REPORT OF TEE CHIEF ASTRONOMER 807 



SESSIONAL PAPER No. 25a 



it was impossible to identify it with any previously recognized fossil type, or 



with any existing species, although it is of interest to find that it is a hard pine 



of the general type of P. glabra, to which it somewhat closely approximates, but 



from which it differs materially in the structure of the medullary ray. In the 



collections of 1905, from the same locality, precisely the same wood was once 



250 

 more brought under my notice, being recognized under the designation — - • 



J 



This more recent material, however, has been found to be in a much better state 



of preservation, conditions of decay not having progressed so far as in the previous 



case, and it therefore served to complete the diagnosis with respect to several 



important characters which were either wholly wanting in the previous material, 



or imperfectly presented. 



There is no record of the wood of Pinus having been found in the same 



horizon in North America, though Knowlton has described two species from the 



Laramie of the Yellowstone National Park, under the names of Pityoxylon 



aldersoni and P. amethystinum (35). Between these and the present specimens, 



however, there are no points of resemblance. The diagnosis for the present 



species is as follows: — 



Pinus Columbian a, n. sp. 



Plates III and IV. 



Transverse. — Growth rings variable though generally very broad in the large stems. 

 Spring wood usually predominant, the transition to the summer wood 

 gradual, but in the narrow rings more or less abrupt and sometimes 

 conspicuously so; the tracheids large, thick-walled and often con- 

 spicuously so, definitely rounded, often radially oval, chiefly uniform, 

 more or less equal, in regular radial rows. Summer wood con- 

 spicuous, dense and often thin. The structure as a whole is that of 

 a rather dense wood of medium hardness. Medullary rays prominent, 

 not very numerous, resinous and distant upwards of 9 or more rarely 

 15 rows of tracheids. Resin passages conspicuous, rather large and 

 scattering throughout the growth ring, the parenchyma cells large, 

 thin-walled and in two rows, or forming large, irregular tracts up- 

 wards of 6-9 tracheids wide ; resinous ; thyloses not obvious. 



Radial. — Medullary rays resinous; the tracheids rather numerous, marginal and 

 interspersed, not obviously predominant, very variable and often as 

 high as or higher than long, sparingly dentate*; the parenchyma cells 

 all of one kind and rather thin-walled, straight and equal to about 4 

 wood tracheids, the upper and lower walls, strongly pitted, the terminal 

 walls straight or diagonal and apparently not pitted, the lateral walls 

 with simple, round or lenticular pits of medium size, 2-4, chiefly 2 per 

 tracheid. Bordered pits on the tangential walls of the summer 

 tracheids small and not numerous, those on the radial walls rather 

 large, round, or oval in one compact row, and generally numerous. 



Tangential. — Fusiform rays rather numerous, short, the broad central tract with 

 thin-walled parenchyma chiefly broken out; the unequal terminals com- 

 posed of broad, oval cells chiefly in one row. Ordinary rays low to 

 medium, uniseriate, not materially contracted by the interspersed 

 tracheids; the parenchyma cells somewhat unequal and variable from 

 oblong (in the summer wood) to broad and oval or round (in the 

 spring wood). 



* Possibly due to conditions of decay. 



