BOTANY 163 



and different systems of classification arose. The description 

 of form and structure necessary to classification developed 

 into the subdivision of external and internal anatomy. The 

 invention of the compound microscope made possible the de- 

 velopment of the science of tissues, histology, and of cytol- 

 ogy, the science of cells, the units of which tissues are made. 

 Inquiry into the interpretation of form and the actual struc- 

 tural value of the various organs gave rise to comparative 

 morphology, embryology, and the history of development; 

 and attempts to explain the cause of structure became organ- 

 ized into experimental morphology. If the point of view 

 taken is that of function, the vital processes of the healthy 

 plant, we have physiology ; and the study of the plant in rela- 

 tion to its immediate surroundings gave rise to the science 

 of the home-life of plants, or ecology. Again we must rec- 

 ognize the study of the distribution of plants in space, or 

 plant geography, and their distribution in time, or fossil 

 botany (palaeontology). 



The study of the diseases of plants, or plant pathology, 

 concerns itself with the behavior of the plant in sickness, and 

 the prevention and cure of plant diseases. This, of course, is 

 a matter of vital concern to the grower of crops, and de- 

 pends for its intelligent pursuit upon a knowledge of normal 

 physiology, of ecology, and of anatomy. Plant breeding is 

 that branch of botany which is concerned with attempts to 

 produce new and improved varieties, and species. These 

 branches constitute the science of pure botany. A study of 

 plants from an economic standpoint has given rise to various 

 sciences of applied botany, such as agriculture (in part), 

 horticulture, silviculture (the study of trees), forestry (trees 

 in the aggregate), and pharmacognoscy (the study of medici- 

 nal plants). The science of bacteriology concerns itself with 

 only one group of plants, though the statement that bacteria 

 are plants is a revelation to many, owing doubtless to the 

 close association of the study with medicine. The relation of 



