_d._ VARIATION IN PYCNIDIA. On the thallus of _Catillaria denigrata_ (_Biatorina synothea_) Hedlund found that there were constantly present two types of pycnidia: the one with short slightly bent spores 4-8 µ × 1·5 µ, the other with much longer bent spores 10-20 µ × 1·5 µ; there were numerous transition forms between the two kinds of spores. Germination took place by the prolongation of the spore; the hypha produced became septate and branches were soon formed. Hedlund found that frequently germination had already begun in the spores expelled from the spermogonium. In newly formed thalline areolae it was possible to trace back the mycelium to innumerable germinating spores of both types, long and short. Lindsay had recorded more than one form of spermogonium on the same lichen thallus, the spermatia varying considerably in size; but he was most probably dealing with the mixed growth of more than one species. The observations of Möller and Hedlund on this point are more exact, but the limits of variation would very well include the two forms found by Möller in _Calicium trachelinum_; and in the different pycnidia of _Catillaria denigrata_ Hedlund not only observed transition stages between the two kinds of spores, but the longer pycnidiospores, as he himself allows, indicated the elongation prior to germination: there is no good evidence of more than one form in any species. F. PYCNIDIA WITH MACROSPORES Tulasne[731] records the presence on the lichen thallus of “pycnidia” as well as of “spermogonia”; the former producing stylospores, larger bodies than spermatia, occasionally septate and containing oil-drops or guttulae. These spores are pyriform or ovoid in shape and are always borne at the tips of simple sporophores. He compared the pycnidia with the fungus genera _Cytospora_, _Septoria_, etc. As a rule they occur on lichens with a poorly developed thallus, on some species of _Lecanora_, _Lecanactis_, _Calicium_, _Porina_, in the family Strigulaceae and in _Peltigera_. There is no morphological difference between pycnidia and spermogonia except that the spermatia of the latter are narrower; but the difference is so slight that, as Steiner has pointed out, these organs found on _Lecanora piniperda_, _L. Sambuci_ and _L. effusa_ have been described at one time as containing microconidia (spermatia), at another macroconidia (stylospores). He also regards as macrospores those of the pycnidia of _Calicium trachelinum_ which Möller was able to germinate so successfully, and all the more so as they were brownish in colour, true microspores or spermatia being colourless.