SIGNS USED IN THIS WORK. 



(I) An annual plant. 



(?'' A biennial plant. 



H. A perennial plant. 

 ? A mark of doubt. 

 ! A mark of affirmation or authentication. 



These signs are, however, very rarely employed in this volume. 



1°, 2', 3". To save space, the sign of degrees (°) is used for feet; of min- 

 utes ('), for inches ; of seconds ("), for lines, — the (English) line being the 

 twelfth part of an inch. 



The dash - between two figures, as " 5 - 10," means from 5 to 10, &c. 



