﻿320 
  C. 
  F. 
  M. 
  SWYNNERTON. 
  

  

  The 
  information 
  I 
  have 
  included 
  in 
  the 
  map 
  on 
  the 
  distribution 
  of 
  fly 
  and 
  sleeping- 
  

   sickness 
  in 
  South 
  Kavirondo 
  is 
  taken 
  from 
  maps 
  which 
  were 
  kindly 
  placed 
  at 
  my 
  

   disposal 
  in 
  Kisumu 
  and 
  Nairobi. 
  The 
  map, 
  and 
  this 
  paper 
  generally, 
  should 
  be 
  

   regarded 
  as 
  preliminary 
  and 
  provisional 
  only, 
  a 
  basis 
  for 
  correction 
  and 
  addition 
  

   by 
  the 
  medical, 
  political, 
  and 
  other 
  officers 
  who 
  are 
  continuing 
  to 
  work 
  on 
  the 
  problem. 
  

  

  The 
  specific 
  names 
  of 
  certain 
  of 
  the 
  plants 
  referred 
  to 
  in 
  the 
  paper 
  are 
  provisional 
  

   also. 
  They 
  will 
  be 
  revised 
  and 
  added 
  to 
  when 
  my 
  plant 
  collection 
  has 
  been 
  worked 
  

   out. 
  I 
  am 
  much 
  indebted 
  to 
  Dr. 
  A. 
  B. 
  Rendle, 
  F.R.S., 
  Dr. 
  H. 
  Harms, 
  Dr. 
  M. 
  Burret, 
  

   Mr. 
  E. 
  G. 
  Baker, 
  and 
  particularly 
  Mr. 
  C. 
  Norman, 
  for 
  their 
  kind 
  assistance 
  in 
  

   connection 
  with 
  the 
  naming. 
  

  

  II. 
  — 
  The 
  Country 
  generally. 
  

  

  As 
  regards 
  vegetation, 
  the 
  country 
  is 
  divisible 
  primarily 
  into 
  (1) 
  perfectly, 
  or 
  

   nearly 
  perfectly, 
  open 
  country, 
  free 
  from 
  tsetse 
  (PL 
  xii, 
  fig. 
  1) 
  ; 
  (2) 
  acacia 
  wooding, 
  

   infested 
  nearly 
  throughout 
  by 
  a 
  new 
  tsetse 
  of 
  the 
  morsitans 
  group 
  (PI. 
  xii, 
  fig. 
  2) 
  ; 
  

   and 
  (3) 
  Brackystegia 
  savannah 
  forest, 
  also 
  fly-infested. 
  

  

  The 
  bulk 
  of 
  the 
  open 
  country 
  itself 
  may 
  be 
  described 
  as 
  " 
  suppressed" 
  acacia 
  

   wooding. 
  The 
  suppressive 
  factors 
  at 
  work 
  are 
  merely 
  temporary, 
  and 
  their 
  removal 
  

   or 
  weakening 
  even 
  for 
  four 
  or 
  five 
  years 
  would, 
  and 
  does, 
  allow 
  this 
  wooding 
  to 
  grow 
  up. 
  

   This 
  results 
  in 
  continual 
  modification 
  in 
  the 
  distribution 
  of 
  the 
  two 
  contrasting 
  types. 
  

   Each 
  of 
  them, 
  however, 
  covers 
  a 
  great 
  area 
  of 
  country, 
  and 
  their 
  present 
  distribution 
  

   is 
  shown 
  approximately 
  in 
  the 
  accompanying 
  rough 
  map. 
  

  

  No 
  primary 
  forest 
  was 
  seen. 
  Though 
  it 
  occurs, 
  it 
  is 
  said, 
  on 
  Rome 
  Island 
  (where 
  

   is 
  a 
  forest 
  reserve) 
  and, 
  in 
  its 
  mountain 
  form, 
  on 
  Oldeani 
  and 
  in 
  some 
  places 
  in 
  the 
  

   volcanic 
  area 
  north 
  of 
  the 
  Renya 
  border, 
  both 
  general 
  indications 
  and 
  native 
  informa- 
  

   tion 
  as 
  to 
  past 
  alternations 
  of 
  acacia 
  savannah 
  and 
  settlement 
  suggest 
  that 
  it 
  is. 
  

   long 
  since 
  it 
  was 
  exterminated 
  in 
  the 
  bulk 
  of 
  the 
  country 
  I 
  have 
  shown 
  on 
  the 
  map. 
  

