422 
JOURNAL  OF  HORTICULTURE  AND  COTTAGE  GARDENER . 
May  7,  1886. 
Dendrobium  PALLENS. 
At  one  of  the  early  meetings  of  the  Royal  Horticultural 
Society  this  year  there  was  exhibited  by  Mr.  W.  H.  White,  Orchid 
grower  to  Sir  Trevor  Lawrence,  Burford  Lodge,  Dorking,  a 
specimen  of  this  chastely  beautiful  Dendrobium.  It  is  said  to  be 
a  cross  between  D.  Findlayanum  and  D.  Ainsworthi.  The  sweetly 
fragrant  flowers  produced  as  depicted  in  the  woodcut  (fig.  69)  are 
of  good  size,  the  sepals  and  petals  being  white  tipped  with  blight 
rosy  pink.  The  lip  also  is  white,  with  the  same  shade  at  the  tip 
as  in  the  other  organs,  while  the  throat  is  pale  lemon  yellow.  The 
Orchid  Committee  adjudged  an  award  of  merit. 
Notes  on  Cattleyas. 
The  importance  of  this  splendid  genus  is  too  well  known  and 
appreciated  for  any  dilatation  on  its  merits  to  be  necessary,  and  a 
few  lines  on  the  details  of  culture  to  be  observed  at  this  season 
will  probably  be  more  acceptable  to  those  interested.  Perhaps  at 
no  other  season  are  Cattleyas  more  likely  to  be  overwatered  than 
now,  when  drying  winds  and  bright  sun  render  so  much  damping  of 
the  stages  necessary.  Of  course  it  is  quite  possible  to  do  this 
without  wetting  the  surface  even  of  the  compost,  and  experienced 
cultivators  need  not  to  be  told  the  advantages  accruing  from  this 
careful  treatment.  But  this  class  of  cultivators  is  not  likely  to 
overwater  their  plants  at  any  season,  and  to  the  inexperienced  these 
lines  therefore  will  moat  appeal.  One  of  the  most  frequent  causes 
of  non-success  in  any  branch  of  Orchid  growing  is  hurry,  a  dash 
with  the  syringe,  making  the  atmosphere  feel  moist,  and  a 
seemingly  expeditious  way  of  getting  out  of  the  difficulty. 
This  may  do  no  harm  one  day,  in  fact  an  occasional  syringing 
is  beneficial  to  most  Orchids  ;  but  if  persisted  in  it  will  be,  and  has 
been,  the  ruin  of  many  fine  collections.  The  young  tender  roots 
are  in  many  instances  running  on  or  near  the  surface  of  the  com¬ 
post,  and  this  being  kept  constantly  moist  by  the  syringing  is  the 
worst  possible  medium  for  them.  Down  among  the  drainage,  on 
the  other  hand,  roots  are  older  and  more  plentiful,  and  therefore 
require  more  moisture  ;  but  there  the  whole  is  as  dry  as  dust,  the 
appearance  of  the  surface  deceiving  the  operator  when  watering  at 
the  root.  Needless  to  say  that  this  state  of  things  cannot  long  go 
on  without  serious  injury,  and  the  advisability  of  more  care  in 
damping  is  at  once  seen.  A  worse  stage  is  reached  in  due  time; 
the  under  roots,  owing  to  the  continued  drought,  losing  the  power, 
as  it  were,  of  absorbing  the  moisture  when  it  is  evident  by  the  state 
of  the  plant  that  something  is  amiss,  and  more  water  is  given. 
These  soon  decay,  and  thus  the  plants  are  killed  by  watering  when 
in  reality  they  have  not  had  enough. 
Then  if  the  atmosphere  is  kept  too  dry,  and  unfortunately  this 
is  frequently  the  case,  the  plants  dry  at  the  root  very  rapidly,  so 
much  so,  in  fact,  that  water  has  to  be  applied  daily,  or  even  twice 
daily,  to  keep  them  moist.  The  compost  in  this  case  soon  becomes 
a  wet,  close  mass,  the  roots  perishing  one  by  one  until  hardly  a 
sound  one  is  left,  and  with  the  natural  result.  Endeavour  then  at 
this  season  to  maintain  plenty  of  atmospheric  moisture  without 
sousing  the  plants  and  sprinkling  the  compost.  Then  it  is 
easily  seen  whether  the  roots  need  water  or  not,  and  a  little  care 
and  observation  only  are  necessary.  As  the  young  growth  in  many 
cases  is  well  on  the  move,  a  rise  in  the  night  temperature  should 
now  be  permitted,  never  allowing  the  house  to  drop  below  58°  if  it 
can  be  avoided,  and,  if  practicable,  leaving  on  a  little  air  at  night. 
