209 HAZEN : Lire Hisrory or SPHAERELLA LACUSTRIS 
sentative of the carotinins, a class of pigments which show much 
greater stability ; the carotin of Trentepohlia keeps its color in the 
dried state for only two months at the longest, while the haemato- 
chrom retains its color for years. 
It appears to me not unreasonable to conclude that in its 
chemical nature haematochrom is closely allied to chlorophyl in 
spite of the fact that it gives the starch reaction with iodine. 
FUNCTION OF THE HAEMATOCHROM 
When we consider what the value of haematochrom may be to 
Sphaerella we come to a very perplexing problem. Haematochrom 
is especially an accompaniment of diminished vitality, and it is, 
therefore, mainly in connection with the resting stage that we must 
study its function. Nevertheless, the red color of Sphaerella must 
have a greater significance, it seems to me, than that found in the 
winter spores of other fresh-water algae, since it forms so much 
more constant and permanent a feature. 
It has been very generally supposed that red coloring matters 
have some relation to light. MacDougal* thinks the red color 
substance of Haematococcus is a protection against the disintegrat- - 
ing effect of light on chlorophyl and protoplasm. That it may 
serve such a purpose in the pure red cells is quite probable, espec- 
ially as I have nearly always found only such cells in the pools 
which are exposed to the glaring sun, even though they were filled 
with water, while on the rock in New York, scantily supplied with 
water but turned away from the sun, I have generally found many 
green celis. 
In the partly green cells, as Engelmann has remarked, the red 
color can have little effect as a protective screen, since it occupies 
a central position in the cell, and the supposed disintegrating rays - 
which it absorbs, viz., those from the green to the violet end of the 
‘spectrum, must pass through most of the chlorophyl and proto- 
plasm before they are acted on by the red pigment. 
The researches of Kny and of Kerner show that red coloring 
matters probably play an important róle in converting light rays into 
heat. Itisentirely possible that the haematochrom serves this pur- 
N J. C. Arthur and D. T. MacDougal. Living Plants and their Properties, 185. 
1898. 
