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University of California Publications in Geological Sciences 



From a floristic standpoint, table 3 shows that the flora contains members of 

 two Tertiary Geofloras. The Areto-Tertiary Geoflora, of holarctic origin, was 

 dominated by conifers and deciduous hardwoods that are represented now by 

 closely similar species in the temperate parts of holarctica. Most of the Verdi 

 plants are members of its West American Element, which includes those fossil 

 species that resesmble plants characterizing the conifer forests in the far West. 

 The Verdi species are chiefly members of its Sierra-Cascade Component, which are 

 similar to trees and shrubs in the forests of the Sierra Nevada and Cascades. Only 

 one species in the flora, Populus subwashoensis, does not have a close relative in 



TABLE 3 



Floristic Composition of the Verdi Flora 

 (Asterisk indicates species occurring in more than one floral element) 



ARCTO-TERTIARY GEOFLORA 



MADRO-TERTIART GEOFLORA 



West American Element 



California Woodland Element 



Sierra-Cascade Component 



*Ceanothus precuneatus 



Abies concoloroides 



Pinus pretuberculata 



Pinus florissanti 



Quercus prelobata 



Pinus prelambertiana 



Quercus renoana 



Populus alexanderi 



Quercus wislizenoides 



Populus pliotremuloides 



Salix truckeana 



Ribes galeana 

 Prunus moragensis 

 Salix boisiensis 



California Chaparral Element 

 *Ceanothus precuneatus 



East Asian Element 





Populus subwashoensis 





the far West. It is a relict of the East Asian and East American Elements, which 

 included deciduous hardwoods and conifers such as beech, elm, hickory, Chinese 

 redwood, water cypress, swamp cypress, katsura, hornbeam, and others that find 

 their nearest living relatives in the summer-wet, eastern parts of the northern 

 continents. Although they dominated the Arcto-Tertiary Geoflora in this region 

 well into the Miocene, commencing at the close of that epoch and continuing 

 through the Pliocene, they were supplanted gradually by species of the West 

 American Element as summer rains were reduced in frequency and in amount. 

 The Madro-Teriary Geoflora comprises the semiarid woodland and chaparral 

 vegetation that had appeared over the drier parts of southwestern North America 

 by the end of the Early Tertiary, and gradually spread over the western part of 

 the continent as dry climate expanded during the middle and later parts of the 

 period. It is represented in the Verdi flora chiefly by members of the California 

 Woodland Element, which resemble plants in the present oak woodland com- 

 munities of California. The species of buckbrush (Ceanothus) occurs not only as a 

 shrub scattered in the woodland, but also forms an important part of the chaparral 

 that borders oak woodland and forest vegetation in California. Plants representing 

 the Sierra Madrean Woodland Element, which are similar to living trees and 