By  day  the  house  may  run  up  to  75°  or  80°  when  the  sun  is  bright, 
always  provided  that  plenty  of  air  is  allowed  and  that  the  rise  from 
the  night  temperature  has  been  gradual. 
Many  plants  have  recently  been  potted,  and  these  are  now 
placed  together  as  much  as  possible,  a  little  more  shade  being 
allowed  them  than  those  well  established  in  their  pots.  For  the  latter 
shade  as  little  as  possible,  but  keep  in  mind  the  young  growing 
shoots,  for  although  they  are  in  many  cases  under  the  protecting 
•hade  of  the  foliage,  this  must  not  be  relied  on,  and  many  losses 
occur  through  inattention  to  this.  It  is  not  too  late  to  repot  any 
that  require  it,  and  in  looking  the  plants  over  for  this  operation 
remember  that  a  year  has  to  elapse  before  potting  time  again  comes 
round,  and  any  the  compost  of  which  seems  in  a  doubtful  condition 
may  perhaps  be  in  a  very  bad  state  ere  then.  Keep  in  mind,  on 
the  other  hand,  that  repotting,  however  carefully  done,  is  harmful 
to  a  certain  extent,  and  do  not  disturb  any  that  do  not  require  it. 
If  water  enters  the  compost  freely  when  poured  upon  it,  and  leaves 
it  with  a  rush  through  the  drainage  hole  beneath,  there  is  no  need 
to  repot  if  the  plants  are  not  root-bound  and  require  a  larger  one ; 
but  if  the  drainage  is  slow,  and  the  compost  appears  close  and  heavy 
on  the  surface,  the  sooner  the  roots  are  out  of  it  the  better. 
I  have  so  often  described  the  modes  of  potting  and  basketing 
these  Orchids  in  the  Journal  that  to  go  into  the  matter  again  seems 
hardly  necessary.  Suffice  it  to  say  then  that  nothing  of  a  sour  or 
heavy  nature  must  be  left  in  the  potB,  and  all  decayed  portions  of 
root  should  be  cut  away.  Use  pots  rather  wide  than  deep, 
especially  for  the  strong -growing  members  of  the  genus,  and  the 
compost  in  a  rough  open  condition.  The  water  supply  must  be 
curtailed  a  little  afterwards  and  until  the  roots  are  moving  freely, 
when  more  will  be  necessary.  Among  those  now  in  flower  perhapi 
the  most  important  are  C.  Lawrenceana  and  C.  Mendelli,  both 
belonging  to  the  labiata  section.  The  former  is  a  highly  coloured 
and  charming  species,  requiring  plenty  of  heat  to  bring  it  to 
perfection,  the  latter  doing  well  in  the  ordinary  Cattleya  house 
temperature. 
C.  Skinneri  is  another  useful  and  interesting  species  now  in 
blossom,  bearing  many-flowered  racemes  varying  considerably  both 
in  size  and  tints  of  colouring.  C.  intermedia,  C.  citrina,  and 
C.  amethystoglossa  are  all  in  full  beauty,  and  the  swelling  sheaths 
on  the  earlier  plants  of  C.  Mossise  give  promise  of  a  rich  and  varied 
display  in  the  near  future. — H.  R.  R. 
GARDEN  PESTS  AND  ANTIDOTES. 
( Continued  from  page  394.) 
In  taking  cognisance  of  the  insecticides  in  use  the  oldest  is 
tobacco,  which,  in  the  form  of  smoke,  liquid,  and  powder  (snuff) 
dates  from  the  last  century.  Tobacco,  or  its  principle  nicotine,  is 
a  poisonous  substance,  with  a  disagreeable  or  repellant  odour  to 
certain  insects,  thus  acting  as  a  preventive  and  remedial  agent. 
