June  17,  1897. 
JOURNAL  OF  HORTICULTURE  AND  COTTAGE  GARDENER. 
527 
The  tubercles  oa  the  roots  of  leguminous  plants  are  formed  by  their 
agency.  They  seem  to  require  the  carbon  of  the  plant  for  growth,  and 
Teturn  it  nitrogen  for  its  growth.  When  there  is  abundant  nitrogen  in 
the  soil  these  tubercles  are  not  formed,  but  when  it  is-  absent  they 
become  the  habitat  of  the  microbes  which  produce  it.  After  a  leguminous 
crop  the  soil  is  fit  to  grow  a  cereal  crop,  which  it  may  not  have  been 
previously,  a  fact  of  which  it  would  appear  the  ancients  were  cognisant. 
By  the  agency  of  nitrogen-forming  microbes — and  there  would  appear 
to  be  a  different  form  of  nitrogen-producing  microbe  for  each  genus  of 
the  Leguminosse — nitrogen  is  stored  up  in  the  soil  during  the  growth  of 
the  leguminous  crop. 
It  may  be  that  each  genus  of  plants  of  other  natural  orders  have 
their  own  particular  attendant  microbes  preparing  out  of  raw  material 
the  aliment  they  require ;  and  in  time  many  of  these  may  be  separated 
and  cultivated,  and  applied  to  their  particular  functions  with  as  great 
certainty  as  the  acidifying  and  flavour-producing  microbes  are  applied 
in  the  making  of  butter.  When  that  time  comes  the  economic  value  of 
the  discovery  must  be  enormous.  Already  some  of  the  nitrogen-forming 
microbes  have  been  isolated  and  cultivated  in  large  quantities,  and  are 
now  produced  in  a  marketable  form.  On  the  Continent  land  which  was 
infertile  has  yielded  large  crops  after  it  bad  been  sown  with  this  nitrogen- 
producing  microbe,  and  garden  sails  in  which  certain  vegetables  and 
flowering  plants  refused  to  grow  are  now  luxuriant  with  them. 
Judging  by  this  success  it  would  seem  not  unreasonable  to  anticipate 
the  time  when  the  life  history  of  the  microbes  which  influence  the 
growth  of  plants  will  be  as  well  known  as  those  which  affect  milk,  and 
that  the  practical  application  of  the  knowledge  gained  will  be  no  less 
successful. — ( Abstract  of  paper  read  by  Dr.  Groves  at  a  meeting  of 
the  Isle  of  Wight  Horticultural  Association  ) 
OUR  BOTANICAL  GEOGRAPHY. 
In  studying  the  botanical  geography  of  the  British  Isles,  the  leading 
important  fact  we  find  established  is  that  they  do  not  grow  a  single 
plant  that  is  peculiar  to  them  which  cannot  be  found  also  in  continental 
Europe.  Another  is  that  tbe  plants  found  here  do  not  all  come  from  the 
same  regions.  In  enumerating  the  various  vegetable  emigrations  which, 
according  to  leading  observers,  have  successfully  colonised  our  islands, 
we  may  cite  first  the  Asturian  type,  which,  owing  to  the  mildness  of  its 
winterp,  has  long  been  established  in  Ireland.  These  Asturian  specimens 
are  the  last  representatives  of  a  colony  from  the  North  of  Spain. 
The  South-West  of  England  and  the  South-East  of  Ireland  exhibit  a 
vegetation  similar  to  that  of  Brittany  and  Normandy,  which  is  termed 
the  Armorican.  Many  of  these  are  found  along  tbe  western  coasts  of 
France  till  the  increasing  rigour  of  the  climate  north  arrests  their  further 
progress.  These  plants,  which  are  to  be  found  with  us  mainly  in  the 
Devon  and  Cornwall  districts  on  the  coasts,  have  crossed  to  Ireland  and 
have  become  naturalised  in  Cork  and  Waterford.  The  mountains  of 
Wales,  Cumberland,  and  Scotland  present  a  peculiar  vegetation  entirely 
different  from  that  of  our  plains.  Analogous  to  that  of  Switzerland, 
it  resembles  even  more  that  of  Iceland  and  Greenland.  It  is  termed 
the  Boreal  type. 
What  is  termed  the  Germanic  is  Cthe  fundamental  type  of  that  of 
England.  Originating  in  the  north  of  Germany  and  France,  it  has  in 
the  course  of  ages  become  so  predominant  as  to  be  called,  but  really  this 
is  a  misnomer,  the  British  type.  Many  plants  found  in  England  have 
never  crossed  St.  George’s  Channel  into  Ireland.  The  marine  plants  of 
our  isles  follow  the  same  laws  of  distribution  as  those  governing  the  flora. 
