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 Linnean 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 Roccelle, which are destitute of a cortical layer, the reaction 
is at once visible ; but in the Parmelie 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 Dirine 
(proving their affinity with Roccella), and in the Urceolaria of 
the group of U. scruposa and its allies. No reaction, however, 
can be detected in Roccella fuciformis (éxcept im the soredia), 
R. hypomecha, R. Gayana, R. intricata, and R. leucophea. 
The red reaction of hypochlorite of lime is observable in the 
medulla of. the following Parmelie—viz. tiliacea, revoluta, carpo- 
rhizans, olivetorum, osteoleuca, hypoleucites, polycarpa, Borreri ; 
whilst no reaction can be detected in P. saxatilis, perlata, perfo- 
rata, cervicornis, levigata, sinuosa, latissima, reducens, tenuirimis, 
mutabilis, physcwordes, livida, hypotropa, caperata, physodes, con- 
spersa, and olwvacea. 
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 
Physcie and Placodia, in the apothecia of the erythrocarpous 
Cladonie, in the apothecia of Lecanora ventosa, hématomma, 
erythromma, Lecidea Domingensis, flavocrocea, chrysosticta, leuco- 
zantha, 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- 
tiscum, Lecidea lucida, yeographica, Thelocarpon, &c. 
The hydrate of potash manifests also the presence of “ usneic” 
and ‘‘lecanoric acids”? by producing a yellow colour on the 
