February  4,  1897. 
JOURNAL  OF  HORTICULTURE  AND  COTTAGE  GARDENER. 
91 
Nitrate,  sulphate,  carbonate,  phosphate,  and  silicate  of  lime  are 
the  forms  in  which  lime  is  found  in  the  soil,  and  the  first,  second, 
»nd  fourth  of  those  compounds  are  the  sources  from  which  plants 
obtain  their  supply.  The  function  of  lime  in  plants  is  not  quite 
understood,  but  it  seems  to  act  chiefly  as  a  carrier  of  nitrogen, 
sulphur,  and  phosphorus  into  them.  It  afterwards  combines  with 
the  organic  acids  (e  rj ,  oxalic  acid)  formed  in  the  plants,  and 
neutralises  them,  thereby  making  them  harmless. 
Iron  (symbol  Fe). — This  element  is  found  widely  diffused  in 
nature  in  a  free  and  combined  state.  It  occurs  in  soils  as  iron 
oxides,  carbonates,  phosphates,  and  sulphates.  The  green  colouring 
■matter  of  leaves  (chlorophyll)  cannot  be  formed  unless  iron  be 
present,  and  in  the  absence  of  this  element  the  leaves  of  plants 
only  assume  a  white  or  yellowish  colour. 
Sodium  (symbol  Na). — This  element  is  a  silver-white  metal, 
never  found  in  a  free  state  in  nature,  but  occurs  in  large  quantities 
in  combination  with  chlorine,  as  rock  salt.  Sodium  unites  with 
oxygen  to  form  the  compound  soda  (Na20),  and  this  substance 
forms  one  of  the  bases,  consequently  will  combine  readily  with 
acids  to  form  salts.  We  have  good  examples  of  the  sodium  salts 
in  nitrate  and  phosphate  of  soda,  both  valuable  fertilisers.  Although 
soda  is  always  found  in  the  ash  of  plants,  it  is  not  considered 
essential  for  their  growth,  for  they  have  been  grown  successfully  in 
water  and  sand  to  which  not  a  trace  of  this  element  was  applied. 
Chlorine  (symbol  Cl) — This  element  is  a  yellowish  green  gas, 
possessing  a  pungent  odour.  It  is  never  found  in  nature  in  a  free 
state,  but  as  chlorides  of  sods,  lime,  magnesia,  or  potash  it  is  found 
almost  universally  distributed.  Some  plants  have  been  grown 
successfully  without  the  aid  of  compounds  containing  chlorine,  but 
it  has  been  found  to  be  necessary  to  apply  it  to  others. 
Silicon  (symbol  Si  ;  weight  29). — This  element,  although  the 
most  abundant  in  nature,  is  never  found  in  a  free  state.  It  is 
found  united  with  oxygen  as  silica  (Si02)  in  large  quantities. 
Silica  is  found  in  a  nearly  pure  state  in  quanz  sand,  in  flints,  and  in 
rock  crystals.  Plants  can  be  grown  without  the  aid  of  this  compound, 
although  it  exists  in  large  quantities  in  the  straw  of  Wheat,  and  in 
stems  of  the  Equisetum. 
Aluminum  (symbol  A1 ;  weight  27). — This  element  is  a  white 
metal,  and  united  with  oxygen  forms  the  substance  known  as 
alumina  (Al203).  Although  this  element  is  not  a  constituent  of 
plants,  it  is,  line  silicon,  a  very  important  ingredient  of  soils. 
Pure  clay  is  composed  of  alumina,  silica,  and  water  chemically 
combined  ;  but  we  shall  deal  more  fully  with  this  element  and 
silicon  when  we  come  to  cocsider  the  composition  of  soils.  The 
we’ghts  of  the  last  two  elements  were  omitted  from  the  table,  but 
are  now  given. — W.  D. 
(To  be  continued .1 
1  hailed  with  delight  the  article  headed  “Chemistry  in  the  Garden,’’ 
lout  when  Icame  to  the  last  paragraph  on  page  47, 1  said,  This  seems  wrong. 
“  W.  D.”  says,  “  The  reason  of  this  is  that  daring  growth  certain  chemical 
changes  are  taking  place,  during  which  oxygen  is  absorbed  and  carbon 
dioxide  exhaled.”  is  this  so  1  Should  it  not  rather  be  C02  is  absorbed, 
and  oxygen  exhaled  ? 
