MAEcn24, 1899.] 



SCIENCE. 



433 



successive layers of tuffs and muds. It 

 maj' be well to state that all this probably 

 took place before the period of basalt erup- 

 tions. This flora has yielded seventy spe- 

 cies, and is regarded as markedly different 

 from that of the earlier breccia, and of later 

 age. As a grouping it shows the closest 

 affinity to the auriferous gravels of Califor- 

 nia, many of the species being identical, 

 while still others have the closest resem- 

 blance to species found only in the gravels. 

 It has been named the Lamar flora, and 

 referred, like the auriferous gravels, to the 

 upper Miocene period. Both the late acid 

 and the late basic breccias have recently 

 yielded, well-preserved leaf impressions, 

 proving the existence of a more or less 

 luxuriant flora in all the great periods of 

 breccia eruptions. Such fragmentary ma- 

 terial as has been found in these later rocks 

 agrees with plants preserved in the early 

 breccia at Fossil Forest, and, therefore, has 

 been correlated with the Lamar flora of 

 upper Miocene age. It was a vegetation 

 essentially characterized by deciduous foli- 

 age. Several species of magnolias, aralias 

 and other equally important groups which 

 are marked features of the auriferous 

 gravels flourished on these volcanic slopes. 

 Specimens of Aralia notata occur widely dis- 

 tributed, and the leaves of some of them 

 are supposed to have measured 3 feet in 

 length by 2 in breadth. Associated with 

 them are leaves provisionally referred to 

 the genus Artocarpus, indicating the pres- 

 ence of the bi-eadfruit tree. According to 

 Professor Knowlton, this flora is extra- 

 tropical and may be compared in many 

 ways to the vegetation as seen to- day in 

 southern Mississippi and the Gulf coast. 

 He says : " It is obvious that the present 

 flora of the Yellowstone National Park has 

 comparatively little relation to the Tertiary 

 flora and cannot be considered as a descend- 

 ant of it. It is also clear that the climatic 

 conditions must have greatly changed. The 



Tertiary flora appears to have originated, 

 or at least to have had its afiinities, at the 

 south, while the present flora is evidently 

 of northern origin. " 



On the slopes of Overlook Mountain, ia 

 the center of the range, nearly 11,000 feet 

 above the present sea level, occurs a pros- 

 trate log, preserved by silicification, meas- 

 uring 2 feet in diameter at its base. Not 

 far distant other logs are found, and in the 

 silts occur impressions of deciduous leaves. 

 From this locality four species of plants 

 have been determined as identical with 

 species found in the fossil forest, among 

 them an Aralia notata. 



In a personal communication Professor 

 Ward informs me that in his opinion the 

 flora of this region grew virtually at sea 

 level. While I recognize his eminent 

 authority in such matters, I am hardly pre- 

 pared to accept such a i-adical view, but I 

 cordially welcome this expression of opin- 

 ion because it in a measure corroborates my 

 own belief that the silts and ashes on which 

 the flora of Overlook Mountain flourished 

 were laid down at a much lower level than 

 that at which they are now found. 



Briefly summarizing the facts brought out 

 by a study of the fossil flora and their bear- 

 ing upon the geology, it is, I think, indis- 

 putable that the flora affords abundant evi- 

 dence "of a great range of Tertiary time 

 during the period of volcanic eruptions, even 

 if geologists do hesitate to accept the pre- 

 cise determinations of the age of the differ- 

 ent floras and their geological sequence. 

 This luxuriant terrestrial vegetation, de- 

 veloped through thousands 'of feet of lava 

 beds, tends to confirm the view that the 

 accumulation of this erupted material was 

 an exceedingly slow process. Again, the 

 character of the vegetation lends a forcible 

 argument to the belief that the entire region 

 must have been elevated since the develop- 

 ment of so varied an extra-tropical vegeta- 

 tion. For my part, I desire to pay tribute 



