hi THE COLOURS AND PIGMENTS OF PLANTS 63 
tion from the brightly coloured leaves of some species 
of Coleus. He found, however, that on boiling these 
leaves with water, he did not obtain a coloured 
solution, although the leaves themselves lost their 
colour. If, however, the colourless solution be 
evaporated to dryness, anthocyan is left behind in 
its blue or violet form. Similarly if the decolorised 
leaves be dried at a gentle heat they regain their 
bright colours. The reason for this remarkable 
phenomenon Molisch found to be as follows. Dur¬ 
ing life the cell-sap in these coloured leaves is faintly 
acid or neutral in reaction, but the protoplasm is as 
usual distinctly alkaline. At the moment of death 
the alkaline protoplasm mingles with the cell-sap, 
and the alkalinity of the protoplasm is strong enough 
to completely destroy the anthocyan colour (cf. action 
of alkalies as explained above). Molisch also found 
tnat leaves which are not decolorised on boiling are 
lemarkable for the large amount of acid contained 
in the cell-sap, this being apparently large enough to 
neutralise the alkalinity of the protoplasm. By 
further experimentation Molisch convinced himself 
that the decolorisation only occurred when the cells 
containing anthocyan were in contact with cells very 
rich in chlorophyll. This he illustrated by a very 
pretty experiment. He took the leaves of a species 
of Saxifrage, Saxifraga sarmentosa ,, in which the epi¬ 
dermal cells of the leaf are very rich in anthocyan, 
and lemoved a small part of the epidermis from 
a leaf. Both the piece of epidermis and the re¬ 
mainder of the leaf were then kept at a temperature 
sufficient to kill the cells, and so bring the cell-sap 
into contact with the protoplasm. In a quarter of 
