1859.] DAWSON DEYONIAK PLANTS. 485 



W. E. Logan, and was shortly described in the ^ Proceedings of the 

 American Association' for 1856. 



The specimen is nine inches in diameter, and presents throughout 

 a series of rings of growth, rather more than one-tenth of an inch in 

 average thickness. Under the microscope, the cross-section exhibits 

 cells perfectly circular in outline, not crowded, but becoming much 

 smaller at the margins of the rings of growth, where some large 

 irregular openings perhaps represent resin-ducts. The medullary 

 rays are marked by clear structureless spaces. In the longitudinal 

 section, parallel to the medullary rays, the wood-cells are seen to be 

 much elongated, and to terminate in conical points ; and their sides 

 are covered with the remains of a double series of spiral fibres, among 

 which are a few scattered roundish spots, which perhaps indicate a 

 single row of discs*. The cells of the medullary rays have been en- 

 tirely disorganized ; but the space which represents them in a tan- 

 gential slice, shows that they must have consisted of several rows of 

 cells. (Pigs. 4 a-c.) 



In my late visit to Gaspe, I was so fortunate as to find a second 

 tree of this species imbedded in the strata, though having its struc- 

 ture in a less perfect state of preservation than the specimen above 

 described. It was in a prostrate position, the trunk lying S.W. and 

 N.E., in a thinly bedded, crumbling, pyritous sandstone. The trunk 

 is silicified, one foot five inches in its greatest diameter, and eleven 

 inches in its least, the difference being due to compression ; a branch 

 five inches in diameter sprang from its side. On the external surface 

 was a thin layer of crumbling coal, probably representing the bark. 

 No pith was perceptible ; but there was a channel or depression along 

 the upper surface, as if a pith-cavity had existed and, when the 

 wood became softened by decay, had given way to pressure. The 

 age of this tree, as indicated by its rings of growth, would be about 

 one hundred and fifty years ; so that, though the tissue appears lax, 

 it was not of more rapid growth than in modern conifers. The 

 growth-rings also in the specimen previously described, as well as 

 in this, are well marked, indicating a decided difference of tempera- 

 ture in the seasons of the Devonian year. I cannot propose for this 

 monarch of the old Devonian forests of Gaspe a better or more ap- 

 propriate name than that of its discoverer, and shall therefore name 

 it Prototaocites Logcmi. 



"With respect to the afiinities of the genus, I can only say that the 

 markings on its wood-cells most nearly resemble those of the two 

 genera of fossil Taxine trees above-mentioned, which are, however, 

 found in much more modern geological formations. Among recent 

 trees known to me by specimens or figures of their tissues, Taxus 

 baccata and Torreya taxifolia most nearly resemble the Gaspe fossil. 

 In the meantime, therefore, it may be included in the subfamily 

 Taxinece. 



I could detect no leaves or fruit likely to belong to the species ; 



* This disc-like structure was first pointed out to me by Mr. Poe, of Montreal, 

 a very zealous and successful microscopist. 



