i] INTRODUCTORY 9 



and chemists. It was, for instance, again (1878) suggested by Gautier 

 (149) on the strength of isolation and analyses of the pigments of various 

 wines. Later, further analyses of Vine pigments were made by Gautier 

 (175) and other investigators, notably Heise (167), but their results 

 were in no way concordant except in so far as they agreed that the 

 pigment contained carbon, hydrogen and oxygen only. These were 

 followed again by analyses of the pigment of Bilberry fruits by Heise 

 (178). 



In 1895 Weigert (179) made the first attempt at a classification of 

 anthocyanins based upon their chemical reactions, and he differentiated 

 two groups, the 'Weinroth' and the 'Riibenroth,' according to the 

 behaviour of the pigment to acids, alkalies and lead acetate solution. 

 The Riibenroth group is however a small group of anthocyanin pigments 

 of the orders Phytolaccaceae, Amarantaceae and Portulacaceae of the 

 Centrospermae ; the Weinroth group, including the greater number 

 of anthocyanins, still remained undifferentiated. 



In 1906 Grafe (197) published the results of some careful analyses 

 of the pigment of the Hollyhock (Althaea rosea), followed by further 

 analyses (222) of the pigment of scarlet Pelargonium flowers in 1911. 

 In this publication Grafe clearly expresses the view that anthocyanin 

 must be regarded as a general term for a number of substances, having 

 similar properties and reactions, but differing somewhat from each 

 other in chemical constitution. 



Meanwhile from the year 1900 and onwards, the study of anthocyanin 

 pigments gained a new impetus through their connection with the 

 inheritance of colour in plants. For many experiments on the cross- 

 breeding of colour- varieties were commenced about this time by Bateson, 

 Punnett, Saunders (475, 487) and others working on the lines of Mendelian 

 inheritance. Two of the first plants to be used for this purpose were the 

 Stock (Matthiola) and the Sweet Pea (Lathyrus). Both these plants 

 have a number of varieties, and although it is doubtful whether we know 

 the character of the original type in Matthiola, it is fairly certain that 

 the original wild Sweet Pea resembled the form known as 'Purple 

 Invincible' which has a chocolate standard and purplish-blue alae. 

 We now know from the teachings of heredity that all the coloured 

 varieties of Sweet Pea, and probably many of those of Stocks, have 

 arisen through the loss of certain factors from the type, and by recrossing 

 selected varieties, the type can be obtained again, the process being 

 known as the phenomenon of 'reversion to type.' One of the most 

 striking results (496) of the experiments on Sweet Peas and Stocks 



