740 



LICHEN. 



Lichen, experiments, on a small scale, on some of the lichens 

 ""V" * which are found on the rocks in the neighbourhood 

 of Edinburgh. Merely by drying and pounding, 

 and then throwing the powder into a phial containing 

 a little liquid ammonia or lime-water, or sometimes a 

 mixture of both, and fitting the phial with a cork, some 

 beautiful colours were procured, not however till after 

 the lapse of several days. Slips of white paper were the 

 only substances stained : the paper ought to be unsized, 

 in which state it may be procured from the manufac- 

 turer ; for India paper, probably merely on account of its 

 being destitute of any glutinous ingredient, received the 

 delicate tints more freely and equally than that of 

 ^nglish manufacture. Treated in this way, Lecanora 

 ventosa, which is plentiful on some parts of the rocks of 

 Arthur Seat hills, gave a beautiful violet tint, superior 

 to what was procured, by the same process, from Leca- 

 nora parella. Ramalina scopulorifm, from sea-rocks at 

 Carolina Park, afforded little or no colour when young 

 plants were used, and a dull orange when old stems or 

 fronds were employed. Parmelia conspersa yielded a 

 very fine gamboge yellow ; and Parmelia parietina a yel- 

 low scarcely inferior in beauty, but approaching to 

 orange : This last species, as intimated in the trivial 

 name, abounds on old walls, and might easily be scraped 

 off and collected in considerable quantity: Both in it, and 

 in P. conspersa, (Lichen centrifugus, Lin.) the central 

 parts of the thallus often decay, and the plants then ap- 

 pear to grow in circles. Lepraria chlorina, which grows 

 along with P. parietina, and in general appearance re- 

 bembles it, having a fine lemon-yellow crust, afforded 

 no yellow colour at all, but rather a peach-blossom tint, 

 which was not permanent. Lecidea sanguinaria, from 

 rocks in the King's Park, instead of yielding a scarlet, 

 as was expected from the red colour of the tubercles 

 when cut, gave only a dull lead-grey. Neither the ex- 

 ternal nor internal colour of the lichen, therefore, afford- 

 ed any indication of the tint which might result from 

 the powder treated with the ammonia and lime-water. 

 By such simple means, however, it may in general be 

 ascertained whether any particular species of lichen is 

 likely to yield colour at all : and it may here be re- 

 marked, that if it yields colour readily and copiously, 

 these are the principal and most desirable qualities ; for 

 brown, purple, or orange, though at first they come dull 

 And dirty, may in general be greatly improved, in in- 

 tensity and brilliancy, by varying the processes, or en- 

 larging the quantities employed ; and it not unfre- 

 quently happens, that the colour which first shows it- 

 self is, after a few days, or in consequence of some slight 

 change of management, replaced by one more agree- 

 able to the eye, and which would prove more valuable 

 in die arts. It may be added, that where the same spe- 

 cies of lichen grows both on rocks and on trees, which 

 is not an uncommon occurrence, the specimens taken 

 i'rom the rocks will be found evidently more productive 

 of colour than those picked from the trees. The parti- 

 cular nature of the colouring matter in lichens does not 

 appear to have been yet subjected to accurate examina- 

 tion by chemists. 



Br. West- This part of the subject has been excellently illustrated 

 ting. by the labours of Dr. Westring of Nordkoping, physician 



to the king of Sweden, who has given ample details 

 of judiciously varied experiments made by him upon 

 most species of lichen indigenous to Sweden, and upon 

 a considerably extended scale, with the view of ascer- 

 taining their eifect in dyeing woollen-stuffs and silks. 

 It may be proper here to detail the general rules laid 

 down by this assiduous experimenter, (translated from 



the Stockholm Transactions into the Annales de C/timie Lichen, 

 for 179 C 2): these rules may easily be followed bv any ^T" 1 " 

 person inclined to pursue the investigation, -aud the 

 subject is by no means exhausted. 



The lichens should be gathered after some days of rain, 

 when they can most easily be detached from the rocks. 

 They are to be well washed ; then thoroughly dried, 

 and reduced to a powder, the finer the better. Pure river 

 water is to be used, the water of wells generally contain- 

 ing some earthy or saline ingredient, which is apt to alter 

 the line. Twenty-five parts of water are to be added to 

 one of powdered lichen. When quicklime is employed, 

 it should be quite fresh ; and one piirt of quicklime is 

 enough to ten parts of powdered lichen. To ten pounds 

 of the lichen, half a pound of sal ammoniac (muriate of 

 ammonia) is sufficient. Before plunging the thread or 

 stuffs to be coloured,' into the dye, they should 1> dip- 

 ped in pure cold water, in ord- thai the colouring mat- 

 ter may act more equally : and they should be immersed 

 in the same way when taken out. When lime and 

 sal ammoniac are used together, the vessel contain- 

 ing the mixture should be closely covered for the first 

 two or three days. Sometimes the addition of a little 

 common salt (muriate of soda,) or of saltpetre (nitrate of 

 potass,) will be found to give a greater lustre to the 

 colours. Dr. Westring did not, in general, employ 

 any mordant ; indeed, any acidity in the mordant 

 could not fail rather to destroy the gummy part of" the 

 lichens, which probably serves to fix their colours. 

 From several species, the Doctor procured colours na- 

 turally so permanent that they resisted both acids and 

 alkalies, and were not affected even by exposure for a 

 considerable time to the sun's rays. In some in- 

 stances, however, he employed different species of ly- 

 copodium as mordants, and with considerable success. 

 He praises, in particular, Lycopodium amiotinum, a 

 species which is found on some of the Scottish moun- 

 tains. Some lichens yielded a good colour when ma- 

 cerated in a cold liquid, and the same species in a hot 

 liquid gave a different and inferior hue.: but the fact 

 was in other instances reversed. 



Dr. Westring made trial of many of the Lick tinea 

 leprosi of Linnanis, especially species belonging to 

 the genera Lecanora and Urceolaria of Achai ins, but 

 including also some species of Porina, Lecidea, and 

 Isidium. The coralline-like species of the last-named 

 genus were found to be extremely rich in colouring 

 matter; and Lichen corallinus of Linnaeus (Isidium 

 corallinum, Ach.), and especially L. pseudo-coral- 

 linus of Swartz (now appropriately nan.ed by Acha- 

 rius, Isidium Westringii,) deserve the particular at- 

 tention of those who practise, and who wish to im- 

 prove, the art of dyeing. I. corallinum is found abun- 

 dantly on the Swedish mountains, amj Westring gives 

 it as his opinion, that it may probably become a lucra- 

 tive object of commerce. It is not uncommon on the 

 rocks in some parts of Scotland. Worsted thread, kept 

 for about three days in the simple infusion ot the li- 

 chen, acquired a pistachio-green colour. When a lit- 

 tle common salt was added to the infusion, it communi- 

 cated to the thread a citron-yellow. From the lichen di- 

 gested in spirit of wine for f'our-and-twenty hours, a wax 

 yellow was procured ; and when the digestion was con- 

 tinued for three days, a deep chestnut-brown resulted. 

 But, what is more interesting, when the lichen was di- 

 gested in simple water for the space of four days, a dark 

 and very beautiful chestnut-brown was procured, of so 

 fixed a nature, that it w.is not destroyed when the thread 

 was dipped in dilute aquafortis. A shred of silk steejv- 



