﻿168 
  

  

  INTRODUCTION 
  TO 
  BOTANY 
  

  

  (Salsola 
  Kali, 
  var. 
  tenuifolia), 
  a 
  most 
  troublesome 
  weed, 
  bears 
  

   from 
  20,000 
  to 
  200,000 
  seeds. 
  Taking 
  the 
  moderate 
  estimate 
  

   of 
  25,000 
  seeds 
  to 
  a 
  plant, 
  and 
  supposing 
  all 
  of 
  these 
  seeds 
  

   to 
  grow 
  into 
  plants 
  equally 
  productive, 
  the 
  offspring 
  of 
  the 
  

   25,000 
  individuals 
  would 
  number 
  625,000,000, 
  and 
  the 
  next 
  

   generation 
  would 
  number 
  15,625,000,000,000. 
  Supposing 
  

  

  FIG. 
  148. 
  Globular 
  clusters 
  of 
  fruits 
  of 
  the 
  

   sycamore 
  in 
  late 
  March 
  

  

  The 
  cluster 
  at 
  the 
  right 
  is 
  hroken, 
  and 
  single 
  

   fruits 
  are 
  being 
  carried 
  off 
  by 
  the 
  wind 
  

  

  FIG. 
  149. 
  Pods 
  of 
  evening 
  

   primrose 
  

  

  The 
  open 
  top 
  allows 
  the 
  seeds 
  to 
  

  

  escape 
  gradually. 
  Throe 
  fourths 
  

  

  natural 
  size 
  

  

  each 
  plant 
  to 
  have 
  a 
  diameter 
  of 
  about 
  3 
  feet 
  and 
  to 
  occupy 
  

   an 
  area 
  of 
  7 
  square 
  feet, 
  the 
  student 
  can 
  readily 
  calculate 
  how 
  

   many 
  square 
  miles 
  of 
  territory 
  the 
  number 
  of 
  plants 
  last 
  

   named 
  would 
  cover 
  if 
  actually 
  in 
  contact 
  with 
  one 
  another. 
  1 
  

  

  1 
  To 
  the 
  teacher 
  : 
  If 
  the 
  class 
  will 
  carefully 
  count 
  and 
  estimate 
  the 
  num- 
  

   ber 
  of 
  seeds 
  produced 
  by 
  some 
  common 
  weeds, 
  and 
  then 
  calculate 
  the 
  

   number 
  of 
  their 
  possible 
  descendants 
  in 
  the 
  course 
  of 
  five 
  or 
  ten 
  years^ 
  

   the 
  computation 
  will 
  prove 
  most 
  instructive. 
  

  

  