Organic and Inorganic Changes of Farkerl a. 51 



decide, merely adding that, as these crystals appear in one of 

 the only two instances of this transformation that I possess 

 it is not improbable that their presence, which is too strikino^ 

 to be overlooked, is not uncommon. 



Let us now return to the evidences of tlie organic chano-es 

 in the tubular structure or coenenchyma of Farkeria caused 

 by the presence of MiUarella, and having described the most 

 striking parts of the latter, viz. the brown mycelium and the 

 white filament, it is only necessary for me to add that in one 

 of the specimens in my collection (which unfortunately is only 

 a thick slice between the centre and the circumference of 

 the Parlceria) where this transformation is most evident, spots 

 of it may be seen like dark " rot " throughout this slice, inter- 

 mixed with the white coenenchyma in its natural state, which 

 presents every gradation, from the dull white continuous 

 structure to that which is broken up and finally lost amidst 

 the brown mycelium and glistening mineralized filaments of 

 the MiUarella. Indeed in some parts the filament appears to 

 have crept along the side of the " lamina " forming the wall 

 of the tubulation, while in others the " lamina " itself appears 

 to be yielding to its influence so as itself to become a '^ glis- 

 tening " white filament. At all events, the destructive 

 character of the MiUarella is evidenced by the gradual disap- 

 pearance of the coenenchymal structure and the presence of 

 that of MiUarella (fig. 10, a, h). 



However, I have got another specimen wherein the trans- 

 formation has extended a little further and the whole of the 

 central part of the Parlceria has passed into MiUarella, while 

 the external part has become hard and petrous, like that 

 observed in the " calcite " transformation of the coenenchyma. 

 This specimen, which was about 1| inch in diameter, has 

 been cut into halves, of which the petrous portion forms a 

 kind of shell about 3-12ths inch thick, while the rest consists 

 of a solid spherical mass of MiUarella 9-12ths inch in dia- 

 meter, but of wiiich unfortunately I have only a tangential 

 section (fig. 7) whose greatest thickness is i3-12ths inch ; 

 therefore it is only the outside third of the spherical mass that 

 I possess, which is amply sufficient for structural description, 

 although I would rather have had the whole or a section' 

 tlirough the centre, that I might also have seen the latter. 



Of the external or petrous portion I need only state that 

 in composition and colour it is precisely like that which 

 surrounds the " calcitic " or inorganic transformation above 

 described, while the spherical mass presents through the 

 tangential section all that is to be found in the " nucleus of 

 MillareUa'' first described — that is, the brown n)ycelium 



4* 



