No. 454-] .LV.I TOAn- Of THE 



discussion at this tmK, IxN.md i; 

 important structural relations. It 



pit's upon both the radial and tan.L' 

 the i)rotoxylem .structure. Such 

 goes rapid moditication whereby it 

 walls ni th. scuuiduN uo,),l \ 



in Poro.xylon where the nniltiseri: 

 form are tyi)icallv i)resc-r\ed, thou-- 

 tendency to segregation to such 

 tmies become round. In this it 

 indication of a character which, w 

 occasionally expressed among the 

 erally characteristic of the related 

 rales. 



Among the Cordaitales theie 

 uhuh ue have heietoloK Ikui 

 that phvlum, and. so lar as ou 

 undoubtedh stands m the closest 

 howe\ei, impiobablc that the two \ 

 and It IS alt<Methei piobd)le that th 



we'must bring into this i)hvlum tw^ 

 higher degree ot development, but 

 ranked with the Abietmea: and wh 

 occupy the highest position m till- 

 able ui^on anatonucal -lounds \\h.> 

 that Agathis and Araucaria (in^ lu 

 Ion) are not .mlv interior to the ( 

 they are distinctly C ordaitean. 

 fact that Agathis is the mteiioi -e 

 Cordaites at the base and Aiaucair 

 the immediately ancestial toim ot 

 not only natural, but it is justihecl 

 The tendency to segregation ot 

 by Poroxylon suggests the relatio 



