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development of a red colour — or more strictly of colorific and 
colourless principles, capable of conversion into red colouring- 
matters. 
XIV. Chloride of lime is not uniformly to be relied on as a lichen- 
colorimeter for 
Table XII. shows, 
a. That the alcoholic solution of certain species may strike no 
blood-red colour with the re-agent, and still yield beautiful red 
and purple colours on ammoniacal maceration, and 
b. Table XIII. shows that, though the alcoholic solution of some 
species do strike this colour [blood-red], it does not follow that 
ammoniacal maceration produces the same or a similar colour, 
or any colour at all. 
XV. Simple maceration in a weak solution of ammonia, aided by a 
moderate heat and moisture, is the surest and simplest means of 
evolving the red colouring matters of the lichens. 
XVI. Alcohol is an excellent solvent of the colorific principles 
of the plants, presenting them in a form readily acted on 
by chemical substances. Its use on the small scale is exceed- 
ingly convenient. The reaction of ammonia on a boiled alco- 
holic solution, allowed to stand for three days, is generally 
the same in tint, though not in degree, as on an aqueous solu- 
tion exposed to the air for very long periods [one to twelve 
months]; but in some cases they differ essentially. 
This difference is probably, in part, attributable to the small 
quantity of materials operated on, and the short period of maceration 
in the former case, and to the large quantity of materials, and the 
abundant exposure to atmospheric oxygen in the latter. 
XVII. The non-evolution of colour in many cases may arise from 
a. Alcohol or water not being the best or proper solvent men- 
struum of the colorific principles in any particular instance. 
b. Ammoniacal maceration not being the proper means of convert- 
ing the colorific into coloured substances. 
c. The plant not containing colorific principles having the same 
chemical composition as orceire, &c., or showing similar reac- 
tions with chloride of lime and ammonia. 
XVIII. If we accept, meanwhile, Stenhouse’s and Helot’s tests as 
sufficiently accurate indicators of colorific value, we should 
arrange the lichen-genera, which contain species yielding co- 
louring matters, according to their value, as follows :— . 
Roccella, Lecanora, Umbilicaria, Gyrophora. Urceolaria, Parmelia, 
