule  and  embryo  within  then  develops 
into  a  seed.  The  growth  of  the  pollen-tube  is 
often  spoken  of  as  germination  of  the  pollen, 
but  it  is  not  germination  in  the  sense  in  which 
the  word  is  used  when  speaking  of  seeds. 

Better  seeds  —  that  is,  those  that  produce 
stronger  and  more  fruitful  plants  —  often  re- 
sult when  thQ  pollen  comes  from  another  flower. 
Fertilization  effected  between  different  flowers 
is  cross -fertilization ;   that  resulting  from  the 

144 


Fig.  193.  —  B,  Pollen  escap- 
ing from  anther ;  A,  pollen 
germinating  on  a  stigma. 
Enlarged. 


Fig.  194.— 
A  Pollen- 
grain  AND 
THE  Grow. 
iNG  Tube. 


THE  FLO  WER  —  PER TILIZA  TION  AND  POLLINA  TION      145 


application  of  pollen  to  pistils  in  the  same  flower  is  close- 
fertilization  or  self-fertilization.  It  will  be  seen  that  the 
cross-fertilization  relationship  may  be  of  many  degrees — 
between  two  flowers  in  the  same  cluster,  between  those 
in  different  clusters  on  the  same 
branch,  between  those  on  different 
plants.  Usually  fertilization  takes 
place  only  between  plants  of  the 
same  species  or  kind. 

In  many  cases  there  is,  in  effect, 
an  apparent  selection  of  pollen  when 
pollen  from  two  or  more  sources  is 
applied  to  the  stigma.  Sometimes 
the  foreign  pollen,  if  from  the  same 
kind  of  plant,  grows,  and  fertiliza- 
tion results,  while  pollen  from  the 
same  flower  is  less  promptly  effec- 
tive. If,  however,  no  foreign  pol- 
len is  present,  the  pollen  from  the 
same  flower  may  finally  serve  the 
same  purpose. 

In  order  that  the  pollen  may  grow,  the  stigma  must  be 
ripe.  At  this  stage  the  stigma  is  usually  moist  and  some- 
times sticky.  A  ripe  stigma  is  said  to  be  receptive.  The 
stigma  may  remain  receptive  for  several  hours  or  even 
days,  depending  on  the  kind  of  plant,  the  weather,  and  how 
soon  pollen  is  received.  Watch  a  certain  flower  every  day 
to  see  the  anther  locules  open  and  the  stigma  ripen.  When 
fertilization  takes  place,  the  stigma  dies.  Observe,  also, 
how  soon  the  petals  wither  after  the  stigma  has  received 
pollen. 

Pollination. — The  transfer  of  the  pollen  from  anther 
to    stigma    is   known    as    pollination.      The    pollen   may 


Fig.  195.  —  Diagram  to 
represent  fertiliza- 
TION. 

J,  stigma;  j/,  style;  <»z',  ovary;  o, 
ovule;  p,  pollen-grain;  pt, 
pollen-tube;  e,  egg-cell;  tn, 
micropyle. 


146  BEGINNERS*  BOTANY 

fall  of  its  own  weight  on  the  adjacent  stigma,  or  it 
may  be  carried  from  flower  to  flower  by  wind,  insects,  or 
other  agents.  There  may  be  self-pollination  or  cross-pol- 
lination, and  of  course  it  must  always  precede  fertilization. 
Usually  the  pollen  is  discharged  by  the  burst- 
ing of  the  anthers.  The  commonest  method  of 
discharge  is  through  a  slit  on  either  side  of  the 
anther  (Fig.  193).  Sometimes  it  discharges 
through  a  pore  at  the  apex,  as  in  azalea  (Fig. 
Anther  OF  196),  rhododendron,  huckleberry,  wintergreen. 
Azalea,      Jj^  some  plants  a  part  of  the  anther  wall  raises 

opening  by 

terminal      or  falls  as  a  Udy  as  in  barberry  (Fig.  197),  blue 

pores.       cohosh.  May  apple.     The  opening  of  an  anther 

(as  also  of  a  seed-pod)  is  known  as  dehiscence  {de^  from ; 

hisco,  to  gape).     When  an  anther  or  seed  pod  opens,  it  is 

said  to  dehisce. 

Most  flowers  are  so  constructed  as  to  increase  the  chances 
of  cross-pollination.  We  have  seen  that  the  stigma  may 
have  the  power  of  choosing  foreign  pollen.  The 
commonest  means  of  necessitating  cross-pollina- 
tion is  the  different  times  of  maturing  of  stamens 
and  pistils  in  the  same  flower.  In  most  cases 
the  stamens  mature  first:  the  flower  is  then 
proterandrous.  When  the  pistils  mature  first, 
the  flower  is  proterogynous.  {Ancr,  andr,  is  a 
Greek  root  often  used,  in  combinations,  for  sta-  barherry 
men,  and  jrytte  for  pistil.)     The  difference  in      stamen, 

'  ^-^  ^  ^  ^         with  anther 

time  of  ripenmg  may  be  an  hour  or  two,  or  it  opening  by 
may  be  a  day.  The  ripening  of  the  stamens  "^• 
and  the  pistils  at  different  times  is  known  as  dichogamy,  and 
flowers  of  such  character  are  said  to  be  dichogamous. 
There  is  little  chance  for  dichogamous  flowers  to  pollinate 
themselves.     Many  flowers  are  imperfectly  dichogamous  — 


THE  FLO  WER — FER  TILlZA  TTON  AND  POLLINA  TION     147 

some  of  the  anthers  mature  simultaneously  with  the  pistils, 
so  that  there  is  chance  for  self-pollination  in  case  for- 
eign pollen  does 
not  arrive.  Even 
when  the  stigma 
receives  pollen 
from  its  own 
flower,  cross-fer- 
tilization may 
result.  The  hol- 
lyhock is  proter- 
androus.  Fig. 
198      shows      a 

flower       recently      fig.  198.  — flower  of  hollyhock;  proterandrous. 

expanded.  The  centre  is  occupied  by  the  column  of  sta- 
mens. In  Fig.  199,  showing  an  older  flower,  the  long 
styles  are  conspicuous. 

Some  flowers  are  so  constructed  as  to  prohibit  self-polli- 
nation.    Very  irregular  flowers  are  usually  of  this  kind. 

With  some  of  them, 
the  petals  form  a 
sac  to  inclose  the 
anthers  and  the  pol- 
len cannot  be  shed 
on  the  stigma  but  is 
retained  until  a  bee 
forces  the  sac  open ; 
the  pollen  is  rubbed 
on  the  hairs  of  the 

bee  and  transported. 

Fig.  199.  — Older  Flower  OF  Hollyhock.        -d    ^   i      a 

^  Regular  flowers  usu- 

ally depend  mostly  on  dichogamy  and  the  selective  power 
of   the  pistil  to   insure  crossing       Flowers  that  are  very 


148 


BEGINNERS'  BOTANY 


irregular  and  provided  with  nectar  and  strong  perfume  are 
usually  pollinated  by  insects.  Gaudy  colours  probably  at- 
tract insects  in  many  cases,  but  perfume  appears  to  be  a 
greater  attraction. 

The  insect  visits  the  flower  for  the 
nectar  (iox  the  making  of  honey)  and 
may  unknowingly  carry  the  pollen. 
Spurs  and  sacs  in  the  flower  are  necta- 
ries (Fig.  200),  but  in  spurless  flowers 
the  nectar  is  usually  secreted  in  the 
bottom  of  the  flower  cup.  This  compels 
the  insect  to  pass  by  the  anther  and 
Fig.  200.—  Flower  of  rub  against  the  pollen  before  it  reaches 
ARKSPUR.  ^j^^  nectar.     Sometimes  the  anther  is  a 

long  lever  poised  on  the  middle  point  and  the  insect 
bumps  against  one  end  and  lifts 
it,  thus  bringing  the  other  end 
of  the  lever  with  the  pollen  sacs 
down  on  its  back.  Flowers  that 
are  pollinated  by  insects  are  said 
to  be  entomophilous  ("  insect  lov- 
ing ").  Fig.  200  shows  a  larkspur. 
The  envelopes  are  separated  in 
Fig.  201.  The  long  spur  at  once 
suggests  insect  pollination.  The 
spur  is  a  sepal.  Two  hollow 
petals  project  into  this  spur,  ap- 
parently serving  to  guide  the 
bee's  tongue.  The  two  smaller 
petals,  in  front,  are  peculiarly 
coloured  and  perhaps  serve  the  bee  in  locating  the  nectary. 
The  stamens  ensheath  the  pistils  (Fig.  202).  As  the  insect 
stands  on  the  flower  and  thrusts  its  head  into  the  centre, 


Fig.  201.  —  Envelopes  of  a 
Larkspur.  There  are  five 
wide  sepals,  the  upper  one  be- 
ing spurred.  There  arc  four 
small  petals. 


THE  FL O  WER—  FER TILIZA  TION  AND  POLLINA  TION     149 


the  envelopes  are  pushed  downward  and  outward  and 
the  pistil  and  stamens  come  in  contact  with  its  abdomen. 
Since  the  flower  is  proterandrous,  the 
pollen  that  the  pistils  receive  from  the 
bee's  abdomen  must  come  from  another 
flower.  Note  a  somewhat  similar  ar- 
rangement in  the  toadflax  or  butter-and- 
eggs. 

In  some  cases  (Fig.  203)  the  stamens 
are  longer  than  the  pistil  in  one  flower 
and  shorter  in  another.  If  the  insect 
visits  siich  flowers,  it  gets  pollen  on  its 
head  from  the  long-stamen  flower,  and 
deposits  this  pollen  on  the  stigma  in  the 
long-pistil  flower.  Such  flowers  are  di- 
morphous (of  two  forms).  If  pollen  from  its  own  flower 
and  from  another  flower  both  fall  on  the  stigma,  the  proba- 
bilities are  that  the  stigma  will  choose  the  foreign  pollen. 


Fig.  202.  —  Stamens 
OF  Larkspur,  sur- 
rounding the  pistils. 


Fig.  203.— Dimorphic  Flowers  of  Primrose. 

