﻿286 
  PROCEEDINGS 
  OF 
  THE 
  CALIFORNIA 
  

  

  observing 
  the 
  distribution 
  of 
  the 
  native 
  trees 
  in 
  all 
  kinds 
  of 
  localities, 
  except 
  

   the 
  portions 
  embraced 
  in 
  about 
  fifteen 
  miles 
  square 
  in 
  the 
  southeastern, 
  and 
  ag 
  

   much 
  more 
  of 
  dry 
  laud 
  in 
  the 
  northeastern 
  corners 
  of 
  the 
  " 
  Bay 
  Map 
  Region." 
  

   On 
  comparing 
  my 
  results 
  with 
  the 
  series 
  of 
  careful 
  observations 
  on 
  plant- 
  

   distribution, 
  given 
  by 
  Prof. 
  Bolander, 
  in 
  our 
  Proceedings, 
  and 
  Prof. 
  Brewer, 
  

   as 
  given 
  in 
  the 
  first 
  volume 
  of 
  Geology 
  of 
  California, 
  I 
  have 
  been 
  able 
  to 
  

   arrive 
  at 
  the 
  following 
  interesting 
  conclusions, 
  tending 
  to 
  indicate 
  the 
  laws 
  

   governing 
  our 
  tree-growth. 
  

  

  FORESTS 
  AND 
  TREES 
  OF 
  THE 
  BAY 
  MAP 
  REGION. 
  

  

  In 
  traveling 
  around 
  the 
  Bay, 
  the 
  most 
  notable 
  fact 
  in 
  Botanical 
  Geography 
  

   likely 
  to 
  attract 
  the 
  observer's 
  notice, 
  is 
  the 
  comparative 
  scarcity 
  of 
  the 
  trees 
  

   and 
  small 
  number 
  of 
  species, 
  as 
  compared 
  with 
  the 
  regions 
  either 
  northward, 
  

   at 
  Russian 
  River, 
  or 
  southward, 
  at 
  Monterey 
  Bay. 
  After 
  careful 
  study 
  of 
  the 
  

   subject, 
  the 
  conclusion 
  is 
  inevitable 
  that 
  the 
  chief 
  cause 
  of 
  this 
  deficiency 
  is 
  the 
  

   prevalence 
  of 
  the 
  strong 
  winds, 
  which, 
  throughout 
  the 
  dry 
  season, 
  blow 
  so 
  

   steadily 
  into 
  the 
  Golden 
  Gate 
  from 
  the 
  northwest, 
  and 
  are 
  drawn 
  by 
  the 
  ascent 
  

   of 
  heated 
  currents 
  far 
  into 
  the 
  interior, 
  following, 
  generally, 
  the 
  course 
  of 
  the 
  

   valleys 
  upward 
  from 
  the 
  Bay. 
  

  

  As 
  to 
  the 
  prevalence 
  of 
  these 
  winds, 
  we 
  have 
  natural 
  records 
  of 
  centuries 
  

   past, 
  in 
  the 
  trees 
  themselves, 
  bent 
  almost 
  to 
  the 
  ground 
  in 
  numerous 
  places. 
  

   Going 
  beyond 
  the 
  vicinity 
  of 
  this 
  Bay, 
  we 
  find 
  a 
  low 
  tract 
  of 
  hills 
  lying 
  be- 
  

   tween 
  Petaluma 
  and 
  Tomales 
  Bay, 
  where, 
  for 
  a 
  distance 
  of 
  ten 
  miles 
  square, 
  

   the 
  Coast 
  Range 
  is 
  depressed 
  to 
  an 
  average 
  height 
  of 
  three 
  hundred 
  and 
  fifty 
  

   feet, 
  with 
  passes 
  through 
  it 
  only 
  one 
  hundred 
  and 
  fifty 
  feet 
  above 
  the 
  sea. 
  

   Here, 
  the 
  winds 
  blow 
  inland 
  with 
  sufficient 
  force 
  to 
  have 
  limited 
  the 
  tree-growth 
  

   to 
  scattered 
  groups 
  on 
  the 
  eastern 
  slopes 
  of 
  the 
  hills. 
  

  

  That 
  soils 
  are 
  only 
  secondary 
  in 
  their 
  influence, 
  is 
  shown 
  well 
  around 
  this 
  

   city, 
  where 
  every 
  variety 
  of 
  metamorphic 
  rock 
  and 
  tertiary 
  sandstones 
  occur, 
  

   as 
  well 
  as 
  abundant 
  alluvium 
  in 
  the 
  valleys. 
  Much 
  the 
  same 
  variety 
  is 
  seen 
  in 
  

   the 
  low 
  hills 
  west 
  of 
  Petaluma, 
  while 
  other 
  openings 
  along 
  the 
  coast 
  to 
  the 
  

   south, 
  such 
  as 
  Salinas 
  Valley, 
  and 
  those 
  along 
  the 
  coast 
  south 
  of 
  Ventura, 
  

   (known 
  to 
  sailors 
  as" 
  Wind 
  Gaps," 
  on 
  account 
  of 
  the 
  strong 
  sea-breezes 
  drawn 
  

   inland 
  where 
  they 
  occur) 
  all 
  prove 
  the 
  prevalence 
  of 
  the 
  same 
  laws. 
  

  

  Elevation 
  above 
  the 
  sea, 
  of 
  course, 
  has 
  some 
  influence, 
  but 
  less 
  than 
  would 
  

   be 
  expected 
  ; 
  for 
  we 
  find 
  a 
  large 
  number 
  of 
  the 
  forty 
  species 
  of 
  trees 
  found 
  in 
  

   these 
  limits, 
  growing 
  with 
  scarcely 
  any 
  difference 
  in 
  size 
  or 
  luxuriance, 
  from 
  the 
  

   sea-level 
  up 
  to 
  4,500 
  feet. 
  Others, 
  however, 
  show 
  a 
  preference 
  for 
  mountains 
  

   or 
  valleys 
  alone, 
  and 
  all 
  are 
  influenced 
  by 
  the 
  eSect 
  of 
  the 
  mountains 
  in 
  moder- 
  

   ating 
  the 
  winds, 
  intercepting 
  fogs 
  and 
  rain-clouds, 
  and 
  producing 
  more 
  extreme 
  

   degrees 
  of 
  cold 
  and 
  heat 
  than 
  prevail 
  in 
  the 
  valleys. 
  The 
  studying 
  out 
  of 
  all 
  

   these 
  influences, 
  as 
  relating 
  to 
  each 
  species, 
  would 
  be 
  a 
  very 
  slow 
  process, 
  and 
  I 
  

   need 
  not 
  attempt 
  more 
  now 
  than 
  to 
  mention 
  such 
  as 
  seem 
  to 
  have 
  a 
  peculiar 
  

   efifect 
  on 
  certain 
  species. 
  The 
  general 
  unfavorable 
  influence 
  of 
  the 
  absence 
  of 
  

   mountains 
  on 
  tree-growth 
  in 
  our 
  climate, 
  is 
  shown 
  by 
  the 
  usual 
  bareness 
  of 
  

   our 
  valleys, 
  and 
  of 
  the 
  lower 
  hills, 
  where 
  unsheltered 
  from 
  the 
  wind. 
  

  

  