BORDERED PITS 



73 



genera must have passed. And inasmuch as this genus ex- 

 hibits a more highly developed multiseriate arrangement than 

 any other within the general phylum, we must concede that it 

 is, with respect to this character, the most primitive of all. 



SERIAL VARIATIONS IN THE BORDERED PITS OF CORDAITES 



The genus Araucaria shows a much more restricted range of 

 variations, there being only four variants pretty uniformly dis- 

 tributed among fourteen species, both recent and fossil (ante, 

 p. 61). While the most highly developed members, four in num- 

 ber, are represented by one-seriate pits, the most primitive form 

 of four-seriate pits occurs in only one case, --A. Robertianum. 

 It is therefore manifest that this genus is obviously of a more 

 advanced type than Corclaites, from which it undoubtedly origi- 

 nated. Dammara being represented by only one species, it is 

 not possible to locate it more definitely than to say that the one- 

 to three-seriate disposition of its pits would place it in a posi- 

 tion equivalent to that occupied by Araucaria Cunninghamii, and 

 therefore about three fourths of the way down the scale for that 

 genus. This fact points with much force to the idea that of the 

 two genera Dammara is of relatively lower type. 