Many  flowers  are  pollinated  by  the  wind.     They  are  said 
to  be  anemophilous  ('^wind  loving").     Such  flowers  pro- 


ISO 


BEGINNEJ^S'  BOTANY 


duce  great  quantities  of  pollen,  for  much  of  it  is  wasted. 
They  usually  have  broad  stigmas,  which  expose  large 
surfaces  to  the  wind.  They  are  usually  lacking  in  gaudy 
colours  and  in  perfume.  Grasses  and  pine  trees  are  typical 
examples  of  anemopliilous  plants. 

In  many  cases  cross-pollination  is  assured  because  the 

stamens  and  the  pistils  are  in  different  flowers  (diclinous). 

.  Monoecious    and 

, ,  /A.    >v  1  A.- 


I'lt 


dioecious  plants 
may  be  polli- 
nated by  wind  or 
insects,  or  other 
agents  (Fig.  204). 
They  are  usually 
wind  -  pollinated, 
although  willows 
are  often,  if  not 
mostly,  insect- 
pollinated.  The 
Indian  corn  is  a 
monoecious  plant. 
The  staminate 
flowers  are  in  a 
terminal  panicle 
(tassel).  The  pistillate  flowers  are  in  a  dense  spike  (ear), 
inclosed  in  *a  sheath  or  husk.  Each  "  silk "  is  a  style. 
Each  pistillate  flower  produces  a  kernel  of  corn.  Some- 
times a  few  pistillate  flowers  are  borne  in  the  tassel  and  a 
few  staminate  flowers  on  the  tip  of  the  ear.  Is  self-fertili- 
zation possible  with  the  corn  ?  Why  does  a  "  volunteer  " 
stalk  standing  alone  in  a  garden  have  only  a  few  grains 
on  the  ear }  What  is  the  direction  of  the  prevailing  wind 
in   summer?     If    only   two  or  three  rows   of. corn  are 


Fig.  204.  —  Flowers  of  Black  Walnut  :  two  pis- 
tillate flowers  at  ^,  and  staminate  catkins  at  B. 


THE  FL  O  WER  —  PER  T I  LIZA  TION  AND  POLLINA  TION     1 5 1 


planted  in  a  garden  where  prevailing  winds  occur,  in  which 
direction  had  they  better  run? 

Although  most  flowers  are  of  such  character  as  to  insure 
or  increase  the  chances  of  cross-pollination,  there  are  some 
that  absolutely  forbid  crossing.  These  flowers  are  usually 
borne  beneath  or  on  the 
ground,  and  they  lack 
showy  colours  and  per- 
fumes. They  are  known 
as  cleistogamous  flowers 
( meaning  self -fertilizing 
flowers).  The  plant  has 
normal  showy  flowers 
that  may  be  insect-pol- 
linated, and  in  addition 
is  provided  with  these 
simplified  flowers.  Only 
a  few  plants  bear  cleis- 
togamous flowers.  Hog- 
peanut,  common  blue 
violet,  fringed  winter- 
green,  and  dalibarda  are 
the  best  subjects  in 
this       country.  Fig. 

205  shows  a  cleistoga- 
mous flower  of  the  blue 
violet  at  a.  Above  the 
true  roots,  slender  stems  bear  these  flowers,  that  are 
provided  with  a  calyx,  and  a  curving  corolla  which  does 
not  open.  Inside  are  the  stamens  and  the  pistils.  Late  in 
the  season  the  cleistogamous  flowers  may  be  found  just 
underneath  the  mould.  They  never  rise  above  ground. 
The  following  summer  one  may  find  a  seedling  plant,  in 


Fig.  205.  — Common  Blue  Violet.  The 
familiar  flowers  are  shown,  natural  size. 
The  corolla  is  spurred.  Late  in  the  season, 
cleistogamous  flowers  are  often  borne  on 
the  surface  of  the  ground.  A  small  one  is 
shown  at  a.  A  nearly  mature  pod  is  shown 
at  b.  Both  a  and  b  are  one  third  natural 
size. 


152 


BEGINNERS*  BOTANY 


some  kinds  of  plants,  w;th  the  remains  of  the  old  cleistog- 
amous  flower  still  adhering  to  the  root.  Cleistogamous 
flowers    usually    appear    after   the   showy    flowers    have 


Fig.  206.  —  Pods  of  Peanuts  ripening  underground. 

passed.  They  seem  to  insure  a  crop  of  seed  by  a 
method  that  expends  little  of  the  plant's  energy.  The 
pupil  will  be  interested  to  work  out  the  fruiting  of  the  pea- 
nut (Fig.  206). 
Unbaked  fresh 
peanuts  grow 
readily  and  can 
easily  be  raised 
in  Canada,  in 
a  warm  sandy 
garden. 

Suggestions.  — 
152.  Not  all  the 
flowers  produce 
seeds.  Note  that 
an  apple  tree  may 
bloom  very  full, 
but  that  only  rela- 
tively few  apples 
may  result  (Fig.  207).  More  pollen  is  produced  than  is  needed  to 
fertilize  the  flowers;    this  increases  the  chances  that  sufficient 


Fig.  207. 


-Struggle  for  Existence  among  the 
Apple  Flowers. 


THE  FLOWER^ FERTILIZA TION  AND  POLLINA TION     1 53 

Stigmas  will  receive  acceptable  pollen  to  enable  the  plant  to 
perpetuate  its  kind.  At  any  time  in  summer,  or  even  in  fall, 
examine  the  apple  trees  carefully  to  determine  whether  any  dead 
flowers  or  flower  stalks  still  remain  about  the  apple ;  or,  examine 
any  full-blooming  plant  to  see  whether  any  of  the  flowers  fail. 
153.  Keep  watch  on  any  plant  to  see  whether  insects  visit  it. 
What  kind?  When?  What  for?  154.  Determine  whether  the 
calyx  serves  any  purpose  in  protecting  the  flower.  Very  carefully 
remove  the  calyx  from  a  bud  that  is  normally  exposed  to  heat 
and  sun  and  rain,  and  see  whether  the  flower  then  fares  as  well  as 
others.  155.  Cover  a  single  flower  on  its  plant  with  a  tiny  paper 
or  muslin  bag  so  tightly  that  no  insect  can  get  in.  If  the  flower 
sets  fruit,  what  do  you  conclude?  156.  Remove  carefully  the 
corolla  from  a  flower  nearly  ready  to  open,  preferably  one  that  has 
no  other  flowers  very  close  to  it.  Watch  for  insects.  157.  Find 
the  nectar  in  any  flower  that  you  study.  158.  Remove  the  stigma. 
What  happens  ?  159.  Which  of  the  following  plants  have  perfect 
flowers :  pea,  bean,  pumpkin,  cotton,  clover,  buckwheat,  potato, 
Indian  corn,  peach,  chestnut,  hickory,  watermelon,  sunflower,  cab- 
bage, rose,  begonia,  geranium,  cucumber,  calla,  willow,  cotton- 
wood,  cantaloupe  ?  What  have  the  others  ?  160.  On  wind- 
pollinated  plants,  are  either  anthers  or  stigmas  more  numerous  ? 
161.  Are  very  small  coloured  flowers  usually  borne  singly  or  in 
clusters  ?  162.  Why  do  rains  at  blooming  time  often  lessen 
the  fruit  crop  ?  163.  Of  what  value  are  bees  in  orchards  ? 
164.  The  crossing  of  plants  to  improve  varieties  or  to  obtain  new 
varieties.  —  It  may  be  desired  to  perform  the  operation  of  polli- 
nation by  hand.  In  order  to  insure  the  most  definite  results, 
every  effort  should  be  made  rightly  to  apply  the  pollen  which  it 
is  desired  shall  be  used,  and  rigidly  to  exclude  all  other  pollen. 
{a)  The  first  requisite  is  to  remove  the  anthers  from  the  flower 
which  it  is  proposed  to  cross,  and  they  must  be  removed  before  the 
pollen  has  been  shed.  The  flower-bud  is  therefore  opened  and  the 
anthers  taken  out.  Cut  ofl*  the  floral  envelopes  with  small,  sharp- 
pointed  scissors,  then  cut  out  or  pull  out  the  anthers,  leaving  only 
the  pistil  untouched ;  or  merely  open  the  corolla  at  the  end  and 
pull  out  the  anthers  with  a  hook  or  tweezers ;  and  this  method  is 
often  the  best  one.  It  is  best  to  delay  the  operation  as  long  as 
possible  and  yet  not  allow  the  bud  to  open  (and  thereby  expose 
the  flower  to  foreign  pollen)  nor  the  anthers  to  discharge  the 
pollen,  (^b)  The  flower  must  next  be  covered  with  a  paper  bag  to 
prevent  the  access  of  pollen  (Figs.  208,  209).  If  the  stigma  is  not 
receptive  at  the  time  (as  it  usually  is  not),  the  desired  pollen  is 
not  applied  at  once.  The  bag  may  be  removed  from  time  to  time 
to  allow  of  examination  of  the  pistil,  and  when  the  stigma  is 
mature,  which  is  told  by  its  glutinous  or  roughened  appearance, 


154 


BEGINNERS*  BOTANY 


the  time  for"  pollination  has  come.  If  the  bag  is  slightly  moist- 
ened, it  can  be  puckered  more  tightly  about  the  stem  of  the  plant. 
The  time  required  for  the  stigma  to  mature  varies  from  several 
hours  to  a  few  days,  {c)  When  the  stigma  is  ready,  an  unopened 
anther  from  the  desired  flower  is  crushed  on  the  finger  nail  or  a 
knife  blade,  and  the  pollen  is  rubbed  on  the  stigma  by  means  of  a 
tiny  brush,  the  point  of  a  knife  blade,  or  a  sliver  of  wood.    The 


Fig.  208.— a  Paper  Bag, 
with  string  inserted. 


Fig.  209.  — The  Bag  tied 
OVER  A  Flower. 


flower  is  again  covered  with  the  bag,  which  is  allowed  to  remain 
for  several  days  until  all  danger  of  other  pollination  is  past.  Care 
must  be  taken  completely  to  cover  the  stigmatic  surface  with 
pollen,  if  possible.  The  seeds  produced  by  a  crossed  flower  pro- 
duce hybrids^  or  plants  having  parents  belonging  to  diff'erent 
varieties  or  species.  165.  One  of  the  means  of  securing  new 
forms  of  plants  is  by  making  hybrids.     Why  ? 


Fig.  210. The  figr  «"  ^  hollow  torus  with  flowers  borne  on  th«  inside, 

and  pollinated  hy   insects  ihat  enrer  at  the  apex. 


