NOTES* 
A NEW APPLICATION OF PHOTOGRAPHY TO THE 
DEMONSTRATION OF CERTAIN PHYSIOLOGICAL 
PROCESSES IN PLANTS.— It is possible by taking advantage 
of their sensitiveness to light, to obtain prints from Protococci , or the 
free swimming swarmspores of many green Algae. Into one end of a 
water-tight box, a thin glass plate is securely fitted. The negative to 
be printed is then placed next the glass, film-side nearest. The box 
is filled with water containing a fairly large quantity of swarmspores. 
The lid is shut down, and the whole is exposed to diffused light. 
In the case of a strong and well-developed negative, the swarmspores 
swim towards the most highly illuminated parts, and there in the 
greatest numbers come to rest, and settle upon the glass, so that 
after some four or six hours, on pouring out the water and removing 
the negative, a print in green swarmspores can be obtained. The 
print is dried, fixed with albumen, stained, and varnished. Whatever 
is the exact chemical nature of. the synthetic formation of proteid and 
protoplasm which takes place in the chlorophyll-corpuscles of plants 
under the influence of light, this is at least clear, that the first visible 
product of the assimilatory activity is the starch found in the corpuscles. 
The presence of this starch can be made manifest by treating a 
decolorised leaf with a water solution of iodine dissolved in potassic 
iodide. If a plant (and preferably a plant with thin leaves) be placed 
in the dark overnight, and then brought out into the light next morning, 
the leaves being covered with a sharp and well-developed negative, 
starch is formed when light is transmitted, and in greatest quantity 
in the brightest areas. Thus a positive in starch is produced which can 
be developed by treatment with iodine, and it might be possible to 
obtain a permanent print, by suitable washing, and treatment with 
a soluble silver salt, silver iodide being formed. 
WALTER GARDINER, Cambridge. 
[Annals of Botany, Vol. IV. No. XIII. November 1889.] 
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