IN 



361 



Lecanora tartarea does not differ specifically from j^aUescens, 

 whilst, oil the contrary, parella, which hitherto has heen united 

 vi-ith ^aUescens, must now be se2)arated from it, since its thallus 

 does not exhibit any reaction with the hypochlorite of lime. The 

 reaction is also observed in Lecanora Reuteri and its neie:hbours, 

 Lecidea decolorans {dindi Jlexuosa) , Lecidea sarcogifnoides, Krbr., &c. 



^Notwithstanding, it is perhaps in the Parmelice that the ery- 

 thrinic reaction presents the most remarkable advantage as the 

 means of distinguishing between those species which differ very 

 little in external appearance. In reality the colourable material 

 lu the Parmelice is found underneath the gonldlal layer, and not 

 upon it or in its exterior as is the case in the Roccellce, Conse- 

 quently it is necessary to cut the thallus of a Parmelia so as to 

 expose the medulla, whenever we wish to ascertain whether tlie 

 species exhibits the erythrlnic action or not on the application of 

 the hypochlorite of lime. 



On examining Parmelia tiliacea^ earporliizans, remluta^ Borreriij 

 ohvetorum (Ach.), osteoleuca, hi/poleiicites, polj/carpa, we imme- 

 diately find that their medulla becomes of an erythrinic red colour, 

 (in some of these species, however, this colour has a rosy tinge.) 

 Most of them contain more colourable matter than the best 



Hoccellcs, 



In other Parm€Ji(Bj on the contrary, we do not observe any 



^uch reaction. Among such are P. saxatilis, perlata, perforata^ 



tenuirimis^ Tayl., reducens, cervicornis, hevigata^ sinuosa, mutahilis^ 



!P'^yscioides^ livida^ liypotropa^ capcruta^ the species belonging to 



the groups o? phgsodes^ oi conspersa^ oiolivacea^ etc. 



The reactive thus demonstrates in the most decided manner, 

 tor example, that P. olivetorum {R, perlata^ var. olivctorum^ Ach.) 

 t a species perfectly distinct irom perlata, with which it has been 

 hitherto united. Certain organic differences without doubt also 

 afford constant marks of distinction between the two species ; but 

 these marks are much less apparent and much more difficult to 

 verify than the chemical diffeixmee here noted ; so that we must 

 uo longer confound them, as has been hitherto done in all the 

 herbaria, since the most inexperienced person is now able to dis- 

 tinguish them by means of the reactive. In Moug. St. Yosg. 

 *8j the two species P. perlata and P. olketoruni arc given under 

 tbe name o^'' P, perlata -;' in Ilepp. Flecht. Eur. 580, under the 

 name of '' perforata ft. olivetorum,'' is given P,p>€rlata\ in Anzi, 

 Laugob. 48, is inx^n the P. olivetorum. In the same way we dis- 

 tingulsh by these means with the greatest facility tlie Parmdia 



2b2 



13 



