24 
THE CHEMISTRY OF SOME COMMON PLANTS. 
P. Q@3 KEEGAN, Lieb 
Patterdale, Westmorland. 
Rock LicHen (Parmelia saxatilis)—This organism is very 
commonly observed on roadside unmortared walls, and some- 
times on withered time-worn hawthorn barks, etc., and is a 
fairly good representative of the class to which it belongs. It 
is divided by systematists into two varieties: one, refiruga, 
containing, according to Hesse, atranorin, protocetraric acid, 
and saxatic acid; the other, ompha/lodes, containing atranorin, 
saxatic acid, and an acid like protocetraric acid. It may be 
advisable to observe here that the chemistry of lichens is very 
difficult and greatly confused for two reasons, viz., the difficulty 
of purifying the constituents extracted by solvents, and the fact 
that these constituents are liable to vary in composition and in 
relative amount at any particular period. Therefore, I shall 
merely present the results of my own rough analysis of this 
species, prosecuted in the ordinary way. The dried substance 
treated with boiling benzene yielded 0.75 per cent. of a brownish- 
yellow extract, which with sulphuric acid gave green, red and 
brown colours, and has a white opaque matter insoluble in cold 
benzene like stearine. The treatment with boiling alcohol (after 
benzene) afforded a crystalline deposit on cooling, and also on 
adding water, and the liquid gave with perchloride of iron a 
violet colour, with solution of bleaching lime a transient violet, 
with ammonia water it dried up to a red-brown mass, with lime 
added and the filtrate acidified by HCl a bright red precipitate 
was presently deposited ; the liquid contained no free phloroglucin 
or sugar. The hot water extract gave reactions similar to the 
foregoing, it had neither sugar nor albumenoid. Dilute caustic 
soda further withdrew a small quantity of mucilage coloured 
red-brown, but still no albumenoid. Dilute HCl did not extract 
any starch or lichenin. The residue (crude ‘ fibre’) amounted 
to 63.7 per cent. of the original. The ash amounted to 5.4 per 
cent., and yielded 13.3 per cent. soluble salts, 55 silica, 2.2 lime, 
17.5 oxide of iron; 4.1,P2O° and 1.1 °SO®% ; there was adittle 
manganese, but no carbonates. It would appear that in the 
above analysis the benzene extracted atranorin, and the alcohol 
a mixture of protocetraric and saxatic acids. The well-known 
dyeing property of the lichen is mainly due to the former acid, 
which seems to be a derivative of betaorcin C8H!°O? =dimethyl 
resorcine, and to result from the hydrolysis of the lichen proteids. 
Naturalist, 
