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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. I to 4 may be seen repre- 

 sentatives of Eozoic and Paleozoic Time: Laurentian, 



