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PINITES RUFFORDI, FROM THE ENGLISH WEALDEN FORMATION. 423 
clear crystalline material, as in fig. 3; in others, again, the 
canal is more or less completely filled with dark coloured and 
somewhat rounded cells. If we compare figs. 4 and 5 with 
those given by Conwentz in his pl. 5. figs. 5 and 6, the two sets 
of canals are found to be practically identical in appearance. 
The filling cells are described by Conwentz as tiillen-like 
ingrowths of epithelial cells; that such an explanation is 
correct, at least in certain canals of Pinites Ruffordt, there is 
fairly clear evidence afforded by an examination of transverse 
and longitudinal sections. In some cases, however, the form 
and arrangement of the cells would seem to be characteristic of 
tissue in process of forming a schizolysigenous canal (e.g., 
fig. 4). These filling cells occupying the canals, cannot well be 
regarded as examples of true tiillen such as Dyer, Williamson, 
and others have described in the trachez of fossil plants; they 
are probably, in part, ingrowths of epithelial cells, and in part 
the ordinary cells of the xylem parenchyma in which the resin 
ducts occur. There frequently occur two resin ducts in close 
contact, as seen in transverse section, and occasionally such 
become fused together; in other words, two longitudinal canals 
anastomose.* 
The darker patches seen in fig. 1 are for the most part 
occupied by broken fragments of tracheids: the tracheids 
which form the limit of these patches usually show signs of 
tearing and disorganisation. Some of the large oval patches 
are bounded by rows of tracheids, which curve round the mass 
of more or less completely destroyed tissue in such a manner 
as to suggest a forcing apart of rows of xylem elements. In 
many of these areas the central portion consists of clear 
crystalline substance, and the periphery of numerous and 
irregular thin brown lines presenting the appearance of delicate 
parenchyma; it is probable that this structure is due to fine 
cracks in a crystalline matrix along which brown colouring 
matter has been introduced. 
The form and manner of occurrence of these disorganised 
patches suggest the presence of a parasitic fungus, such as 
Trametes radiciperda ; a comparison of fig. 1 with Hartig’s figure 
of a piece of spruce fir attacked by this fungus shows a fairly 
close resemblance.t 
* Cf. Kny, ‘ Botanische Wandtafeln,’ p. 210, fig. 5. 
t Marshall Ward, ‘Timber and Some of its Diseases,’ p. 151, fig. 13. 
