﻿IV 
  

  

  diversity 
  of 
  their 
  character 
  in 
  different 
  plants, 
  especially 
  the 
  enfoliation 
  

   of 
  layers 
  of 
  bark 
  in 
  such 
  trees 
  as 
  the 
  Plane. 
  

  

  The 
  following 
  year 
  (1836) 
  Yon 
  Mohl 
  developed 
  his 
  theory 
  of 
  an 
  inter- 
  

   cellular 
  substance 
  in 
  which 
  the 
  cells 
  of 
  tissues 
  were 
  held 
  to 
  be 
  imbedded. 
  

   This 
  supposed 
  cement 
  is 
  now 
  known 
  to 
  belong 
  to 
  the 
  cell-walls 
  them- 
  

   selves, 
  and 
  not 
  to 
  be 
  a 
  substance 
  independent 
  of 
  them. 
  Mohl 
  indeed, 
  

   later 
  in 
  life, 
  practically 
  withdrew 
  his 
  views 
  upon 
  the 
  matter 
  (' 
  Die 
  vege- 
  

   tabilische 
  Zelle,' 
  1850). 
  He 
  also, 
  in 
  1836, 
  gave 
  an 
  account 
  of 
  the 
  singular 
  

   caudex 
  of 
  Tamus 
  (Testudinaria) 
  elephantipes. 
  

  

  In 
  1837 
  Von 
  Mohl 
  published 
  the 
  results 
  of 
  his 
  investigations 
  with 
  

   regard 
  to 
  chlorophyl. 
  They 
  still 
  remain, 
  essentially 
  undisturbed. 
  He 
  

   showed 
  that 
  chlorophyl-granules 
  were 
  soft 
  and 
  homogeneous 
  bodies, 
  and 
  

   not 
  vesicular, 
  as 
  had 
  been 
  supposed 
  ; 
  he 
  detected 
  in 
  them 
  the 
  presence 
  

   of 
  starch. 
  Nageli 
  having 
  asserted 
  that 
  chlorophyl-granules 
  possess 
  a 
  

   cellulose 
  investment, 
  Yon 
  Mohl 
  returned 
  to 
  the 
  subject 
  in 
  1855, 
  and 
  

   showed 
  that 
  this 
  view 
  was 
  untenable. 
  During 
  1837 
  he 
  also 
  published 
  a 
  

   dissertation 
  on 
  the 
  structure 
  of 
  vegetable 
  membrane, 
  in 
  which 
  he 
  declared 
  

   " 
  secondary 
  cell-membranes 
  to 
  possess 
  a 
  fibrous 
  structure." 
  The 
  objec- 
  

   tive 
  fact 
  observed 
  by 
  Yon 
  Mohl 
  is 
  one 
  of 
  very 
  general 
  truth, 
  although 
  a 
  

   rather 
  different 
  set 
  of 
  considerations 
  are 
  now 
  brought 
  to 
  its 
  explana- 
  

   tion. 
  His 
  paper 
  on 
  the 
  porous 
  cells 
  of 
  Sphagnum 
  finally 
  put 
  to 
  rest 
  the 
  

   controversy 
  as 
  to 
  their 
  nature. 
  He 
  contributed 
  an 
  examination 
  of 
  some 
  

   abnormal 
  cones 
  to 
  the 
  difficult 
  question 
  of 
  the 
  floral 
  morphology 
  of 
  

   Coniferse. 
  In 
  his 
  observations 
  on 
  the 
  sporangium 
  in 
  the 
  vascular 
  Crypto- 
  

   gams 
  he 
  established 
  the 
  real 
  nature 
  of 
  this 
  structure 
  in 
  ferns. 
  In 
  the 
  

   case 
  of 
  Selaginella, 
  Bischoff's 
  view, 
  that 
  the 
  sporangium 
  is 
  an 
  axillary 
  

   bud, 
  was 
  abandoned 
  by 
  Hofmeister 
  for 
  the 
  explanation 
  given 
  by 
  Yon 
  

   Mohl. 
  

  

  In 
  1838 
  he 
  published 
  the 
  first 
  account 
  of 
  the 
  development 
  of 
  stomata, 
  

   which 
  he 
  observed 
  in 
  Hyacinthus 
  orientalis. 
  He 
  also 
  corrected 
  the 
  account 
  

   which 
  Mirbel 
  had 
  given 
  of 
  the 
  origin 
  of 
  the 
  stomata 
  of 
  Marchantia. 
  His 
  

   dissertation, 
  ' 
  Ueber 
  den 
  Einfluss 
  des 
  Bodens 
  auf 
  die 
  Yertheilung 
  der 
  

   Alpenpflanzen,' 
  has 
  served 
  as 
  a 
  basis 
  for 
  the 
  more 
  extended 
  investigations 
  

   of 
  Alphonse 
  De 
  Candolle 
  on 
  the 
  same 
  subject. 
  

  

  In 
  1839 
  he 
  discussed 
  the 
  structure 
  of 
  annular 
  vessels, 
  contending 
  

   against 
  Schleiden 
  that 
  they 
  were 
  not 
  a 
  derivative 
  form 
  of 
  spiral 
  vessels. 
  In 
  

   his 
  ' 
  Die 
  vegetabilische 
  Zelle 
  ' 
  he 
  maintained 
  a 
  similar 
  view 
  with 
  regard 
  

   to 
  reticulated 
  and 
  other 
  vessels. 
  He 
  published 
  some 
  important 
  observa- 
  

   tions 
  on 
  the 
  development 
  of 
  the 
  spores 
  of 
  Anihoceros. 
  

  

  In 
  1840 
  he 
  described 
  the 
  peculiar 
  phenomena 
  of 
  the 
  growth 
  of 
  Isoetece; 
  

   and, 
  as 
  Hofmeister 
  has 
  remarked 
  (' 
  On 
  the 
  Higher 
  Cryptogams,' 
  p. 
  337), 
  

   " 
  since 
  Yon 
  Mohl's 
  discoveries 
  the 
  special 
  attention 
  of 
  botanists 
  has 
  been 
  

   almost 
  constantly 
  directed 
  to 
  this 
  interesting 
  family." 
  

  

  In 
  1842 
  he 
  published 
  remarks 
  on 
  the 
  structure 
  of 
  dotted 
  ducts. 
  In 
  

   this 
  he 
  gave 
  the 
  first 
  explanation 
  of 
  the 
  structure 
  of 
  bordered 
  pores. 
  In 
  

   the 
  corrected 
  form 
  given 
  to 
  it 
  by 
  Schacht 
  (1859) 
  this 
  is 
  probably 
  the 
  

  

  