No. 439.] NORTHERN GAM OPETALOUS FLOWERS. 459 



should be stricken from the list of plant pigments. Etiolated 

 plant organs owe their coloring exclusively to carotin, with which 

 is often associated anthocvan. Also identical with carotin are 



Carotin ^C,,; H :; J is easily dissolved bv ether but is insoluble in 

 water. The melting point is 167.SC. Concentrated sulphuric 

 and nitric acid color it a dark blue. Its crystals are rhombic. 

 The functions of carotin, according to Kohl, are threefold. First 

 it aids in assimilation. Its absorption band- lie in the blue half 

 of the spectrum, and. together with those of chlorophyll, give 

 the absorption spectra of the crude leaf-green. "Both take an 

 important, though unlike part, in the assimilatory work of the 

 chloroplasts, both absorb supplementary to each other a part of 

 the sunlight and assist in the decomposition of the atmospheric 

 carbonic acid." Secondly, carotin may serve as a reserve product, 

 as in a number of Fungi and Alga? and in the root of Daunts 

 carota. Thirdly, it is of biological importance because it renders 



theii 



nervosum, Adorns rerun /is. Cueurbita pepo, Erauthis hy 



In the peel or pericarp "of theMemon, in the flowers 

 yellow dahlia, in Liuaria vulgaris, Corydaljs In tea, the 

 parts of Antirrhinum majus, and in all the yellow fio 

 thistles, as well as" in other flowers, the yellow pigmen 

 not occur in plastids, but dissolved in the cell sap. What 

 pigment ? In a solution of crude leaf-green, in addition t 

 tin, there are two other yellow pigments, one of whic 

 obtained by Tschirch in 1896 and the other by Schui 

 1899. Kohl proposes to designate the latter of these tu 

 ments as a-xanthophyll and the former as yS-xanthophyll. 



The a-xanthophyll occurs in small quantities in normal « 

 plasts and yellow autumn leaves. It is the 0-xanthophyll 

 colors the peel of the lemon and the flowers with yello 



