1880.] Note on some Fossil Wood from the Mackenzie River. 147 



II. ; ' Note on the Microscopic Examination of some Fossil Wood 

 from the Mackenzie River." By C. SchroTER, Assistant at 

 the Botanical Laboratory of the Polytechnic Institution, 

 Zurich. Communicated by Robert H. Scott, F.R.S. Re 

 ceived October 22, 1880. 



In the summer of 1880, Professor Oswald Heer transmitted to 

 me seven specimens of fossilized wood from the Miocene beds of the 

 Mackenzie River for microscopical examination, and, if possible, de- 

 termination of the species, &c. Professor Heer's determination of the 

 leaves and other remains of the flora of the locality in question have 

 already appeared in the " Proc. Roy. Soc," vol. 30, p. 560, having 

 been communicated to the Society at the end of the last session. 



The following are the species which I have been able to de- 

 termine : — 



1. Sequoia Canadensis, Schroter n. sp. (Specimens 1 and 2).* — This 

 wood is very well preserved. (It belongs to the group Gupressoxylon 

 of Kraus.) Its anatomy shows a great resemblance to that of Sequoia 

 gigantea. The principal differences are the following : — 



(a.) In the cells of the medullary rays of S. Canadensis, the radial 

 pores are always arranged in one horizontal row, whilst S. gigantea has 

 two rows of pores in the extreme ranges of cells. 



(/3.) The number of superposed ranges of cells in the medullary 

 rays in S. Canadensis is 76. In S. gigantea it is only 55. 



The differences between S. Canadensis and S. sempervirens are 

 greater than those between the former and S. gigantea, so that S. Cana- 

 densis cannot belong to S. Langsdorffii, which occurs at the same 

 locality, and which is the Tertiary ancestor of S. sempervirens. It is, 

 therefore, probable that the wood which I have examined belongs to 

 one of the other Tertiary species of Sequoia (perhaps 8. Sternbergii, 

 which approaches very closely S. gigantea). Until this identity is 

 established I designate it provisionally as 8. Canadensis. 



2. Ginkgo spec. (Specimens 4 to 7.) Although not so well pre- 

 served as the preceding instances of wood, these specimens are easily 

 recognisable as belonging to the genus Ginkgo by their very charac- 

 teristic medullary rays. Perhaps they should be placed under the 

 species G. adiantoides, Ung., which is the commonest of Tertiary 

 Ginkgos, and has been found in Saghalien and in Greenland, between 

 which two localities the Mackenzie River lies. 



3. Platanus aceroides, Grp. (Specimen No. 2.) A dicotyledonous 



* All the specimens referred to in this paper are to be deposited in the British 

 Museum . 



