=4. Red.= Several different kinds of red have been distinguished: “Urceolaria-red,” visible as an interrupted layer on the upper side of the medulla in the thallus of _Diploschistes ocellatus_, a continental species with a massive, crustaceous, whitish thallus that shows a faint rose tinge when wetted. “Phialopsis-red” is confined to the epithecium of the brightly coloured apothecia of _Phialopsis rubra_. “Lecanora-red,” by which Bachmann designates the purplish colour of the hymenium, is an unfailing character of Lecanora atra; the colouring substance is lodged in the middle lamella of the paraphysis cells; it occurs also in _Rhizocarpon geographicum_ and in _Rh. viridiatrum_; it becomes more deeply violet with potash. M. C. Knowles[890] noted the blue colouring of _Rh. geographicum_ growing in W. Ireland near the sea and she ascribed it to an alkaline reaction. Two more rare pigments, “Sagedia-red” and “Verrucaria-red,” are found in species of Verrucariaceae. These tinge the calcareous rocks in which the lichens are embedded a beautiful rose-pink. They are scarcely represented in our country. =5. Brown.= A frequent colouring substance, but also presenting several different kinds of pigment which may be arranged in two groups: =(1) Substances with some characteristic chemical reaction.= These are of somewhat rare occurrence: “Bacidia-brown” in the middle lamella of the paraphyses of _Bacidia fuscorubella_ stains a clear yellow with acids or a violet colour with potash; “Sphaeromphale-brown,” which occurs in the perithecia and in the cortex of _Staurothele clopismoides_, becomes deep olive-green with potash, changing to yellow-brown on the application of sulphuric acid; “Segestria-brown” in _Porina lectissima_ changes to a beautiful violet colour with sulphuric acid, while “Glomellifera-brown,” which is confined to the outer cortical cells of the upper surface of _Parmelia glomellifera_, becomes blue with nitric and sulphuric acids, but gives no reaction with potash. Rosendahl[891] confirmed Bachmann’s discovery of this colour and further located it in corresponding cells of _Parmelia prolixa_ and _P. locarensis_.