INTRODUCTION 11 



Hence there was no question of any real relationship such as now is 

 universally accepted among biologists. These early efforts to estab- 

 lish a uniform system of classification, while necessarily more or less 

 artificial, still laid the foundation for the modern " natural " system. 

 The aim of the modern systems is to express as exactly as possible 

 the degree of relationship existing between different groups of organ- 

 isms. Thus the two great divisions the animal and vegetable 

 kingdoms are divided into branches or sub-kingdoms, these into 

 classes, classes into orders, etc., each expressing a closer degree of 

 kinship than the one above. Thus the White Elm of our Eastern States 

 was named by Linne Ulmus Americana to distinguish it from all other 

 Elms, which with it comprise the genus Ulmus, These are united 

 with the Hackberries and a small number of other trees into the 

 family Ulmacece. The following table will illustrate : 



Sub-kingdom Spermatophyta (Seed-bearing plants). 

 Class Angiospermae (Plants with closed ovary). 

 Sub-class Dicotyledones (Seed-plants with two seed-leaves). 

 Order Urticales ; Elms, Nettles, Figs, etc. 

 Family Ulniacese ; Elm family. 



Genus Ulmus I White E lm. 

 Species Americana ) 



Geographical Distribution. The study of the distribution of plants 

 upon the earth is a most interesting phase of botany, and may be 

 treated as a special department under the name of Plant Geography, 

 or Phyto-geography. As this is largely a question of adaptation to 

 environment, it is really a part of (Ecology. 



Geological Distribution. While the fossil remains of plants are 

 often imperfect, and the geological record has many extensive gaps 

 in it, nevertheless much light has been thrown upon the develop- 

 ment of plant-life upon the globe by a study of the fossils which 

 have been discovered ; and it may be confidently expected that much 

 more remains to be accomplished. These discoveries are of special 

 importance in connection with Morphology and Taxonomy, but we 

 may consider the fossil plants apart, as the subject of the special 

 branch of botany known as Palseophytology, or Fossil Botany. 



