These quotations will serve to illustrate the confusion which existed formerly, and which even new exists In many minds as to the relation which the two bodies bear to each other.
In the paper to which I have alluded, I endeavoured to show, contrary to the the received view, that starch granules and chlorophyll bodies were really the same bodies, chlorophyll granules being merely and essentially starch granules pigmented, or coloured, on some part or parts of their surface, of a green colour, by the action of light; that it was a chemical product rather than a vital secretion, or not in a fuller sense than starch was; and that, if the starch granule were not a living entity, as is the protoplasm, whence and by which it is produced, neither was the so-called chlorophyll granule, inasmuch as the colour could be produced by light without growth, or without any indication whatever of vital action. As proof of this I exhibited then, as I have over and over again subsequently, potato tubers in which chlorisation or pigmentation had occurred, or a coating of green given to the surface of the peripheral starch granules, wherever exposed to light, and a certain temperature. This light need not be the sun's direct rays, but it must be accompanied with a certain temperature in order that the chemical process shall take place. This may be easily proved. Clean potato tubers can be placed on a table, and be exposed to the direct rays of the sun, in a room the temperature of which does not exceed 40° to 45° Fah., and, if examined in a week or more, it will be found that no chemical, or no appreciable chemical change has taken place, and no pigmentation or chlorisation has been effected. Repeat this experiment in a room with a temperature of 62° Fah., and in a week the surface exposed to light will have been densely chlorized, and without direct sun-light. Extend the exposure during a few more days, and the effect will be more intense. If, now, a small portion of the substance of this green peripheral matter be scraped off and mounted in water and examined by the microscope, it will be seen that in the short space of a few days the starch granules will have been converted into what are termed chlorophyll bodies or grannies; but in reality showing, inferentially, that there is no such substance at all as a chlorophyll granule as distinct from the starch grain. It may be added that, if exposed to light and a proper temperature, granules of starch are pigmented or chlorized more or less, as soon as they are secreted, or take on substance, as seen in leaves and other organs primarily exposed to light. Hence, uncoloured starches are known to inhabit the parts of plants excluded from light, as pith, rhizomes, subterranean stems, and fruits protected by bracts impenetrable to light.
I quote one short passage from the article alluded to, and must further refer the reader to the report itself[1] "During several years of close examination of vegetable tissue, the author has found the attempt to divide these two substances (starch and chlorophyll) into two distinct bodies a source of perplexity; and, after a series of experiments and investigations, he arrived at the conclusion that these two series of granules must be considered fundamentally the same, one series being merely coloured or chlorized."
I shall now quote one or two short passages from the latest German authorities, to show views more or less approximative to those expressed by me in 1865, and that the tendencies of the most recent scientific opinion are certainly in this direction,
Sachs[2] states that with extremely few exceptions, grains of starch[3]
- ↑ Report of British Association, 1866, page 81.
- ↑ Julius Sachs, 1875 translation, page 46.
- ↑ The italics are my own.
