in] OF ANTHOCYANINS 37 



any particular tissue of the leaf, yet Parkin (77), in a recent investigation 

 on the localisation of anthocyanin, points out the prevalency of the 

 idea among botanists that anthocyanin is usually formed in the epidermis. 

 Parkin's researches are interesting because they give an indication as 

 to the particular localisation of the pigment when formed under varying 

 circumstances and under the influence of different factors. He examined 

 400 cases and classified his results as follows : 



1. Transitory anthocyanin of young leaves. This is a feature of 

 the young foliage of many plants in the tropics and temperate regions. 

 The number of species examined was 235, and the distribution was 

 classified as: 



Epidermis Mesophyll Epidermis and mesophyll 



20 % 64 % 16 % 



2. Autumnal anthocyanin. The number of species examined was 

 81 and the distribution : 



Epidermis Mesophyll Epidermis and mesophyll 



11% 78% 11% 



3. The permanent anthocyanin of mature leaves. In this case 

 the pigment appears as the leaf matures, and persists throughout the 

 life of the leaf as a normal character. This class includes (a) leaves 

 with uniformly red lower surfaces; (6) leaves with definite pigmented 

 areas in the form of spots, blotches or zones ; and (c) leaves of horti- 

 cultural varieties with coloured foliage. The number of species examined 

 was 54, and the distribution: 



Epidermis Mesophyll Epidermis and mesophyll 



70% 17% . 13% 



4. The accidental anthocyanin of mature leaves. This is not 

 normally present in mature leaves but arises only under exceptional 

 conditions such as: (a) excessive insolation, followed by cool nights, 

 as seen in Alpine plants, and in evergreens during winter; (6) the 

 result of injury, when a reddish zone often appears round a wound in a 

 leaf; (c) through the accidental exposure of lower surface to the full 

 rays of the sun. The number of cases examined was 30, and in the 

 majority the anthocyanin was confined to the mesophyll. Parkin 

 sums up by saying that anthocyanin of young and autumnal leaves is 

 usually confined to the mesophyll ; of mature leaves, when a normal 

 feature, to the epidermis; and, when exceptional, to the mesophyll. 



