^""■jan-^S™'}         ReceM  Researches  in  Botany.  49 
the  lever  is  most  striking;  indeed,  so  rapid  is  its  movement,  tliat  it  travels 
in  many  cases  over  ten  millimetres  in  one  minute. 
The  stimulating  effect  of  alcohol  was  first  tried.  Methylated  spirit  2  per 
cent,  being  used,  the  acceleration  was  100  :  loO.^ 
The  stimulating  effect  of  ether  vapor  was  then  tried,  the  pith  in  these 
experiments  being  allowed  to  grow  in  damp  air.  A  known  quantity  of  ether 
was  poured  into  a  jar  of  known  capacity.  The  mouth  of  the  cylinder  was 
closed  by  a  divided  glass  disk  which  allowed  the  passage  of  the  thread 
attaching  the  pith  to  the  lever. 
The  atmosphere  of  ether  was  kept  as  constant  in  strength  as  was  possible. 
The  following  table  shows  the  percentage  of  ether  in  the  atmospheres  which 
caused  acceleration,  the  amount  of  quickening  being  given  in  a  parallel 
column. 
Percentage  of  ether.  Acceleration  of  growth. 
0-27°  100  :  118 
0-37°  100  :  146 
0-40°  100  : 200 
With  chloroform  the  results  were — 
Per  cent. 
0"008  Retardation  of  growth. 
0-05   No  effect. 
0.1  No  effect. 
0"9  Slow  contraction. 
An  aqueous  solution  of  camphor,  said  to  be  0*1  per  cent.,  was  tried,  but 
no  effect  on  the  "  growth  "  of  the  pith  was  observed. 
Weak  solutions  of  ammonia  were  found  to  have  a  well-marked  stimula- 
ting effect. 
strength  of  solution.  Amount  of  acceleration. 
0-  5  100  :  145 
1-  9  100  :  103 
2-  0  No  effect. 
2.2  100  :  121 
2-4                                                            100  :  129 
Various  acids  were  tried.  As  a  rule  they  had  no  accelerating  effect  on 
growth,  but  caused  either  retardation  or  actual  contraction  of  the  pith. 
Acetic  acid  and  hydrochloric  acid  caused  decided  retardation.  The  effect 
of  nitric  acid  was  not  very  evident. 
Carbolic  acid  of  '5  per  cent,  and  1  per  cent,  did  not  seem  to  have  any 
effect,  but  3  per  cent,  caused  a  contraction  of  the  pith. 
The  effect  of  prussic  acid  was  very  striking.  It  did  not  produce  a  con- 
traction, as  might  have  been  expected,  but  either  a  temporary  acceleration 
or  else  a  remarkably  steady  high  rate  of  growth  continued  for  a  prolonged 
period. 
^  One  hundred  represents  a  definite  amount  of  acceleration,  i.  e.,  increase  in 
h  ngth  at  the  rate  of  0'46  million  per  minute. 
