632  Vegetation  of  Yellowstone  Hot  Springs.  \^d^\^mt' 
Bohemia.  Later,  Cohn,  in  1862,  showed  that  the  algae  of  these 
springs  deposited  travertine.  Sir  William  Hooker,  in  1809,  found 
confervace/E  at  the  borders  of  many  of  the  hot  springs  there.  Con- 
ferva limosa,  C.  flavescens,  C.  rivularis  were  abundant  in  the  water. 
Baring  Gould,  who  visited  the  Icelandic  geyser  region  in  1864, 
found  in  the  overflow  channels  of  the  spring,  Tunguhver,  a  species 
of  the  genus  Hypheothrix,  common  in  hot  waters  all  over  the  world. 
In  New  Zealand,  the  presence  of  algae  in  hot  springs  has  been  deter- 
mined. In  the  hot  springs  of  the  Azores,  Mr.  Moseley  found  algae 
forming  a  pale  yellowish-green  layer  an  inch  and  a  half  thick.  The 
temperature  of  the  water  was  1760  F.  to  1940  F.  A  thick,  brilliant 
green  growth,  consisting  of  Chroococcns  was  found  at  the  edge  of  a 
shallow  pool  of  hot  water,  where  the  temperature  was  between 
1490  F.  and  1560  F. 
In  the  hot  springs  of  the  Yellowstone  no  plant  life  has  been  found 
at  a  temperature  exceeding  1 85 0  F.,  some  degrees  below  the  boil- 
ing point  of  water,  which,  at  the  altitude  of  the  park  (7,000-8,500 
feet)  is  1980  F.  The  most  luxuriant  growth  of  algae  is  found  in 
water  which  has  cooled  down  to  a  temperature  of  1040  F.  to  122°  F. 
In  water  of  a  temperature  ranging  from  ioo°  F.  to  1250  F.,  we 
have  the  greatest  display  of  color,  because  many  green  algae  can 
live  in  water  of  that  degree  of  heat.  In  the  hottest  waters  (1850  F.) 
only  white  filamentous  bacteria  are  found,  which  gradually  become 
of  a  sulphur-yellow  color  at  1750  F.  This  yellow  growth  is  due  to 
a  species  of  Beggiatoa,  a  plant  which  may  be  classed  with  the  Bac- 
teriace^:,  and  which,  during  life,  deposits  sulphur  granules. 
As  the  water  cools  down,  other  forms  of  vegetable  lile  appear,, 
give  variety  to  the  colorations  and  give  beauty  to  the  borders 
of  the  hot  pools  and  overflow  channels  leading  from  them.  The 
sequence  of  temperatures  and  of  colors  is  somewhat  as  follows  1 
white,  1600  F.-1850  F.;  yellow,  1450  F.-1600  F.;  red,  1300  F;  green, 
110°  F.-1300  F.;  green-orange-brown,  950  F.  There  are  varia- 
tions, however,  in  the  sequence  of  these  colors,  owing  to  various 
environmental  conditions.  Thus,  in  the  Black  Sand  Basin  and 
Specimen  Lake,  the  range  of  color  is  somewhat  this:  White,  yel- 
low, flesh  pink,  bright  pink,  yellowish-green,  emerald. 
Studying  the  growths  at  the  several  temperatures,  we  find  Lepto- 
thrix  laminosa  growing  at  1 35 0  F.-1850  F.;  Phormidium  at  1650  F.  • 
Beggiatoa  at  1 500  F.-1650  F.,  and  Spirulina  at  a  lower  temperature. 
