896 Wisconsin Academy of Sciences , Arts, and Letters. 
Literature on Haematein. 
Baeyer, — Ber., 4, p. 457. 
Erdmann, — Ann., 44, p. 294; 216, p. 236. 
Halberstadt, — B., 14, p. 611. 
Hesse, — Ann., 109, p. 337. 
Mayer, — €hem. Centralbl., 1904, I. p. 228. 
Perkin, — Ber., 15, p. 2337; Jr. Chem. Soc., 41, p. 368; 93, p. 
1115; 95, p. 381. 
PIGMENTS REFERABLE TO HYDROCARBONS OF THE DEGREE OF SATU¬ 
RATION C n H 2n - 18 . 
There occur in plants pigments referable to four hydrocar¬ 
bons of four distinct structural configurations, falling under 
this degree of saturation, as follows: 
I. Nine double bonds and one cycle. 
The chlorophylls. 
II. Eight double bonds and two cycles. 
Pigments referable to diphenyl-1, 7-heptadiene-1, 6. 
III. Seven double bonds and three cycles. 
Pigments referable to phenyl-dihydronaphthalene. 
IV. Six double bonds and four cycles. 
Pigments referable to anthracene. 
With the exception of the first configuration under which we 
find the two chlorophylls chlorophyll-a and chlorophyll-b, so far 
as is known only one pigment under each structural configura¬ 
tion has been isolated. These are II. Curcumin, III. Trifoletin, 
IY. Chrysarobin. 
I. Pigments referable to hydrocarbons of the configuration 
NINE DOUBLE BONDS AND ONCE CYCLE. 
The Chlorophylls. 
The chemistry of chlorophyll has attracted more attention and 
has been the subject of more investigations than that of any 
other plant pigment. This is due not only to the extremely 
wide distribution and abundant occurrence of chlorophyll in 
plants but also to its physiological importance and the role 
