B,—CHEMISTRY. 58 
that, although since the days of de Saussure (1804) chlorophyli has been 
regarded as the fundamental agent in the photosynthesis of living 
matter, there is no experimental evidence that the primary agent may 
not be contained in the colourless part of the chloroplast, chlorophyll 
thus being the result of a later synthetic stage. ‘The function of 
the chlorophyll may be a protective one to the chloroplast when exposed 
to light, it may be a light screen as has been suggested by Pringsheim, 
or it may be concerned in condensations and polymerisations subsequent 
to the first act of synthesis with production of formaldehyde’ (p. 55). 
In this connection it is significant that chlorosis of green plants will 
follow a deficiency of iron even in presence of sunlight (Molisch, 1892), 
and that development of chlorophyll can be restored by supplying this 
deficiency, although iron is not a component of the chlorophyll molecule ; 
moreover, green leaves etiolated by darkness and then exposed to light 
regain their chlorophyll, which is therefore itself a product arising from 
photosynthesis. 
H. Thiele (1907) recorded the swift conversion of nitrate into nitrite 
by the rays from a mercury quartz lamp, whilst O. Baudisch (1910) 
observed that daylight effects the same change, and from allied observa- 
tions was led (1911) to conclude that assimilation of nitrate and nitrite 
by green plants is a photochemical process. Moore found (1918) that 
in solutions of nitrate undergoing this reduction green leaves check the 
accumulation of nitrite, indicating their capacity to absorb the more 
active compound. Proceeding from the hypothesis that one of the 
organisms arising earliest in the course ~of evolution must have 
possessed, united in a single cell, the dual function of assimilating both 
carbon and nitrogen, he inquired (1918) whether the simplest unicellular 
alge may not also have this power. He satisfied himself that in 
absence of all sources of nitrogen excepting atmospheric, and in presence 
of carbon dioxide, the unicellular alge can fix nitrogen, grow and form 
proteins by transformation of light energy; the rate of growth is 
accelerated by the presence of nitrites or oxides of nitrogen, the latter 
being supplied in gaseous form by the atmosphere. From experiments 
(1919) with green seaweed (Enteromorpha compressus), Moore con- 
cluded also that marine alge assimilate carbon from the bicarbonates 
of calcium and magnesium present in sea-water, which thereby increases 
in alkalinity, and further convinced himself that the only source of 
nitrogen available to such growth is the atmosphere. A description of 
these experiments, which were carried out in conjunction with 
E. Whitley and T. A. Webster, has appeared also in the Proceedings 
of the Royal Society (1920 and 1921). 
For the purpose of distinguishing between (1) the obsolete view 
of a vital force disconnected with such forms of energy as are exhibited 
by non-living transformers and (2) the existence in living cells of only 
such energy forms as are encountered in non-living systems, Moore 
uses the expression ‘biotic energy’ to represent that form of energy 
peculiar to living matter. ‘The conception, in brief, is that biotic 
energy is just as closely, and no more, related to the various forms 
of energy existing apart from life, as these are to one another, and that 
in presence of the proper and adapted energy transformer, the living 
