292 



PITYEAE 



[CH. 



with Pitys^. The above account is based in part on Zalessky's 



description and partly on specimens in Dr Kids ton's possession. 



Miss Elkins and W. Wieland 2 have recently described some 



Upper Devonian wood from Indiana characterised by a grouping 



B 



FIG. 489. Callixylon Trifilievi. A, C, the inner margin of the secondary 

 xylem showing strands of primary xylem, a, b, and C. B, tracheids of the 

 secondary xylem. (A, C, from photographs supplied by Prof. Zalessky; 

 B, Cambridge Botany School.) 



of the circular or elliptical bordered pits in the radial walls of the 



tracheids similar to those in Callixylon Trifilievi which they include 



1 Scott (12) p. 1024. 2 Elkins and Wieland (14). 



