JEFFREY. — ARAtrCARIOXYLON TYPE. 535 



of the cell walls might stand out more clearly. It is obvious from the 

 pitting of the tracheids seen on the left of the figure, that we have to 

 do \\ith araucarian wood, since the pits are alternating. The ray 

 cells very strongly pitted on all their walls, towards the right of the 

 figure, towards the left thin out and assume the ordinary Araucarian 

 type. Figure c, Plate 1, shows part of the foregoing very highly 

 magnified. The nature and abundance of the pits are now very 

 clearly seen. 



Not only does the cone of Agathis australis, clearly show the strongly 

 pitted rays, which are found in the Jurassic and Lower Cretaceous 

 woods, referred by the majority of recent investigators, to araucarian. 

 affinities, but we find that the Mesozoic type of ray may be recalled 

 by injuries to the root and the seedling stem. Figure /, Plate 1, 

 illustrates the modification of ray structure which frequently occurs 

 in the old roots of Agathis australis as the result of injury. The cells 

 in this case too are mucli thickened and strongly pitted. The normal 

 seedling rays of A. australis have not been observed to show pitting 

 or thickening on their terminal or horizontal walls in any case. The 

 mature stem rarely shows reversion in ray structure to the earlier 

 Mesozoic t^'pe as a result of injury. Agathis australis merely furnishes 

 a good illustration of a condition of affairs in normal and traumatic 

 anatomy, which so far as it goes, in accordance with accepted bio- 

 logical principles, Aouches for the descent of the existing representa- 

 tives of the Araucarian stock from ancestors in the Mesozoic, which 

 possessed rays like those of living as well as extinct representatives 

 of the Abietineae. Similar facts have been observed in other cases 

 not only in the genus Agathis but also in Araucaria. It appears un- 

 necessary to enlarge upon these at the present time. 



Attention may now be given advantageously to the question of 

 w^ood parenchyma in the Araucariineae. As is well known the Cor- 

 daitales, from which perhaps the majority of botanists at the present 

 time directly derive the Araucarian Conifers, were characterized by 

 the complete absence of wood parenchyma. The living species of 

 Agathis and Araucaria, manifest this condition likewise in the normal 

 mature wood of the stem and thus present prima facie evidence of 

 close affinity with Cordaitales and other ancient Gymnosperms. 

 Here again we may turn with advantage to the historical evidence 

 and then to comparative anatomical and experimental data in the 

 living representatives of the Araucarian stock. Figure a, Plate 2, 

 shows a longitudinal section of an Araucarian wood from the Ilaritan 

 Cretaceous of Kreischerville, Staten Island, X. Y. Certain dark 



