March  3,  1904. 
JOURNAL  OF  HORTICULTURE  AND  COTTAGE  GARDENER, 
187 
Producing  Hew  Breeds  of  Plants. 
In  the  eonrse’of  an  address  on  “  IIow  new  breeds  of  agricultural 
plants  are  produced,”  before  the  (Glasgow  Society,  Mr.  W.  G.  Rattray 
of  Edinburgh  observed,  that  in  the  great  majority  of  flowers,  the 
pollen,  whether  it  was  deposited  by  Avind,  insects  or  any  other  agency, 
or  Avhether  it  Avas  extraneous  pollen  introduced  by  the  Avould-be  pro¬ 
ducer  of  new  breeds  (after  having  manipulated  the  floAver,  and  rendered 
it  antherless  by  amputation) — began  to  germinate  on  the  receptive 
surface  of  the  stigma,  and  to  produce  a  pollen  tube.  This  Avas  the 
commencement  of  the  actual  process  of  fertilisation  or  impregnation. 
Of  course,  it  Avas  of  the  utmost  importance  that  extraneous  pollen 
applied  to  the  art  of  artificial  crossing  shorxld  be  in  the  proper  condition, 
neither  too  old  nor  too  young.  The  operator  Avith  his  instruments 
remoA’ed  the  pollen  from  the  stamens  of  the  floAvers  selected,  and 
applied  it  to  the  stigmatie  surface  of  the  floAver  operated  upon — in 
other  words,  the 
breeder  undertook 
to  a  limited  extent 
the  duties  of  Na¬ 
ture.  He  prevented 
self-fertilisation  by 
remoA’ing  the  an¬ 
thers  at  an  early 
stage  in  the  groAvtii 
of  thefloAver  select¬ 
ed  for  manipula¬ 
tion,  and  Avith  the 
guidance  of  knoAv- 
ledge  and  experi¬ 
ence  selected  the 
extraneous  pollen 
Avhich  he  intended 
to  introduce  Avith 
a  regard  to  Avhat- 
ever  dominating  in¬ 
fluences  or  qualities 
it  carried  Avith  it, 
thus  stamping  the 
future  seed  Avith  its 
potency. 
The  pollen-tube 
greAV  in  lengths  Avith 
greater  or  less  ra¬ 
pidity  in  different 
species  of  plants, 
and  in  the  process 
forced  its  Avay 
through  the  con¬ 
ducting  tissues  in 
the  interior  of  the 
style  until  it  reach¬ 
ed  the  ovarian  cavi¬ 
ty.  It  might  be  in 
the  ovary  that  one 
or  more  ovules  Avere 
found,  and  they 
could  ahvays  distin¬ 
guish  in  them  cer¬ 
tain  parts,  viz.,  a 
central  mass  of  cel¬ 
lular  tissue,  knoAvn 
as  the  nucellus,  en¬ 
closed  in  either  one 
or  tAvo  coats,  called 
by  botanists  the  in¬ 
teguments,  and  the  Avhole  Avas  attached  to  the  placenta  by  a  short 
stalk.  The  integuments,  hoAvever,  Avere  not  entire,  as  there  Avas  a 
minute  aperture  at  the  anterior  end,  termed  the  mieropyle.  through 
Avhieh  the  pollen-tube  could  enter  in  order  to  reach  the  embryosae, 
Avhich  Avas  Avithin  the  tissues  of  the  nucellus.  The  necessity  tor  the 
pollen-tube  to  reach  the  embryosae,  so  that  the  contents  of  the  former 
might  be  brought  in  contact  Avith  the  contents  of  the  latter,  became 
evident. 
The  result  of  impregnation  Avas  that,  inside  the  embryosae,  an 
embryo  began  to  form,  and  at  the  same  time  the  fertilised  ovule 
increased  in  size,  until  finally,  Avith  the  contained  embryo,  and  occa¬ 
sionally  Avith  some  reserve  food  material  in  addition,  it  formed  Avhat 
Avas  called  a  ripe  seed.  It  might  be  thought  that,  since  in  most 
floAvering  plants  the  stamens  were  so  closely  related  in  position  to  the 
carpels,  it  Avould  be  a  relatively  easy  matter  for  pollen  to  fall  on  the 
stigma  and  fertilise  the  ovules  of  its  OAvn  floAver.  But  this  rarely 
happened,  although  barley  and  some  of  the  grasses  furnished  examples 
Avhere  such  a  thing  did  take  place,  for  it  Avas  known  that  they  Avere 
persistently  self-pollinated  Avithout  the  .species  seeming  to  suffer 
deterioration  from  this  in-and-in  breeding.  Here  it  Avas  that  Nature 
played  into  the  hands  of  the  producer  of  ucav  breeds,  Avho  had  been 
able  to  cliange  a  tAvo-roAved  into  a  six-roAA'ed  barley,  Avith  all  the 
characters  of  a  first-class  malting  A'ariety.  An  infinite  number  of  ncAv 
and  distinct  breeds  of  oats,  barley,  Avheat.  clovers,  grasses  and  roots 
had  been  produced  by  dexterous  manipulation  of  the  floAvers  before 
they  had  pollinated  themseh’cs.  In  some  fioAvers,  this  self-fertilisation 
Avas  prevented  by  mechanical  means,  the  respective  lengths  or  positions 
of  the  involved  organs  being  unsuitable. 
