ANALYSIS OF OEGANISMS 161 



both samples. These variations in the chemical composition of the same 

 form are due, doubtless, to the fact that the samples represent different 

 stages in the life cycle of the alga. 



Hyams and Richards 1 found, for example, that young, green fila- 

 ments of the blue-green alga Oscillatoria prolifica contained 9.0 per cent 

 of nitrogen, while mature, brown colored specimens yielded only 7.9 

 per cent; the ash in the former amounted to only 4.5 per cent, while 

 in the latter it ranged from 6.1 per cent to 6.7 per cent. (See table 51.) 

 Most of the difference in the ash was due to a greater abundance of 

 silica in the mature material ; the silica in the young amounted to 1.46 

 per cent and in the mature to 2.90 per cent. This evidence seems to 

 indicate that an alga collected during a period of rapid growth and 

 vigorous reproduction differs somewhat in chemical composition from a 

 sample of the same alga which is collected after the form has become 

 fully mature. 



In other analyses Hyams and Richards obtained 11.0 per cent of 

 nitrogen in one sample of Oscillatoria prolifica and 10.3 per cent in 

 another; both of these percentages are higher than the maximum of 

 nitrogen in the samples of blue-green algae shown in table 49. 



Turner 2 also analyzed samples of Oscillatoria prolifica and found 

 that the air dried material contained 9.7 per cent of moisture, 7.4 per 

 cent of nitrogen, 2.2 per cent of ether extract, and 6.4 per cent of ash. 

 When recalculated on an oven dry basis, the nitrogen equals 8.2 per 

 cent, the ether extract 2.4 per cent, and the ash 7.1 per cent. (Table 

 51.) His results for nitrogen, therefore, are substantially the same as 

 those found in four samples of blue-green algae in this series of analy- 

 ses, and his percentages of ether extract and ash are also similar to 

 some of the results obtained on this Wisconsin material. 



Whipple and Jackson 3 found 9.6 per cent of nitrogen in Anabaena 

 and 8.3 per cent in Microcystis (Clathrocystis). (Table 51.) The for- 

 mer is higher than the percentage of nitrogen in the Anabaena material 

 obtained from Lake Mendota on September 19, 1914, while the latter is 

 substantially the same as the average of the four samples of Microcystis 

 shown in table 49. 



Chlorophyceae. The sample of Ankistrodesmus was grown in a cul- 

 ture containing Knop's solution; this nutrient solution yielded a pre- 

 cipitate which was removed from the water by the centrifuge along 

 with the alga. This made the ash content of the sample too high, 

 namely 41.61 per cent, so that the results for Ankistrodesmus are given 

 only on an ash free basis. The percentage of nitrogen in this alga is a 



technology Quarterly, Vol. 15, 1902, pp. 308-315. 



E Jour. Amer. Chem. Soc, Vol. 38, 1916, p. 1402. 



8 Jour. N. E. Waterworks Assoc, Vol. 14, 1899, pp. 1-25. 



