IN FRESH- WATER ALG.E 



It has been shown by Jamieson, 1 in several species of higher 

 plants, that when a minimal amount of nitrogen is supplied, these 

 grow, increase in weight, and form far more combined nitrogen 

 both in soil and plant than has been supplied in original soil and 

 added media. These experiments of Jamieson' s were carried out 

 with the utmost care, attention being paid to every possible source 

 of gain or loss of nitrogen. Moreover, they are supported by several 

 other series of observations, such as gain of nitrogen in aquatic 

 plants with no soil roots, growth of large trees rooted in clefts in 

 basaltic and granitic rocks, where the total nitrogen in the soil could 

 not afford sufficient for one annual crop of leaves, analysis for nitro- 

 gen of plants found growing in hard mortar in walls where the 

 amount of nitrogen available, except from the atmosphere, was 

 practically negligible. 



A careful perusal of the wealth of facts published by Jamieson 

 in the " Annual Reports of the Aberdeen Agricultural Research 

 Association," against which there are only to be set these negative 

 results of Boussingault and Lawes, is convincing as to the 

 positive solution of the problem in favour of the assimilation of 

 nitrogen from the air by the green cell. These results have been 

 confirmed by Mameli and Pollacci 2 at Pavia; they are reinforced 

 by the experiments described in this chapter upon Fresh- Water 

 Algae, and also by others to be recorded later upon Marine Algae. 



Our approach to this problem has been from a different point of 

 view from those who have preceded us; they have been engaged 

 in its consideration in relation to the biochemistry of the plant, or 

 its importance in nutrition in agricultural chemistry; we have been 

 investigating the matter from the point of view of the primeval 

 origin of living organisms, before there was yet anything so com- 

 plicated as a green cell upon the earth, and when organic compounds 

 were first being synthesised from inorganic sources. 



The minutest micrococcus visible under the microscope contains 

 organic nitrogenous compounds in the form of proteins; it is 

 probable that the ultra-microscopic particles, called filter-passers, 

 which can pass through a Chamberland filter and yet can reproduce 

 themselves in organic media, and transmit diseases, also contain 



1 Jamieson, " Keports Agricultural Research Association, Aberdeen," 

 1905-1911. 



2 Mameli and Pollacci, " Sull' Assimilazione, dell' Azoto atmosferico nei 

 Vegetal!," Pavia, Atti. 1st. Bot., vol. xiv, pp. 159-257 (1911). 



