170 Dr. W. Nylander on new Chemical Tests for Lichens. 



strated and enhanced by the fact that the very smallest frustule 

 is sufficient to determine the lichen submitted to them, and that 

 whether in the sterile or fertile state, and even in the youngest 

 condition. They are the hypochlorite of lime and the hydrate 

 of potash ; and the details of their reaction will be found in the 

 'Flora' of May 12 and 13, 1866, and more at large in an ela- 

 borate paper in the Journal of the Linnsean Society of London. 

 The reactions take place in a powder or colorable material 

 which is generated in the gonidial stratum of the thallus. In 

 the Roccella, which are destitute of a cortical layer, the reaction 

 is at once visible ; but in the Parmelice and all other lichens which 

 possess a cortical layer it is necessary to scrape off that organ, 

 and to expose the subjacent medulla, in which the reaction takes 

 place ; and this is perfectly visible to the naked eye, and requires 

 no aid of the microscope. Dr. Nylander attributes the red re- 

 action of the hypochlorite of lime to the presence of " erythric 

 acid;" and its operation is beautifully exhibited in Combea mol- 

 lusca, Roccella Montagnei (soredia not coloured), R, Sinensis, R. 

 tinctoria, R. phycopsis (soredia not coloured), in the Dirince 

 (proving their affinity with Roccella), and in the Urceolarice of 

 the group of U. scruposa and its allies. No reaction, however, 

 can be detected in Roccella fuciformis (except in the soredia), 

 R. hypomecha, R. Gayana, R. intricata, and R. leucophaa. 



The red reaction of hypochlorite of lime is observable in the 

 medulla of the following Parmelice — viz. tiliacea, revoluta, carpo- 

 rhizans, olivetorum, osteoleuca, hypoleucites, polycarpa, Borreri; 

 whilst no reaction can be detected in P. saxatilis, perlata, perfo- 

 rata, cervicornis, laevigata, sinuosa, latissima, reducens, tenuirimis, 

 mutabilis, physcioides, livida, hypotropa, caperata, physodes, con- 

 spersa, and olivacea. 



The other reactive, hydrate of potash, is of practical importance 

 in Lichens whose natural colour is yellow, orange, or red ; and 

 the reaction occurs in the powder generated on the surface of the 

 thallus and the apothecia. The red or purple colour produced 

 on the application of the reagent is due to the presence of 

 *' chrysophanic acid," and it is visible in Physcia parietina and 

 lychnea, in the species of the group of Lecanora cerina, in young 

 Physcice and Placodia, in the apothecia of the erythrocarpous 

 Cladonice, in the apothecia of Lecanora ventosa, hcematomma, 

 erythromma, Lecidea Domingensis, Jlavocrocea, chrysosticta, leuco' 

 xantha, cinnabarina, russula, &c. On the contrary, no red re- 

 action is observable in Lecanora candellaria and vitellina, or in 

 chrysophthalma, epanora, Schleicheri, chlorophana, oreina, Derma- 

 iiscum, Lecidea lucida, geographica, Thelocarpon, &c. 



The hydrate of potash manifests also the presence of "usneic" 

 and " lecanoric acids" by producing a yellow colour on the 



