VI PREFACE. 



I have begun with what is called Organography 

 (Book I.) ; or an explanation of the exact structure of 

 plants ; a branch of the subject which comprehends 

 all that relates either to the various forms of tissue of 

 which vegetables are constructed, or to the external 

 appearance their elementary organs assume in a state 

 of combination. It is exceedingly desirable that 

 these topics should be well understood, because they 

 form the basis of all other parts of the science. In 

 physiology, every function is executed through the 

 agency of the organs : systematic arrangements de- 

 pend upon characters arising out of their consider- 

 ation ; and descriptive Botany can have no logical 

 precision without the principles of Organography 

 are first exactly settled. A difference of opinion 

 exists among the most distinguished botanists, upon 

 some points connected with this subject, so that it 

 has been found expedient to enter occasionally into 

 much detail, for the purpose of satisfying the student 

 of the accuracy of the facts and reasonings upon 

 which he is expected to rely. 



To this succeeds Vegetable Physiology (Book 

 II.) ; or the history of the vital phenomena that have 

 been observed both in plants in general, and in par- 

 ticular species, and also in each of their organs taken 

 separately. It is that part of the science which has 

 the most direct bearing upon practical objects. Its 

 laws, however, are either unintelligible, or suscep- 

 tible of no exact appreciation, without a previous 

 acquaintance with the more important details of Or- 

 ganography. Much of the subject is at present 

 involved in doubt, and the accuracy of some of the 

 conclusions of physiologists is inferred rather than 

 demonstrated ; so that it has been found essential 

 that the grounds of the more popularly received 



