408 DIVISION III. — MODE OF LIFE OF THE FUNGI. 



membranes of the rind of Cetraria islandica, except those of the superficial coloured cells, 

 turn a beautiful blue with solution of iodine alone, as Schleiden 1 has observed, 

 owing to the presence of DragendorfPs Lichen-starch in the cells (see page 10). 

 The membranes of the medulla of Sphaerophoron coralloides show the same colour 

 with iodine ; Schwendener found that the rind of Cornicularia tristis and of some other 

 species not precisely determined became blue with iodine only here and there. 



The membranes of the rind, especially the superficial layers, in many Lichens are of 

 different hues owing to the presence of a colouring matter uniformly diffused through 

 the substance of the rind, as in Cetraria islandica, Bryopogon jubatus and many others ; 

 the dark colour of the under rind of Evernia furfuracca comes from the colouring of the 

 outer lamellae of the membranes ; the narrow lumina are seen in section surrounded 

 by thick colourless membranes, between which arc dark brown bands forming boundary 

 lines ; the matters imparting this uniform colouring have not yet been thoroughly 

 investigated, at least not microchemically. 



Asecond series of colourings is caused by granular imbeddings or incrustations. The 

 tissue of very many Lichens is seen to contain small round or elongated granules of some 

 organic substance lying partly on the free surface and on the medullary hyphae, partly 

 imbedded in the membranes which are united together without interstices. Granules of 

 this kind, which are either colourless or only of a faint yellow colour even in the mass, 

 occur for instance in the upper rind of Placodium cartilagineum and other species, in 

 Imbricaria caperata, Dill., I. incurva, P. and other species, on the medullary hyphae of 

 Peltigera, Solorina saccata and some species of Sticta (Schwendener), on the rind of 

 Roccella, especially R.fuciformis and of Thamnoliaand in the inner rind of Sphaerophoron 

 coralloides ; distinctly or intensely yellow granules are found outside the rind of Evernia 

 vulpina and Physcia parietina, or imbedded in the peripheral region of the rind of 

 Cetraria straminea (Schw.) and Usnea barbata and in the whole of the membranes of the 

 rind of Psoroma gypsaceum, or scattered in groups through the rind of Bryopogon diver- 

 gens (Ach.) and B. sarmentosus and especially of B. ochroleucus where they form an 

 uninterrupted layer near the surface, and in the medullary hyphae of Sticta aurata 

 and S. crocata and some other species ; red incrustations are found on the medullary 

 hyphae of Solorina crocea. The presence of these bodies in the substance of the thallus 

 and on it causes either a lively coloration, or, as in Thamnolia and Roccella, a dull yellow 

 aspect and opaqueness in the parts in which they are found. They are all readily 

 soluble in alkali either without change or with loss of colour, or at least deliquesce and 

 become turbid under the influence of these agents, as in Physcia parietina and Solorina 

 crocea, in the latter also without change of colour. It was not improbable therefore 

 that the granules consisted of lic/iinic acid, and Fr. Schwarz has recently proved that 

 this is the case in a number of species. 



Another series of infiltrations and imbeddings is composed of inorganic matter. 

 First and foremost is the rust-colour not unfrequently assumed by individuals ('formae 

 oxydatae') of many crustaceous Lichens which are typically of another colour ; it has 

 often been stated and has now been proved by Giimbcl, that this colour is due to the 

 infiltration of a salt of iron, perhaps of a vegetable acid. Still more remarkable 

 is the occurrence of calcium oxalate in many Lichens especially of the crustaceous 

 division, either in the form of octahedral crystals, or of irregular crystalline bodies, or of 

 small granules. In accordance with the rule which prevails in the rest of the Fungi it 

 is never found inside the cells, but cither on the surface of the rind, or on the medullary 

 hyphae or in the interstices between them, or imbedded in the shape of minute granules 

 in the membranes of the compact tissue of the rind. The latter is the case for instance 

 in Psoroma lentigerum, in which the entire rind is wholly opaque and white in reflected 

 light, owing to the close array of granules of the salt. Besides the above species, in 

 which the medullary hyphae are also incrusted with granules, they occur also in Ochro- 



1 i irundzuge, II. 



