566 PROCEEDINGS OF THE AMERICAN ACADEMY. 



in the seedling of our only deciduous occidental conifer the larch, for 

 here in the seedling the leaves are persistent for two or three years and 

 only gradually become annually deciduous. There can be no doubt 

 that in the case of the larch we have to do with a tree, which 

 originally had evergreen leaves, as is the case with the other conifers, 

 and that its seedling perpetuates that condition. Vice versa in Agathis 

 we have to do with a coniferous genus, which originally had its leaves 

 moderately persistent as in conifers in general and that only later did 

 the extreme condition of persistence of the leaf trace found only 

 among living conifers in the mature stems and lateral branches of 

 the genera Agathis and Araucaria, become established. It is to be 

 emphasized then as a result of the examination of the seedling 

 anatomy of Agathis that not only the pitting of the older Mesozoic 

 type Brachyoxylon persists in the seedlings of the living genera but 

 also the evanescent character of the foliar trace. Seedlings of 

 Araucaria BidwiUii were examined with similar results, the only 

 difference being that the leaf traces here are somewhat more per- 

 sistent in the lower region of the cotyledonary stem than they are in 

 Agathis. It appears unnecessary to furnish further illustrations, 

 since the facts seem to be so conclusive and so much in accord with 

 the natural theoretical expectation. 



Having made it clear that both the anatomical conditions found 

 in the older Mesozoic woods of Araucarian affinities (Brachyoxyla) 

 and the developmental data supplied by the seedlings of the modern 

 forms, vouch for the fact that the persistent leaf trace characteristic 

 of the woody cylinder of the living genera of the Araucariineae and of 

 woods of a similar type from the Mesozoic, (true Araucarioxyla) is not 

 an ancestral feature of the stock, and consequently not phylogeneti- 

 cally important, we may appropriately pass on to the consideration 

 of the pith in the primitive Araucarian type, in connection with the 

 affinities of the Araucarian stock. 



Figure d, Plate 8, illustrates the structure of the pith in the stems, 

 the wood of which has been described by the author under the appella- 

 tion Araucarioxylon norchoracense.^^ At quite regular intervals the 

 pith is characterized by the presence of lighter bands, which represent 

 regularly recurring transverse diaphragms of sclerotic tissue. Figure 

 e, Plate 8, illustrates the same feature in the pith of an undescribed 

 and different species of Araucarioxylon from the Raritan Cretaceous 

 of Cliffwood, New Jersey. Sclerotic diaphragms appear at intervals 



49 Op. cil. 



