84 THE ROYAL SOCIETY OF CANADA 



Miss Holden, whose scientific career was unfortunately cut short 

 through the war, made frequent use of Miss Gerry's generaHzation 

 in her work in fossil botany (4), (5), (6) and (7), considering the pre- 

 sence of bars of Sanio "by far the most reliable criterion for disgnosing 

 coniferous woods." 



In 1912 Jeffrey (8) recorded the discovery of bars of Sanio in 

 the secondary wood of the cone axis of four species of Araucaria. He 

 notes in his description that each bar does not extend across the 

 tracheid but only across the width of a single pit. The forking where 

 the two rims separate at the ends is also emphasized as one of the 

 indications that the structures are true bars of Sanio. The presence 

 of such bars in a conservative region, like the cone axis, of a form 

 where, as recorded in Miss Gerry's work, it is normally absent, was 

 held by Jeffrey to indicate ancestry from forms which normally had 

 bars of Sanio in their tracheids, and contributed largely to his general 

 conclusions that "the Araucarineae cannot have been derived from 

 the Cordaitales" and "any hypothesis as to the origin of the Coni- 

 ferales in general must start with the Abietineae as the most primitive 

 tribe." In further support of this theory he states his failure to 

 find bars of Sanio in regions near the primary wood of Cycas, Zamia, 

 Ginkgo, or even Pinus. All of these forms, except the last, are by 

 general consent placed among the most primitive living gymnosperms, 

 where Jeffrey's theory also places Pinus, although the position of the 

 latter is disputed by other botanists. 



Thomson (12) also noted the presence of a bar of Sanio in Arau- 

 carian wood and considers that it is present in rudimentary form not 

 only in the transitional region of such parts as the cone axis, but in the 

 normal stem wood of all the Araucarineae. He noted that the type 

 of bar in conservative regions of the Abietineae resembles the Arau- 

 carian bar, while that in more specialized parts differs from it con- 

 siderably. The suggestion was made that this difference may be 

 connected with an increase in the size of the pitting. 



Groom and Rushton (3) made a careful chemical study of the 

 structures in Pinus Merkusii, concluding that they are at least partly 

 pectic, and not composed of cellulose as assumed by other writers. 

 After giving an account of their microchemical investigations they 

 say: 



Combining the above given facts with Sanio's account of the development of 

 pits in the primary pit-areas the following would, therefore, appear to be the truth. 

 When young the actual marginal portion of the primary pit-area does not thicken 

 by deposits of lignified wall so soon as it does elsewhere (except on the pit-closing 

 membrane) but thickens by successive deposits of pectic substance until a stage is 