Again  in  unisexual  floAvers — those  containing  stamens  only,  or 
carpels  only — self-fertilisation  could  ncA’cr  take  place,  and  in  not  a  fcAv 
instances  the  stamens  and  carpels  of  the  same  floAver  did  not  ripen  at 
the  same  time.  The  union  of  tAvo  sexual  cells  in  the  act  of  impi-egna- 
tion  Avas,  as  a  rule,  only  possible  Avhen  they  Avere  derived  from  closely 
related  parents,  for  it  Avas  only  then  that  they  exercised  Avhat  might 
be  called  an  attractive  influence  upon  each  other,  resulting  in  a  fusing 
together  in  the  act  of  sexual  reproduction.  Such  a  union  Avas  knoAvn 
as  hybridisation  and  its  pi'oducts  as  hy))rids.  It  also  proA'cd  that  the 
real  purpose  of  the  sexual  union  in  the  plant  Avas  the  combination  of 
the  dominating  properties  of  both  parents,  but  it  Avas  seldom  that  the 
hybrid  resembled  one  ancestor  almost  exclusively.  Hence  it  became 
cicar  that  the  inherited  characteristics  of  both  the  male  and  female 
cells  Avere  trans¬ 
mitted  by  sexual 
reproduction  to  the 
hybrid.  Derivative 
hybrids  arose  Avhen 
hybrids  Avere  again 
crossed  Avith  one 
another,  or  Avith 
one  of  the  original 
parent  forms.  By 
this  means  it  was 
possible  to  unite 
six  species  into  one 
hybrid,  and  this  Avas 
Avhat  the  breeder 
termed  composite 
or  compound  ei’oss- 
ing. 
In  addition  to 
this  inherited  qual¬ 
ity,  hybrids  exhibit¬ 
ed  neAV  peculiarities 
of  groAvth  not  de¬ 
rived  from  their 
parent  forms,  in¬ 
cluding  a  tendency 
to  variability,  Avhicii 
Avas  greatly  enhanc¬ 
ed  in  some  hybrids, 
especially  in  those 
arising  from  the 
hybridisation  of  dif¬ 
ferent  A^ai'ieties  of 
die  same  species. 
Those  from  nearly 
related  parents  pro¬ 
duced  more  vigor¬ 
ous  vegetative 
groAvth,they  bloom- 
'ed  earlier,  and  Avere 
more  prolific  alto¬ 
gether  than  the  un¬ 
crossed  plant. 
They  came  noAv 
to  a  consideration 
of  the  breeder’s  art. 
It  Avould  serve  no 
useful  purpose  to 
produce  new  breeds 
of  agricultural 
crops  Avhich  Avere  not  highly  endoAved  Avith  the  poAver  of  producing, 
under  ordinary  conditions  of  cultivation,  an  abundant  supply  of 
germinating  seed.  It  must,  hoAvever,  be  borne  in  mind,  that  plants 
varied  much  Avith  respect  to  the  amount  of  seed  Avhich  they  ultimately 
brought  to  maturity.  It  Avas  not  their  habit  to  produce  a  large 
quantity  of  useless  seed,  but  rather  to  mature  a  feAV  seeds,  and  leave 
the  remainder  undeveloped  or  in  a  rudimentary  state.  An  annual  plant 
produced  seed,  and  there  its  duties  ended,  Avhile  a  perennial  plant,  on 
the  other  hand,  only  did  so  Avhen  atmospheric  influences  and  sur¬ 
rounding  conditions  Avere  fav'ourable.  But  under  the  influence  of  the 
breeder’s  properly  selected  exti’aneous  pollen,  improA'ements  Avere 
produced,  the  plants  sporting  freely  under  the  introduction  of  Avhat 
might  be  termed  neAV  A'itality.  In  short,  the  method  of  composite 
crossing,  Avhen  folloAved,  Avas  sure  to  produce  from  fixed  types,  neAv 
breeds  Avhich  Avere  better  than  the  original  parent  plants.  Tlie  pro¬ 
ducer  of  noAV  breeds  in  the  vegetable  kingdom  must  also  assure  himself 
that  he  Avas  quite  able  to  control  and  correct  defects  in  the  respective 
plants  Avhich  he  had  taken  in  hand — that  was,  that  he  could  diminish 
or  increase  vegetative  luxuriance,  or  that  ho  could  increase  the 
number  of  floAvers  Avhieh  produced  perfect  seeds,  and,  if  required, 
transform  the  sterile  nature  into  the  prolific.  ^V'ith  these  objects  in 
vicAv,  seedsmen  had  from  time  to  time  procured  samples  of  every 
knoAvn  A'ariety  of  cereal  seed  distributed  over  the  face  of  the  earth. 
The  Double  White  Primula. 
