Dr. D. Ellis — A Jurassic Fossil Fungus. 105 



2. The structures may have been caused by insect borings. — If the 

 causation of these threads and vesicles is not to be ascribed to a 

 mineral infiltration, and an organic origin is granted, there still 

 remains another possible origin, viz. that the tubes were due to 

 insect borings. This possibility has been suggested to account for 

 the tubes and vesicles. This criticism would have weight were it 

 not for the extreme smallness of the tubes. These measure only 

 -1^-5- mm. In previous cases where this criticism had weight, as for 

 example in the case of the Rhizomorpha Sigillariece of Lesquereux, 

 the tubes under consideration were 2-3 mm. in diameter, and the 

 claim was made that they were rhizomorphal cords of fungal hyphse. 

 J3eing commensurate in size with known insect borings, the criticism 

 that they might have been produced by insects was quite legitimate. 

 We are here, however, dealing not with cords of hyphae, but rather 

 with the individual strands such as are commonly found in the woody 

 tissues of many plants. The possibility of their preservation need not 

 be discussed, as their appearance in the tissues of fossil wood is toe- 

 common and too well known to admit of any doubt on the matter. 

 It is not conceivable that any insect either during Mesozoic times or 

 at any time could make borings which simulated the biological 

 characteristics of a fungus on such a minute scale. It is the more 

 incredible when we reflect that these supposititious borings would be 

 excavated in the body of some animal fragment, the natural habitat 

 of many phycomycetous fungi, and not in the harder tissues of 

 trees in which insect borings are usually found. 



3. Criticisms arising from the fact that ivhilst the parasite (or sapro- 

 phyte') has been preserved the details of structure of the host in ivhich it 

 lived have not been preserved. — In answer it may be stated that 

 the discovery of this organism was not entirely due to an accidental 

 circumstance, but was rather the successful issue of a specific 

 search. In the author's researches on modern iron-bacteria, the 

 membranes of which are impregnated with the highly resistant 

 ferric oxide, he was led to the conclusion that if iron-bacteria or 

 their representatives existed in former ages the chances of their 

 preservation in fossil form were very strong. When the opportunity 

 occurred ironstones and ferruginous limestones of various ages were 

 carefully searched for iron-absorbing micro-organisms. The tough- 

 ness and hardness of such membranes can be observed by anyone who 

 cares to examine the dead membranes of the modern ochre-bacillus 

 (Leptothrix ochracea). The search did not reveal fossil iron-bacteria 

 as was expected, but it did bring to light a fungus possessing the 

 same characteristic of absorbing iron-compounds from the sui'rounding 

 water. An organism thus protected would obviously stand a much 

 better chance of preservation than the soft tissues of the animal 

 fragments inside which a fungus of this character must necessarily 

 abide. The slides containing these structures consist of fragments 

 of organic matter embedded in a calcite matrix (PL VII, Fig. 3). 

 The threads and vesicles were invariably found inside the organic 

 fragments and not in the matrix. An example is shown at a in 

 PL VII, Fig. 3. This fragment is seen photographed on a higher scale 

 of magnification in PL VII, Fig. 4. In the latter case the threads 



