152 On the Formation of Anthocyanin 



Sugar-Feeding. 

 It is obvious that in the consideration of such an hypothesis as that 

 which I have formulated, any evidence of a connection between in- 

 creased pigmentation and increased concentration of sugars brought 

 about by artificial feeding of plants or parts of plants with various 

 sugars would be of considerable value. 



Such a method of research has been adopted by Overton(13). This 

 author maintains that the conversion of sugar into starch is lessened 

 by a lowering of the temperature. Hence the pigment of autumnal 

 leaves and evergreen leaves in winter is due to excess of sugar induced 

 by low temperature. 



In order to test his hypothesis, Overton made a number of sugar- 

 feeding experiments with both water and land plants. The water 

 plants were grown either submerged or floating in solutions of cane- 

 sugar, glucose, fructose, etc. In the case of land plants, the cut ends of 

 leafy stems or the petioles of leaves were placed in the solutions. 



Many of the species used {Hydrocharis morsus-ranae, Utricularia 

 spp., Lilium Martagon, Ilex aquifolium, Hedera Helix, Ligustrum 

 vulgare, Saxifraga spp., Crassula spp., Aquilegia vulgaris, Tm^axacum 

 vulgare, Eupatorium cannahinum and Epilohium parviflorum), showed 

 increased formation of pigment, but in other cases (Potamogeton spp., 

 Lemna spp., Fritillaria imperialis, Mahonia aquifolium, Anthriscus 

 sylvestris, Rubus spp., white flowers of Pelargonium zonale, and Anemone 

 japonica) there was a negative result. 



Increased colour sometimes appeared in control plants kept in 

 distilled water under good illumination. 



Corroborative results have also been obtained by Kati6(5) with 

 plants of Hydrilla, Elodea canadensis, Hydrocharis morsus-ranae, leaves 

 of Sagittaria natans, Canna indica, Veronica chamaedrys, Rosa sp., 

 Saxifraga cordifolia, Pittosporum undulatum and Bellis perennis. 



Overton has proved his results to be due to the chemical nature of 

 the dissolved substance and not to any osmotic action by the use of 

 control solutions of neutral salts, i.e. sodium chloride, sodium sulphate, 

 potassium sulphate of osmotic strengths equivalent to those of the sugar 

 solutions employed. In no case where a neutral salt was used, was there 

 any increase in pigmentation. In Lilium Martagon, an increase of 

 pigment resulted from the use of ethyl and methyl alcohol solutions. 



In view of Overton's suggestion that increased sugar concentration 

 may under some conditions be brought about by a decreased starch- 

 forming capacity, I thought it possible that some connection might 

 exist between the reddening of leaves and starch formation in sugar- 



