2S0 Sinnott and Bartlett — Coniferous Woods. 



search, on the outside of lignitied logs which were charred by 

 fire before burial as well as in small fragments. 



It is worthy of note that Dicotyledones are not represented 

 at either locality. The beds are within a mile of the contact 

 between the ancient crystalline rocks of the Piedmont region 

 and the Cretaceous deposits, and represent the base of the 

 Potomac formation as it is developed on the Maryland side of 

 the Potomac River. !N"o fossils were found which at all sug- 

 gested the supposed primitive Dicotyledones which have been 

 found in deposits of similar age near Fredericksburg, Virginia. 



In the great majority of cases the lignitic material is very 

 poorly preserved, having suffered much compression and dis- 

 tortion, but a few pieces were found which proved to be in 

 excellent condition. In the large and unique collection of 

 charcoal fragments, on the other hand, there are many beauti- 

 fully preserved specimens, although the brittle tracheid walls 

 are often considerably cracked and broken. Remains of 

 fungus mycelia are of rather frequent occurrence. By careful 

 embedding in celioidin thin sections of both lignite and char- 

 coal were obtained. A study of the large amount of material 

 at hand showed it to be composed of the two types, both of 

 them coniferous, which are named and described below. 



Podocarpoxylon McGeei (Knowlton) n. comb. 



[Podocarpoxylon Goth an, Abb. konigl. preuss. geolog. 



Landesanstalt. Neue Folge, Heft 44, p. 



103, 1905.] 

 Cupressinoxylon McGeei Knowlton, Bull. U. S. Geol. Surv. No. 



56, p. 46, 1889. 



Annual rings poorly marked. Wood parenchyma present 

 but not abundant. Tracheids usually very broad, their radial 

 walls provided with large bordered pits in one or more rarely 

 two rows, pits in the latter case opposite. So-called "bars of 

 Sanio " well developed. Pits from tracheid to ray generally 

 one or twa to the crossing field, large. Pore from rather small 

 and obliquely vertical (" podocarpoid ") to very large (" eipo- 

 rig "). Rays thin-walled, pitless, frequently biseriate, and in 

 many cases exceedingly tall, often attaining a height of sixty or 

 more cells. 



Localities : Central High School and Meridian Hill Park, 

 Washington, D. C. 



Horizon : Patuxent. (Lower Cretaceous.) 



Structure. 



The tracheids of Podocarpoxylon McGeei are unusually 

 broad, averaging 35-i0 to the millimeter in the transverse sec- 

 tion. The annual rings vary greatly in width and are usually 