A  sea  admittedly  once  covered  most  of  the  south  of  Europe  and  the 
north  of  Africa,  for  this  is  proved  by  the  numerous  identical  shells 
found  at  numberless  points  from  Greece  to  France.  It  follows  that  the 
upheaval  of  this  ocean  bed,  which  constitutes  tbe  last  tertiary  deposit*, 
gave  rise  to  a  vast  continent,  comprising  Spain,  Ireland,  the  Azores,  and 
part  of  Africa.  This  is  from  where  the  Armorican  type  found  its  way. 
The  submersion  of  this  continent  was  followed  by  a  long  period  during 
which  a  lower  temperature  prevailed,  and  then  it  was  that  the  migra¬ 
tion  of  Arctic  plants  took  place. 
The  oldest  of  these  floras  now  comprising  our  vegetation  would  seem 
to  be  undoubtedly  that  of  the  mountains  of  the  West  of  Ireland. 
The  distribution  of  the  second  flora,  next  in  point  of  probable  date, 
depended  on  the  extension  of  a  barrier,  the  traces  of  which  are  still  in 
evidence  from  the  West  of  France  to  the  South-East  of  England,  and 
thence  to  Ireland.  The  third  flora  depended  on  the  connection  of  the 
coasts  of  France  and  England  towards  the  eastern  part  of  the  Channel. 
Of  the  former  existence  of  this  union  no  one  can  entertain  a  doubt. 
The  distribution  of  the  fourth  or  Alpine  flora  of  Scotland  and  Walep,  was, 
it  would  appear,  effected  during  the  glacial  period,  when  our  mountain 
summits  were  low  islands  extending  to  Norway  through  a  glacial  sea,  and 
clothed  with  an  arctic  vegetation,  which  in  the  gradual  upheaval  of  those 
islands,  and  consequent  change  of  climate,  became  limited  to  the 
summits  of  the  newly  formed  and  still  existing  mountains.  The  distri¬ 
bution  of  the  fifth,  or  Germanic  flora,  depended  upon  the  upheaval  of 
the  bed  of  the  glacial  sea,  and  the  consequent  connection  of  England 
with  Ireland,  and  also  with  Germany,  by  great  plains,  the  fragments  of 
which  are  still  existent,  and  upon  which  many  now  extinct  great  animals 
lived.  The  breaking  up,  or  rather  submergence,  of  the  first  barrier  led  to 
the  destruction  of  the  second,  and  then  that  of  the  second  caused  that 
of  the  third  ;  but  the  well-marked  epoch  of  migration  of  the  German 
flora  clearly  indicates  the  subsequent  formation  of  the  Straits  of  Dover 
d  of  the  Irish  Sea  as  now  existing. — Wm.  Norman  Brown, 
Our  Next  Issue. — As  intimated  last  week,  tbe  next  issue  of  the  Journal 
of  Horticulture ,  June  24th,  will  be  devoted,  not  to  descriptions  of  the 
Queen’s  Gardens  only,  but  to  methods  of  procedure  in  them — a  blend,  it  is 
hoped,  of  matter  of  interest  and  usefulness,  for  almost  every  feature  in  garden¬ 
ing,  ornamental  and  serviceable,  will  be  represented.  This  will  be  supplemented 
by  Mr.  D’Ombrain’s  review  of  Horticulture,  and  the  changes  brought  about 
as  he  remembers  them  during  the  past  sixty  years.  Though  the  number  will 
be  considerably  enlarged,  its  whole  space  will  be  occupied  in  “  Honour  of  the 
Queen,”  and  neither  communications  in  hand,  or  which  may  be  received  during 
the  ensuing  week,  nor  reports  of  shows,  can  possibly  appear  till  the  issue 
succeeding.  We  have  reason  to  believe  that  the  change  from  ordinary  routine 
during  something  like  a  holiday  week,  consequent  on  the  passing  of  a  great 
historical  event,  will  be  equally  acceptable  to  amateurs  and  gardeners. 
-  Events  of  the  Week. — Rose  shows  have  now  started  in  real  earnest, 
and  the  list  of  fixtures  of  which  we  have  been  informed  will  be  found  on 
page  524.  On  Wednesday,  the  23rd  inst.,  the  Yictorian  Era  Flower  Show 
will  be  held  at  the  Crystal  Palace,  while  the  Old  Deer  Park,  Richmond, 
will  be  ew  f&te  with  the  Richmond  Horticultural  Society’s  Exhibition. 
