ANTHOCYAX IX THE PETALOID CALYX. 6 



eye, but its microscopical structure shows no colour. This green 

 pigment in the epidermal cell-sap is present in such a very small 

 amount that it is hardlv recoo'uizeable in a thin section. I 

 intend to call anthocyan in this primitive stage colourless 

 protanthocyan ; from this yellow anthocyan is next derived. The 

 latter is a true colour-generator. Zopf^' studied the developmental 

 phases of anthocyan in Fumariaceiie and observed that a colourless 

 chromogen barely makes its appearance, then frequently a yellow 

 pigment in some species, and lastly red anthocyan. His colourless 

 ,, Chromogen," AVigand's"^ colourless ,, Cyanogen" and my protan- 

 thocyan are probably; identical, since they all consist of a certain 

 tannin compound. Moreover, according to Harvey''^ the develop- 

 ment of colour in flowers probably begins with green, which i.s 

 followed successively by 3'ellow, white and red, and ends with 

 violet or blue. This is almost the same order as that in the 

 case of the formation of anthocyan in red Hortense. How 

 protanthocyan changes into the variously coloured anthocyans 

 will be more fully discussed later on, but it may here be 

 mentioned that l)oth internal and external influences are active 

 in ])roducing these changes. 



Of the existence of the blue or violet crystals of anthocyan, 

 which I have found in the petaloid-calyx of red Hortense in the 

 latest stage, only very little has hitherto known. Probably the 

 " blue star " in the epithelial cells of the Delphinium petals*^ 

 and the violet crystals in the epidermal cells of the coffee-berry 



1) Znpf, W.— Ueher die Gerbstuff und Antliocytin-Behältcr der Fumuriaceen und einiger 

 anderen Pflanzen. 188(5. 



2) Wigand. — Einige Sätze ül)er die physiologischen. Bedeutung der Gerbstoflès und 

 Pflanzen. Farbe. (Bot. Ztg. 18G2, 122). 



3) Harvey, E. W. — Observation on the colour of Flowers. 1899. 



4) Cf. Weiss, A. — Anatomie der Pflanze. 1878, p. 130, and Slrasburger, Ed.— 'Das 

 Botanische Practicuni 1897, p. 122. 



