2 MANUAL OF BOTANY 



the organism from the point of view of its internal structure, 

 without reference to its form. We deal in this connection with 

 structural units of plants ; the vegetable cell as an individual, 

 and the combinations of cells to form the filaments, plates, or 

 masses of which the plant consists ; tracing the various modifi- 

 cations of cell structure, the alterations in their forms, and the 

 ways in which they are arranged together in the various parts of 

 the organism : this forms the department of Vegetable Anatomy 

 or Histology. Again, we may look upon the plant as a living 

 organism, and study the way in which it carries out the various 

 processes of its life, and the way in which it reacts to its environ- 

 ment. This section is known as Vegetable Physiology. Another 

 department is Taxonomy, which considers plapts in their rela- 

 tionship to each other, and includes a loiowledge of the principles 

 upon which they may be classified. This is generally known as 

 Systematic Botany. Geographical Botany, again, deals with the 

 distribution of plants over the surface of the earth at the present 

 time, and investigates the causes of such distribution. Palseo- 

 phytography, or Fossil Botany, considers the nature and distri- 

 bution of plants through the past ages of the earth's existence, 

 and describes the structure of those found in a fossil state in the 

 different strata of which the earth is composed. The first four 

 departments only are those that come within the scope of the 

 present work ; the latter two being of too special and extensive 

 a nature to be treated of in this Manual. There are also several 

 sections of what may be called Applied Botany, which are 

 founded on a knowledge of the above department, such as 

 Descriptive Botany, Vegetable Materia Medica, Agricultural, 

 Horticultural, and Economic Botany, but to these special works 

 are commonly devoted. 



