542 TEANSACTIONS AND PROCEEDINGS OF THE [Sess. lx. 



Thus red anthocyan can be converted into blue by the 

 addition of a small amount of an alkali, while the blue can 

 be converted into red by the addition of acids. The 

 addition even of a small amount of a strong alkali like 

 caustic potash or soda produces a greenish colour, which 

 becomes yellow on further additions of alkali, and finally 

 becomes colourless. The cautious addition of a salt like 

 disodium hydrogen phosphate, on the other hand, to red 

 anthocyan, produces first a violet and finally a blue colour 

 (Hansen). These reactions can be very readily observed 

 with anthocyan obtained from a rosy apple. A pretty and 

 familiar illustration of the same fact is seen in nature in 

 the change of colour in the flowers of many Boraginaceai! 

 from pink to blue, which is associated with a corresponding 

 change in the reaction of the cell-sap. 



It is curious to note that, while there are practically no 

 suggestions as to the functions of the lipochromes, those as 

 to the meaning of the anthocyan pigments are as numerous 

 as could be desired. As, however, in most cases these 

 suggestions have been offered in relation to particular cases, 

 it may be well first to give a complete list of the conditions 

 under which anthocyan is found to occur. Frank in his 

 Lehrbuch der Botanik (Bd. I. s. 646) classifies the organs 

 in which anthocyan occurs under the following heads : — 

 First, in flowers and fruits ; Second, in vegetative organs. 

 In vegetative organs in the following conditions : — (a) In 

 many young growing shoots in spring ; (h) In many 

 autumnal leaves ; (c) In many organs when exposed to 

 cold, whether in spring or autumn ; (d) In many stems, 

 petioles, etc., on the side which is exposed to the sun ; 

 (e) In many leaves and fruits at spots M'here injury has 

 taken place ; (/) In many parts of plants as a variation. 

 To tliis list may be added the case of Alpine plants, which 

 exhibit a general tendency to develop anthocyan. 



As to the meaning of the anthocyan the commonest 

 suggestion, based especially on conditions c and d, is of 

 course that it is a direct adaptation destined to prevent 

 the decomposition of chlorophyll by strong light. Detmer 

 especially supports this theory in his Pflanzenphysiologie, 

 pointing to the reddening of some evergreen leaves in 

 winter, and to an experiment by Kerner, who transplanted 



