284 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



glucosides during the formation of anthocyanin, the latter 

 cannot be formed at the expense of pre-existing glucosidic 

 chromogens. It arises rather by direct synthesis (de toutes 

 pieces) in the presence of considerable quantities of sugars. 



As pointed out by Combes (1914), in certain cases 

 Ampelopsis hederacea, for example a yellow pigment may 

 be obtained from the green leaves, which he claims to have 

 converted into anthocyanin by reduction. But even in 

 this case he urges that the amount of yellow pigment 

 present does not seem to be sufficient to justify the con- 

 clusion that, all the anthocyanin of the red leaves has arisen 

 from it. The view held by Combes as to the production 

 of anthocyanin is, clearly, very different from those of Pal- 

 ladin and Wheldale, both of which have already been men- 

 tioned. Its consideration has been deferred to this stage, 

 as, though it may seem more logical to discuss all the 

 theories of anthocyanin formation in the same place, it is 

 far more convenient to consider each in relation to the 

 evidence on which it is based. 



Combes (1910) also studied the gaseous exchanges of 

 green leaves during the formation of anthocyanin in them, 

 and a similar investigation upon the flowers of Coboea 

 scandens (which are green when they open, and then 

 become red) has recently been completed by Rose (1914). 

 In the two researches the same conclusion was reached 

 that there was no relation between the variation in the 

 intensity of respiration due to the red pigmentation. In 

 both floral and foliage leaves assimilation was less in the 

 red than in the green stage. Whilst in these and other 

 respects the red and green agreed closely, yet during the 

 formation of the anthocyanin it was found, by examina- 

 tion of the diurnal gaseous exchanges, that oxidations are 

 more active than in the normal conditions of vegetation. 



From a study of the total sugars and glucosides of the 