CHAPTER   XX 


FLOWER-CLUSTERS 


have    seen   that 
Sometimes  the 


Origin    of   the    Flower-cluster.  —  We 

branches  arise  from  the  axils  of  leaves, 
leaves  may  be  reduced  to  bracts 
and  yet  branches  are  borne  in 
their  axils.  Some  of  the  branches 
grow  into  long  limbs  ;  others  be- 
come short  spurs;  others  bear 
flowers.  In  fact,  a  flower  is  it- 
self a  specialized  branch. 

Flowers  are  usually  borne 
near  the  top  of  the  plant.  Often 
they  are  produced  in  great  num- 
bers. It  results,  therefore,  that 
flower  branches  usually  stand 
close  together,  forming  a  clus- 
ter. The  shape  and  the  arrange- 
ment of  the  flower-cluster  differ 
with  the  kind  of  plants  since 
each  plant  has  its  own  mode  of 
branching. 

Certain  definite  or  well-marked 
types  of  flower-clusters  have  re- 
ceived names.  Some  of  these 
names  we  shall  discuss,  but  the 
flower-clusters  that  perfectly  match  the  definitions  are  the 
exception  rather  than  the  rule.     The  determining  of  the 

XS5 


Fig.  211.  —Terminal  Flowers 

OF  THE  WHITEWEED  (in  some 
places  called  ox-eye  daisy). 


ise 


BEGLWNERS*  BOTANY 


kip  is  of  flower-clusters  is  one  of  the  most  perplexing  sub- 
jects in  descriptive  botany.  We  may  classify  the  subject 
aronnd  three  ideas :  solitary  flowers,  centrifugal  or  deter- 
minnte  clusters,  centripetal  or  indeterminate  clusters. 

Solitary  Flowers.  —  In  many  cases  flowers  are  borne 
singly;  they  are  separated  from  other  flowers  by  leaves. 
Tbey  are  then  said  to  be  solitary.     The  solitary  flower  may 

be  either  at  the  end  of  the 
main  shoot  or  axis  (Fig.  2\\\ 
when  it  is  said  to  be  terminal ; 
or  from  the  side  of  the  shoot 
(Fig.  212),  when  it  is  said  to 
be  lateral  or  axillary. 

Centripetal  Clusters.  —  If 
the  flower-bearing  axils  were 
rather  close  together,  an  open 
or  leafy  flower-cluster  might 
result.  If  the  plant  continues 
to  grow  from  the  tip,  the 
older  flowers  are  left  farther 
and  farther  behind.  If  the 
cluster  were  so  short  as  to  be 
flat  or  convex  on  top,  the  out- 
ermost flowers  would  be  the 
older.  A  flower-cluster  in  which  the  lower  or  outer  flowers 
open  first  is  said  to  be  a  centripetal  cluster.  It  is  some- 
times said  to  be  an  indeterminate  cluster,  since  it  is  the 
result  of  a  type  of  growth  which  may  go  on  more  or  less 
continuously  from  the  apex. 

The  simplest  form  of  a  definite  centripetal  cluster  is  a 
raceme,  which  is  an  open  elongated  cluster  in  which  the 
flowers  are  boi-ne  singly  on  very  short  branches  and  open 
from  below  (that  is,  from  the  older  part  of  the  shoot) 


Fig.  212,  — Lateral  Flower  of 
AN  Abutilon.  a  greenhouse 
plant. 


FLOWER-CLUSTERS 


157 


upwards  (Fig.  213).     The  raceme  may  be  terminal  to  the 
main  branch;  or  it  may  be  lateral  to  it,  as  in  Fig.  214^ 

Racemes  often  bear  the 
flowers  on  one  side  of 
the  stem,  thus  form- 
ing a  single  row. 
When  a  cen- 
tripetal flower- 
cluster  is  long 
and  dense  and 
the   fl9wers    are 
sessile  or  nearly  so, 
it  is  called  a   spike 
(Fig.  215).    Common 
examples    of    spikes 
are   plantain,  migno- 
nette, mullein. 

A  very  short  and 
dense  spike  ^s  a. head. 
Clover  (Fig.  216)  is 
a  good  example.  The 
sunflower  and  related 
plants  bear  many 
small  flowers  in  a 
very  dense  and  often  flat  head.  Note  that  in  the 
sunflower  (Fig.  189)  the  outside  or  exterior  flowers 


Fig.  215.— 
Spike  of 
Plantain. 


Fig.  213.—  Raceme  of  Currant. 
Terminal  or  lateral  ? 


Fig.  214.  —  Lateral  Racemes  (in  fruit)  of  Barberry. 


158 


BEGINNERS'  BOTANY 


open  first.  Another  special  form  of  spike  is  the  catkin, 
which  usually  has  scaly  bracts,  the  whole  cluster  being 
deciduous  after  flowering  or  fruiting,  and  the  flowers  (in 
typical  cases)  having  only  stamens  or  pistils.     Examples 

are  the  "pussies"  of  willows  (Fig. 

182)  and  flower-clusters  of  oak  (Fig. 

180),  walnuts  (Fig.  204),  poplars. 


Fig.  216.  — Head  of  Clo- 
ver Blossoms. 


Fig.  217.  — Corymb  of  Candy- 
tuft. 


When  a  loose,  elongated  centripetal  flower-cluster  has 
some  primary  branches  simple,  and  others  irregularly 
branched,  it  is  called  a  panicle.  It  is  a  branching  raceme. 
Because  of  the  earlier  growth  of  the  lower  branches,  the 
panicle  is  usually  broadest  at  the  base  or  conical  in  outline. 
True  panicles  are  not  very  common. 

When  an  indeterminate  flower-cluster  is  short,  so  that 


FLOWER^CLUSTERS  1 59 

the  top  is  convex  or  flat ^  it  is  a  corymb  (Fig.  217).  The 
outermost  flowers  open  first  Centripetal  flower-clusters 
are  sometimes  said  to  be  corymbose  in  mode. 

When  the  branches  of  an  indeterminate  cluster  arise  from 
a  common  pointy  like  the  frame  of  an  umbrella,  the  cluster 
is  an  umbel  (Fig.  218).  Typical  umbels  occur  in  carrot, 
parsnip,  caraway,  and  other  plants  of  the  parsley  family : 
the  family  is  known  as  the  Umbelliferae,  or  umbel-bearing 


Fig.  218.  —  Remains  of  a  Last  Year's  Umbel  of  Wild  Carrot. 

family.  In  the  carrot  and  many  other  Umbelliferae,  there 
are  small  or  secondary  umbels,  called  umbellets,  at  the  end 
of  each  of  the  main  branches.  (In  the  centre  of  the  wild 
carrot  umbel  one  often  finds  a  single,  blackish,  often 
aborted  flower,  comprising  a  i -flowered  umbellet.) 

Centrifugal  or  Determinate  Clusters. — When  the  ter- 
minal or  central  flower  opens  first,  the  cluster  is  said  to  be 
centrifugal.  The  growth  of  the  shoot  or  cluster  is  deter- 
minate, since  the  length  is  definitely  determined  or  stopped 
by  the  terminal  flower.  Fig.  219  shows  a  determinate  or 
centrifugal  mode  of  flower  bearing. 


i6o 


BEGINNERS*   BOTANY 


Dense  centrifugal  clusters  are 
usually  flattish  on  top  because  of 
the  cessation  of  growth  in  the 
main  or  central  axis.  These  com- 
pact flower-clusters  are  known 
as  cymes.  Centrifugal  clusters 
are  sometimes  £aid  to  be  cymose 
in  mode.  Apples,  pears  (Fig. 
220),  and  elders  bear  flowers  in 
cymes.  Some  cyme-forms  are 
like  umbels  in  general  appear- 
ance. A  head-like  cymose  clus- 
ter is  a  glomerule ;  it  blooms  from 
the  top  downwards  rather  than 
from  the  base  upwards. 

Mixed  Clusters.  —  Often  the 
cluster  is  mixed,  being  determi- 
nate in  one  part  and  indeterminate 
in  another  part  of  the  same  clus- 
ter. The  main  cluster  may  be  indeterminate,  but  the 
branches  determinate.  The  cluster  has  the  appearance  of 
a  panicle,  and  is  usually  so  called,  but  it  is  really  a  thyrse. 
Lilac  is  a  familiar  example  of  a 
thyrse.  In  some  cases  the  main 
cluster  is  determinate  and  the 
branches  are  indeterminate,  as  in 
hydrangea  and  elder. 

Inflorescence.  —  The  mode  or 
method  of  flower  arrangement  is 
known  as  the  inflorescence.  That 
is,  the  inflorescence  is  cymose,  co- 
rymbose, paniculate,  spicate,  solitary,  determinate,  inde- 
terminate.    By  custom,  however,  the  word  "  inflorescence  " 


Fig.  219.  — Determinate  or 
Cymose  Arrangement.— 
Wild  geranium. 


Fig.  220.  — Cyme  of  Pear. 
Often  imperfect. 


FLO  WER-CL  USTERt, 


i6i 


M 

\ 

3     . 

\ 

2 

\ 

1     2     3    t*   !♦    3     2  .  '^ 


Fig.  221.  — Forms  of  Centripetal  Flower-clusters. 

Z*  raceme;  2,  spike;  3,  umbel;  4,  head  or  anthodium ;  5,  corymb. 


Fig.  222.  —  Centripetal  iNFLORESCEfiCE,  continued. 

6,  spadix ;  7,  compound  umbel ;  8,  catkin. 


WW 


./^ 


?/ 


Fig.  223.  — Centrifugal  Inflorescence. 

I,  cyme;  2,  scirpioid  raceme  (or  half  cyme). 


1 62  BEGINNERS'  BOTANY 

has  come  to  be  used  in  works  on  descriptive  botany  for 
the  flower-cluster  itself.  Thus  a  cyme  or  a  panicle  may  be 
called  an  inflorescence.  It  will  be  seen  that  even  solitary 
flowers  follow  either  indeterminate  or  determinate  methods 
of  branching. 

The  flower-stem.  —  The  stem  of  a  solitary  flower  is 
known  as  a  peduncle;  also  the  general  stem  of  2i  flower- 
cluster.  The  stem  of  the  individual  flower  in  a  cluster  is 
a  pedicel.  In  the  so-called  stemless  plants  the  peduncle 
may  arise  directly  from  the  ground,  or  crown  of  the  plant, 
as  in  dandelion,  hyacinth,  garden  daisy ;  this  kind  of 
peduncle  is  called  a  scape.  A  scape  may  bear  one  or 
many  flowers.  It  has  no  foliage  leaves,  but  it  may  have 
bracts. 

