236 HISTORY OF BOTANY 



studied in great detail, but the whole subject was in a 

 hopeless state of confusion, until Willstatter, with the 

 aid of ingeniously devised methods and excessive care 

 in manipulation, elucidated the relationships of these 

 manufactured products. I cannot do more here than 

 summarise a few of his chief results in a sentence or two ; 

 for details I must refer you to the original volume, or 

 to the excellent outline given by Jorgensen and Stiles 

 in the New Phytologist for 1917. 



When acted on by alkalies chlorophyll yields salts of 

 acids known as " chlorophyllins " which contain mag- 

 nesium. On heating these chlorophyllins with strong 

 alcoholic alkalies a series of " phyllins," also containing 

 magnesium, are obtained, and the magnesium is separated 

 from them when they are treated with acids, the resulting 

 compounds being " porphyrins." 



When chlorophyll is acted on by acids, on the other 

 hand, a body known as " phaeophytin " is produced, 

 which possesses no magnesium, from which in turn by 

 action of alkalies, among other derivatives, an alcohol 

 called " phytol " is obtained. Further, Willstatter pos- 

 tulates an enzyme present in alcoholic solution which 

 acts on the chlorophyll, producing a series of bodies 

 known as " chlorophyllides," which were mistaken for 

 crystalline chlorophyll by the earlier workers. The 

 acid phaeophytin from a - chlorophyll forms olive 

 green phytochlorin, and that from b - chlorophyll red 

 phytorhodin. 



Willstatter next proceeds to discuss the chemical 

 and physical characters of all these derivatives, as also 

 of the yellow pigments carotin and xanthophyll, which 

 latter are stable in alkalies but unstable in acids. He 

 also treats in great detail of the methods he and his 

 fellow-workers adopted in isolating and purifying these 

 various pigments and their derivatives. It is interesting 

 to note that he emphasises the advantages of nettle 

 leaves as sources of the pigments for laboratory investiga- 



