i] INTRODUCTORY 3 



and alkali reactions: "...it is somewhat surprizing to see,. ..how 

 Differingly-colour'd Flowers, or Blossoms,... how remote soever their 

 Colours be from Green, would in a moment pass into a deep Degree of 

 that Colour, upon the Touch of an Alcalizate Liquor." The gradual 

 evolution of the idea of the multiplicity of pigments included under 

 anthocyanin can only be realised in a comprehensive survey of the 

 subject. 



After the preliminary and somewhat diffuse observations of the 

 earliest scientists, there follows a period during which certain definite 

 lines of investigation emerge, and it is practically to these lines that 

 the chapters in this book correspond. It may not be out of place, 

 however, to give a general account of the different phases and kinds of 

 investigation showing how they have developed, and how they are 

 related to each other in the complete history. 



The above lines of investigation may be enumerated thus: the 

 morphological and histological distribution of the pigments, the factors 

 controlling their formation, their function, their chemical composition, 

 their mode of origin, and lastly, the part they have played in heredity. 



First let us consider their distribution. Contributions to this portion 

 of the subject naturally formed a great part, though by no means the 

 whole, of the earlier work on pigments, since it merely involved general 

 observation and microscopical examination of petals and leaves. 

 Various writers published full accounts of the pigments of flowers, 

 fruits, leaves, etc., showing how some colours are due to plastid, others 

 to soluble pigments, and others again are the result of the combination 

 of both in the cells. As would be expected, this form of investigation 

 has tended to diminish in later years for, the histological basis once 

 laid down, the physiological, chemical and biochemical aspects have 

 come to the front. Mention must be made, however, of the publications 

 of Buscalioni & Pollacci (17) in 1903 on the histological distribution 

 of anthocyanin, and of a paper on similar lines read by Parkin (77) 

 at the meeting of the British Association of the same year. Still 

 later work of this kind is that of Gertz (19) which appeared in 1906; 

 this author made a most thorough and systematic investigation of the 

 occurrence of anthocyanin in representative genera of all natural 

 orders, but the publication of his work in Swedish unfortunately 

 restricts the circulation of his results. 



The question of factors controlling anthocyanin formation is the 

 next line of enquiry most convenient for consideration. The main 

 factors concerned are light, temperature and nutrition. 



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