16 INTRODUCTION. 



scientific Agriculture, &c. Tlie relations of plants to the earth, 

 considered in reference to their natural distribution over its surface 

 and the laws that regulate that distribution, especially as connected 

 with climate, give rise to Geographical Botany, a subject which 

 connects Botany with Physical Geography. Under the same gen- 

 eral department naturally falls the consideration of the changes 

 which the vegetable kingdom has undergone in times anterior to 

 the present state of things, as studied in the fossil remains of plants, 

 (a contribution which Botany offers to Geology,) as well as of those 

 changes which man has effected in the natural distribution of 

 plants, and the alterations in their properties or products which 

 have been developed by culture. 



8. Of these three great departments of the science, that of 

 Physiological Botany, forming as it does the basis of all the rest, 

 first demands the student's attention. 



