R. W. Chanei/— Flora of Payette Formation. 221 



today that the physical conditions under which it existed 

 may be postulated with a reasonable degree of accuracy. 

 The most dominant genus is Quercus, with 7 species. 

 It may be said, although further mention of the taxo- 

 nomic aspects of the flora is not within the province of 

 this paper, that several of these species can hardly be 

 considered distinct in view of the large number of inter- 

 grading specimens and the great variation among living 

 oaks of a single species. But the genus Quercus is 

 dominant even without regard to the number of species 

 in that its individual leaves outnumber all others together. 

 There is a close resemblance of all the fossil species of 

 oak to the type represented by the living species Quercus 

 cliry sole pis and Q. sadleriana. Both of these species 

 occupy the dry slopes of the upper foothills and summits 

 of the coast ranges and the west slopes of the Sierras 

 and Siskiyous of northern California and southwestern 

 Oregon. Their fossil relatives appear to have had the 

 coriaceous texture which is characteristic of leaves in 

 such a habitat, and to have made up a forest on the slopes 

 of an area of high relief and consequent exposure. And 

 while these oaks may have ranged down into the canyons, 

 as does Quercus chrysolepis today, the typical stream 

 border flora comprised Platanus dissecta, Acer n. sp. 

 Juglans oregoniana, and the various species of Salix 

 which are found in the Payette. Swampy stream or 

 lake borders are indicated by the fragments of Typha 

 (?), grasses, and Equisetum. The local dominance of 

 Populus eotremuloides, which is found with birches of the 

 occidentalis type only at the Cartright ranch locality, may 

 be due to the presence of certain moist slopes, or possibly 

 to a forest fire and the subsequent development of a burn 

 subsere. Sequoia angustijolia, which is abundantly 

 represented in the Mascall flora of the John Day Basin, 

 is of rare occurrence in the Payette, suggesting a lower 

 humidity. In accord with the idea of a dry slope habitat, 

 as suggested by the abundance of chrysolepis oaks and 

 the scarcity of Sequoia, is the occurrence of Pinus knowl- 

 toni and the scrub species of Odostemon, which is closely 

 related to the living Oregon grape, and of Castanopsis, 

 Philadelphus, and Rhus, all three of which have been 

 doubtfully recorded because of incomplete material. 

 In general, the Payette flora indicates a habitat with 



