﻿T. 
  Holm 
  — 
  Vitality 
  of 
  some 
  Annual 
  Plants. 
  307 
  

  

  The 
  plant 
  illustrates 
  then 
  at 
  once 
  the 
  two 
  stages 
  of 
  a 
  bien- 
  

   nial 
  growth 
  : 
  the 
  leafy 
  roset, 
  which 
  will 
  winter 
  over, 
  and 
  the 
  

   flowering 
  stems 
  from 
  a 
  similar 
  roset 
  of 
  the 
  preceding 
  year. 
  

   The 
  age 
  of 
  this 
  specimen 
  is 
  at 
  least 
  three 
  years, 
  for 
  there 
  is 
  a 
  

   distinct 
  stem-part 
  (S 
  1 
  ) 
  to 
  be 
  seen 
  between 
  the 
  primary 
  root 
  and 
  

   the 
  now 
  faded 
  roset 
  of 
  leaves. 
  This 
  part 
  of 
  the 
  stem 
  is 
  in 
  

   contrast 
  to 
  the 
  upper 
  part 
  which 
  is 
  horizontal 
  and 
  fixed 
  to 
  the 
  

   ground 
  by 
  strong 
  roots 
  in 
  addition 
  to 
  the 
  persistent 
  primary 
  

   one. 
  The 
  plant 
  has 
  undoubtedly 
  merely 
  developed 
  a 
  leafy 
  

   roset 
  in 
  its 
  first 
  year, 
  when 
  the 
  seed 
  germinated, 
  probably 
  

   flowered 
  the 
  second 
  year 
  and 
  produced 
  the 
  stem-part 
  S\ 
  flow- 
  

   ered 
  again 
  in 
  the 
  third 
  year, 
  producing 
  contemporarily 
  a 
  shoot 
  

   that 
  will 
  flower 
  next 
  year, 
  until 
  finally 
  an 
  inflorescence 
  will 
  

   terminate 
  the 
  main 
  axis 
  and 
  the 
  entire 
  individual 
  die 
  away 
  

   after 
  the 
  ripening 
  of 
  the 
  fruits. 
  

  

  The 
  closely 
  allied 
  A. 
  lyrata 
  L. 
  has 
  been 
  mentioned 
  by 
  Hil- 
  

   debrand 
  (1. 
  c.) 
  as 
  being 
  annual 
  or 
  biennial. 
  It 
  occurs, 
  however, 
  

   also 
  as 
  perennial, 
  and 
  most 
  commonly 
  so 
  in 
  the 
  Southern 
  United 
  

   States. 
  I 
  have 
  collected 
  several 
  specimens 
  in 
  the 
  vicinity 
  of 
  

   Washington, 
  which 
  were 
  all 
  decidedly 
  perennial, 
  and 
  most 
  of 
  

   the 
  individuals 
  in 
  the 
  National 
  Herbarium 
  from 
  other 
  parts 
  of 
  

   North 
  America 
  showed 
  the 
  same 
  fact. 
  Some 
  specimens 
  from 
  

   Japan 
  were, 
  however, 
  annual, 
  with 
  flowers 
  and 
  leaves 
  devel- 
  

   oped 
  in 
  the 
  first 
  year 
  and 
  at 
  the 
  same 
  time. 
  The 
  perennial 
  

   form 
  shows 
  nearly 
  the 
  same 
  habit 
  as 
  above 
  described 
  for 
  

   A. 
  dentata, 
  but 
  commonly 
  with 
  a 
  profuse 
  development 
  of 
  

   lateral 
  leafy 
  shoots 
  together 
  with 
  the 
  inflorescences, 
  so 
  that 
  the 
  

   life 
  is 
  secured 
  for 
  a 
  considerably 
  longer 
  time 
  than 
  in 
  the 
  pre- 
  , 
  

   ceding 
  species. 
  

  

  That 
  also 
  Arabis 
  laevigata 
  Poir. 
  may 
  occur 
  as 
  perennial 
  has 
  

   been 
  recorded 
  by 
  Hildebrand 
  (1. 
  a), 
  but 
  without 
  data 
  ; 
  Gray 
  

   has 
  considered 
  this 
  species 
  as 
  truly 
  biennial, 
  in 
  which 
  form 
  it 
  

   occurs 
  exclusively 
  around 
  Washington, 
  where 
  it 
  is 
  very 
  abun- 
  

   dant. 
  

  

  Washington, 
  D. 
  C, 
  July 
  22d, 
  1891. 
  

  

  EXPLANATION 
  OF 
  PLATE 
  X. 
  

  

  Fig. 
  1. 
  — 
  Hypericum 
  nudicaule. 
  The 
  base 
  of 
  the 
  stem, 
  showing 
  two 
  densely 
  

  

  leaved 
  shoots. 
  Natural 
  size. 
  

   Fig. 
  2. 
  — 
  Tragus 
  racemosus. 
  Part 
  of 
  a 
  stolon 
  A-A, 
  with 
  secondary 
  branches 
  S 
  

  

  and 
  several 
  crowded 
  shoots. 
  Natural 
  size. 
  

   Fig. 
  3. 
  — 
  Same. 
  Part 
  of 
  a 
  stolon, 
  showing 
  two 
  leafy 
  shoots 
  in 
  the 
  axils 
  of 
  two 
  

  

  leaves, 
  belonging 
  to 
  the 
  stolon. 
  P. 
  the 
  prophyllum. 
  Slightly 
  enlarged. 
  

   Fig. 
  4. 
  — 
  Same. 
  The 
  prophyllum 
  ; 
  a, 
  side, 
  and 
  b, 
  back 
  view. 
  

   Fig. 
  5. 
  — 
  Same. 
  Transverse 
  section 
  of 
  the 
  prophyllum. 
  

   Fig. 
  6. 
  — 
  Cyperus 
  flavescens. 
  The 
  base 
  of 
  a 
  perennial 
  specimen, 
  showing 
  the 
  

  

  stolons. 
  F, 
  the 
  base 
  of 
  the 
  flowering 
  stem. 
  Natural 
  size. 
  

   Fig. 
  7. 
  — 
  Arabis 
  deniata. 
  The 
  base 
  of 
  the 
  plant, 
  showing 
  the 
  primary 
  root 
  (R) 
  

  

  and 
  some 
  secondary 
  ones 
  (r). 
  L, 
  L 
  1 
  and 
  L- 
  indicate 
  the 
  leafy 
  rosets 
  

  

  of 
  1st, 
  2d 
  and 
  3d 
  year. 
  F, 
  the 
  lower 
  part 
  of 
  flowering 
  stems. 
  

  

  Natural 
  size. 
  

  

  