- -  W eather  in  London  .  —  The  weather  in  the  metropolis  during 
several  days  of  the  past  week  and  the  early  days  of  this  was  of  a  quite 
tropical  character.  Thursday  and  Friday  were  fine,  and  Saturday  was 
magnificent,  the  sun  shining  with  great  power.  The  thermometer  reached 
77°  in  the  shade,  this  being  exceeded  on  Sunday  by  7°,  84°  in  the  shade 
being  the  maximum.  Monday  was  duller  and  a  trifle  cooler,  Tuesday  again 
being  bright  and  warm,  but  more  pleasant,  owing  to  breezes  that  prevailed 
throughout  the  day.  Yesterday  (Wednesday)  was  cooler,  and  rain  fell  at 
intervals. 
- Weather  in  the  North. — The  weather  for  tbe  past  fortnight  has 
been  extremely  variable.  Saturday,  the  5th  inst.,  was  the  warmest  day  of 
the  season,  the  thermometer  showing  79°  in  the  shade.  On  the  morning  of 
the  8th  Potatoes  and  tender  foliage  were  in  some  districts  blackened  by  a  sharp 
frost.  Thunder  and  very  heavy  rains  have  latterly  been  prevalent,  and  on 
Tuesday  morning  the  air  was  distinctly  cold. — B.  D.,  S.  Perthshire. 
-  Manchester  Show. — Our  reporter  writes:  —  “By  an  oversight  I 
omitted  to  mention  that  the  medals,  awarded  to  Messrs.  Sander  &  Co., 
H.  Low  &  Co.  (both  having  splendid  exhibits),  and  Charlesworths  at  the 
late  Show  were  all  lai'ge  and  of  equal  value.  May  I  also  bear  testimony 
to  the  choice  stand  of  hybrid  Cypripediums  staged  by  Mr.  Chapman,  gardener 
to  R.  I.  Measures,  Esq.,  Camberwell,  for  several  of  which  Mr.  Chapman  had 
the  honour  of  receiving  certificates.  I  should  also  like  to  say  how  much  the 
success  of  the  Exhibition  was  due  to  their  courteous  attention  to  all  and 
interest  taken  in  every  possible  way  by  Mr.  Weathers,  the  new  Curator,  and 
his  assistant  Mr.  Paul.” 
-  Exhibition  at  Ghent.— The  programme  of  the  fourteenth  Inter¬ 
national  Horticultural  Exhibition  of  the  Societe  Royal  d’ Agriculture  et  de 
Botanique  de  Gand  has  reached  us.  From  this  it  appears  the  show  will 
be  the  163rd  that  has  been  held  under  the  auspices  of  this  Society,  and  the 
dates  fixed  are  from  the  16th  to  the  24th  of  April,  1898.  The  schedule 
forms  a  book  of  nearly  100  pages,  and  comprises  twenty-eight  sections, 
amongst  which  are  divided  716  classes.  The  President  is  Count  0.  de 
Kerchove  de  Denterghem,  and  the  Secretary  Mons.  E.  Fierens,  of  whom 
we  gave  a  potograph  a  short  time  back.  We  hope  to  make  further  reference 
to  this  show  at  a  future  date. 
- The  Crystal  Palace  Victorian  Era  Flower  Show.— Judging  by 
the  schedule,  this  show,  to  be  opened  on  June  23rd,  should  be  both  interesting 
and  imposing.  It  is  to  be  essentially  an  exhibition  of  groups— of  Begonias, 
Caladiums,  Cannas,  Coleuses,  Ferns,  Conifer®,  fine-foliaged  plants, 
Gloxinias,  Alpines,  hardy  herbaceous  plants,  Orchids,  Palms,  Pelargoniums, 
and  Roses,  the  prize*  ranging  from  £20  downwards.  In  addition,  Crystal 
Palace  commemorative  medals  are  provided  for  the  best  group  of  miscellaneous 
plants  arranged  for  effect  in  a  space  of  300  square  feet ;  also  for  the  best  group 
of  plants  introduced  during  her  Majesty’s  reign,  arranged  in  a  space  not 
exceeding  500  square  feet.  Money  prizes  are  also  provided  in  these  classes. 
There  are  only  twenty-six  classes  in  the  schedule,  but  they  are  of  a  nature 
to  afford  scope  for  a  grand  exhibition,  worthy  of  the  occasion  and  of  the 
Palace.  There  must  be  no  delay  in  sending  entries  to  Mr.  G.  Caseltou',  garden 
superintendent,  and  a  request  in  the  schedule  should  not  be  ignored  namely- 
that  those  who  have  entered,  and  find  that  they  cannot  exhibit,  send  a 
telegram,  or  communicate  to  that  effect,  to  Mr.  Caselton,  the  day  before  the 
show.  This  will  be  most  helpful  to  the  manager,  and  add  materially  to  the 
effect  of  the  exhibition. 
