Remarks on Mr. Carruthers Views of Prototaxites. 69 



to be an external structure. I have examples both in Mesozoic 

 conifers and in carboniferous plants. Long soaking in water and 

 decay have thus often made what may have been the lining of wood- 

 cells appear as an intercellular matter, or an external thickening of 

 the walls, (8.) In decayed woods the mycehum of fungi often 

 wanders through the tissues in a manner very perplexing ; and I 

 suspect, though I cannot be certain of this, that some fossil woods 

 have been disorganized in this way. At the time when my descrip- 

 tion was published, I felt uncertain to which of these causes to 

 attribute the peculiar appearance of Prototaxites. I have now, from 

 subsequent study of the cretaceous Taxineae of British Columbia,* 

 little hesitation in adopting the first and second explanations, or 

 one of them, as probable. 



Mr. Carruthers does not believe in the medullary rays of Proto- 

 taxites. The evidence of these is the occurrence of regular lenti- 

 cular spaces in the tangential section, which appear as radiating 

 lines in the transverse section. The tissues have perished ; but 

 some tissues must have occupied these spaces ; and in fossil woods 

 the medullary rays have often been removed by decay, as one some- 

 times sees to be the case with modern woods in a partially decayed 

 state. Mr. Carruthers should have been more cautious in this 

 matter, after his rash denial, on similar grounds, of medullary rays 

 in Sigillaria and Stigmaria, contrary to the testimony of Brongniart, 

 Goeppert, and the writer, and the recent exposure of his error 

 by Professor Williamson. That the wood-cells have been in part 

 crushed into the spaces left by the medullary rays is only a natural 

 consequence of decay. The fact that the medullary rays have de- 

 cayed, leaving the wood so well preserved, is a strong evidence for the 

 durabihty of the latter. The approval with which Mr. C. quotes from 

 Mr. Archer, of Dublin, the naive statement that " the appearance 

 of medullary rays was probably produced by accidental cracks or fis- 

 sures," would almost seem to imply that neither gentleman is aware 

 that radiating fissures in decaying exogenous woods are a conse- 

 quence of the existence of medullary rays. 



Perhaps the grossest of all Mr. Carruthers' histological errors is 

 his affirming that some of my specimens of Prototaxites show merely 

 cellular structures, or are, as he says, " made up of spherical cells." 

 Now, I affirm that in all my specimens the distinct fibrous structure 

 of Prototaxites occurs, but that in parts of the larger trunks, as is 

 usual with fossil woods, it has been replaced by concretionary struc- 

 ture, or by that pseudo-cellular stracture which proceeds from the 

 formation of granular crystals of silica in the midst of the tissues. 

 Incredible though it may appear, I know it to be a fact, as all the 



* Keport of Geol. Survey of Canada, now in course of publication, The col- 

 lections contain wood showing the structure of j^ew, cypress, oak, birch, and 

 poplar, all from rocks of cretaceous age. 



G 2 



