White gelatinous pustules found amongst the fruit-bodies of Stereum sanguinolentum ([p. 176]) have a hard white centre. On examination these ‘nuclei’ are aborted structures of the stereum covered in the jelly-fungus Tremella encephala Persoon. This fungus is apparently parasitic; it is closely related to Tremella foliacea and T. mesenterica described on [page 184].
G. APPENDIX
(i) Species list of specialised habitats
INTRODUCTION
Although some fungi prefer one type of woodland more than another many fungi are less specialised and may be found in all kinds of woods. Indeed many fungi which we usually associate with a woodland fungus flora can also be commonly seen in pastures and gardens, e.g. Laccaria laccata (Fries) Cooke, Hygrophoropsis aurantiaca (Fries) Maire.
It is useful to consider the fungi of different woodland types separately, but this in some cases is very difficult because some species are not exclusive; indeed some species may grow in completely contrasting habitats, e.g. Amanita muscaria (Fries) Hooker in both birch and conifer woods, or on contrasting substrates, e.g. Fomes fomentarius (Fries) Kickx on birch in Scotland and beech on the continent of Europe. The picture becomes even more complex because frequently woods, in fact, often include several tree species growing in close proximity and it is then difficult to draw connections between a fungus and the tree with which it is truly growing—we know little or nothing except for mycorrhizal fungi, why certain fungi prefer certain habitats.
A parallel example is that phenomenon seen in certain polypores which only attack twigs or branches and not stumps or trunks, whilst others grow exclusively on stumps. We know little of the reasons for these demarcations, even when they occur within the same host. Mycology, therefore, offers to the beginner and the professional many opportunities in physiology and ecology.
In grassland areas it is difficult to know where to draw the line between one plant-community and another when listing species, for although ecologically distinct both would come under the name grassland. In the field, however, this is often very obvious and there is little doubt that fungi can give just as accurate an indication as to the soil-type, as many mosses or vascular plants. In sand-dune systems, the mobile dunes offer a different ecological niche to that of the fixed dunes which in many ways resemble grasslands. Thus although the lists below are split into easily manageable units, some flexibility must still be allowed. It is meant only as a guide—and will differ in some cases from one place to another, even within the British Isles.