204 ANATOMY OF THE GYMNOSPERMS 



SYNOPSIS OF SPECIES 

 I. ARAUCARIA 



Existing species confined to the southern hemisphere and unknown in the 

 fossil state. 



A. Growth rings obscure or wanting 



Bordered pits in 1-3 rows, hexagonal. 



Resin-bearing tracheids (radial) wanting. 



1 . A. Cunninghamii 



Resin-bearing tracheids (radial) numerous, the resin in thick plates like 

 Sanio's bands. 



2. A. excelsa 



B. Growth rings obvious 



Bordered pits crowded in i row, more or less rounded, not strictly hexagonal. 

 Rays (radial) locally and strongly resinous, the lateral walls at such 

 points with sieve-plate structure. 



3. A. Bidwillii 



II. * * ARAUCARIOXYLON 



Extinct species occurring in Mesozoic and Tertiary strata, the remains 

 being usually silicified or calcified. 



A. Growth rings obscure or wanting 



Bordered pits in 1-3 rows. 



4. * * A. Woodworthi. 

 Bordered pits in 1-2 rows. 



5. * * A. virginianum. 

 Bordered pits chiefly in i row. 



Growth rings wholly wanting. 



6. * * A. Prosseri. 

 Growth rings present but obscure. 



7. * * A. arizonicum. 



B. Growth rings obvious 

 Bordered pits in 1-2 rows. 



8. * * A. Hoppertonas. 

 Bordered pits chiefly in i row. 



9. * * A. Edvardianum. 



Araucarioxylon obscurum of Knowlton {Mesozoic Floras of the United 

 States, p. 418) does not belong here at all, but is cited now for future 

 reference. 



