RED PIGMENT OF FLOWERING PLANTS. 415 



in the case of the Alpine plants Linum and Satureja to 

 which reference has been made, Stahl suggests that the 

 red Satitrcja thrives because its anthocyan enables it to take 

 the fullest advantage of the sun's rays. Owing to it, the 

 leaf reaches a higher temperature than it otherwise would ; 

 and, in consequence, its general metabolic processes, not 

 merely those of carbohydrate translocation, are favoured. 

 The flax plants wither because they lack the colouring 

 matter which would enable them to take advantage of any 

 favourable change of temperature. And he observes a 

 fact which, it must be confessed, however, might be taken 

 to have merely a pathological significance, that in flax 

 grown at 1800 metres, after exposure to nights during 

 which the temperature fell to o°C., the leaves were full of 

 starch. A real difficulty seems to object itself to this 

 simple interpretation : to wit, that, as Stahl shows, tissues 

 containing anthocyan not only become warm more quickly 

 than the ordinary green parts, but that, when the source of 

 heat is removed, they become cool more quickly ; and until 

 it be shown that excessive radiation is not a source of 

 danger to such plants as those growing in high altitudes, it 

 must appear at all events possible that what the plant gains 

 by heat absorption during the day it loses, by increased 

 radiation, during- the night. Stahl is careful to point out 

 that much of the foregoing is speculative, and contents 

 himself with the statement that, in any case, his view of 

 an acceleration of general metabolic activity by the heat- 

 absorbing anthocyan (erythrophyll) has pressing claims for 

 consideration. Pick's results Stahl explains in a similar 

 way. The anthocyan is of importance not because it 

 brings the red rays to bear on the translocation process in 

 particular, but because by its heat-absorbing properties it 

 furthers "die Stoff- und Kraft-wechsel Processe " of the 

 plant. 



The occurrence of anthocyan in very many localities, as 

 for example extrafloral nectaries, the secreting end-cells of 

 glandular hairs and at the foot of many sap-containing hairs 

 is noted by Stahl, who expressly contents himself with 

 pointing out that possibly here the colouring matter may 