Suggestions. — 166.  Name  six  columns  in  your  notebook  as 
follows :  spike,  raceme,  corymb,  umbel,  cyme,  solitary.  Write 
each  of  the  following  in  its  appropriate  column :  larkspur,  grape, 
rose,  wistaria,  onion,  bridal  wreath,  banana,  hydrangea,  phlox, 
China  berry,  lily-of-the-valley,  Spanish  dagger  (or  yucca),  sorghum, 
tuberose,  hyacinth,  mustard,  goldenrod,  peach,  hollyhock,  mul- 
lein, crepe  myrtle,  locust,  narcissus,  snapdragon,  peppergrass, 
shepherd's  purse,  coxcomb,  wheat,  hawthorn,  geranium,  carrot, 
elder,  millet,  dogwood,  castor  bean ;  substitute  others  for  plants 
that  do  not  grow  in  your  region.  167.  In  the  study  of  flower- 
clusters,  it  is  well  to  choose  first  those  that  are  fairly  typical  of  the 
various  classes  discussed  in  the  preceding  paragraphs.  As  soon 
as  the  main  types  are  well  fixed  in  the  mind,  random  clusters 
should  be  examined,  for  the  pupil  must  never  receive  the  impres- 
sion that  all  flower-clusters  follow  the  definitions  in  books.  Clus- 
ters of  some  of  the  commonest  plants  are  very  puzzling,  but  the 
pupil  should  at  least  be  able  to  discover  whetljer  the  inflorescence 
is  determinate  or  indeterminate.  Figures  221  to  223  illustrate  the 
theoretical  modes  of  inflorescence.  The  numerals  indicate  the  order 
of  opening. 


CHAPTER  XXI 
FRUITS 

The  ripened  ovary,  with  its  attachments,  is  known  as  the 
fruit.  It  contains  the  seeds.  If  the  pistil  is  simple,  or  of 
one  carpel,  the  fruit 
also  will  have  one  com- 
partment. If  the  pistil 
is  compound,  or  of 
more  than  one  carpel, 
the  fruit  usually  has  an 
equal  number  of  com- 
partments. The  com- 
partments in  pistil  and 
fruit  are  known  as  lo- 
cules  (from  Latin  locus^ 
meaning  "a  place"). 

The  simplest  kind 
of  fruit  is  a  ripened 
\-loculed  ovary.  The 
first  stage  in  complex-  fig.  224.. 
ity  is  a  ripened  2-  or 
many-loculed  ovary.  Very  complex  forms  may  arise  by  the 
attachment  of  other  parts  to  the  ovary.  Sometimes  the  style 
persists  and  becomes  a  beak  (mustard  pods,  dentaria, 
Fig.  224),  or  a  tail  as  in  clematis ;  or  the  calyx  may  be 
attached  to  the  ovary ;  or  the  ovary  may  be  embedded  in 
the  receptacle,  and  ovary  and  receptacle  together  consti- 
tute the  fruit ;  or  an  involucre  may  become  a  part  of  the 

16^ 


Dentaria,  or  Tooth-wort,  in 

fruit. 


164 


^EGINNEIiS'  BOTANY 


fruit,  as  possibly  in  the  walnut  and  the  hickory  (Fig.  225), 
and  the  cup  of  the  acorn  (Fig.  226).  The  chestnut  and  the 
beech  bear  a  prickly  involucre,  but  the  nuts, 


Fig.  225.  —  Hickory-nut. 
The  nut  is  the  fruit,  con- 
tained in  a  husk. 


Fig.  226.  — Live-oak  Acorn. 
The  fruit  is  the  "  seed  "  part ; 
the  involucre  is  the  "  cup." 


or  true  fruits,  are  not  grown  fast  to  it,  and  the  involucre 
can  scarcely  be  called  a  part  of  the  fruit.  A  ripened  ovary 
is  a  pericarp.  A  pericarp  to  which  other  parts  adhere  has 
been  called  an  accessory  or  reenforced  fruit.  (Page  169.) 
Some  fruits  are  dehiscent,  or  split  open  at  maturity  and 
liberate  the  seeds ;  others  are  indehiscent,  or  do  not  open. 
A  dehiscent  pericarp  is  called  a  /  pod 
The  parts  into  which  such 
a  pod  breaks  or  splits  are 
known  as  valves.  In  inde- 
hiscent fruits  the  seed  is 
hberated  by  the  decay  of 
the  envelope,  or  by  the 
rupturing  of  the  envelope 
by  the  germinating  seed. 
Indehiscent  winged  peri- 
carps are  known  as  samaras  or  key  fruits. 


Fig.  227.  —  Key  of 
Sugar  Maple. 


Fig.  228.  —  Key 

of  Common 
American  Elm. 


Maple  (Fig. 


227),  elm  (Fig.  228),  and  ash  (Fig.  93)  are  examples. 


FRUITS 


165 


Fig.  229.— 
Akenes  of 
Buttercup. 


Fig.  230.  — Akenes 
OF  Buttercup, 
one  in  longitudi- 
nal section. 


Pericarps.  —  The  simplest  pericarp  is  a  dry,  one- 
seeded,  indehiscent  body.  It  is  known  as  an  akene.  A 
head  of  akenes  is  shown  in  Fig.  229,  and  the 
structure  is  explained  in  Fig. 
230.  Akenes  may  be  seen  in 
buttercup,  hepatica,  anemone, 
smartweed,  buckwheat. 

A  i-loculed  pericarp  which 
dehisces  along  the  front  edge 
(that  is,  the  inner  edge,  next 
the  centre  of  the  flower  is  a  follicle.  The  fruit  of  the 
larkspur  (Fig.  231)  is  a  follicle.  There  are  usually  five  of 
these  fruits  (sometimes  three  or 
four)  in  each  larkspur  flower,  each 
pistil  ripening  into  a  follicle.  If 
these  pistils  were  united,  a  single 
compound  pistil  would  be  formed. 
Columbine,  peony,  ninebark,  milk- 
weed, also  have  folHcles. 

A  i-loculed  pericarp  that  de- 
hisces on  both  edges  is  a  legume. 
Peas  and  beans  are  typical  exam- 
ples (Fig.  232);  in  fact,  this  character  gives 
name  to  the  pea  family,  —  Leguminosae. 
Often  the  valves  of  the 
legume  twist  forcibly  and 
expel  the  seeds,  throwing 
them  some  distance.  The 
word  "  pod  "  is  sometimes  restricted  to 
legumes,  but  it  is  better  to  use  it  generi- 
cally  /or  all  dehiscent  pericarps. 

A  compound  pod  —  dehiscing  peri- 
carp of  two  or  more  carpels  —  is  a  capsule  (Figs.  233,  234,* 


Fig.  231.— 
Follicle 
OF  Lark- 
spur. 


Fig.  232.— a 
Bean  Pod. 


Fig.  233.  — Capsule  of 
Castor  -  oil  Bean 
AFTER  Dehiscence. 


i66 


BEGINNERS'  BOTANY 


Fig.  234.  — Cap- 
sule OF  Morn- 
ing Glory. 


236,  237).  Some  capsules  are  of  one 
locule,  but  they  may  have  been  compound 
when  young  (in  the  ovary  stage)  and  the 
partitions  may  have  vanished.  Sometimes 
one  or  more  of  the  carpels  are  uniformly 
crowded  out  by  the  exclusive  growth  of 
other  carpels  (Fig.  235).  The  seeds  or 
parts  which  are  crowded  out  are  said  to 
be  aborted. 

There  are  several  ways  in  which  cap- 
sules dehisce  or  open.  When  they  break 
along  the  partitions  (or  septa),  the  mode  is  known  as  septi- 
cidal  dehiscence  (Fig.  236); 
In  septicidal dehiscence  the 
fruit  separates  into  parts 
representing  the  original 
carpels.  These  carpels 
may  still  be  entire,  and 
they  then  dehisce  individu- 
ally, usually  along  the  inner 
edge  as  if  they  were  follicles.     When  the  compartments 

split  ill  the  middle^  between  the 
partitions,  the  mode  is  loculicidal 
dehiscence  (Fig.  237).  In  some 
cases  the  dehiscence  is  at  the  top, 
when  it  is  said  to  be  apical  (al- 
though several  modes  of  dehis- 
cence are  here  included).  When 
the  luhole  top  comes  off,  as  in  purs- 
lane and  garden  portulaca  (Fig. 
238),  the  pod  is  known  as  a  pyxis.  In  some  cases  apical 
dehiscence  is  by  means  of  a  hole  or  clefts. 

The  peculiar  capsule  of  the  mustard  family,  or  Cruci- 


Fig.  235.  —  Three-carpeled  Fruit 
OF  Horse-chestnut.  Two  locules 
are  closing  by  abortion  of  the  ovules. 


Fig.  236.  — 
St.   John's 
Wort.  Sep- 
ticidal. 


Fig.  237. — 
Loculici- 
dal Pod  of 
Day-lily. 


FRUITS 


167 


ferae,  is  known  as  a  silique  when  it  is  distinctly  longer  than 
broad  (Fig.  224),  and  a  silicle  when  its  breadth  nearly 


Fig.  238.  —  Pyxis  of  Poktu- 
LACA  OR  Rose-moss. 


Fig.  239.  — Berries  of  Goose- 
berry.   Remains  of  calyx  at  c^ 


equals  or  exceeds  its  length.  A  cruciferous  capsule  is 
2-carpeled,  with  a  thin  partition,  each  locule  containing 
seeds  in  two  rows.  The  two  valves  detach  from  below 
upwards.     Cabbage,  turnip,  mustard,  water-cress,  radish, 

rape,  shepherd's  purse, 
sweet  alyssum,  wall- 
flower, honesty,  are 
examples. 


Fig.  240.—  Berry  of  the  Ground  Cherry 
or  Husk  Tomato,  contained  in  the  inflated 
calyx. 

The  pericarp  may  h^  fleshy  and 
indehiscent.  A  pulpy  pericarp 
with  several  or  many  seeds  is  a 
berry  (Figs.  239,  240,  241).  To 
the  horticulturist  a  berry  is  a 
small,  soft,  edible  fruit,  without 


Fig.  241.— Orange;  example 
of  a  berry. 


