vin] THE SIGNIFICANCE OF ANTHOCYANINS 129 



growing wild in the Mediterranean region and in cultivation in gardens 

 where it is known as the Summer Savory. In the shade it is green; 

 exposed to the sun its stems and leaves are dark violet. Kerner sowed 

 the seeds of this plant in his Alpine garden, 2195 metres above sea-level, 

 in the Tyrol. There, as a result, it is supposed, of the intensity of 

 the sun's rays, it produced anthocyanin in extraordinary abundance. 

 Such an adaptation, as he points out, can only take place in plants which 

 are able to form the pigment. Seeds of Linum usitatissimum were 

 sown next to the Savory ; the seedlings turned yellow and failed to 

 survive owing to the fact, in Kerner's opinion, that they are unable 

 to form anthocyanin to protect the chlorophyll and are also without 

 any development of hairs. 



In 1885 Reinke 1 published further results which, if accepted, make 

 it difficult to uphold the 'light-screen' hypothesis. The problem he set 

 out to investigate was the effect of the different parts of the spectrum 

 on the destruction of chlorophyll, and he claims to have shown that 

 the red rays have the maximum destructive effect, and that this power 

 decreases in the other parts in the following order orange, violet, 

 yellow, blue, dark red and green : when this sequence is compared 

 with the absorption spectrum of chlorophyll, it will be seen that the 

 rays which are most absorbed by chlorophyll have the greatest destruc- 

 tive effect upon it, and those which are least absorbed, do not have 

 any effect upon it. 



Further support was given by Hassack (393)' in 1886 to the screen 

 hypothesis, though his work is chiefly confined to the histological 

 distribution of anthocyanin in leaves. 



In 1887 a paper appeared by Engelmann (394) which has considerable 

 bearing on the problem. By means of a microspectral photometer, 

 Engelmann investigated the spectra of the pigments in red leaves, 

 and found that the absorption of red pigment is, on the whole, comple- 

 mentary to that of chlorophyll. Hence we are confronted with this 

 dilemma. Anthocyanin absorbs those rays which are not absorbed 

 by chlorophyll; the rays least absorbed by chlorophyll are, according 

 to Reinke, the least harmful to chlorophyll. Therefore anthocyanin 

 absorbs the rays which are least, and not most, harmful to chlorophyll. 

 How then can it be a protective screen ? If we accept Reinke's results, 

 a green screen would be the best protection as it would absorb the rays 



1 Reinke, J., 'Die Zerstorung von Chlorophylllosungen durch das Licht und eine 

 neue Methode zur Erzeugung des Normalspectrums,' Bot. Ztg., Leipzig, 1885, XLUI, 

 pp. 65-70, 81-89, 97-101, 113-117, 129-137. 



w P. 9 



