We have thus rapidly, briefly, and casually indicated the habitats to which the majority of the larger groups of fungi are attached, regarding them from a systematic point of view. There is, however, another aspect from which we might approach the subject, taking the host or matrix, or in fact the habitat, as the basis, and endeavouring to ascertain what species of fungi are to be found in such positions. This has partly been done by M. Westendorp;[E] but every year adds considerably to the number of species, and what might have been moderately accurate twelve years since can scarcely be so now. To carry this out fully a special work would be necessary, so that we shall be content to indicate or suggest, by means of a few illustrations, the forms of fungi, often widely distinct in structure and character, to be found in the same locality. The stems of herbaceous plants are favourite habitats for minute fungi. The old stems of the common nettle, for example, perform the office of host to about thirty species.[F] Of these about nine are _Pezizæ_, and there are as many sphæriaceous fungi, whilst three species of _Dendryphium_, besides other moulds, select this plant. Some of these have not hitherto been detected growing on any other stems, such as _Sphæria urticæ_ and _Lophiostoma sex-nucleatum_, to which we might add _Peziza fusarioides_ and _Dendryphium griseum_. These do not, however, include the whole of the fungi found on the nettle, since others are parasitic upon its living green parts. Of these may be named _Æcidium urticæ_ and _Peronospora urticæ_, as well as two species described by Desmazières as _Fusisporium urticæ_ and _Septoria urticæ_. Hence it will be seen how large a number of fungi may attach themselves to one herbaceous plant, sometimes whilst living, but most extensively when dead. This is by no means a solitary instance, but a type of what takes place in many others. If, on the other hand, we select such a tree as the common lime, we shall find that the leaves, twigs, branches, and wood bear, according to M. Westendorp,[G] no less than seventy-four species of fungi, and of these eleven occur on the leaves. The spruce fir, according to the same authority, nourishes one hundred and fourteen species, and the oak not less than two hundred.