1 68 


BEGINNERS'  BOTANY 


particular  reference  to  its  structure.  The  botanical  and 
horticultural  conceptions  of  a  berry  are,  therefore,  unlike. 
In  the  botanical  sense,  gooseberries,  currants,  grapes,  to- 
matoes, potato-balls,  and  even  eggplant  fruits  and  oranges 
(Fig.  241)  are  berries;  strawberries,  raspberries,  black- 
berries are  not. 

A  fleshy  pericarp  containing  one  relatively  large  seed 
or  stone  is  a  drupe.  Examples  are  plum  (Fig.  242),  peach, 
cherry,  apricot,  olive.  The  walls  of 
the  pit  in  the  plum,  peach,  and  cherry 
are  formed  from  the  inner  coats  of 
the  ovary,  and  the  flesh  from  the 
outer  coats.  Drupes  are  also  known 
as  stone-fruits. 

Fruits  that  are  formed  by  the  sub- 
sequent union  of  separate  pistils  are 
aggregate  fruits.  The  carpels  in 
aggregate  fruits  are  usually  more  or  less  fleshy.  In  the  rasp- 
berry and  the  blackberry  flower,  the  pistils  are  essentially 
distinct,  but  as  the 
pistils  ripen  they  co- 
here and  form  one 
body(Figs.  243,  244). 


Fig.  243.  —  Fruit  of  Rasp- 
berry. 


Each  of  the  carpels  or  pistils  in  the 
raspberry  and  the  blackberry  is  a 
little  drupe  or  drupelet.  In  the 
raspberry  the  entire  fruit  separates 
from  the  torus,  leaving  the  torus  on 
the  plant.     In  the  blackberry  and 


Fig.  242.  — Plum;  exam- 
ple of  a  drupe. 


Fig.  244.  — Aggregate 

Fruit  of  Mulberry; 

and  a  separate  fruit. 


FRUITS 


169 


the  dewberry  the  fruit  adheres  to  the  torus,  and  the  two  are 

removed  together  when  the  fruit  is  picked. 
Accessory  Fruits.  —  When  the  pericarp  and  some  other 

part  grow  together,  the  fruit  is  said  to  be  accessory  or 
reenforced.  An  example  is  the  straw- 
berry (Fig.  245).  The  edible  part  is  a 
greatly  ett large d  tonis,  and  the  pericarps 
are  akenes  embedded  in  it.  These  akenes 
are  commonly  called  seeds. 

Various  kinds  of  reenforced  fruits  have 
received  special  names.  One  of  these  is 
the  hip,  characteristic  of  roses.  In  this 
case,  the  torus  is  deep  and  hollow,  like  an 
urn,  and  the  separate  akenes  are  borne 
inside  it.     The  mouth  of  the  receptacle 

may  close,  and  the  walls  sometimes  become  fleshy ;  the 

fruit  may  then  be  mistaken  for  a  berry.     The  fruit  of  the 

pear,  apple,  and  quince  is  known  as  a 


{i'lG.  245.  —  Straw- 
berry; fleshy 

torus  in  which  akenes 
are  embedded. 


Fig.  246.  — Section  of 
AN  Apple. 


Fig.  247.  —  Cross-section 
OF  AN  Apple. 


pome.  In  this  case  the  five  united  carpel?  are  completely 
buried  in  the  hollow  torus,  and  the  torus  makes  most  of 
the  edible  part  of  the  ripe  fruit,  while  the  pistils  are  repre- 
sented by  the  core  (Fig.  246).  Observe  the  sepals  on  the 
top  of  the  torus  (apex  of  the  fruit)  in  Fig.  246.  Note 
the  outUnes  of  the  embedded  pericarp  in  Fig.  247. 


I70  BEGINNERS'  BOTANY 

Gymnospermous  Fruits. — In  pine,  spruces,  and  their  kin, 
there  is  no  fruit  in  the  sense  in  which  the  word  is  used 
in  the  preceding  pages,  because  the^-e  is  7to  ovary.  The 
ovules  are  naked  or  uncovered,  in  the  axils  of  the  scales  of 
the  young  cone,  and  they  have  neither  style  nor  stigma. 
The  pollen  falls  directly  on  the  mouth  of  the  ovule.  The 
ovule  ripens  into  a  seed,  which  is  usually  winged.  Because 
the  ovule  is  not  borne  in  a  sac  or  ovary,  these  plants  are 
called  gymnosperms  (Greek  for  "naked  seeds").  All  the 
true  cone-bearing  plants  are  of  this  class;  also  certain 
other  plants,  as  red  cedar,  juniper,  yew.  The  plants  are 
monoecious  or  sometimes  dioecious.  The  staminate  flowers 
are  mere  naked  stamens  borne  beneath  scales,  in  small 
yellow  catkins  which  soon  fall.  The  pistillate  flowers  are 
naked  ovules  beneath  scales  on  cones  that  persist  (Fig. 
29).     Gymnospermous  seeds  may  have  several  cotyledons. 

Suggestions. — 168.  Study  the  following  fruits,  or  any  five  fruits 
chosen  by  the  teacher,  and  answer  the  questions  for  each:  Apple, 
peach,  bean,  tomato,  pumpkin.  What  is  its  form?  Locate  the 
scar  left  by  the  stem.  By  what  kind  of  stem  was  it  attached? 
Are  there  any  remains  of  the  blossom  at  the  blossom  end?  De- 
scribe texture  and  colour  of  surface.  Divide  the  fruit  into  the  seed 
vessel  and  the  surrounding  part.  Has  the  fruit  any  pulp  or  flesh? 
Is  it  within  or  without  the  seed  vessel?  Is  the  seed  vessel  simple 
or  sub-divided?  What  is  the  number  of  seeds?  Are  the  seeds 
free,  attached  to  the  wall  of  the  vessel,  or  to  a  support  in  the 
centre?  Are  they  arranged  in  any  order?  What  kind  of  wall  has 
the  seed  vessel?  What  is  the  difference  between  a  peach  stone 
and  a  peach  seed?  169.  The  nut  fruits  are  always  available  for 
study.  Note  the  points  suggested  above.  Determine  what  the 
meat  or  edible  part  represents,  whether  cotyledons  or  not.  Figure 
248  is  suggestive.  170-  Mention  all  the  fleshy  fruits  you  know, 
tell  where  they  come  from,  and  refer  them  to  their  proper  groups. 
171.  What  kinds  of  fruit  can  you  buy  in  the  market,  and  to  what 
groups  or  classes  do  they  belong?  Of  which  fruits  are  the  seeds 
only,  and  not  the  pericarps,  eaten?  172.  An  ear  of  corn  is  always 
available  for  study.  What  is  it— a  fruit  or  a  collection  of  fruits? 
How  are  the  grains  aranged  on  the  cob?  How  many  rows  do 
you  count  on  each  of  several  ears?       Are  all  the   rows  on  an  ear 


FRUITS  17, 

equally  close  together?  Do  you  find  an  ear  with  an  odd  number 
of  rows?  How  do  the  parts  of  the  husR  overlap?  Does  the 
husk  serve  as  protection  from  rain?  Can  birds  pick  out  the  grains? 
How  do  insect  enemies  enter  the  ear?  How  and  when  do  weevils 
lay  eggs  on  corn?  173.  Study  a  grain  of  corn.  Is  it  a  seed? 
Describe  the  shape  of  a  grain.  Colour.  Size.  Does  its  surface 
show  any  projections  or  depressions!  Is  the  seed-coat  thin  or 
thick?  Transparent  or  opaque?  Locate  the  hilum.  Where  is 
the  silk  scar?  What  is  the  silk?  Sketch  the  grain  from  the  two 
points  of  view  that  show  it  best.  Where  is  the  embryo?  Does 
the  grain  have  endosperm  ?  What  is  dent  corn?  Flint  corn? 
How  many  kinds  of  corn  do  you  know?       For  what  are  they  used? 


Fig.  248.  — Pecan 
Fruit. 


Note  to  Teacher. — There  are  few  more  interesting  subjects 
to  beginning  pupils  than  fruits, — the  ■j)ods  of  many  kinds,  forms, 
and  colours,  the  berries,  and  nuts.  This  interest  may  well  be 
utilized  to  make  the  teaching  alive.  All  common  edible  fruits 
of  orchard  and  vegetable  garden  should  be  brought  into  this  dis- 
cussion. Of  dry  fruits,  as  pods,  burs,  nuts,  collections  may  be 
made  for  the  school  museum.  Fully  mature  fruits  are  boat  for 
study,  particularly  if  it  is  desired  to  see  dehiscence.  For  com- 
parison, pistils  and  partially  grown  fruits  should  be  had  at  the 
same  time.  If  the  fruits  are  not  ripe  enough  to  dehisce,  they 
may  be  placed  in  the  sun  to  dry.  In  the  school  it  is  well  to  have 
a  collection  of  fruits  for  study.  The  specimens  may  be  kept  in 
glass  jars.  Always  note  exterior  of  fruit  and  its  parts;  interior 
of  fruit  with  arrangement  and  attachment  of  contents. 


CHAPTER  XXII 


DISPERSAL  OF  SEEDS 


It  is  to  the  plant's  advantage  to  have  its  seeds  distributed 
as  widely  as  possible.  //  has  a  better  chance  of  sjirviving 
in  the  struggle  for  existence.  It  gets  away  from  competi- 
tion. Many  seeds  and  fruits  are  of  such  character  as  to 
increase  their  chances  of  wide  dispersal.  The  commonest 
means  of  dissemination  may  be  classed  under  four  heads : 
explosive  fruits  ;  transportation  by  wind ;  transportation  by 
birds ;  burs. 


Fig.  249.  -^  Explosion  of 
THE  Balsam  Pod. 


Fig.  250.  —  Explosive 
Fruits  of  Oxalis. 

An  exploding  pod  is  shown 
at  c.  The  dehiscence  is 
shown  at  l>.  The  structure 
of  the  pod  is  seen  at  a. 


