36 CAROTINOIDS AND RELATED PIGMENTS 



It remained for Arnaud (1885), however, to first recognize and 

 prove the identity of the orange-red crystals apparently first observed 

 by Fremy (1865) and later called chrysophyll, erythrophyll, xanthin, 

 etc., with the carotin from carrots, which had been known and studied 

 for 60 years. Arnaud (1885) first observed the identity in form and 

 properties of carotin which he isolated from carrots and the red 

 rhombic crystals which he isolated from spinach leaves (Spinachia 

 oleracea and glabra) , mulberry leaves (Moms alba), the leaves of 

 peach (Persica vulgaris) and sycamore (Acer pseudoplatanus) trees, 

 and the leaves of the English ivy vine (Hedera helix) , as well as from 

 pumpkins (Cucurbita pepo). In a succeeding paper Arnaud (1886) 

 proved this identity by his analyses of the crystals obtained from 

 carrots, to which reference has already been made, the results leading 

 to the proposal of the formula C 2G H 38 for the pigment. Arnaud did 

 not make any analyses of the apparently identical crystals which he 

 obtained from leaves, so that strictly speaking the final proof of the 

 identity of the crystals was not furnished until Willstatter and Mieg 

 performed their comparative analysis many years later (1907). How- 

 ever, following Arnaud, investigators with few exceptions adopted his 

 terminology and called the red crystalline pigment carotin which could 

 be isolated so generally from chlorophyll forming plants, as well as 

 many fruits and seeds, and from cryptogamic forms. Immendorff 

 (1889), in fact, soon after Arnaud's work, isolated carotin from barley 

 and rye leaves and submitted the crystalline pigment to analysis. His 

 data corresponded best with Zeise's older formula, C 5 H 8 , but he pre- 

 ferred to accept the Arnaud formula because it appeared to be sub- 

 stantiated by Arnaud's analysis of the iodine derivative of carotin. 

 Willstatter and Mieg, however, starting with 100 kilos of dried 

 nettle (Urtica) leaves, isolated carotin in sufficient quantity to estab- 

 lish for it the correct formula, C 40 H 56 . Their analyses gave the 

 average composition of 89.29 per cent carbon and 10.53 per cent hydro- 

 gen as compared with the theoretical values 89.48 and 10.52 per cent 

 carbon and hydrogen, respectively. 



Plurality of Yellow Pigments in the C hloroplastids 



The next group of investigations dealing with the yellow pigments 

 of the chloroplastids had to do with the question whether more than 

 one yellow pigment is a constant accompaniment of the chlorophyll. 

 This question brings us up to the present time for notwithstanding the 



