CAROTINOIDS IN THE PHANEROGAMS 71 



pigment. The method is strikingly pretty but has the serious objec- 

 tion that the various carotinoids arc likely to lose some of their char- 

 acteristic properties through oxidation before a pure pigment is ob- 

 tained. According to Tswctt (1906c), the differentiation into zones 

 is not due to adsorption, as in his method, but merely to a combined 

 effect of surface evaporation and precipitation of pigments having 

 varying degrees of insolubility in the increasingly dilute alcohol. It 

 is difficult to believe, however, that colloidal adsorption does not play 

 a part in this phenomenon. 



Bidgood's addition to the subject of flower pigments is a list of 

 flowers whose orange, brown and green tones are due to the combined 

 effect of carotinoids and crimson and blue anthocyanins. 



The author has attempted to collect in Tables 4, 5, 6 and 7 the 

 results of the work of the various investigators mentioned. It is seen 

 that a very large number of yellow flowers owe their color wholly or 

 in part to carotinoids. It should be understood that the tables include 

 only those which have been studied, and that the lists are not neces- 

 sarily complete. A few statements may be necessary in explanation 

 of the separate tables. The carotin-containing flowers in Table 4 

 must not be regarded as containing this pigment only. As a matter 

 of fact carotin apparently never exists alone, at least in flowers and 

 leaves, although it may be the predominating pigment, as in the 

 corona of the poet's Narcissus, and the daffodil where it is found 

 already crystallized in the plastids (Courchet, Bidgood, van Wissel- 

 ingh). The orange colored pigment of the pollen of the so-called 

 mullein (Verbascum thapsijorma L.) appears to consist wholly of 

 carotin (Bertrand and Poirault, 1892). The flowers which are starred 

 in Table 4 were placed there largely because they have been found 

 to yield microchemical crystals by the acid method, which may, at 

 least provisionally, be regarded as specific for carotin on account of 

 the great sensitiveness of xanthophylls toward acid. The presence of 

 carotin in the other flowers in Table 4 has been substantiated by other 

 observations. Arnaud determined quantitatively that the flower petals 

 of the sweet violet (Viola odorata) contain 124 mg. carotin per 100 

 gms. of dried petals. The xanthophyll-containing flowers of Table 5, 

 similarly, do not necessarily contain this class of carotinoids only, 

 although it is possible that this may be the case for those which are 

 starred, judging from van Wisselingh's study of this question. This 

 investigator's conclusion that the flowers which are double starred in 

 the table contain only one xanthophyll should be substantiated by 



