FORM AND STRUCTURE 



older, in others they persist. The best opinion now is that 

 they are openings for the purpose of admitting air to the 

 living internal tissues. 



SPECIES AND GENUS. 



Under the term Species are included all individuals which 

 possess in common such a number of constant characters that 

 they may be considered to be descended from a common an- 

 cestral form. In the course of multiplication new peculiari- 

 ties may arise and individuals characterized by these peculi- 

 arities are regarded in classification as Varieties. 



When several species resemble each other so distinctly 

 that their general characters indicate relationship they are 

 grouped together in a Genus. Genera are not fixed, they 

 vary with the views of botanists. 



The Scientific Name of a plant consists of two words, the 

 first indicating the genus, the second the species. If a third 

 is added it indicates the variety. 



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