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the first appearance of plant life on the earth, as far as the 
remains of extinct plants have been preserved. The 
general arrangement adopted is therefore based upon the 
sequence of the geological time divisions: Eozoic, Paleozoic, 
Mesozoic and Neozoic, and their subdivisions into periods; 
Laurentian, Cambrian, Lower Silurian, Upper Silurian, 
Devonian, Carboniferous, Triassic, Jurassic, Cretaceous, 
Tertiary, Quaternary and Modern. This arrangement is 
therefore geological, but incidentally it is also biological, 
and follows the same system as that on which the synoptic 
collection of the museum of systematic botany is arranged, 
inasmuch as the plants of the earlier periods are low in the 
scale of life, consisting of thallophytes and pteridophytes 
and plants of uncertain botanical determination, while 
those which appear in the successively later periods are of 
successively higher and more complex types, represented 
by cycads, conifers and both monocotyledonous and dicoty- 
ledonous plants closely related to our living flora. 
Each specimen on display, with the exception of the 
very large ones, is placed upon a separate wooden block, 
and each one is labeled, giving the generic and specific 
name; the family, order or class of plants to which it is 
referred; the geologic period and subdivision in which it 
belongs, and the locality or region where it was collected. 
All essential information of a botanical and geological 
nature in relation to each specimen is, therefore, included 
in the label. Whenever a figure of any specimen can be 
obtained this is placed on the same block with the specimen, 
and pictures of ideal landscapes, showing the extinct vege- 
tation of certain geologic periods, as well as restoration of 
certain extinct plants, are displayed in their proper cases. 
The series of exhibits begins in the first cases to the left 
as one enters the east hall of the basement. The sequence 
of the specimens in the wall cases corresponds to that of 
the floor cases. 
In floor- and wall-cases Nos. 1 to 4 may be seen repre- 
sentatives of Eozoic and Paleozoic Time: Laurentian, 
