Notes. 
1 19 
2. The amount of formaldehyde present in the leaf bears a definite relation to 
the intensity of illumination. 
If water extracts be made of leaves (in the way above described) at different 
hours of the day or after exposure to different intensities of sunlight, other conditions 
remaining constant, the depth of the colour zone in the above test varies, being most 
intense when the leaves have been exposed to diffuse light, and feeble or absent when 
the leaves have been placed either in very weak or very intense light. These results 
are quite in accord with those obtained by previous investigators and especially by 
Pantanelli (1904), who found that the optimum decomposition of carbon dioxide took 
place when the light intensity amounted to one quarter of that of direct sunlight, but 
that as the light intensity increased photosynthesis decreased, other conditions 
remaining constant. 
3. Formaldehyde may be synthesized from carbon dioxide in presence of water by 
feeble electric discharge. 
In my first experiments I used the simple method of saturating distilled water 
with carbon dioxide gas and passing a current from a dry cell through the solution, 
using platinum or copper electrodes. In some cases, I thought I was able to detect 
minute traces of formaldehyde, but notwithstanding several modifications in my 
apparatus I failed to convince myself of its constant occurrence. My colleague, 
Dr. F. J. Brislee, directed my attention to Loeb’s paper (Zeit. f. Elektrochemie, 1906), 
and by employing his apparatus and a silent electric discharge, the presence of 
formaldehyde could be demonstrated with the gallic-sulphuric test in every case. 
Loeb, in discussing the bearing of his results on photosynthesis, holds that formaldehyde 
becomes by polymerization glycolaldehyde, which readily undergoes transformation 
into a sugar, but holds that the function of the chlorophyll is to remove the oxygen 
and at the same time to absorb the carbon dioxide, acting physiologically in an 
analogous but reverse manner to haemoglobin. 
4. Electric discharges of sufficient intensity occur in photosynthetic tissues when 
adequately illuminated. 
The researches of Ivunkel (1882), Haake (1892) and others have demonstrated 
the existence of electric currents in green plant-organs, and Klein’s (1898) 
investigations have shown that these currents are subject to regular variations 
according to the degree of illumination to which the parts are subjected. It would 
seem, however, that Klein considers the electric currents as something apart from 
the light and merely influenced by it ; according to the theory here proposed the 
electric currents are the expression of the transformation of the rays absorbed 
by the chlorophyll. 
5. The light rays absorbed by chlorophyll are those specially concerned in the 
generation of the electric currents demonstrable in phoiosynthetic tissues. 
Nagamatsz (1886) and, more recently, Griffon (1900) have shown that no 
photosynthesis takes place in a leaf illuminated by light which has passed through 
other leaves (indicated in their experiments by absence of starch). I have con- 
firmed this by other methods and found that no formaldehyde can be demonstrated 
in an extract of a leaf which has been exposed to light which has passed through 
another, although the upper leaf shows the presence of, formaldehyde quite distinctly. 
