CHAPTER VII 



GROWTH 



1. The study of the mode of growth of plants 

 is so closely dependent on that of their internal 

 structure (another branch of Botany called HISTO- 

 LOGY with which this book does not deal), that we 

 cannot go fully into it ; but there are a few main 

 facts that can be made out without much difficulty. 



If you watch from day to day the ends of the 

 branches of any tree or bush that is putting out 

 new leaves, you will see that they increase in length 

 by the growth of the internodes of the bud, new 

 pieces being literally added on in this way one after 

 the other. To prove that this is the only way in which 

 a branch increases in length and that the other parts 

 do not themselves become longer, we have only to 

 take any quickly growing branch or stem and mark 

 on it thin black lines with India ink at equal distances, 

 say one-eighth inch apart. In a day or two those on 

 the youngest internode will be much further apart, 

 showing that it has really lengthened as a whole. The 

 next internode may also show slight signs of growth, 

 but after two or three days the marks remain exactly the 