Its  smoke  is  fatal  to  aphides  and  thrips,  two  of  the  most  destructive 
pests  of  crops,  but  tobacco  smoke  has  little  effect  on  the  scale  and 
red  spider.  The  oil,  however,  or  nicotine,  makes  an  end,  when 
vaporised,  of  mealy  bug,  and  greatly  reduces  the  arachnoid  in 
number.  Both  the  smoke  and  vaporised  fumes  render  the  structure 
and  the  plants  on  which  they  are  used  repugnant  to  insects  for  some 
time,  consequently  fumigation  by  either  method  acts  as  a  pre¬ 
ventive  of  attack  for  some  time  afterwards,  and  it  i#  a  notable  fact 
that  where  periodical  fumigation  or  vaporisation  is  had  recourse  to 
at  sufficiently  frequent  intervals  there  are  no  insects  of  the  aphid 
or  thrip  order.  In  powder  form  the  odour  is  more  subdued,  yet 
the  plants  are  made  distasteful  to  such  insects  for  a  greater  or 
lesser  time,  according  as  it  remains  on  the  plant. 
When  in  decoction,  whether  of  the  tobacco  itself  or  of  the 
expressed  juice  in  manufacturing  smoking  tobacco,  both  aphides 
and  thrips  readily  succumb,  provided  they  are  moistened  by  it, 
which  is  not  always  the  case,  as  aphides  have  smooth  bodies  and 
watery  substances  do  not  adhere  to  them,  hence  decoction  of 
tobacco  is  not  as  powerful  as  tobacco  juice,  which  contains  some 
oil  and  clings  to  the  bodies  of  the  insects  to  a  greater  extent.  But 
even  oils  do  not  hold  so  well  to  smooth  surfaces  as  saponified 
substances,  hence  we  have  nicotine  soap,  so  as  to  cause  the 
insecticide  to  have  a  better  grip  on  the  insect’s  body,  and  thus 
secure  the  advantages  of  both  the  tobacco  and  of  the  soap  as  a 
destroyer  of  insects,  and  preventive  of  their  recurrence. 
Soaps  of  the  potash  and  soda  class  come  next  in  antiquity  as 
insecticides,  but  their  manufacture  and  use  on  a  large  scale  dates 
only  from  about  the  year  1823,  when  Chevreul  published  his 
famous  researches  on  the  animal  fats.  Soaps  are  metallic  salts  of 
the  higher  fatty  acids,  and  the  process  by  which  these  salts  are 
produced  from  the  natural  fats  is  called  saponification.  In 
ordinary  language  the  name  is  limited  to  the  sodium  and  potassium 
salts  of  these  acids,  hard  soap  being  a  soda  and  softsoap  a  potash 
soap.  Soapsuds  have  long  been  used  as  an  insecticide,  but  are  now 
almost  wholly  neglected,  though  still  of  essential  service  when  used 
in  proper  manner  and  form.  Softsoap  in  various  ways  is  one  of 
the  chief  insecticides,  and  in  some  cases  fungicides,  used  in  gardens. 
When  not  containing  the  higher  fatty  acid*  in  the  free  state  soft- 
soap  is  one  of  the  safest  substances  to  use,  as  it  can  do  no  harm  to 
the  foliage  or  growth  unless  used  in  excessive  amounts,  or  to  the 
roots  of  plants  ;  but  some  benefit  on  account  of  the  reduction  of 
the  organic  matter  and  the  presence  of  the  potash.  Grishurst  com¬ 
pound  comes  under  this  category,  being  the  natural  fats — palma- 
tine,  stearine,  and  ole;ne — saponified. 
In  successional  order  come  the  wood  oils,  such  as  Fir-tree,  a 
combination  of  hydro-carbon  oils  made  soluble  in  water,  containing 
small  portions  of  paraffin  and  petroleum  in  Fir-tree  oil  insecticide, 
with  larger  portions  of  oils  from  the  various  species  of  Pine  trees, 
treated  in  such  manner  that  they  become  perishable  in  the  soil,  so 
as  not  to  destroy  the  roots  of  plants,  which  often  prove  the  case 
