395 
NOTES ON THE BLUE-GREEN ALG&, 
mitt A. KEY TO THE.SPECIES OF OSCILLA- 
TORIA AND PHORMIDIUM. 
HAROLD WAGER, F.R.S. 
THE Blue-green Alge (Cyanophycee, Myxophycee or Schizo- 
phycee) form a group of plants which resemble the green 
Algee in some respects, but are sharply differentiated from 
them in the structure of the cell. They are characterized by 
the presence of a bluish purple colouring matter called phyco- 
cyanin which is contained in the cells in addition to the 
ordinary chlorophyll. This colouring matter is soluble in 
water, and can be easily extracted by allowing the plants to 
stand in water for some time, or better, by placing them in 
water to which a few drops of chloroform have been added. 
The constitution of the colouring matter is unknown. The 
plants vary in colour from a bright blue-green to reddish 
purple, violet, dark green, or even black, according to the 
amount of phycocyanin present. The darker colouring is 
found mainly in plants growing in a shady situation, the 
lighter colours, as a rule, in those growing more in the light. 
It has been found possible to vary the intensity of the colour 
by growing a given species under different light conditions 
and under various light filters. 
The cell structure of these plants is much simpler than that 
of the green alge and other plants. In most cases two distinct 
regions can be recognized in the protoplasm, a central clear 
region commonly known as the central body and a peripheral 
region in which the colouring matters are contained. Both 
show a reticulate or vesicular structure and both contain 
deeply stainable granules. The staining reactions of the 
central body show that it possesses some of the characteristics 
of a nucleus, but its structure is much simpler than the nucleus 
of the higher plants. The peripheral area gives the staining 
reaction of cytoplasm. Among the granules present three 
distinct kinds can be recognized. In the central body chro- 
matin granules, recognized by their reaction to nuclear stains 
and by the fact that they are found to contain phosphorus, 
are found, together with bright refringent granules easily seen 
in the living cell, which stain a reddish blue in a solution of 
methylene blue and which are known as metachromatin 
granules. In the peripheral area, and especially on the trans- 
verse walls, there are bright refringent granules, visible in the 
living cell, and easily differentiated by the bright red colour 
which they take in a solution of carmine. These are cyanophycin 
granules. The function of the metachromatin and cyano- 
I913 Aug. I. 
