Decomjwsition of Chlorophyll. 195 



nesium oxide, and in another 7.4%. The discrepancy is consider- 

 able, but the difficulty of purifying without great loss of material 

 is very great. The amounts of solid obtained for incineration were 

 only 0.35 and 0.42 gram, respectively. Presumably, the original 

 precipitate consists of a darker waxy solid, with a high magnesium 

 content, and a paler wax with little or no magnesium, which may 

 possibly partly be derived from the wax impregnating the cuticle, 

 and have nothing to do with chlorophyll. 



The wax present in the cuticle does not, however, decrease with 

 starvation, and increases in amount with increasing age. In a 

 further experiment the seedlings were grown in darkness until 

 nearly starved, and the yellow leaves were treated as before. The 

 waxy solids obtained after separation fiom petrol ether and crystal- 

 lization from hot alcohol gave a yield of 5.1% magnesium oxide. 

 The amount obtained was insufficient for the separation into mag- 

 nesium containing and non-magnesium containing waxes, but the 

 result indicates that the waxy solids with little or no magnesium 

 decrease during starvation, and hence are not derived wholly from 

 the cuticle. 



The decomposition of chlorophyll in grass leaves in darkness. 



Plots of barley grass (Hordeum murinum) were kept in darkness 

 from just before the commencement of flowering until the greater 

 part of the leaves turned yellow or yellowish red. These parts were 

 cut away and extracted. A little chlorophyll was still present, as 

 well as xanthophyll and carotin, in the approximate proportions 

 of 1, 3 and 12 respectively. The pale brownish white wax obtained 

 ,as previously described yielded 1.15% of ash. After washing with 

 warm alcohol the darker residue remaining yielded as much as 

 12.9% of ash, but the whole of this did not consist of magnesium 

 oxide. 



Many of tlie old grass leaves were bright red in colour, and 

 remain so in darkness, until they died and shrivelled. These 

 were extracted with absolute alcohol and petrol ether until all caro- 

 tin and xanthophyll were removed. They were still red. They 

 imparted a red tinge to water and the red pigment rapidly dis- 

 solved in dilute hydrochloric acid or dilute potash. The neutral 

 solution in water was precipitated by lead acetate, turned yellow 

 with sodium hydrate, reddish brown with hydrochloric acid, and 

 dark reddish l)rown, with ferric chloride. It was apparently, 

 therefore, a flavone, and as it appeared to develop in or in the 

 neighbourhood of the chloroplastids, it may be one of the products 



Sa 



