VARIETIES OF CHLOROrHYLL 229 



0*856 percent of chlorophyll calculated on their dry weight. 

 Similar calculations for other leaves showed a variation in 

 chlorophyll content from 0-5 to i per cent. This is rather 

 lower than the figures given by Tschirch, namely, 2 to 4 per 

 cent. 



CRYSTALLINE AND AMORPHOUS CHLOROPHYLL. 



Crystals of chlorophyll were first observed by Borodin.* 

 This author found that sections of green leaves moistened 

 with alcohol and allowed to evaporate slowly under a cover- 

 slip revealed the presence of crystals when examined under a 

 microscope. He states that out of 770 plants examined 190 

 gave crystals of chlorophyll. 



The chlorophyll obtained by any of the methods of ex- 

 traction outlined above is in the great majority of cases 

 amorphous, but it is occasionally crystalline ; thus Willstatter 

 and Benzf found that Galeopsis tetrahit was about the only 

 plant which gave any appreciable quantity. The explanation 

 for this apparent contradiction of Borodin's observation was 

 supplied by Willstatter and OppeJ in a later paper, in which 

 they record that an alcoholic solution of amorphous chloro- 

 phyll, when left in contact with the plant tissues, is converted 

 into the crystalline variety by the action of an enzyme chloro- 

 phyllase ; the comparatively high yields of crystallized chloro- 

 phyll obtained from some plants must therefore be attributed 

 to the slow method of extraction ; the change can be avoided 

 by using a more rapid method. 



Since leaves of 200 different species all yielded amorphous 

 chlorophyll, it must be regarded as reasonably certain that this 

 is the form in which chlorophyll occurs naturally, and that the 

 crystalline variety is only a secondary decomposition product. 



The view formerly held that crystalline chlorophyll was 

 only a purified form of amorphous chlorophyll has been finally 

 disproved by showing that the two substances are in reality 

 different esters of the same tricarboxylic acid — 



C3iH23N,Mg(COOH)3 

 for which Willstatter proposes the name Chlorophyllin. 



* Borodin : " Bot. Ztg.," 1882, 40, 608. 



t Willstatter and Benz : " Annalen," 1908, 358, 267. 



J Willstatter and Oppe : id., 1910, 378, i. 



