132 THE SIGNIFICANCE OF ANTHOCYANINS [CH. 



glass, a second by light through ruby glass, a third by light passing 

 through anthocyanin solution (of beet-root), while a fourth remained 

 in bright insolation. All the lobes were illuminated thus for four hours. 

 He then found that the insolated lobes had more starch in the palisade 

 parenchyma, though there was a considerable amount in the spongy 

 tissue too, whereas the lobes covered by red glass and anthocyanin 

 solution had more starch in the spongy parenchyma ; of the lobe 

 covered by orange glass, there was nothing in particular to note. From 

 these results Pick concludes that the lobes illuminated by ruby glass 

 and anthocyanin solution had assimilated as much as the directly 

 insolated lobe, but translocation had been more rapid. 



Pick's conclusions were adversely criticised by Wortmann (619) 

 who maintained that the observations on starch distribution in red 

 leaves are valueless because, first, it was not noted whether green 

 leaves behave differently under similar circumstances, and secondly, 

 the effect of red light on diastase activity outside the cell should 

 be investigated also. As regards the experiment on the Ricinus leaf, 

 he points out that, according to Stahl, the palisade cells and chloro- 

 plastids are adapted to starch formation in bright light, while those 

 of the spongy parenchyma are adapted to diffuse light. Hence the 

 distribution of starch in the lobes exposed to red light may be explained 

 on the ground that they receive less light than the directly insolated 

 leaf. Since Wortmann's criticisms have not been refuted, the question 

 still remains unsolved. Later, Ewart (406) also criticises Pick's 

 deductions. Pick has stated at one point that young red leaves have 

 little starch because the translocation is furthered, but as the leaves 

 mature, and the pigment disappears, more starch develops. Ewart 

 makes what appears to be a more natural suggestion, namely that 

 photosynthetic activity increases as the leaf matures and this is so 

 even if the leaf should retain its red colour. 



More recently Koning & Heinsius (416) have again reopened the 

 question as to whether anthocyanin acts as a screen for diastatic activity. 

 These authors quote the results of Brown & Morris to the effect that 

 the diastase content of leaves decreases after a period of exposure to 

 bright light, and that the enzyme is chiefly destroyed by the violet 

 and ultra violet rays. Koning & Heinsius claim to have shown experi- 

 mentally that the above-mentioned rays are absorbed, not only by a 

 water extract of anthocyanin, but also by the pigment in the living 

 leaves; also, by placing branches of Quercus rubra and other species 

 under double-walled vessels filled with anthocyanin solution, that it 



