Some examples of possible Ascomycetous fungi have been recently recorded by Potonié from leaves and other portions of plants of Permian age. There is a distinct superficial resemblance between the specimens he figures and the fructifications of recent Ascomycetes, but in the absence of internal structure, it would be rash to do more than suggest the probable nature of the markings he describes. For one of the fungus-like impressions Potonié proposes the generic name _Rosellinites_; he compares certain irregularly shaped projections on a piece of Permian wood with the perithecia of _Rosellinia_, a member of the Sphaeriaceae, and describes them as _Rosellinites Beyschlagii_ Pot.[406] Various other records of similar Ascomycetes-like fossils may be found in palaeobotanical literature[407], but it is unnecessary to examine these in detail. Unless we are able to determine the nature of the supposed fungus by microscopical methods our identifications cannot in most cases be of any great value. An example of the perithecia of a fungus (_Rosellinia congregata_ [Beck])[408] has been recorded from the Oligocene of Saxony, which would appear to rest on a more satisfactory basis than is often the case. In this particular instance the small projections on a piece of fossil coniferous stem present a form which naturally suggests a fungus perithecium. In cases where the black spots on a fossil stem or leaf possess a definite form and structure, it is perfectly legitimate to refer them to a group of fungi; but in very many instances the forms referred to such genera as _Sphaerites_ and others are of little or no value. Many forms of scale-insects and galls on leaves present an obvious superficial resemblance to epiphyllous fungi, and might readily be mistaken for the fructifications of certain Ascomycetous species. As examples of scale-insects simulating fungi, reference may be made to such genera of the Coccineae as _Aspidiotus_, _Diaspis_, _Lecanium_, _Coccus_, and others. The female insects lying on the surface of a leaf, if preserved as a fossil impression, might easily be mistaken for perithecia[409]. Another pitfall in fossil mycology may be illustrated by a description of a supposed fungus, _Sclerotites Salisburiae_[410], Mass. on a Tertiary _Ginkgo_ leaf. The figure given by Massalongo represents a _Ginkgo_ leaf with well marked veins, the lamina between the veins being traversed by short discontinuous and longitudinally-running lines; the latter are referred to as the fungus. In a recent _Ginkgo_ leaf one may easily detect with the naked eye a number of short lines between and parallel to the veins, which if examined in section are found to be secretory canals. There can be little doubt that _Sclerotites Salisburiae_ owes its existence to the preservation of these canals.