22 



branches without ribs and with leaf scars very different in 

 form from those of the trunk. 



The question now arises whether these different trunks 

 can belong to one genus, or even to one family ; whether, 

 in short, we may not have been confounding very different 

 types, of trees under the name of Sigillarice f The first of 

 the above types, that of Diploxylon, corresponds with the 

 structure of undoubted Sigillarice, as illustrated by William- 

 son and other British palseobotanists, and conforms so 

 closely to that of Lepidodendron that we can scarcely doubt 

 the close affinity of this particular type with the Lycopo- 

 diaceous Acrogens. 



On the other hand, so many of the erect ribbed trees at 

 the South Joggins have afforded tissues of a much higher 

 type that we cannot doubt the existence there of trees simi- 

 lar in external characters to the ordinary Sigillarice., yet 

 with internal structures conforming rather to the type of 

 Cordaitece. In these circumstances, while we must admit 

 the Gymnospermous affinities of the latter family, we must 

 wait for further information before being able to define its 

 precise relations to the Sigillarise on the one hand, and the 

 Conifers on the other. 



I have referred above to Sternbergia piths. These are 

 usually sandstone casts, but in some instances shreds of 

 the enveloping tissues remain. In a few instances the in- 

 ternal structure is preserved. Where the latter occurs it is 

 seen to be cellular, arranged in tubulse in the manner 

 which I have explained as occurring in the young pith of 

 the Balsam Fir and in the stem of Cecropia peltata. Such 

 piths I have described as occurring in large and well pre- 

 served stems of Dadoxylon of different species from the 

 Middle Devonian to the Permian. The large size of the 

 pith would seem to indicate that the young branches were 

 very thick, in which case they could not have resembled 

 those of Walchia or Araucarites, which other wise might be 

 supposed to represent the foliage of these trees, unless, in- 

 deed, there were thick branches bearing slender branchlets, 

 or unless, as Williamson has affirmed to have been the case 



