72 Comparative Anatomy and Affinities of the Araucarinece. 



Corclaitales. In medullary ray structure, too, all the forms are Cordaiteau — 

 the ray cells thin walled and with numerous pits on the tracheids where the 

 cells come into contact with them. In both groups the rays are resinous but 

 devoid of resin canals. In both there are ligneous parenchyma cells and 

 resinous tracheids in the secondary wood. The latter are considered the 

 ancestral form of the resin tissue from which the other types in the secondary 

 wood of the conifer series have been derived. With regard to leaf traces, too, 

 both groups agree — the trace may be single or double even while it is still in 

 the secondary wood. In the leaf there is centripetal primary wood directly 

 opposite the protoxylem. 



In no case was there found in the primitive regions of the Araucarian forms 

 any indication of Abietinean structure, which would be expected if the view 

 of the Abietinean ancestry of Araucarinese which is advocated by Jeffrey be 

 correct. In contrast to this, in the primitive regions of the Abietinese there 

 are evidences of Araucarian pitting, etc. In addition, evidence is advanced to 

 show that the transitional forms upon which the claim for the greater age of 

 the Abietineae is based, indicate rather the derivation of the Abietinese from 

 the Araucarinese or Cordaitales. Of special interest in this connection is the 

 evidence that the traumatic resin canals of Araucariopitys are of a primitive 

 type and in the process of acquirement. The determining points are the 

 resemblance of these to both the normal ones of the cone and to the traumatic 

 series of the vegetative parts of the living pine and their difference from those 

 of such a form as Abies, where it has been shown that resin canals are revived 

 by injury. The Abietinean theory of the ancestry of the Araucarinese 

 recognises only traumatic series of the " revival " type, and yet there is no 

 record of authentic Abietinean forms, as has been recently shown, either 

 in or previous to the Triassic, in which the first Araucarian supposed to be 

 derived from the Abietinese (Woodworthia) makes its appearance. Thus 

 geologically as well as structurally the superior antiquity of the Araucarinese 

 rests upon a very firm basis. This basis is made the more secure by the 

 practically unbroken sequence of forms with essentially Araucarian structure 

 right up to the Triassic. 



In every respect confirmation of the old view has been found, which regards 

 the Araucarinese as anatomically very closely associated with the Cordaitales. 



