128 THE SIGNIFICANCE OF ANTHOCYANINS [CH. 



sunlight. When in light of only 200 times the intensity, there was no 

 bleaching of Elodea even after two hours' exposure. 



Kerner (398) appears to be one of the first, if not the first, to make 

 suggestions as to the significance of anthocyanin, though in his Pflanzen- 

 leben (1885) 1 , he by no means confines himself to one use of antho- 

 cyanin to explain its appearance in different places under various 

 conditions. Thus, for instance, in stems and petioles, he says, it may 

 be of use in keeping back light rays which would decompose the travelling 

 materials. (This view may be original or may be taken from Pick, 

 see p. 131.) In other cases it is produced temporarily for the same 

 purpose when there is a transmission of metabolic substances on a 

 large scale as in the seedlings of certain starchy seeds (polygonums, 

 oraches, palms and grasses). Again, in spring, it appears in young leaves 

 and shoots when supplies are travelling to them from their place of 

 storage in the stem. In autumnal leaves, all materials of use to the 

 plant are passing out for storage ; hence the value of autumnal colora- 

 tion. Anthocyanin developed on the under surfaces of leaves, is, on 

 the contrary, not protective but absorbs light and changes it into heat 

 which is serviceable for growth, metabolism and translocation. When, 

 in shrubs and herbs, anthocyanin appears on the under leaf-surfaces, 

 this is only the case in the lowest leaves near the ground ; the upper 

 leaves remain green and so do not prevent light from passing through 

 to the leaves beneath them. The development on the under surface 

 of leaves of marsh plants and floating plants has similar uses. Thus, 

 there is not only retention by anthocyanin of rays injurious to meta- 

 bolism, but there is, at the same time, a useful transformation into heat. 

 When, he continues, the surrounding temperature is low, plants are 

 often entirely reddened, as in some small annuals developing early 

 in the spring (Saxifraga, Hutchinsia, Androsace) ; also in seedlings 

 germinating at low temperatures. It is, for the same reason, common 

 in the vegetative parts of many High Alpine plants. Of similar value 

 is its distribution on the under surface of petals and perianth leaves 

 of flowers which close by night. 



Two further observations of interest are mentioned by Kerner. 

 One, that plants which have leaves covered with a felt or wool of hairs 

 rarely develop anthocyanin, since such leaves do not need so much 

 protection from light. 



The second observation is that made on Satureja hortensis, a plant 



1 The Pflanzenleben appears to have been issued in parts several years before the 

 6rst edition in 1888. 



