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same colour with the thallus, and which grow on trees and 
woods. 
VII. The colours educible from lichens are liable to be materially 
affected, both as to quantity and quality according to a 
a. Age of the specimen operated on, 2. e., length of period that has 
elapsed since collection and desiccation. 
b. The geologic or other nature of its habitat. 
c. The nature of its basis of support, whether moist or dry, rock, 
stone, tree, or earth, &c. 
d. The amount of exposure to sunlight and atmospheric oxygen. 
e. Amount of moisture in the air. 
jf. Temperature of the locality. 
g. Elevation above the sea. 
h. Season and vicissitudes of the weather. 
2. Longitude and latitude in the two hemispheres. 
k. Decomposition of organic bodies in vicinity. 
VIII. Westring’s triple division of lichens according to the fixity 
or permanence of the colours they yield with or without mor- 
dants, &c., and his quadruple division according as these 
colours are extractable by cold, luke-warm, hot or boiling water, 
aided or not by various accessions, are inconsistent and unna- 
tural, and therefore not to be commended or followed. 
1X. Westring’s test of colorific power is inferior to Helot’s or Sten- 
house’s ; but all are fiequently fallacious, and are far from being 
applicable in all cases. Itis probable that different alkalies 
and re-agents are suitable in different cases for the elimination 
of colouring matters. 
X. The same circumstances, which modify the development of 
these colours on the small scale, cause material alteration in the 
results of manufacture. The result, however, is not always 
proportionate to the nature and amount of the modifying cause, 
insignificant circumstances frequently giving rise to most im- 
portant and opposite changes. 
XI. Speaking generally, the same process is equally applicable to 
the evolution of the red colouring matters of all lichens ; but it 
is equally true that a slight modification of the process may 
cause a great variety in the degree or tint in any given species. 
XII. The chief tint educible from lichens, which can be of any 
_ permanent utility in the arts, is red: brown is also useful in a 
minor degree. 
XIII. Chloride of lime and aqua ammoniz are only suitable for the 
