CHAPTER XII 



SPECIES AND GENUS 



COMMON experience shows us that all the leaves of a 

 plant are very much alike and arranged in the same 

 way on all the branches, though they may differ in 

 size, and though sometimes those which grow on the 

 younger branches are more or are less regular in 

 shape, than those on the older, and in a few plants 

 which grow in water, the submerged leaves are 

 different from those above water. With these excep- 

 tions all the leaves of a plant resemble each other 

 in shape, thickness and feel. Every one recognizes 

 too that there are different kinds of plants jus,t as 

 there are of animals and that all the members of 

 any one kind however much they may differ from one 

 another in size that depending so much on external 

 conditions, such as the state of the soil and the amount 

 of water and light available yet resemble each other 

 very closely in regard to their flowers, general habit and 

 leaves, and differ, especially, in their leaves from those 

 of all other kinds. 



We conclude, therefore, that the nature and ap- 

 pearance of its leaves are characteristic not only of the 



