104 Dr. D. Ellis — A Jurassic Fossil Fungus. 



whilst not characteristic of modern fungi this feature is characteristic 

 of other plants.) 



4. They are uniform in size. 



.5. They form terminal dilatations which are comparable to the 

 sporangia of modern fungi. This is particularly so with regard to 

 their size as compared with the tubes which bear them, to their 

 shape, and to their terminal position. In all respects they suggest 

 the development of terminal reproductive organs on hyphse (PI. VII, 



6. In two instances, one of which is shown in PI. VII, Pig. 2, 

 rounded structures have been noted inside the terminal dilatations 

 which in every essential particular suggest the spores which are 

 formed inside the sporangia of modern fungi. 



7. The structures in question are found in an organically formed 

 rock (PI. VII, Pig. 3). 



The circumstantial evidence upon which alone the whole case 

 naturally rests seems thus, from a biological standpoint, to be 

 complete enough to allow of little doubt as to the matter. The 

 points with which we shall now be dealing have had their inspiration 

 in the minds of those accustomed to regard such matters more from 

 the geological and mineralogical than from the biological standpoint. 



1. The structures in question may be of mineral and not of organic 

 origin. — Throughout the history of this subject mineral secretions 

 have been repeatedly mistaken for organic remains. So far as the 

 imitation of plant organs is concerned, the structures imitated are 

 leaves and cellular tissues. But from the nature of the case the 

 plant patterns executed by these secretions are of a simple form and 

 their variety of a very limited order. Whilst such secretions may 

 imitate a cellular or a tubular structure, it is difficult to see how the 

 whole atmosphere in which a phycomycetous fungus lives can be 

 simulated so very faithfully by a mineral secretion that not only are 

 hyphse and hyphal membranes reproduced but also sporangia (PI. VII, 

 Pig. 1) and even spores (PI. VII, Pig. 2). Further, the relative 

 dimensional proportions of the parts are so faithfully adhered to that 

 even when examined with the highest powers of the microscope, 

 a trained eye cannot detect any details of structure inconsistent with 

 the structural plan of phycomycetous fungi. Such wonderful fidelity 

 in detail would demand strong evidence of an opposing nature to 

 dismiss the claim that the structures in question are fossilized fungal 

 remains. The slides have been submitted to several competent 

 mineralogists for their opinion of the structures from the minera- 

 logical standpoint. In no single case was evidence forthcoming to 

 suggest that a mineral interpretation of these tubes and expansions 

 would fit the facts of the case. Among those to whom the slides were 

 submitted was Dr. Plett, of the Geological Survey, Edinburgh, whose 

 opinion on this point will command respect. Dr. Plett stated that he 

 was prepared to accept the organic origin of the structures indicated 

 to him and that he knew of nothing in the mineralogical world that 

 approximated to them. Prom the mineralogical standpoint no single 

 positive fact has been brought to light which invalidates the claim 

 for organic origin made from a study of the biological data. 



