384 BOTANICAL GAZETTE [DECEMBER 
Fixed alkalies added to the red solution resulting from the 
action of acids on the blue first restore the blue color, then, if 
in excess, produce a green, which in turn disappears as has just 
been described; and in like manner shaking with air or addition 
of hydrogen peroxid restores the blue. From neither acid nor 
from alkaline solution will solvents such as petroleum ether, 
ether, chloroform, benzene, amyl alcohol, etc., extract any color- 
ing matter. = 
As to the important question whether the organism produces 
the blue pigment or a compound which turns blue in air, the 
writers do not yet feel justified in advancing an opinion. 
When the clear blue solution (obtained by dissolving in 
water the coloring matter isolated from potatoes by the method 
described above) is placed before the spectroscope, a fairly well 
defined absorption band is seen in the neighborhood of the Dline. 
The maximum intensity of this absorption band has approxi- 
mately a wave-length of %=594, in the case of the purest pig- 
ment thus far obtained ; its width and intensity varies, naturally, 
with the concentration and thickness of layer of the solution 
examined. There is also a slight darkening of the spectrum in 
the red, and a similar cutting off in the blue extending to the far 
violet. In the red this absorption seems to begin somewhere 
from A=680 to A= 690, but is so gradual that no satisfactory 
measurements can be made. In the green, blue, and violet the 
increasing absorption is so gradual that no reliable decision can 
be made as to just where the absorption begins. Fig. I gives the 
absorption spectrum of solutions 10™ thick, containing i 
liter of the purest pigment obtained; fig. 2, same solutions 1n 
layers 25™™ thick; fig. 3, same pigment in solutions of “ae wed 
liter, examined in layers 10™™ thick. In 25™™ layers the absorp: 
tion bands of these last solutions are too intense to permit of their 
being represented on the same scale as those figured. Blue 
solutions obtained by mere filtration of water extracts of colored 
potatoes usually show more marked absorption in the red an 
violet ends of the spectrum than do solutions of the pigment 
separated as previously described. Fig. 76 shows the spectrum 
Sent eae NG TRO TEES Ee ee ee eS i ane epi ee Oe 
