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LICHEN NOTES No. 6. 
A List of the Parmelia Species of British North America, contained in 
the Herbarium of the Canadian Government at Ottawa, with 
Descriptions of those Species not Mentioned in Tucker= 
man’s Synopsis, and of Several New Forms. 
G. K. Merrill. 
It is thought best to make this list the vehicle for description of a num- 
ber of Parmelia forms not commonly recognized by American students. 
Differentiated by Nylander for the most part, these unfamiliar names may 
be said to owe their origin to a refinement of analysis on the part of those 
proposing them, for groups hitherto viewed as individual. 
Tuckerman viewed the genus Parmelia through the eyes of Fries, and 
giving no credence to the value of reagents in dissociating species and vari- 
eties, we find in his Synopsis what appears to be an unwarranted neglect of 
the labors of the European workers for the period just prior to its publi- 
cation. The so-called “chemical criteria ” have received almost universal 
adoption in Europe, and believing in their value ourselves, we have together 
with the names cited, recorded the reaction for each. This is done with 
the purpose of placing in the hands of our students, particularly those of the 
Northern United States, a working compendium. No other Lichen genus 
offers more instructive or useful material for the employment of reagents 
than Parmelia, and while contradictory results are sometimes met with, these 
are no more diverse than are the morphological contrasts for a given species. 
We unhesitatingly deplore the practice of [establishing species on purely 
chemical grounds, but affirm our belief in the reasonableness of making 
chemical discrepancies as important as variation in size of spores, presence or 
absence of isidia, soredia, cilia, etc., in the separation of varieties and 
forms. Knowledge of American Parmelia spebies in this country is as yet very 
rudimentary. This is in part due to the very low ebb marking the interest 
in Lichenoldgy, but principally to the influence of Tuckerman’s disposition of 
the species, and to the fact that the examples in our herbaria are for the most 
part identified in accordance with his views. But nineteen species of 
Parmelia were described in the Synopsis, while the names of more than a 
hundred are recorded in various foreign publications as having been col- 
lected in North America. The majority of these are entirely unknown to our 
collectors, although it is safe to say that our larger herbaria contain exam- 
ples in unsuspected profusion. The time seems at hand to attempt a widen- 
ing of our acquaintance with Parmelia, and to emancipate ourselves from the 
limits prescribed by Fries. 
Some explanation of the symbols, and method of employing the 
reagents, seems desirable. K is made to stand for a solution of potassic 
hydrate in water (one in two, by bulk). C a solution of chloride of lime 
(saturated). If on application of K or C to the surface of a plant a distinct 
yellow coloration is immediately noted an affirmative sign + is placed after 
the symbol; if no color is produced a negative — , thus K-|- or C — as the 
case may be. Where the symbol reads as in P. physodes Kt, it means that 