   But 
  an 
  enormous 
  area 
  of 
  " 
  miombo 
  " 
  or 
  Brackystegia 
  savannah 
  forest, 
  already 
  

   described 
  and 
  figured 
  by 
  me 
  under 
  its 
  Shangan 
  name 
  " 
  itondo 
  " 
  (Bull. 
  Ent. 
  Res.,. 
  

   xi, 
  p. 
  320, 
  PI. 
  xvi) 
  fills 
  the 
  west 
  of 
  Tanganyika 
  Territory 
  and 
  borders 
  the 
  special 
  

   area 
  I 
  am 
  here 
  dealing 
  with 
  on 
  its 
  west 
  and 
  south. 
  It 
  is 
  infested 
  throughout 
  by 
  

   G. 
  morsitans, 
  and 
  its 
  possible 
  infection 
  constitutes 
  the 
  greatest 
  danger 
  of 
  the 
  present 
  

   outbreak. 
  

  

  The 
  general 
  geological 
  formation 
  is 
  granite. 
  Granite 
  boulders, 
  and 
  kopjes 
  and 
  

   hills 
  composed 
  of 
  them 
  and 
  reminiscent 
  of 
  Mashonaland 
  (PI. 
  xv, 
  fig. 
  2), 
  are 
  scattered 
  

   thinly 
  or 
  in 
  groups 
  over 
  both 
  the 
  wooded 
  and 
  the 
  open 
  areas 
  and 
  everywhere 
  crown 
  

   rising 
  ground. 
  Hilly 
  plateaux, 
  a 
  small 
  one 
  at 
  Rilalo, 
  a 
  greater 
  one 
  in 
  Ushashi 
  and 
  

   the 
  country 
  to 
  its 
  north, 
  occur 
  in 
  the 
  granite. 
  

  

  Schistose, 
  diorite 
  and 
  diabase 
  hills 
  of 
  more 
  rounded 
  outline 
  occur 
  at 
  Zagayu 
  

   (Mount 
  Sansui) 
  and 
  at 
  Ngasamo, 
  and 
  (as 
  a 
  view 
  from 
  the 
  last-named 
  hill 
  showed) 
  

   become 
  very 
  general 
  in 
  the 
  direction 
  of 
  Ikoma. 
  They 
  are 
  associated 
  with 
  a 
  red 
  soil 
  

   that 
  contrasts 
  with 
  the 
  grey 
  and 
  sandier 
  soil 
  of 
  the 
  granite. 
  

  

  North 
  of 
  Ikoma 
  both 
  the 
  above-mentioned 
  formations 
  are 
  said 
  to 
  give 
  place 
  to 
  

   ancient 
  shales 
  and 
  quartzites 
  that 
  fail 
  to 
  reach 
  the 
  coast 
  but 
  extend 
  far 
  into 
  Renya 
  

   Colony. 
  These 
  are 
  associated 
  on 
  the 
  whole, 
  it 
  would 
  appear, 
  with 
  lighter 
  types 
  

   of 
  bush. 
  Doubtless 
  not 
  everywhere, 
  for 
  where 
  the 
  Mara 
  crosses 
  the 
  border 
  there 
  

   is, 
  at 
  the 
  foot 
  of 
  the 
  Isuria 
  Escarpment, 
  an 
  area 
  inhabited 
  by 
  G. 
  pallidipes. 
  

  

  On 
  the 
  coast 
  just 
  north 
  of 
  the 
  Renya 
  border 
  the 
  intervening 
  granite 
  gives 
  place 
  

   to 
  the 
  volcanic 
  rocks 
  of 
  the 
  Tertiaries 
  and 
  generally 
  loftier 
  country. 
  The 
  change 
  in. 
  

   the 
  form 
  of 
  the 
  hills 
  is 
  very 
  noticeable 
  from 
  the 
  Lake. 
  A 
  similar 
  geological, 
  not 
  

   physical, 
  change 
  takes 
  place 
  also 
  on 
  the 
  eastern 
  border 
  of 
  the 
  three 
  great 
  bush-covered 
  

   Sultanates 
  of 
  Ututwa, 
  Ranadi, 
  and 
  Meatu, 
  on 
  reaching 
  the 
  Serengeti 
  Plain. 
  The 
  

   change 
  in 
  each 
  case 
  appears 
  to 
  coincide 
  with 
  a 
  change 
  in 
  the 
  general 
  vegetation. 
  

  

  