| Popis: |
1. Pinoxylon dakotense Knowlton is a coniferous wood from the Lakota sandstone of the Black Hills, South Dakota. 2. It has been related to Pinus, but differs (1) in the absence of horizontal resin ducts; (2) in the presence of wood parenchyma; and (3) in the partly araucarian character of the pits on the radial walls of the tracheids. 3. The rays are abietinean, and show marginal elements which resemble tracheids markedly. 4. Protopiceoxylon Gothan is generically identical with Pinoxylon Knowlton, and consequently is synonymous. 5. The rings of growth indicate considerable seasonal variation in climate. 6. This wood, showing as it does features which relate it to both the Abietineae and the Araucarineae, cannot definitely be assigned to either tribe with impunity, owing to our present incomplete knowledge of the early history of the Coniferae. |
