46 SECTIONAL ADDRESSES. 
Even to chemists it is only during the last decade that the 
mechanism of blossom-chemistry has been revealed. The subject has 
indeed excited their attention since an early period in the history of 
the organic branch, and the existing class-name for blossom-pigments 
was first used by Marquart in 1835 to distinguish blue colouring- 
matters occurring in flowers. It is also interesting to us to notice 
that in the following year Dr. Hope, who presided over the birth of 
the Chemistry Section at the Edinburgh meeting in 1834, described 
experiments conducted with blossoms representing many different 
orders, and devised a classification of the pigments which they contain. 
The recognition of glucosides amongst the anthocyans appears to have 
been first made as recently as 1894, by Heise; about that period, also, 
it gradually became clear that the various colours assumed by flowers 
are not variations of a single substance common to all, but arise from 
a considerable number of non-nitrogenous pigments. Prior to 1913 the 
most fruitful attempt to isolate a colouring-matter from blossoms in 
quantity sufficient for detailed examination had been made by Grafe 
(1911), but the conclusions to which it led were inaccurate. In the 
year mentioned, however, Willstitter began to publish with numerous 
collaborators a series of investigations, extending over the next three 
years, which have brought the subject within the realm of systematic 
chemistry. For the purpose of distinguishing glucosidic and non- 
glucosidie anthocyans the names anthocyanin and anthocyanidin 
respectively were applied. The experimental separation of anthocyanins 
from anthocyanidins was effected by partition between amyl alcohol 
and dilute mineral acid, the latter retaining the diglucosidic antho- 
cyanins in. the form of oxonium salts and leaving the anthocyanidins 
quantitatively in the amyl alcohol, from which they are not removed 
by further agitation with dilute acid; the monoglucosidic anthocyanins 
were found in both media, but left the amyl alcohol when offered fresh 
portions of dilute acid. 
The earliest of these papers, published in conjunction with A. E. 
Everest, dealt with cornflower pigments, and indicated that the dis- 
tinct shades of colour presented by different parts of the flower are 
caused by various derivatives of one substance; thus the blue form 
is the potassium derivative of a violet compound which is convertible 
into the red form by oxonium salt-formation with a mineral or plant 
acid. Moreover, as found in blossoms, the chromogen was observed 
to be combined with two molecular proportions of glucose and was 
isolated as crystalline cyanin chloride; hydrolysis removed the sugar 
and gave cyanidin chloride, also crystalline. Applying these methods 
more generally, Willstatter and his other collaborators have examined 
the chromogens which decorate the petals of rose, larkspur, hollyhock, 
geranium, salvia, chrysanthemum, gladiolus, ribes, tulip, zinnia, pansy, 
petunia, poppy, and aster, whilst the fruitskins of whortleberry, bil- 
berry, cranberry and cherry, plum, grape, and sloe have also been 
bie ‘to yield the pigment to which their characteristic appearance 
is due. 
The type of structural formula by which the anthocyanidins 
are now represented was proposed in 1914, simultaneously and 
