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PHARMACEUTICAL BOTANY 
8. Phytopalaeontology or Geological Botany treats of plants of 
former ages of the earth’s history traceable in their fossil remains. 
9. Etiology is the study of the causes of various phenomena ex¬ 
hibited by plants. 
10. Economic or Applied Botany deals with the science from a 
practical standpoint, showing the special adaptation of the vegetable 
kingdom to the needs of everyday life. It comprises a number of 
subdivisions, viz.: Agricultural Botany, Horticulture, Forestry, 
Plant Breeding, and Pharmaceutical Botany. Pharmaceutical 
Botany considers plants or their parts with reference to their use 
as drugs. It interlocks very closely with other departments of 
botanical science. 
PRINCIPLES OF CLASSIFICATION 
The classification of plants is an attempt to express the exact 
kinship which is believed to exist among them. By grouping to¬ 
gether those plants which are in some respects similar and combining 
these groups with others, it is possible to form something like an 
orderly system of classification. Such a system based upon natural 
resemblances is called a natural system. In a natural system of 
classification every individual plant belongs to a species, every species 
to a genus, every genus to a family , every family to an order, every 
order to a class, every class to a division . In many instances species 
may be subdivided into varieties or races. The crossing of two 
varieties or species, rarely of two genera, gives rise to a hybrid. 
Thus, the species Papaver somniferum which yields the opium of the 
Pharmacopoeia belongs to the genus Papaver, being placed in this 
genus with other species which have one or more essential character¬ 
istics in common. The genera Papaver, Sanguinaria and Cheli- 
donium, while differing from each other in certain essential respects, 
nevertheless agree in other particulars such as having latex, perfect 
flowers, capsular fruits, etc., and so are placed in the Papaveracece 
family. The Papaveracece family and the Fumariaceoe family are 
closely allied, the latter only differing from the former in having 
irregular petals, usually diadelphous stamens and non-oily albumen 
and so both of these families are placed in the order Papaverales. 
The orders Papaverales, Geraniales, Sapindales, Rhamnales, etc., are 
