844 
Book  Reviews. 
{Am.  Jour.  Pharm. 
November,  1920. 
are  given  in  the  book.  A  double  page  color  plate  gives  the  range  of 
tints  resulting  from  different  degrees  of  hydrogen  ion  concentration  in 
action  with  a  series  of  indicators  of  comparatively  recent  intro- 
duction and  special  adaptability  to  the  problem  in  hand. 
The  book  will  be  a  great  aid  to  the  working  chemist  and  es- 
pecially to  the  bio-chemist.  It  is  well  printed,  on  good  paper  with 
good  type  and  the  literary  merit  is  high,  the  language  being  clear 
and  concise.  An  extensive  bibliography  and  an  account  of  many 
of  the  applications  of  the  principle  are  added. 
The  book  bears  the  statement  "Published  by  the  permission  of 
the  Secretary  of  Agriculture."  Well,  we  suppose  it  is  all  right.  Dr. 
Clark  is  a  subordinate  of  that  official,  and  presumably  his  work  be- 
longs to  the  government,  and  it  is  likely  that  the  "permission"  is 
mere  routine,  yet  it  does  give  the  independent  chemist  a  twinge  to 
see  the  publication  of  such  meritorious  work  even  nominally  de- 
pendent on  an  official  who  may  not  know  anything  about  the  matter. 
Henry  Lkffmann. 
"A  Critical  Revision  of  the  Genus  Eucalyptus."  By  J.  H. 
Maiden,  I.S.O.,  F.R.S.,  F.I^.S.,  Government  Botanist  of  New 
South  Wales  and  Director  of  the  Botanic  Gardens,  Sydney.  Vol. 
V,  Part  2. 
This  constitutes  part  XLH  of  the  complete  work,  which 
we  have  reviewed  from  time  to  time  as  the  parts  have  been  received. 
The  present  contribution  to  this  monographic  study  of  the  interest- 
ing Genus  Eucalyptus  covers  the  following  species:  E.  eximia 
Schauer;  E.  peltata  Bentham;  E.  Watsoniana  F.  v.  M.;  E.  trachyphloia 
F.  V.  M.;  E.  hybrida  Maiden;  E.  Kruseana  F.  v.  M.;  E,  Dawsoni; 
R.  T.  Baker;  E.  polyanthemos  Schauer;  E.  conica  Deane  and  Maiden; 
E.  concolor  Schauer. 
The  same  style  of  description  and  excellence  of  illustrations  that 
characterize  the  former  parts  of  this  voluminous  study  are  exhibited 
in  the  part  now  before  us.  G.  M.  B. 
