414 THE PIGMENT SYSTEM CHAP. 15 



variations between 5 and 50 in 12 green fresh-water algae; in three 

 flagellates, the ratios of [x]:[c] were 5.4, 6.0 and 11.4, respectively; and 

 in seven fresh-Avater Rhodophyceae (some of them green and some brown 

 or reddish), it varied between 3.4 and 8.3. 



The ratio of [total chlorophyll] : [total carotenoids] also varies over 

 a wide range. In table 15. Ill, the values for the higher plants are 

 between 4.6 and 8.0. However, the Seybold-Egle (1939) list of 24 alpine 

 plants contains values between 1.6 and 3.7, and the list of seven lowland 

 plants, values from 2.6 to 4.3. The low values (~ 1) of the quotient 

 ([a] + [b]) : ([c] + [x]) for "fucoxanthol algae," found by Will- 

 statter and Stoll, were revised by Seybold and Egle (1938) to 4 or 5, in 

 consequence of the larger chlorophyll concentrations which they found 

 in these organisms (cf. page 408). The figures given by Seybold, Egle, 

 and Hiilsbruch (1941) for 12 fresh-water Chlorophyceae varied between 

 0.5 and 3.5, and those given for seven fresh- water Rhodophyceae, from 

 0.76 to 1.9. On the whole, it seems that the concentration of carotenoids 

 relative to that of chlorophyll is somewhat higher in algae than in land 

 plants; but this rule is by no means general, and the brown color of 

 Phaeophyceae, for example, is brought about not so much by a quanti- 

 tative preponderance of carotenoids as by the spectroscopic difference 

 between the yellow leaf "xanthrophylls" and the fucoxanthol, which, 

 although also yellow in solution, appears to be orange in the living cell. 



The only known nonchlorotic and nondecaying plants with an 

 abnormally low ratio of [chlorophyll] : [carotenoids] are leaves of the 

 aurea varieties, which contain about ten times less chlorophyll (and 

 only slightly less carotenoids) than the corresponding green varieties. 

 The ratio ([a] -\- [b]) : ([x] + [c]) in the aurea variety of Samhucus 

 nigra, for example is only 0.3, as against 4.8 in green leaves of the same 

 species (Willstatter and Stoll 1913). The aurea leaves also contain, 

 according to Seybold and Egle (1938), a large excess of carotenols 

 ([x]:[c] = 7). Montfort (1936) thought that the pigment relations in 

 brown algae are similar to those in aurea leaves, but this similarity 

 disappears if the newer data of Seybold and Egle (1938) are substituted 

 for those of Willstatter and Page (1914), 



A certain similarity exists, however, between aurea leaves and the 

 yellow autumn leaves — not only in respect to the ratio ([a] + [b]): 

 ([x] + [c]), but also in respect to the specific nature of the most abun- 

 dant carotenoids. Strain (1938) found that the yellow leaves of Evony- 

 mus japonica are characterized by a preponderance of zeaxanthol, and 

 that the same is true of yellow autumn leaves, while the main carotenoid 

 constituent of normal summer leaves is luteol. Chlorotic pear leaves, 

 on the other hand, have been found by Strain to contain the normal 

 assortment of carotenols. 



