272 
(Oct.  I,  1895. 
THE  TROPICAL  AGRICULTURIST. 
and  he  would  be  glad  to  furnish  information,  es- 
pecially as  the  palmirah  fibre  industry  which  he  at 
one  time  encouraged  is  fast  dying  out  ; and 
hundreds  of  people  in  the  interior  villages  of  Jaffna 
who  used  to  make  a living  out  of  it  are  thrown 
out  of  employment. 
With  their  numerous  buildings,  cheap  lime  is  a 
great  desideratum  in  Colombo  and  Kandy,  not  to 
mention  the  other  towns  which  are  rising  into  im- 
po^ance.  Already  there  Is  a thriving  trade  between 
Jaffna  and  the  Ports  of  Chilaw,  Calpentyn,  Pattalam, 
ffc.  in  lime,  and  the  trade  would  speedly  develope 
It  the  supply  could  be  maintained  at  a reduced  rate. 
Ihe  value  now  paid  for  lime  in  the  above  ports  is 
enormous,  almost  triple  of  what  it  costs  in  .Jaffna. — 
Yours  faithfully,  PRO  BONO  PUBLICO. 
PHYSIOLOGY  OF  THE  CIRCULATION 
IN  PLANTS.— CAMPHOR  TREES  IN 
SOUTHERN  INDIA. 
South  India,  Aug.  22. 
Dear  Sir,— Will  you  kindly  allow  me  the  oppor- 
tunity of  commending  to  the  notice  of  my  hrotlier 
planters  a suggestive  book  called  “ The  Physiology 
of  the  Circulation  in  Plants,  in  the  lower  animals 
and  in  man.”  This  book  comprehends  a series  of 
lectures  delivered  at  the  Royal  College  of  Surgeons. 
Would  it  not  be  helpful  if  you  devoted  a column 
regularly  to  the  review  of  any  works  that  may  ap- 
pear from  time  to  time  that  are  likely  to  be  heli)- 
ful  to  planters  by  throwing  side-lights  perhaps  on 
important  agricultural  questions.  The  title  of  the 
book  mentioned  may  not  appear  likely  to  pi'omise 
any  practical  help.  But  if  wo  are  to  acquire  a 
thorough  knowledge  of  the  laws  of  health  and  vigour 
in  plants  we  must  begin  systematically  at  the  begin- 
ning and  surely  a thorough  acquaintance  with  the 
various  processes  in  the  normal  circulation  of  the 
sap  in  plants,  may  be  considered  to  be  almost 
the  first  essential.  Before  meeting  with  this  book  I 
had  come  to  the  conclusion  that  the  circulation  of 
sap  in  plants,  and  the  resulting  processes  of 
nutrition,  could  not  be  thoroughly,  and  intelligently 
understood  apart  from  some  insight  into  the  processes 
of  the  circulation  of  the  blood  in  animals  and  in 
man,  for  an  insight  into  the  one  helps  to  elucidate  the 
other,  as  there  is  a striking  analogy  between  all  the 
processes  of  circulation  in  plant,  animal  and  man. 
I imagine  I hear  some  practical  man  incredulously 
exclaim  ; “ How  on  earth  can  there  be  any  analogy 
between  a plant  that  takes  up  its  sap  mechani- 
cally by  its  roots,  and  the  intricate  organs  of  the 
animal  and  human  body?”  Such  a man  however 
is  too  practical  to  be  aware  of  the  fact  that  the  villi  of 
the  animal  and  human  intestines  are  exactly  analogous 
to  the  roots  of  plants,  and  performexactly  the  same 
office  interiorly  that  the  root  does  exteriorly. 
Of  course  with  each  rise  in  the  scale  of  organiza- 
tion the  construction  of  each  organ  is  increas- 
ingly elaborate  and  complicate,  but  the  principle 
in  all  remains  the  same.  When  we  bear  in 
mind  that  the  very  same  law  of  osmoses 
that  govern  the  transmission  of  the  sap  through  the 
membranes  of  the  cellular  tissue  of  plants,  also 
controls  the  transmission  of  the  blood  through  the 
membranes  of  the  cellular  tissue  of  the  human  body, 
we  begin  to  apprehend  how  close  the  relationship 
must  be.  In  the  volume  under  remark,  there  is 
collected  a vast  amount  of  information  regarding  the 
various  ]irocesses  of  jilant  life,  which  has  been  care- 
fully culled  from  the  works  of  the  best  authorities — 
specially  from  our  great  lion  Herbert  Spencer,  but 
unfortunately  many  erroneous  statements  have  been 
perpetuated  in  its  pages  such  as  the  theory  of  the 
capillnry  ascent  of  the  sap.  However  it  is  correctly 
stated  tliat  the  ascent  of  the  sap  is  also  governed 
by  the  law  of  the  diffusion  of  liquids,  or  fluids.  The 
editor  liowover  seems  lo  bo  ignorant  of  the  fact  that 
the  principal  factor  that  controls  tlic  ascent  of  the 
sap  is  the  rarilication  of  the  air  within  the  intercel- 
lular spaces  of  the  plant,  in  the  presence  of  light  and 
sunshine.  The  editor  contends  that  there  are  two 
prino'iial  currents  of  sap  in  plants.  That  a downwar 
diffusion  of  sap  is  needed  in  order  to  store  up 
the  contents  of  the  sap  within  the  bark,  Ac. 
in  autumn,  is  evident,  but  to  affirm  the  existence  of 
a continuous  downward  current  is  unwarrantable. 
