2 METASPERMAE OF THE MINNESOTA VALLEY. 
list there will be found reference to many of the lower plants, 
but the number here determined can hardly represent more 
than a small fraction of all which certainly exist within the 
limits of Minnesota. 
During the three years of 1889, 1890 and 1891, the collection 
of data in this comparatively unexplored region has been 
diligently prosecuted by the Botanical Department of the 
University of Minnesota, and the information thus obtained 
has become the property of the survey. It is intended at some 
time in the future, barring unforeseen contingencies, to present 
as complete a list as possible of the fungi and algae of the 
state. While this reconnoisance has been in progress much 
labor has been expended upon the enlargement of our know!l- 
edge of those plant-groups which have already commanded, 
from their greater prominence, the attention of students of the 
Minnesota flora. Owing to the changes in nomenclature and 
the never-finished revision-work which modifies our conception 
of genera and species as well as of the larger divisions, and in 
the light of constantly advancing scientific knowledge, there is 
brought near to us the necessity of re-examining somewhat of 
the botanical work already done. By such examination it alone 
becomes possible to present the most modern aspect of such a 
study as is, under the law, directed towards the vegetable 
products of Minnesota. 
In the present volume a mass of revisional and considerable 
new material bearing upon the plants of Minnesota has been 
collected. Fora proper limitation of the work within bounds 
a natural group of- plants—the higher seed-plants, or metas- 
permz—has been selected, and these plants have been consid- 
ered with reference to a limited, but natural portion of the total 
area of the state. In this way new facts are conveniently 
grouped and the old facts are brought into a somewhat different 
angle of vision. 
The importance of studying a natural area. It is not com- 
monly the custom of those who compile local floras to select dis- 
tricts limited by nature rather than by man,as the area for inves- 
tigation. It is far more usual for some political district to be 
chosen, such as, for example, a group of states, a single state, 
a county, a town or a region within a circle drawn with arbitrary 
radius around some central city, lake or valley. Ina list of 
local floras published in North America (8), Dr. N. L. Britton 
enumerates 791 titles of works that have been published since 
(4), Britton: A list of State and Local Floras. Contr. Col. College Herb. (1890.) 
x 