I  was  once  told  by  a  head  gardener  that  to  become  proficient  I  ought 
to  he  able  to  analyse  the  ash  of  a  plant  to  see  what  elements  went  to 
build  up  its  tissues  ;  the  result  was  I  joined  chemistry  and  botany 
classes  The  teacher,  a  professor  of  chemistry,  told  us  amongst  other 
things  that  plants  took  in  carbon  dioxide  (C02)  the  C02  was  split  up, 
the  carbon  wa3  assimilated  by  the  plant,  and  the  oxygen  given  off  ; 
that  animals  on  the  contrary  took  in  oxygen,  part  of  which  combined 
with  the  superfluous  carbon,  and  was  given  off  again  as  C0.2.  This 
seems  just  the  opposite  of  what  “  W.  D.”  says. 
On  turning  to  “Oliver’s  Botany,”  p.  14,  par.  7,  he  says,  “  With  regard 
to  the  important  element  carbon  experiments  clearly  show  that  it  is 
absorbed  in  combination  with  oxygen  as  carbonic  acid  gas . 
The  green-coloured  organs  of  plants,  under  the  influence  of  sunlieht 
possess  the  power  of  abstrac  iag  it  directly  from  the  air.  Par.  8,  But 
the  most  remarkable  circumstance  attending  this- absorption  of  carbonic 
acid  gas  is  the  liberation  of  oxygen  gas  by  the  leaves  ....  This 
fixation  of  carbon,  and  liberation  of  the  oxygen  of  carbonic  acid  gas 
has  been  termed  vegetable  respiration  ;  but  as  the  condi'ions  which 
obtain  are  the  reverse  of  those  characteristic  of  animal  respiration,  it 
may  be  more  correctly  spoken  of  as  characterising  the  process  of 
vegetable  assimilation.”  I  should  like  to  know  what  “  W.  D.”  has  to 
say  further  on  the  subject.  I  believe  that  chemistry,  if  well  understood 
and  practically  applied  to  gardening,  is  one  of  the  great  helps  to  success. 
—Henri. 
Visitors  to  Kew  Gardens  during  1896. — The  number  of 
persons  who  visited  the  Royal  Gardens  during  the  year  1896  was  1,396  875. 
That  for  1895  was  1,407,369.  The  average  for  1886-95  was  1,425  526. 
The  total  number  on  Sundays  was  536,181,  and  on  week  days  855,715. 
The  maximum  number  of  visitors  on  any  one  day  was  86  399  on  May  25th, 
and  the  smallest  62  on  March  18th. — (“  Kew  Bulletin.”) 
POLYANTHA  AND  CHINA  ROSES. 
Polyantha  Roses  are,  I  am  gratified  to  learn,  steadily  increasing 
in  popularity,  nevertheless  1  think  they  should,  assuredly,  be  more 
widely  cultivated.  They  have  many  valuable  attributes.  They  are  easy 
of  culture,  extremely  hardy  in  character,  and  vigorous  in  habit ;  they 
flower  early  and  late,  and  produce  multitudes  of  miniature  and  ex¬ 
tremely  graceful  flowers.  Some  of  this  family  are  very  fragrant,  such 
for  example  is  the  pure  white  Anna  Marie  de  Montravel,  which  is  surely 
one  of  the  sweetest  Roses  in  existence. 
For  many  of  the  finest  of  the  Polyantha  Roses  we  are  primarily 
indebted  to  that  consummate  French  rosarian,  the  late  M.  Guillot. 
From  his  famous  Lyons  rosarium  came  Ma  Paquerette  in  1875,  Mig¬ 
nonette  in  1881,  and  the  beautiful  rose-coloured  Gloire  de  Polyantha  in 
1887.  Dabreuil  has  given  us  two  veritable  gems — Etoile  d’Or  and  Perle 
o’Or,  of  which  the  latter  Rose,  with  its  lovely  orange  centre,  is  perhaps 
the  most  attractive  of  the  Polyantha  race. 
Of  climbing  varieties,  whose  number  is  as  yet  sufficiently  circum¬ 
scribed,  the  most  valuable  are  undoubtedly  Polyantha  grandiflora,  a 
splendid  pillar  Rose  ;  and  Turner’s  Crimson  Rambler,  one  single  truss  of 
which  produced  last  summer  in  my  garden  120  flowers.  One  of  the 
most  valuable  qualifications  of  this  phenomenal  Rose,  originally 
brought  by  an  engineer  from  Japan,  is  that  of  retaining  its  remarkable 
brightness  for  several  weeks,  especially  when  grown,  as  it  is  here,  in  a 
partially  shaded  situation.  I  have  seen  the  original  plant  of  this  world- 
famous  variety  in  the  garden  of  the  late  Mr.  Chas.  Jenner,  near  Edin¬ 
burgh.  He  was  a  brother  of  Sir  William  Jenner,  the  head  of  a  great 
firm  and  a  distinguished  cultivator  of  alpine  flowers. 