The  circulation  of  the  'sap  in  plants  cannot  be 
altogether  compared  with  the  circulation  of  the  blood, 
as  the  sap  is  of  varying  density  and  composition  in 
different  parts  of  the  same  plants.  I'l  the  stem  near 
the  roots,  for  instance,  the  sap  is  in  a diluted  state, 
whereas  in  the  leaves  it  is  considerably  thickened  by 
the  cvi-porat'on  of  a largo  percentage  of  its  contained 
moisture.  Of  course  the  editor  might  here  refer  me 
to  the  density  of  the  contents  of  the  chyle  ducts 
in  the  human  body,  but  that  is  just  the  reverse 
of  the  conditions  in  plants.  Again  the  author 
has  perpetuated  the  error  that  the  stomata  of 
plants  close  in  dry  weather  and  open  in  wet  I The 
fact  is  that  the  opening  of  the  stomata  depends 
chiefly  upon  the  degree  of  pressure  exerted  upon  the 
guard  cells  by  the  aqueous  vapour  within  according 
to  its  varying  density.  The  author  also  seems  to  be 
unaware  that  leaves  possess  both  air  stomata  and 
water  stomata.  The  air  stomata  under  the  leaves 
and  the  water  stomata  along  the  margin  of  the  leaf. 
E irly  in  the  morning  of  a warm  day  large  drops  of 
m-'isture  may  be  noticed  on  the  margin  of  some 
loaves,  which  one  would  be  apt  to  call  dew,  but  is 
really  water  excreted  by  the  water  ducts. 
But  I have  not  time  at  present  to  add  more  to  these 
hasty  remarks.  Perhaps  I may  be  permitted  another 
opportunity  of  doing  so.  Meanwhile  I would  only  add 
that  the  careful  study  of  a book  of  this  kind  will  give 
the  clue  to  much  that  is  obscure  and  perplexing,  in 
our  study  of  plant  life. 
With  reference  to  the  cultivation  of  Camphor.  The 
Camphor  trees  I have  grown  here  although  of  vigorous 
growth  show  a tendency  towai'ds  a huslni  habit  of 
growth  instead  of  making  a clear  stem.  The  same 
tendency  is  observable  in  the  Camphor  trees  growing 
in  the  Botanical  Gardens  at  Ootacamund.  May  I 
enquire  whether  it  is  the  same  in  Ceylon  ? — Yours 
faithfully,  J.  BIcKENZIE. 
“LADY-BIRD”  BEETLES  AND  MR.  E.  E. 
GREEN’S  EXPERIMENTS. 
Mote  Hall,  Bearsted,  Kent,  August  23. 
Dkar  Sir, — I learn  from  your  la.st  issue  of  the 
Tropirnl  AcfricuUurist  just  to  hand,  that  the  parcel 
of  “lady-bird”  beetles  has  at  last  turned  up,  but 
that  the  beetles  themselves  were  all  ilead.  Mr. 
Bagot  considers  this  failure  to  be  due  to  the  fact 
that  they  were  packed  in  closed  bo.xes.  But  I 
think  that  the  long  and  inexplicable  delay  in 
tran.sit  is  the  real  cau.se.  It  is  a mistake  to 
suppose  that  insects  require  a large  amount  of 
air.  They  w’ill  generally  obtain  a sufficient  supply 
through  the  natural  crevices  between  the  lid  and 
the  box.  In  fact  in  my  experience  of  the  receipt 
of  living  insects  by  jiost,  I have  more  frequently 
had  to  complain  of  over-ventilation,  leading 
either  to  the  escape  of  the  insects  or  the  drying 
up  of  the  food  plant.  In  the  case  of  the  “lady- 
bird ” beetles  from  California,  Mr.  Crow  has  had 
a large  experience  in  sending  these  insects  to 
various  p.arts  of  the  world.  He  despatched  them 
in  the  full  fed  larval  stage  with  a sufficiency  of 
food  to  last  them  until  they  had  pui)ated.  It 
was  calculated  that  the  l»eetles  would  l»e  hatching 
out  .about  the  time  of  their  arrival  in  ('eylon. 
But  a delay  of  .about  three  weeks  naturally  up.set 
these  cali'ulatioiis.  Perhaps  it  w ould  be  advisable 
on  another  occasion  to  have  the  parcel  consigned 
to  the  U.S.  (-onsul.  It  might  come  with  less 
delay  in  the  official  mail  bag. 
Did  Mr.  Bagot  examine  the  cotton  wool  or 
.any  debris  in  the  boxes?  'I’liis  wouhl  probably 
have  cont.ained  eggs  l.aid  by  the  beetles  before 
dying,  .and  a brood  of  young  larva'  might  have 
been  raised  from  them. — Yours  very  truly, 
E.  ERNE8T  GREEN, 
