292 Sinnott and Bartlett — Coniferous Woods. 



tion. These were found to belong to two types, both conif- 

 erous. 



2. The first is characterized by wide tracheids with opposite 

 pitting, " bars of Sanio " and few and large pits uext the rays ; 

 wood parenchyma ; and thin-walled, frequently biseriate rays 

 which are often extremely high. It is regarded as a Podocar- 

 poxylon, identical with Cupressinoxylon McGeei Knowlton, 

 and is accordingly treated as Podocarpoxylon McGeei (Knowl- 

 ton) n. comb. It is believed to represent the wood of a species 

 of JSTageiopsis and to have close affinities with the Podocar- 

 pineae. 



3. The second type is characterized by narrow tracheids 

 with small, unflattened pitting, no " bars of Sanio," and few 

 pits next the ray cells ; wood parenchyma ; thin-walled, very 

 shallow rays ; and well-developed traumatic resin canals. It 

 is treated as Paracwpressinoxylon potomacense n. sp., and is 

 believed to represent the wood of a species of Arthrotaxopsis 

 and to belong to that group of small-leaved Mesozoic conifers 

 which are preponderantly araucarian in their affinities. 



This investigation was carried on in part at the JBussey Insti- 

 tution of Harvard University and in part at the Bureau of 

 Plant Industry, U. S. Department of Agriculture. 



Connecticut Agricultural College, Storrs, Conn. 

 University of Michigan. 



EXPLANATION OF FIGURES. 

 PoDOCARPOXYLOisr McG-eei (Knowlton) n. comb. Pp. 281, 283. 



Fig. 1. Transverse section, showing annual rings. 



Fig. 2. Transverse section, showing wood parenchyma cells filled with 

 resin, and distinctly biseriate medullary rays. 



Fig. 3. Tangential section, showing extremely tall medullary rays. 



Fig. 4. Tangential section, showing partially biseriate rays and espec- 

 ially the resin-filled condition of certain of the ray cells. 



Fig. 5. Radial section, showing clearly the so-called "bars of Sanio " 

 and the transition from opposite pitting to a single row of pits 

 in the same tracheid. 



Eadial section, showing tracheids with a double row of pits, 

 which are usually opposite but in a few cases alternate. 

 Radial section, showing "bars of Sanio" between mutually 

 flattened pits, the variation in size of pits in the same tracheid, 

 and also a longitudinal view of a l^esiniferous wood parenchyma 

 cell. 



Radial section, showing pitting of the tracheids. 

 Radial section, showing bordered pits between medullary rays 

 and tracheids, and the highly resiniferous nature of the alter- 

 nate rows of ray cells. 



Fig. 10. Radial section, showing variation in the pitting between tracheids 

 and l'ay cells. 



Paracttpressinoxylon potomacense n. sp. P. 289. 



Fig. 11. Transverse section, showing annual rings. 



Fig. 12. Transverse section, showing uniseriate medullary rays and 

 numerous resiniferous wood parenchyma cells. 



Fig. 



6, 



Fig. 



7. 



Fig. 



Fig. 



8. 

 9. 



