Other cases of facultative parasitism have been studied by Hofmann[934], more especially three different species, _Lecanora dispersa_, _Lecanora_ sp. and _Parmelia hyperopta_, which were found growing on the thick foliose thallus of _Dermatocarpon miniatum_. These grew, at first independently, on a wall along with many examples of _Endocarpon_ on to which they spread as opportunity offered. The thallus of the latter was in all cases distorted, the area occupied by the invaders being finally killed. The attacking lichens had benefited materially by the more nutritive substratum: their apothecia were more abundant and their thallus more luxuriant. The gonidia especially had profited; they were larger, more brightly coloured, and they increased more freely. Hoffmann offers the explanation that the strain on the algae of providing organic food for the hyphal symbiont was relaxed for the time, hence their more vigorous appearance. _Arthonia subvarians_ is always parasitic on the apothecia of _Lecanora galactina_, and Almquist[935] discovered that the hymenium of the host alone is injured, the hypothecium and excipulum being left intact. The “parasitism” of _Pertusaria globulifera_ on _Parmelia perlata_ and _P. physodes_, as described by Bitter[936], may also be included under antagonistic symbiosis. The hyphae pierce the _Parmelia_ thallus, break it up and gradually absorb it. Chemical as well as mechanical influences are concerned in the work of destruction as both the fungus and the alga of the victim are dissolved. _Lecanora tartarea_ already dealt with as a marauding lichen[937] over decaying vegetation may spread also to living lichens. Fruticose soil species, such as _Cetraria aculeata_ and others, die from the base and the _Lecanora_ gains entrance to their tissues at the decaying end which is open. Arnold[938] speaks of these facultative parasites that have merely changed their substratum as pseudo-parasites, and he gives a list of instances of such change. In many cases it is rather the older thalli that are taken possession of, and, in nearly every case, the invader is some crustaceous species. The plants attacked are generally ground lichens or more particularly those that inhabit damp localities, such as _Peltigera_ or _Cladonia_ or certain bark lichens. Drifting soredia or particles of a lichen would easily take hold of the host thallus and develop in suitable conditions. To give a few of the instances observed, there have been found, by Arnold, Crombie and others: on _Peltigera canina_: _Callopisma cerina_, _Rinodina turfacea_ var., _Bilimbia obscurata_ and _Lecanora aurella_; on _Peltigera aphthosa_: _Lecidea decolorans_; on _Cladoniae_: _Bilimbia microcarpa_, _Bacidia Beckhausii_ and _Urceolaria scruposa_, etc.