PART I 



GENERAL ACCOUNT 

 CHAPTER I 



INTRODUCTORY 



The subject of the anthocyanin pigments of plants has received 

 considerable attention, yet the results are comparatively slight. Such 

 colouring matters have sometimes been spoken of as soluble pigments, 

 since they are in a state of solution in the cell-sap, as contrasted with 

 those which are in some way bound up with the structure of organised 

 protoplasmic bodies known as plastids. The innumerable shades of 

 blue, purple, violet, mauve and magenta, and nearly all the reds, which 

 appear in flowers, fruits, leaves and stems are due to anthocyanin pig- 

 ments. On the other hand, green, and the large majority of orange 

 and yellow colours, are in the form of plastid pigments. Other colours, 

 again, notably some scarlets and orange-reds, browns and even black, 

 are produced by the presence of both plastid and anthocyanin pig- 

 ments together in the tissues. 



For almost a hundred years botanists have employed one term to 

 denote the soluble pigments anthocyanin 1 (avOos, /cvavos), a word 

 first coined by Marquart (5) 2 for these substances in 1835 and retained 

 in the same sense to the present day ; other rival terms, now obsolete, 

 such as erythrophyll, cyanophyll and cyanin have also been used 

 from time to time. 



Vegetable pigments served as matter for investigation at a very 

 early date, and the property which first attracted attention was their 

 behaviour towards acids and bases, that is, the reddening by acids 

 and the formation of green coloured products with a base. Thus, in 

 1661, in the Experiments and Considerations touching Colours of Robert 



1 In the present volume anthocyanin is largely used in the collective sense, that is 

 as a term which we know to include a number of substances ; sometimes however, when 

 the context demands it, the plural form is used. 



2 Numbers in brackets refer to papers, etc., in the Bibliography at the end of the book, 

 and such references are either entirely concerned with anthocyanins, or have some direct 

 bearing upon them. References, on the contrary, in the foot-notes are not directly 

 concerned with anthocyanins. 



W. P 1 



