XXXII] 



ERISTOPHYTON 



197 



Eristophyton. Zalessky. 



Eristophyton fasciculare (Scott). The generic name Eristo- 

 phyton 1 was proposed by Zalessky 2 for two incomplete stems 

 of Lower Carboniferous age provisionally 3 referred by Scott to 

 Araucarioxylon and subsequently to Calamopitys*. The species 

 E. fasciculare was founded on material obtained by Dr Kidston 

 from the Lower Carboniferous of Dumbarton, Scotland, and on 

 a specimen in the Williamson collection from Northumberland. 

 There is a small pith of parenchyma, 2 3 mm. in diameter, with 

 eight strands of primary xylem of varying diameter (fig. 457) 



FIG. 457. Eristophyton fasciculare. Transverse section showing the relation of 

 primary (black) to secondary xylem. (After Scott.) 



and in each a single protoxylem-group. The primary xylem 

 elements are considerably larger than the secondary tracheids. 

 These xylem-bundles are leaf-traces and their disposition points 

 to a phyllotaxis of f . The traces attain their maximum size 

 when about to pass out through the secondary xylem. The 

 tracheids are reticulate and scalariform while some have an 

 intermediate type of pitting. A leaf-trace on reaching the pith 

 gradually moves further from the xylem-cylinder and may be 

 separated from it by 2 6 layers of parenchyma: as it passes 

 down the pith the protoxylem strand assumes an almost endarch 

 position consequent on the reduction of the centripetal xylem. 

 In Scott's words, 'each circummedullary strand branches at regular 



1 e/3i(rros, to be disputed. 

 3 Scott 



2 Zalessky (11). 

 4 Scott (02). 