Explosive  Fruits.  —  Some  pods  open  with  explosive  force 
and  discharge  the  seeds.  Even  beans  and  everlasting  peas 
do  this.  More  marked  examples  are  the  locust,  witch 
hazel,  garden  balsam  (Fig.  249),  wild  jewel-weed  or  impa- 
tiens  (touch-me-not),  violet,  crane's-bill  or  wild  geranium, 
bull  nettle,  morning  glory,  and  the  oxalis  (Fig.  250).     The 

172 


DISPERSAL    OF  SEEDS 


173 


oxalis  is  common  in  several  species  in  the  wild  and  in 
cultivation.  One  of  them  is  known  as  wood  sorrel.  Figure 
250  shows  the  common  yellow  oxaHs.  The  pod  opens 
loculicidally.  The  elastic  tissue  suddenly  contracts  when 
dehiscence  takes  place,  and  the  seeds  are  thrown  violently. 
The  squirting  cucumber  is  easily  grown  in  a  garden  (pro- 
cure seeds  of  seedsmen),  and  the  fruits  discharge  the  seeds 
with  great  force,  throwing  them  many 
feet. 

Wind  Travelers.  —  Wind -transported 
seeds  are  of  two  general  kinds :  those 
that  are  provided  with  wingSy  as  the  flat 
seeds  of  catalpa  (Fig.  251)  and  cone-bear- 
ing trees  and  the  samaras  of  ash,  elm, 
tulip-tree,  ailanthus,  and  maple;  and 
those  which  have  feathery  buoys  or  para- 
chutes to  enable  them  to  float  in  the  air. 
Of  the  latter  kind  are  the  fruits  of  many 
composites,  in  which  the  pappus  is 
copious  and  soft.  Dandelion  and  thistle 
are  examples.  The  silk  of  the  milkweed 
and  probably  the  hairs  on  the  cotton  seed 
have  a  similar  office,  and  also  the  wool  of 
the  cat-tail.  Recall  the  cottony  seeds  of 
the  willow  and  the  poplar. 

Dispersal  by  Birds.  —  Seeds  of  berries  and  of  other 
small  fle&hy  fruits  are  carried  far  and  wide  by  birds.  The 
pulp  is  digested,  but  the  seeds  are  not  injured.  Note  how 
the  cherries,  raspberries,  blackberries,  June-berries,  and 
others  spring  up  in  the  fence  rows,  where  the  birds  rest. 
Some  berries  and  drupes  persist  far  into  winter,  when  they 
supply  food  to  cedar  birds,  robins,  and  the  winter  birds. 
Red  cedar  is  distributed  by  birds.     Many  of  these  pulpy 


Fig.  251.  —  Winged 
Seeds  of  Catalpa. 


174 


BEGINNERS'  BOTANY 


fruits  are  agreeable  as  human  food,  and  some  of  them 
have  been  greatly  enlarged  or  "  improved  "  by  the  arts  of 
the  cultivator.     The  seeds  are  usually  indigestible. 

Burs.  —  Many  seeds  and  fruits  bear  spines,  hooks,  and 
hairs,  which  adhere  to  the  coats  of  animals  a7id  to  clothing. 
The  burdock  has  an  involucre  with  hooked  scales,  contain- 
ing the  fruits  inside.  The  clotbur  is  also  an  involucre. 
Both  are  composite  plants,  allied  to  thistles,  but  the 
whole  head,  rather  than  the  separate 
fruits,  is  transported.  In  some  com- 
posite fruits  the  pappus  takes  the 
form  of  hooks  and  spines,  as  in  the 
"  Spanish  bayonets  "  and  "  pitch- 
forks." Fruits  of  various  kinds  are 
known  as  "stick  tights,"  as  of  the 
agrimony  and  hound's-tongue.  Those 
who  walk  in  the  woods  in  late  sum- 
mer and  fall  are  aware 
that  plants  have  means 
of  disseminating  them- 
selves (Fig.  252).  If  it 
is  impossible  to  iden- 
tify the  burs  which  one 
finds  on  clothing,  the  seeds  may  be  planted  and  specimens 
of  the  plant  may  then  be  grown. 


Fig.  252.  — Stealing  a  Ride. 


Suggestions.  — 174.  What  advantage  is  it  to  the  plant  to  have 
its  seeds  widely  dispersed?  175.  What  are  the  leading  ways  in 
which  fruits  and  seeds  are  dispersed?  176.  Name  some  explosive 
fruits.  177.  Describe  wind  travelers.  178.  What  seeds  are  car- 
ried by  birds?  179.  Describe  some  bur  with  which  you  are 
familiar.  180.  Are  adhesive  fruits  usually  dehiscent  or  indehis- 
cent?  181.  Do  samaras  grow  on  low  or  tall  plants,  as  a  rule? 
182.  Are  the  cotton  fibres  on  the  seed  or  on  the  fruit?  183. 
Name  the  ways  in  which  the  common  weeds  of  your  region  are 
disseminated.     184.    This  lesson  will  suggest  other  ways  in  which 


DISPERSAL    OF  SEEDS 


175 


seeds  are  transported.  Nuts  are  buried  by  squirrels  for  food ;  but 
if  they  are  not  eaten,  they  may  grow.  Tiie  seeds  of  many  plants 
are  blown  on  the  snow.  The  old  stalks  of  weeds,  standing  through 
the  winter,  may  serve  to  disseminate  the  plant.  Seeds  are  carried 
by  water  down  the  streams  and  along  shores.  About  woollen  mills 
strange  plants  often  spring  up  from  seed  brought  in  the  fleeces. 
Sometimes  the  entire  plant  is  rolled  for  miles  before  the  winds. 
Such  plants  are  "  tumbleweeds."  Examples  are  Russian  thistle, 
hair  grass  or  tumblegrass  {Panicu7n  capillare),  cyclone  plant 
{Cycioloma  platyphyllujti)^  and  white  amaranth  {Amaranti4s 
albus).  About  seaports  strange  plants  are  often  found,  having 
been  introduced  in  the  earth  that  is  used  in  ships  for  ballast. 
These  plants  are  usually  known  as  "  ballast  plants."  Most  of  them 
do  not  persist  long.  185.  Plants  are  able  to  spread  themselves  by 
means  of  the  great  numbers  of  seeds  that  they  produce.  How 
many  seeds  may  a  given  elm  tree  or  apple  tree  or  raspberry  bush 
produce  ? 


Fig.  253.  — The    Fruits 
OF  THE  Cat-tail  are 

LOOSENED       BY       WiND 

AND  Weather. 


CHAPTER   XXIII 


PHENOGAMS  AND  CRYPTOGAMS 


Fig.  254.  —  Christmas  Fern. 
—  Dryopteris  acrostichoides ; 
known  also  as  Aspidium. 


The  plants  thus  far  studied  produce  flowers;  and  the 

flowers  produce  seeds  by  means  of  which  the  plant  is  prop- 
agated. There  are  other  plants, 
however,  that  produce  no  seeds, 
and  these  plants  (including  bac- 
teria) are  probably  more  numer- 
ous than  the  seed-bearing  plants. 
These  plants  propagate  by  means 
of  spores,  which  are  generative  cells  ^ 
tisiially  simple y  containing  no  em- 
bryo. These  spores  are  very  small, 
and  sometimes  are  not  visible  to 
the  naked  eye. 
Prominent  among  the  spore- 
propagated  plants  are  ferns.     The 

common  Christmas  fern  (so  called 

because  it  remains  green   during 

winter)  is  shown  in  Fig.  254.    The 

plant  has  no  trunk.     The  leaves 

spring  directly  from  the  ground. 

The   leaves    of   ferns   are    called 

fronds.     They   vary   in  shape,  as 

other    leaves    do.     Some    of    the 

fronds  in  Fig.  254  are  seen  to  be      F'«-  ^55- fruiting  frond 

OF  Christmas  Fern. 

narrower  at  the  top.     If  these  are     „  ,        ^  .  ^ .   , 

Son  at  a.    One  sorus  with  its  in- 

examined  more  closely  (Fig.  255),  dusiumat^. 

176 


PHENOGAMS  AND   CRYPTOGAMS 


177 


it  will  be  seen  that  the  leaflets  are  contracted  and  are 
densely  covered  beneath  with  brown  bodies.  These  bodies 
are  collections  of  sporangia  or  spore-cases. 


Fig.  256.  — Common  Polypode  Fern. 
Polypodium  vulgare. 


Fig.  257.  — Sori  and  Spo- 
rangium of  Polypode. 
A  chain  of  cells  lies  along 
the  top  of  the  sporangium, 
which  springs  back  elasti- 
cally  on  drying,  thus  dis- 
seminating the  spores. 


Fig.  258.  — The  Brake 
Fruits  underneath 
THE  Revolute 
Edges  of  the  Leaf. 


The  sporangia  are  collected  into  little  groups,  known  as 
sori  (singular,  sorus)  or  fruit-dots.  Each  sorus  is  covered 
with  a  thin  scale  or  shield,  known  as 
an  indusium.  This  indusium  sepa- 
rates from  the  frond  at  its  edges,  and 
the  sporangia  are  exposed.  Not  all 
ferns  have  indusia.  The  polypode 
(Figs.  256,  257)  does  not;  the  sori 
are  naked.     In  the  brake  (Fig.  258) 

and  maidenhair  (Fig.  259)  the 
edge  of  the  frond  turns  over 
and  forms  an  indusium.  The 
nephrolepis  or  sword  fern  of 
greenhouses  is  allied  to  the 
polypode.  The  sori  are  in  a 
single  row  on  either  side  the 
midrib  (Fig.  260).  The  indu- 
sium is  circular  or  kidney- 
Fig.  259.— Fruiting  Pinnules 

OF  Maidenhair  Fern.  shaped  and  open  at  one  edge 


1/8 


BEGINNERS'  BOTANY 


Fig.  260.  —  Part  of  Frond  of 
Sword  Fern.  To  the  pupil :  Is 
this  illustration  right  side  up  ? 


or  finally  all  around.  The 
Boston  fern,  Washington  fern, 
Pierson  fern,  and  others,  are 
horticultural  forms  of  the 
common  sword  fern.  In  some 
ferns  (Fig.  261)  an  entire 
frond  becomes  contracted  to 
cover  the  sporangia.  • 
The  sporangium  or  spore-case  of  a  fern  is  a  more  or  less 
globular  body  and  usually  with  a  stalk  (Fig.  257).  //  con- 
tarns  the  spoi'es.  When  ripe  it 
bursts  and  the  spores  are  set  free. 
In  a  moist,  warm  place  the  spores 
germinate.  They  produce  a  small, 
flat,  thin,  green,  more  or  less  heart- 
shaped  membrane  (Fig.  262).  This 
is  the  prothallus.  Sometimes  the 
prothallus  is  an  inch  or  more  across, 
but  oftener  it  is  less  than  a  ten  cent 
piece  in  size.  Although  easily 
seen,  it  is  commonly  unknown  ex- 
cept to  botanists.  Prothalli  may 
often  be  found  in  greenhouses  where  ferns  are  grown. 