China  Roses  possess,  like  the  Polyanthas,  this  important  qualifica¬ 
tion,  that  from  earliest  summer  till  latest  autumn  they  are  in  constant 
bloom.  Of  these,  perhaps  the  most  highly  endowed  are  Laurette 
Messimy,  of  most  distinctive  colour,  raised  by  Guillot;  Cramoisie 
Superieure,  velvety  crimson  in  colour,  of  climbing  tendencies  and  very 
prolific  ;  the  ’•  Brave  Old  Monthly,’’  deservedly  eulogised  by  Dean  Hole  ; 
Mrs.  Bosanquet,  supposed  by  some  rosarians  to  be  of  Bourbon  origin  ; 
Laffay’s  Fabvier,  of  brilliant  scarlet  hue  ;  Queen  Maband  Duke  of  York, 
both  valuable  acquisitions  for  the  adornment  of  our  gardens,  for  which 
we  are  indebted  to  Mr.  William  Paul,  whose  latest  introduction, 
Enchantress,  is  worthy  at  least  of  China  extraction.  It  derives  much 
iaterest,  in  addition  to  its  great  beauty,  from  its  winter-flowering 
qualifications. — David  R.  Williamson. 
DISCOLOURATION  IN  POTATOES. 
“  W.  G.”  has  raised  a  very  interesting  question  (page  76)  when  he  deals 
with  that  form  of  discolouration  known  as  blacXnes<  of  flesh  so  often 
found  in  Potatoes.  That  what  he  refers  to  is  not  due  to  rough  treatment 
or  to  bruises  is  undoubtedly  true.  A  good  deal  of  blackness  is  produced 
by  rough  usage  we  all  know,  and  especially  is  it  so  with  the  softer 
fleshed  or  more  starchy  flesh  of  certain  varieties  when  roughly  handled. 
But  rough  usage  promoting  blackness  of  one  form,  whilst  the  effect  is 
precisely  the  same,  yet  does  not  help  to  the  elucidation  of  the  other 
constitutional  blackness  which  is  referred  to.  I  have  found  some  curious 
differences  in  reference  to  soil  capacities  in  connection  with  certain 
varieties.  One,  a  very  fine  white  kidney,  and  should  have  made  a 
splendid  market  variety,  used  to  boil  very  black  in  West  Middlesex, 
which  soon  destroyed  its  reputation.  Down  in  Berkshire  it  does 
splendidly,  and  is  one  of  the  most  favoured  varieties  of  the  district. 
What  I  assume,  therefore,  is  that  Potatoes,  like  Apples,  have  diverse 
requirements,  which  certain  soils  do  not  alwavs  furnish,  but  other  soils 
do  ;  hence  they  are  good  in  one  place  and  indifferent  in  another.  What 
those  requirements  are  in  these  certain  varieties  chemists  alone  can  tell, 
that  is  if  their  analysis  should  reveal  the -secret.  It  may  be  deficiency 
of  starch,  or  of  some  other  essential  constituent  which  the  soil  fails  to 
create  in  needful  quantity.  Then  if  there  be  both  soils  that  fail  to 
provide  these  requirements  and  varieties  on  that  soil,  evidence  in  the 
blackness  of  their  flesh  that  something  is  wanting,  or  may  be  in  excess, 
then  how  useful  would  it  be  on  such  soils  and  with  such  varieties  to 
test  various  compounds  of  manurial  form — soot,  lime,  phosphate,  potash, 
or  other  ingredients — that  it  may  be  ascertained  whether  in  that  way 
amelioration  is  possible  or  not.  In  these  days  of  advanced  scientific 
knowledge  it  seems  incredible  that  a  difficulty  of  this  nature  should 
exist  without  the  cause  being  speedily  ascertained.  I  have  often  noticed 
when  attacks  of  disease  have  destroyed  the  leafage  early  that  tubers, 
especially  in  the  heel  ends,  have  manifested  the  complained  of  blackness 
very  materially.  The  conclusion  in  that  case  is  that  the  tubers  are 
deficient  in  starch  or  some  other  ingredient,  because  their  leaf  laboratory 
was  so  early  destroyed. 
No  doubt  the  Potato  does  suffer  more  than  any  ordinary  edible 
vegetables  from  any  disease,  not  only  because  the  Peronospora  induces 
rot  or  disease  in  the  tubers,  but  also  because,  through  the  premature 
destruction  of  the  leafage,  the  tubers  too  seldom  come  to  full  maturity. 
That  is  specially  so  with  large  tubers,  and  an  excellent  reason  why  we 
