122 MR. E. SCHUNCK ON A COLOURING MATTER 
VIII.— On a Yellow Colouring Matter obtained from 
the Leaves of the Polygonum Fagopyrum, 
or Common Buckwheat. 
By Epwarp Scuunck, Pu. D., F.R.S. 
Read October 6th, 1857. 
Amone the many plants which have been supposed to 
contain or yield indigo-blue, the Polygonum Fagopyrum 
or common buckwheat, a plant extensively cultivated in 
some countries for the sake of its seed, which is used as 
an article of food, is mentioned by some authors. In the 
Mechanic’s Magazine for November 1830, for instance, 
the following directions are given for obtaining a blue 
colour from this plant : — “Take the buckwheat out of the 
ground before the seed has become quite hard and lay it 
on the ground in the sun, until it is dry. Then throw 
the plant into heaps, moisten it and allow it to ferment, 
until decomposition commences, when it will assume a 
blue colour. It must now be formed into cakes, which 
may be dried either in the sun or ina stove. It imparts 
to boiling water a blue colour, which is not changed either 
by acetic or sulphuric acid. A durable blue may be dyed 
with it.” Though it does not follow from this that the 
blue colouring matter thus obtained was really indigo- 
blue, still it seemed not improbable that it might be 
identical with the latter, since another species belonging 
