Dyeing Properties of Lichens. — 249 
Ill. The influence of heat, moisture, exposure to atmospheric oxygen, 
&c., in assisting the development of the lichen colouring matters. 
a. Several other species were operated on ; various other combina- 
tions of the alkalies and alkaline earths, &c., and other reagents 
were used ; the experiments were conducted in the greatest possible 
variety, as regards the amount of heat and exposure to the air, the 
length of the maceration, the strength and degree of dilution of the 
reagents, &c.; but the results, though differing sometimes slightly, 
or in some insignificant features, were essentially the same. 
b. The period of maceration varied from a few hours to as many 
weeks or months ; the shortest was half an hour, the longest period 
a year. Beyond a certain point, prolonged maceration did not 
_appear materially to affect the nature or degree of tint; nay, in 
some cases, the colour was greatly deteriorated or destroyed. In 
‘some species, the colouring matters were rapidly produced; in 
others, again, very slowly ; in the former case, therefore, a short, 
while, in the latter, a long period of maceration was necessary. 
ce. The same remarks apply to the degree of heat applied; up toa 
certain point, it is an important auxiliary, but beyond this it be- 
comes very deleterious. . : 
d. During the course of the experiments, some of the solutions very 
rapidly became mouldy, while others stood for nine months or a 
year with little or no appearance of mould of any kind. It is 
‘foreign to my present subject here to specify the instances in which 
__ this phenomena did or did not occur ; the results possess interest 
merely as showing the effects of certain chemical reagents in pro- 
moting, retarding, or destroying the development and growth of 
fyngi. 
é. In some of the solutions, a flocculent, or granulo-flocculent pre- 
q cipitate was thrown down. Of the nature of this, in most cases, I 
| am unable to speak, the question being a purely chemical one; 
but, in some instances, it undoubtedly consists of the colorific 
principle of the plant. 
f. After the exhaustion of the red colouring matter of Lecanora tar- 
tarea and the Roccellas by ammonia, they yielded very rich crim- 
son tints to alcohol; and similar, though less brilliant, colours to 
solutions of carbonate of potash and carbonate of soda, &e. 
g. In some cases, the full colour was evolved only on second ma- 
ceration, or after the application of a series of reagents. 
h. In the case of solutions of salts used as macerants, the quantity 
or proportion of grains to the 3i of water is given, 
[To be imridiaaied in the January Number of Jameson’s Journal.] 