Look  on  the  moist  stone  or 
brick  walls,  or  on  the  firm  soil 
of  undisturbed  pots  and  beds ; 
or  spores  may  be  sown  in  a 
damp,  warm  place. 

On   the   under   side  of   the 
prothallus  two  kinds  of  organs 

are     borne.     These     are    the 
Fig.  262.  — Prothallus  of  a  ,  .  /        .    •    • 

FERN.   Enlarged.  archegonium   (contammg   ^gg- 

Archegonia  at  a  ;  antheridia  at  b.  CcUs)  and  the  anthcridium  (COU- 


FiG.  261.— Fertile  and 

Sterile  Fronds  of  the 

Sensitive  Fern. 


PHENOGAMS  AND    CRYPTOGAMi>  179 

taining  sperm-cells).  These  organs  are  minute  specialized 
parts  of  the  prothallus.  Their  positions  on  a  particular 
prothallus  are  shown  at  a  and  b  in  Fig.  262,  but  in  some 
ferns  they  are  on  separate  prothalli  (plant  dioecious).  The 
sperm-cells  escape  from  the  a7itheridinm  and  in  the  water 
that  collects  on  the  prothallus  are  carried  to  the  archegoniumy 
where  fertilizatiori  of  the  egg  takes  place.  From  the  ferti- 
lized egg-cell  a  plant  grows,  becoming  a  "fern."  In 
most  cases  the  prothallus  soon  dies.  The  prothallus  is  the 
gametophyte  (from  Greek,  signifying  the  fertilized  plant). 

The  fern  plant,  arising  from  the  fertilized  0,^^  in  the 
archegonium,  becomes  a  perennial  plant,  each  year  pro- 
ducing spores  from  its  fronds  (called  the  sporophyte) ;  but 
these  spores — which  are  merely  detached  special  kinds  of 
cells  —  produce  the  prothallic  phase  of  the  fern  plant, 
from  which  new  individuals  arise.  A  fern  is  fertilized  but 
once  in  its  lifetime.  The  "fern"  bears  the  spore,  the 
spore  gives  rise  to  the  prothallus,  and  the  egg-cell  of  the 
prothallus  (when  fertilized)  gives  rise  to  the  fern. 

A  similar  alternation  of  generations  runs  all  through  the 
vegetable  kingdom,  although  there  are  some  groups  of 
plants  in  which  it  is  very  obscure  or  apparently  wanting. 
It  is  very  marked  in  ferns  and  mosses.  In  algae  (includ- 
ing the  seaweeds)  the  gametophyte  is  the  "  plant,"  as 
the  non-botanist  knows  it,  and  the  sporophyte  is  incon- 
spicuous. There  is  a  general  tetidency,  in  the  evolution  of 
the  vegetable  kingdo^n^  for  the  gametophyte  to  lose  its  rela- 
tive importance  a7id  for  the  sporophyte  to  become  larger  and 
more  highly  developed.  In  the  seed-bearing  plants  the 
sporophyte  generation  is  the  only  one  seen  by  the  non- 
botanist.  The  gametophyte  stage  is  of  short  duration  and 
the  parts  are  small ;  it  is  confined  to  the  time  of  fertiliza« 
tion. 


l80  BEGINNERS'  BOTANY 

The  sporophyte  of  seed  plants,  or  the  ** plant"  as  we 
know  it,  produces  two  kinds  of  spores  —  one  kind  becom- 
ing pollen -grains  and  the  other  kind  embryo-sacs.  The 
pollen-spores  are  borne  in  sporangia,  which  are  united  into 
what  are  called  anthers.  The  embryo-sac,  which  contains 
the  egg-cell,  is  borne  in  a  sporangium  known  as  an  ovule. 
A  gametophytic  stage  is  present  in  both  pollen  and  embryo 
sac  :  fertilization  takes place^  and  a  sporophyte  arises.  Soon 
this  sporophyte  becomes  dormant,  and  is  then  known  as  att 
embryo.  The  embryo  is  packed  away  within  tight-fitting 
coats,  and  the  entire  body  is  the  seed.  When  the  condi- 
tions are  right  the  seed  grows,  and  the  sporophyte  grows 
into  herb,  bush,  or  tree.  The  utility  of  the  alternation  of 
generations  is  not  understood. 

The  spores  of  ferns  are  borne  on  leaves ,-  the  spores  of 
seed-bearing  plants  are  also  borne  amongst  a  mass  of 
specially  developed  conspicuous  leaves  known  as  flowers ; 
therefore  these  plants  have  been  known  as  the  flowering 
plants.  Some  of  the  leaves  are  developed  as  envelopes 
(calyx,  corolla),  and  others  as  spore-bearing  parts,  or  spo- 
rophyllff  (stamens,  pistils).  But  the  spores  of  the  lower 
plants,  as  of  ferns  and  mosses,  may  also  be  borne  in  spe- 
cially developed  foliage,  so  that  the  line  of  demarcation 
between  flowering  plants  and  flowerless  plants  is  not  so 
definite  as  was  once  supposed.  The  one  definite  distinction 
between  these  two  classes  of  plants  is  the  fact  that  07te  class 
produces  seeds  and  the  other  does  not.  The  seed-plants  are 
now  often  called  spermaphytes,  but  there  is  no  single 
coordinate  term  to  set  off  those  which  do  not  bear  seeds. 
It  is  quite  as  well,  for  popular  purposes,  to  use  the  terms 
phenogams  for  the  seed-bearing  plants  and  cryptogams  for 
the  others.  These  terms  have  been  objected  to  in  recent 
years  because  their  etymology  does  not  express  literal  facts 


PHENOGAMS  AND   CRYPTOGAMS 


i8i 


{phenogam  signifying  "showy  flowers,"  and  cryptogam 
"hidden  flowers"),  but  the  terms  represent  distinct  ideas 
in  classification.  The  cryptogams  include  three  great 
series  of  plants  —  the  Thallophytes  or  algae,  lichens,  and 
fungi ;  the  Bryophytes  or  mosslike  plants;  the  Pteridophytes 
or  fernlike  plants. 

Suggestions.  — 186.  The  parts  of  a  fern  leaf  The  primary 
complete  divisions  of  a  frond  are  called  pinnae,  no  matter  whether 
the  frond  is  pinnate  or  not.  In 
ferns  the  word  "pinna"  is  used  in 
essentially  the  same  way  that  leaf- 
let is  in  the  once-compound  leaves 
of  other  plants.  The  secondary 
leaflets  are  called  pinnules,  and  in 
thrice,  or  more,  compound  fronds, 
the  last  complete  parts  or  leaflets 
are  ultimate  pinnules.  The  dia- 
gram (Fig.  263)  will  aid  in  making 
the  subject  clear.  If  the  frond 
were  not  divided  to  the  midrib,  it 
would  be  simple,  but  this  diagram 
represents  a  compound  frond. 
The  general  outline  of  the  frond, 
as  bounded  by  the  dotted  line,  is 
ovate.  The  stipe  is  very  short. 
The  midrib  of  a  compound  frond 
is  known  as  the  rachis.  In  a  de- 
compound frond,  this  main  rachis 
is  called  the  primary  rachis.  Seg- 
ments (not  divided  to  the  rachis) 
are  seen  at  the  tip,  and  down  to 
h  on  one  side  and  to  m  on  the 
other.  Pinnae  are  shown  at  /,  k,  /,  Oy  n.  The  pinna  0  is  entire ; 
n  is  crenate-dentate ;  /  is  sinuate  or  wavy,  with  an  auricle  at  the 
base  ;  k  and  /are  compound.  The  pinna  k  has  twelve  entire  pin- 
nules. (Is  there  ever  an  even  number  of  pinnules  on  any  pinna?) 
Pinna  /  has  nine  compound  pinnules,  each  bearing  several  entire 
ultimate  pinnules.  The  spores.  — 187.  Lay  a  mature  fruiting  frond 
of  any  fern  on  white  paper,  top  side  up,  and  allow  it  to  remain  in 
a  dry,  warm  place.  The  spores  will  discharge  on  the  paper. 
188.  Lay  the  full-grown  (but  not  dry)  cap  of  a  mushroom  or 
toadstool  bottom  down  on  a  sheet  of  clean  paper,  under  a  venti- 
lated box  in  a  warm,  dry  place.     A  day  later  raise  the  cap. 


Fig.  263.  — Diagram  to  explain 
THE  Terminology  of  the 
Frond. 


CHAPTER   XXIV 

STUDIES   IN   CRYPTOGAMS 

The  pupil  who  has  acquired  skill  in  the  use  of  the  com- 
pound microscope  may  desire  to  make  more  extended  ex- 
cursions into  the  cryptogamous  orders.  The  following 
plants  have  been  chosen  as  examples  in  various  groups. 
Ferns  are  sufficiently  discussed  in  the  preceding  chapter. 

Bacteria 

If  an  infusion  of  ordinary  hay  is  made  in  water  and  allowed  to 
stand,  it  becomes  turbid  or  cloudy  after  a  few  days,  and  a  drop 
under  the  microscope  will  show  the  presence  of  minute  oblong 
cells  swimming  in  the  water,  perhaps  by  means  of  numerous  hair- 
like appendages,  that  project  through  the  cell  wall  from  the  pro- 
toplasm within.  At  the  surface  of  the  dish  containing  the  infusion 
the  cells  are  non-motile  and  are  united  in  long  chains.  Each 
of  these   cells   or    organisms    is   a   bacterium  (plural,  bacterid), 

(Fig.  135.) 

