36 THE HISTOLOGICAL DISTKIBUTION [CH. 



Massart), and a very detailed classification is recorded by Buscalioni 

 & Pollacci. 



A less detailed classification due to Gertz is quoted as follows : 



A. Permanent anthocyanin. 



1. In the epidermis. Ex. Orchis, Canna, Maranta, atropurpurea- 

 forms of Fagus, Corylus and Acer, and also of Beta vulgaris, Atriplex 

 hortensis and Croton sp. 



2. In peripheral layer of the ground tissue. Ex. Dracaena, Eucomis 

 punctata, Erythronimn Dens-Canis, Arum maculatum, Arisarum vulgare, 

 Berberis vulgaris atropurpurea. 



3. In both epidermis and ground tissue. Ex. Aerua sanguinolenta, 

 Aeschynanthus atropurpureus, Iresine Herbstii, Coleus sp. 



4. In median ground tissue. Ex. Higginsia refulgens, Sinmngia 

 purpurea, Gesneria Donkelaari, Pellionia Daveauana. 



B. Periodic anthocyanin. 



(a) In young leaves and spring leaves. 



1. In the epidermis. Ex. Rubus, Rosa, Rhus, Silene, Malva. 

 Veronica, Odontites, Ajuga, Salvia. 



2. In the ground tissue. Ex. Salix, Populus, Fagus, Acer, Cydonia, 

 Vicia, Stellaria, Cerastium, Campanula, Taraxacum. 



3. In hairs. Ex. Quercus rubra, Q. macrocarpa, Castanea vesca, 

 Chenopodium album, Mallotus japonicus, Vitis alexandrina, V. Labrusca. 



(b) In older and autumnal leaves. 



1. In the epidermis. Ex. Philadelphus, Deutzia, Euonymus 

 europaeus, and some Oenotheraceae. 



2. In ground parenchyma. Ex. Populus, Salix, Quercus, Rhus, 

 Acer, Vitis, Ampelopsis, Prunus, Cornus, Viburnum. 



(c) In winter leaves. 



1. In the epidermis. Ex. Silene, Oenothera, Gaura, Veronica, 

 Lamium. 



2. In the ground tissue. Ex. Secale, Hedera, Calluna, Empetrum. 



One or two further observations of interest are mentioned by Gertz. 

 This author notes that in some leaves there is an indication of division 

 of labour as regards anthocyanin. When the pigment appears princi- 

 pally in the epidermis, it is often found in addition in isolated mesophyll 

 cells which are poor in chlorophyll (Spiraea, Rosa and Rubus). 



Although, as we have seen, from the observations of the above- 

 mentioned authors, anthocyanin formation is by no means limited to 



