THE ANTHOCYAN PIGMENTS 603 



gains its original colour as evaporation takes place, is not even 

 mentioned. 



Very different in character from these papers of Griffiths is 

 the beautifully clear and descriptive publication of the botanist 

 Molisch (Bot. Ztg. 1905, 145), and a greater incentive to re- 

 search upon these pigments than lies in this paper one cannot 

 easily imagine. Molisch, after giving a summary of the literature 

 dealing with the then very doubtful appearance of solid antho- 

 cyan pigments in plants, described how, on examination of a 

 number of anthocyan-containing flowers and leaves, he found 

 that these pigments existed not only in solution in the cell sap, 

 but were without doubt, in many cases, present also in the solid 

 state, sometimes as small spheres, sometimes as definitely 

 crystalline formations. Of some of the more well-defined cases 

 he gave illustrations. Having described the appearance of 

 anthocyan crystals in the living plant, he followed up these ob- 

 servations with a description of his attempts to obtain crystals 

 of these pigments outside the plant. In this, also, he was, in 

 several cases (pelargonium, rose, anemone fulgens), successful, 

 and of the resultant microscopic c^stals he gave illustrations. 

 Having thus established the fact that some of these pigments 

 readily crystallise, he pointed out that it should not be difficult 

 to prepare them in sufficiently large quantities for chemical 

 examination. In a very slightly modified form, the method 

 whereby Molisch obtained his crystals is so simple and certain, 

 that it is worth describing. One or two petals of the flower 

 are laid upon a piece of glass slightly larger than a microscope 

 slide and upon which are one or two drops of 75% acetic acid, 

 the cell structure broken down by rolling a glass rod over them, 

 leaving the petals flattened on the glass with the cell sap beside 

 or upon them ; two or three more drops of 75% acetic acid are 

 then placed on the petals, and a microscope slide pressed 

 down upon them ; the whole is then placed under a clock-glass 

 (to ensure slow "evaporation), when, after some 12 to 24 hours 

 crystals begin to appear, either round the edge of the slide, or 

 round or on the petals. Scarlet pelargonium gives the best 

 results and very rarely fails ; in some cases, using these flowers 

 the author has obtained clusters of crystals so large as to be 

 readily discernible by means of the naked eye. 



As mentioned above, Grafe was moved, by the work of 

 Molisch, to attempt the chemical investigation of some of these 