Bacteria  are  very  minute  organisms, — the  smallest  known, — 
consisting  either  of  separate  oblong  or  spherical  cells,  or  of 
chains,  plates,  or  groups  of  such  cells,  depending  on  the  kind. 
They  possess  a  membrane-like  wall  which,  unlike  the  cell  walls  of 
higher  plants,  contains  nitrogen.  The  presence  of  a  nucleus  has 
not  been  definitely  demonstrated.  Multiplication  is  by  the  fission 
of  the  vegetative  cells ;  but  under  certain  conditions  of  drought, 
cold,  or  exhaustion  of  the  nutrient  medium,  the  protoplasm  of  the 
ordinary  cells  may  become  invested  with  a  thick  wall,  thus  form- 
ing an  endospore  which  is  very  resistant  to  extremes  of  environ- 
ment.    No  sexual  reproduction  is  known. 

Bacteria  are  very  widely  distributed  as  parasites  and  saprp- 
phytes  in  almost  all  conceivable  places.  Decay  is  largely' caused 
by  bacteria,  accompanied  in  animal  tissue  by  the  liberation  of 
foul-smelling  gases.  Certain  species  grow  in  the  reservoirs  and 
pipes  of  water  supplies,  rendering  the  water  brackish  and  often 
undrinkable.  Some  kinds  oi  fermentation  (the  breaking  down  or 
decomposing  of  organic  compounds,  usually  accompanied  by  the 

182 


STUDIES  IN  CRYPTOGAMS  ^  1 83 

formation  of  gas)  are  due  to  these  organisms.  Other  bacteria 
oxidize  alcohol  to  acetic  acid,  and  produce  lactic  acid  in  milk  and 
hutyric  acid  in  butter.  Bacteria  live  in  the  mouth,  the  stomach,  the 
intestines,  and  on  the  surface  of  the  skins  of  animals.  Some  secrete 
gelatinous  sheaths  around  themselves;  others  secrete  sulphur  or 
iron,  giving  the  substratum  a  vivid  colour. 

Were  it  not  for  bacteria,  man  could  not  live  on  the  earth,  for 
not  only  are  they  agents  in  the  process  of  decay,  but  they  are 
concerned  in  certain  healthful  processes  of  plants  and  animals. 
We  have  learned  in  Chapter  VITT  how  bacteria  are  related  to  nitro- 
gen-gathering. 

Bacteria  are  of  economic  importance  not  alone  because  of  their 
effect  on  materials  used  by  man,  but  also  because  of  the  disease- 
producing  power  of  certain 'species.  Pus  is  caused  by  a  spherical 
form,  tetanus  or  lock-jaw  by  a  rod-shaped  form,  diphtheria  by 
short  oblong  chains,  tuberculosis  or  ^^  consumption^' 'hy  more  slen- 
der oblong  chains,  and  typhoid  fever ^  cholera^  and  other  diseases 
by  other  forms.  Many  diseases  of  animals  and  plants  are 
caused  by  bacteria.  Disease-producing  bacteria  are  said  to  be 
pathogenic. 

The  ability  to  grow  in  other  nutrient  substances  than  the  natu- 
ral one  has  greatly  facilitated  the  study  of  these  minute  forms 
of  hfe.  By  the  use  of  suitable  culture  media  and  proper  precau- 
tions, pure  cultures  of  a  particular  disease-producing  bacterium 
may  be  obtained  with  which  further  experiments  may  be  con- 
ducted. 

Milk  provides  an  excellent  collecting  place  for  bacteria  coming 
from  the  air,  from  the  coat  of  the  cow  and  from  the  milker.  Dis- 
ease germs  are  sometimes  carried  in  milk.  If  a  drop  of  milk  is 
spread  on  a  culture  medium  (as  agar),  and  provided  with  proper 
temperature,  the  bacteria  will  multiply,  each  one  forming  a  colony 
visible  to  the  naked  eye.  In  this  way,  the  number  of  bacteria 
originally  contained  in  the  milk  may  be  counted. 

Bacteria  are  disseminated  in  water,  as  the  germ  of  typhoid  fever 
and  cholera;  in  milk  and  other  fluids;  in  the  air;  and  on  the 
bodies  of  flies,  feet  of  birds,  and  otherwise. 

Bacteria  are  thought  by  many  to  have  descended  from  algae  by 
the  loss  of  chlorophyll  and  decrease  in  size  due  to  the  more 
specialized  acquired  saprophytic  and  parasitic  habit. 

ALGiE 

The  algae  comprise  most  of  the  green  floating  "  scum*"  which 
covers  the  surfaces  of  ponds  and  other  quiet  waters.  The  masses 
of  plants  are  often  called  ''  frog  spittle."  Others  are  attached  to 
stones,  pieces  of  wood,  and  other  objects  submerged  in  streams 


1 84 


BEGINNERS'  BOTANY 


and  lakes,  and  many  are  found  on  moist  ground  and  on  dripping 
rocks.  Aside  from  these,  all  the  plants  commonly  known  as  seaweeds 
belong  to  this  category ;  these  latter  are  inhabitants  of  salt  water. 
The  simplest  forms  of  algae  consist  of  a  single  spherical  cell, 
which  multiplies  by  repeated  division  or  fission.  •  Many  of  the 
forms  found  in  fresh  water  are  filamentous,  i.e.  the  plant  body 
consists  of  long  threads,  either  simple  or  branched.  Such  a  plant 
body  is  termed  a  ihallus.  This  term  applies  to  the  vegetative 
body  of  all  plants  that  are  not  differentiated  into  stem  and  leaves. 
Such  plants  are  known  as  thallophytes  (p.  i8i).  All  algae  contain 
chlorophyll,  and  are  able  to  assimilate  carbon  dioxide  from  the  air. 
This  distinguishes  them  from  the  fungi. 

Nostoc.  —  On  wet  rocks  and  damp  soil  dark,  semitransparent 
irregular  or  spherical  gelatinous  masses  about  the  size  of  a  pea  are 
often  found.  These  consist  of  a  colony  of  contorted  filamentous 
algae  embedded  in  the  jelly-like  mass.  The  chain  of  cells  in  the 
filament  is  necklace-like.  Each  cell  is  homogeneous,  without 
apparent  nucleus,  and  blue-green  in  colour,  except  one  cell  which 
is  larger  and  clearer  than  the  rest.  The  plant  therefore  belongs 
to  the  group  of  blue-green  algce.  The  jelly  probably  serves  to 
maintain  a  more  even  moisture  and  to  provide  mechanical  protec- 
tion. Multiplication  is  wholly  by  the  breaking 
up  of  the  threads.  Occasionally  certain  cells 
of  the  filament  thicken  to  become  resting- 
sporesy  but  no  other  spore  formation  occurs. 

Oscillatoria.  — The  blue-green  coatings 
found  on  damp  soil  and  in  water  frequently 
show  under  the  microscope  the  presence  of 
filamentous    algae    composed   of  many  short 


Fig.  264. —Filament  of  Oscillatoria,  showing  one 
dead  cell  where  the  strand  will  break. 

homogeneous  cells  (Fig.  264).  If  watched 
closely,  some  filaments  will  be  seen  to  wave 
back  and  forth  slowly,  showing  a  peculiar  power 
of  movement  characteristic  of  this  plant. 
Multiplication  is  by  the  breaking  up  of  the 
threads.     There  is  no  true  spore  formation.  ' 

Spirogyra.  —  One  of  the  most  common  forms 
of  the  green  algae  is  spirogyra  (Fig.  265).     This 


Fig.  265.  — Strand 
OF  Spirogyra, 
showing  the  chlo- 
rophyll bands. 
There  is  a  nu- 
cleus at  a.  How 
many  cells,  or 
parts  of  cells,  are 
shown  in  this  fig- 
ure? 


STUDIES  IN  CRYPTOGAMS 


185 


plant  often  forms  the  greater  part  of  the  floating  green  mass  (or 

"  frog  spittle  ")  on  ponds.    The  threadlike  character  of  the  thallus 

can  be  seen  with  the  naked  eye  or  with  a  hand 

lens,   but   to   study  it  carefully  a   microscope 

magnifying    two    hundred   diameters   or  more 

must  be  used.     The  thread  is  divided  into  long 

cells  by  cross   walls  which,  according  to   the 

species,  are  either  straight  or  curiously  folded 

(Fig.    266).     The   chlorophyll    is   arranged    in 

beautiful  spiral  bands  near  the  wall  of  each  cell. 

From  the  character  of  these  bands  the  plant 

takes  its  name.    Each  cell  is  provided  with  a 

nucleus  and  other  protoplasm.     The  nucleus  is 

suspended  near  the  centre  of  the  cell  («,  Fig. 

265)  by  delicate  strands  of  protoplasm  radiat- 
ing toward  the  wall  and  terminating  at  certain 

points  in  the  chlorophyll  band.    The  remainder 

of  the  protoplasm  forms  a  thin  layer  lining  the 

wall.     The   interior  of  the  cell  is  filled  with 

cell-sap.     The  protoplasm  and  nucleus  cannot 

be  easily  seen,  but  if  the  plant  is  stained  with 

a  dilute  alcoholic  solution  of  eosine  they  become 

clear. 

Spirogyra  is  propagated  vegetatively  by  the 

breaking  off  of  parts  of  the  threads,  which  con- 
tinue to  grow  as  new  plants.     Resting-spores, 

which  may  remain  dormant  for  a  time,  are  formed  by  a  process 
known  as  conjugation.  Two  threads  lying  side 
by  side  send  out  short  projections,  usually  from 
all  the  cells  of  a  long  series  (Fig.  266).  The 
projections  or  processes  from  opposite  cells 
grow  toward  each  other,  meet,  and  fuse,  form- 
ing a  connecting  tube  between  the  cells.  The 
protoplasm,  nucleus,  and  chlorophyll  band  of 
one  cell  now  pass  through  this  tube,  and  unite 
with  the  contents  of  the  other  cell.  The  en- 
tire mass  then  becomes  surrounded  by  a  thick 
cellulose  wall,  thus  completing  the  resting- 
sporCy  or  iy go  spore  (z,  Fig.  266). 


Fig.  266. —Con- 
jugation OF 
Spirogyra. 
Ripe  zygospores 
on  the  left;  a, 
connecting 
tubes. 


Fig,  267.  — Strand, 
OR  Filament  of 
Zygnema,  freed 
from  its  gelatinous 
covering. 


Zygnema  is  an  alga  closely  related  to  spiro- 
gyra and  found  in  similar  places.  Its  life 
history  is  practically  the  same,  but  it  differs 
from  spirogyra  in  having  two  star-shaped 
chlorophyll  bodies  (Fig.  267)  in  each  cell,  in- 
stead of  a  chlorophyll-bearing  spiral  band.