534 
Belladonna  and  Hyoscyamus. 
/Am.  Jour.  Pharm. 
\  December,  1914. 
confined  to  particular  races.  De  Vries  presents  experimental  evidence 
to  prove  that  biennial  species  which  possess  this  semi-latent  capacity- 
are,  in  becoming  annuals,  largely  influenced  by  external  factors. 
A  large  number  of  plants  will  become  annual  if  the  seeds  germinate 
early  or  biennial  if  their  seeds  germinate  late ;  here  the  stimulus  of 
the  spring  frost  or  cool  weather  is  in  some  cases  a  factor  which 
causes  annuals  or  bolting,  as  in  the  sugar  beet.  In  addition,  many 
plants  possess  an  inherited  variability  to  be  either  annuals  or  biennials. 
Fig.  2. — Flowering  branches  of  Hyoscyamus  niger,  annual. 
In  summing  up  experiments  on  CEnothera,  De  Vries  shows  that 
"biennial  species  which  possess  in  a  semi-latent  state  the  capacity  to 
produce  annual  specimens  can  be  induced  to  manifest  this  anomaly 
to  a  much  greater  extent  by  supplying  them  with  more  food.  Crowd- 
ing of  plants,  shading,  lack  of  manure,  or  cultivation  on  sand  favors 
the  production  of  biennials ;  but  the  more  space,  light,  and  nourish- 
ment in  the  soil  there  is  at  the  disposal  of  the  individual  plants  the 
greater  will  be  the  number  of  those  which  will  produce  stems,  flower, 
and  ripen  their  seed  the  first  summer."   Continued  selection  fails  to 
