436 GYMNOSPERMS 



The crowded pitting and the absence of bars of Sanio are claimed 

 to indicate a close relationship between the Araucariaceae and 

 Cordaitales, but, in araucarian seedlings, the pitting is not crowded, 

 and in xylem, near the pith of the ovulate cone, the pits are neither 

 crowded nor alternating. On the contrary, there is a strong tendency 

 to opposite arrangement, and there are definite bars of Sanio, which 

 are lacking in adult wood of living araucarians. 



The Abietaccae and Ginkgoales have opposite pitting and bars of 

 Sanio, both of which features are absent from the Cordaitales. 

 These features were developed later in Pinus, because they are ab- 

 sent from conservative regions, like the inner wood of the cone axis 

 and the inner wood of the root, although they appear farther back 

 from the primary xylem. In these conservative regions ray tracheids 

 are also lacking, although they appear elsewhere. Pinus also lacks 

 a torus in the membrane of the bordered pits near the primary wood, 

 agreeing, in this respect, with Cordaitales. In the Araucariaceae the 

 opposite is true, for the torus is present in the membrane of pits near 

 the primary xylem, and absent elsewhere. If only the structure of 

 the cone axis is considered, Pinus, representing the Abietaceae, has 

 come from an ancestor with wood structure like that of the Cordai- 

 tales. 



In general, Jeffrey believes that the structure of the wood in- 

 dicates relationship between the Abietaceae and Cordaitales, rather 

 than between Araucariaceae and Cordaitales. 



The ovulate scale and bract are separate in the Abietaceae. This 

 seems to be a primitive character. Whether they are fused or not in 

 the rest of the Pinares may be questionable. There may be no more 

 fusion than in a gamopetalous corolla. The "fused" condition may 

 be due to zonal growth, which gives rise to perigyny and epigyny. 

 However, in these cases, the condition is regarded as more advanced 

 than in hypogyny. Similarly, the "fused" bract and ovuliferous 

 scale may represent a more advanced condition than the separate 

 bract and scale. Then, in this respect, the Araucariaceae would be 

 more advanced than the Abietaceae. 



Evidence from the gametophytes has received little attention; 

 but, in our opinion, it is much more definite than the evidence from 

 the anatomy of woody structures. The development of prothallial 



