*jouriLlsept?riS'] Royal Microscopical Society. 129 
seen in the blue. The tint of this solution is not permanent ; 
decomposition takes place, and the bands disappear. The red 
poppy is very similar in its reactions. The ranunculus gives a 
band in the red and orange, and deepens the rest of the spectrum. 
The solutions of the crimson petals of the geranium behave in a 
precisely similar way. The Iris imparts a fine reddish-purple 
colour to alcohol and water, the solution of which gives a band in 
the red, orange, and green, and partially absorbs the blue end of 
spectrum ; the addition of citric or mineral acid deepens the colour 
of the solution, and destroys the several bands, producing a general 
absorption of one end of the spectrum ; alkalies do not restore 
the bands in the spectrum. 
Litmus, a well-known colouring matter, prepared from Bocella 
tinctoria (canary archill or orchill), and which yields a valuable 
dye, and is employed largely for dyeing broadcloth, to which it com- 
municates a peculiar purple lustre when viewed in a certain light, 
is soluble in water and alcohol, to which it imparts a beautiful 
violet colour. This solution produces a fine band in the red, and 
another broad one which completely absorbs the orange and yellow 
and a portion of the green, while it deepens the violet end of the 
spectrum. Acids redden the solution and change the position of 
the spectrum ; the red is rendered more intense, the orange and 
yellow are restored, and a broad band appears in the green and 
blue. Carbonate of soda restores the violet colour of the solution ; 
at the same time the band in the red reappears, a separation of the 
green band takes place, and a faint one is produced in the blue. 
Tradescantia virginica (Spider wort), the jointed hairs of which 
show the circulation of the chlorophyll, so interesting to micro- 
scopists, yields to alcohol and water a reddish-purple solution, of 
the same colour as the flowers, the spectrum of which somewhat 
resembles that of Lohelia speciosa, but is more decided and curious. 
The red is intensified ; sharply-defined bands appear in the yellow 
and green, and 1 believe in the blue ; but owing to the exaltation 
of this end of the spectrum it is not quite easy to say. Larkspur 
yields a pale reddish-blue solution, and produces four absorption 
bands in the red, green, and blue ; there is no action on the yellow, 
although the colour has a good deal of blue in its composition. 
Vegetable blues are not invariably acted upon by acid or alkalies. 
It does not follow that acid converts them into red, and alkalies 
into green. In Mr. Sorby's experience of the solution of Coesaljpina 
crista (Brazil wood), called yellow, but which when first acted 
upon by water forms a red solution, and turns yellow after stand- 
ing some time, probably owing to a deoxidation of the solution, 
he observed that the yellow solution became pink on the addition 
of an alkali ; Brazil wood, however, is used as a red dye, while 
from other varieties of the Coesalpina black dyes are made, and 
even fine black ink. The yellow solution of this substance forms 
