588 METASPERMAE OF THE MINNESUTA VALLEY. 
come in their final analyses, like other problems of biology, 
studies in evolution. The understanding of relationships is 
prior to the understanding of juxtapositions, separations or 
isolations of species, individuals, families or formations. The 
knowledge of embryology, phylogeny, comparative anatomy, 
classification, help to a knowledge of relationship. By the study 
of buried plants, fossil in the rocks of former ages, by the inti- 
mate observation of developmental stages in the plants of to- 
day, by the systematic examination and enlightened arrange- 
ment of all forms of plants and animals living within the range 
of human observation, and by the critical comparison of 
results in each of these three departments of scientitic botany, 
lies the method of reconstructing the past history of vegeta- 
tion. Such a reconstruction must perforce be general in its 
character, tentative in its statement of details. Nevertheless 
there are some conclusions that present themselves and these 
will be discussed in their proper place. 
NATURAL VEGETATION REGIONS OF THE EARTH. 
Grisebach: Under the notions of separate centers of devel- 
opment the most important classification of the land areas of 
the globe into vegetation-regions is that of Grisebach. By 
this writer twenty four regions are recognised, as follows: 
I. Arctic region. XIII. Prairie region. 
II. Forest region of the Eastern XIV. Californian Coast region. 
Continent. XV. Mexican region. 
III. Mediterranean region. XVI. West Indies region. 
IV. Region of the Asiatic XVII. Cisequatorial South Am- 
Steppes. erican region. 
V. Chinese-Japanese region. XVIII. Hylaea, or Amazonian re- 
VI. Indian-Malayan region. gion. 
VII. Sahara region. XIX. Brazilian region. 
VIII. Soudan, or Central African XX. Tropical Andes region. 
region. XXI. Pampas region. 
IX. Kalahari region. XXII. Chilean transition region. 
X. Cape of Good Hope region. XXIII. Antarctic forest region. 
XI. Australian region. XXIV. Oceanic Island region. 
XII. Forest region of the West- 
ern Continent. 
Engler: Under the notions of general development and mi- 
gration the most important classification is thatof Engler. By 
this writer the surface of the globe is divided into four princi- 
pal realms (florenreichen), each of these into regions and each 
region into provinces. The realms and regions are as follows: 
A. Northern Extra-Tropical Realm. 
(1) Arctic region. 
(2) Sub-Arctic, or Conifer region. 
