flora). However, these trees are not very successful competitors 

 with Coast Redwood, for reasons that will be discussed below. 



The fossil history of Coast Redwood suggests that it has 

 grown with its present major plant associates or their ancestors 

 for some time. Some years ago, Ralph Chaney, of the Department 

 of Paleontology at the University of CaUfornia, Berkeley, ex- 

 amined the fossil flora from deposits near Bridge Creek in the 

 John Day River basin of north-central Oregon. This fossil deposit 

 dates from Miocene times and represents an assemblage of fossil 

 plants that grew together in that part of Oregon between fifteen 

 and twenty million years ago. The present xerophytic vegetation 

 of the Bridge Creek area is a very different one from that present 

 in Miocene times. Chaney identified almost 21,000 individual 

 fossil remains from the Bridge Creek deposit. Fragments of 

 Coast Redwood or its Miocene counterpart were common in 

 these remains. Then Chaney scooped up and catalogued the plant 

 fragments that had been deposited in recent times in the bed of 

 a stream running through Muir Woods in Marin County, Cali- 

 fornia, an area occupied by a modern Coast Redwood forest. The 

 following chart compares the composition of the Miocene Red- 

 wood forest in Oregon and the modern Coast Redwood forest 

 in Marin County: 



FREQUENCY FREQUENCY 



MUIR WOODS (In Percent) BRIDGE CREEK (In Percent) 



Sequoia sempervirens 39 S. langsdorfii 15 



Alnus oregona 27 A. carpinoides 54 



Lithocarpus densiflora 5 Quercus consimilis 9 



Umbellularia californica 13 Umbellularia sp. 9 



84 87 



The chart requires some explanation. The column on the left 

 gives the name of the four tree species that are most commonly 

 encountered in the bed of the Muir Woods stream as leaf,, twig, 

 or cone fragments. The proportion of the plant remains that is 

 made up by each of them is also given. That is, 39 percent of the 

 fragments found in the Muir Woods stream are Coast Redwood 

 twigs, leaves, and cones. The column on the right gives the 

 figures for the representation of the four most common woody 

 species encountered in the Miocene Bridge Creek flora. The 



89 



