THE "EYES" OF PLANTS.

Oamaru Mail, Volume XXXVI, Issue 10042, 9 January 1909, Page 4 (Supplement)

THE "EYES" OF PLANTS.

The sensitiveness of plants to light was treated recently by Dr D. T. Macdougal, director of the Department of Botanical Research of the Carnegie Institution, in an article from which extracts were made in these calumns. In a paper read about the same time by Harold Wager before the British Association for the Advancement of Science, the author described interesting experiments conducted by him and other -biologists on tho epidermal plant-cells that serve as lenses for the concentration of light in their tissues. Says The Scientific American, October 17 : —"He exhibited photographs taken through the epidermal cells of the leaves of plants. "Hie upper and lower surfaces of leaves are covered by a thin transparent skin, which can in many cases be very easily peeled off. When examined under the microscope, as Dr Macdougal showed in his article and as Mr Wager reiterates, this skin is seen to consist of innumerable compartments or cells, many thousands of which are found on a single leaf. They contain a clear watery sap, and their shape is 6uc-h that they behave like ordinary convex or plano-convex lenses, the rays of light which fall upon them being converged and brought to a focus in the substance of the leaf. According to Professor Haberlandt, a German botanist, these cells enable the plant to perceive the difference between light and dark, and set lip a stimulus which results in, the movement of the leaf into such a position that it can obtain the maximum amount of light; or it may be, as Mr Wager is inclined to think, that these cells serve for the more efficient illumination of the green grains within the leaf upon which the effective food-supply of the plant depends. Possibly both play some part in aiding the leaf to perform its work more efficiently. These cells are found in practically all plants, but are most- clearly seen in some shade plants. Professor Haberlandt was able in one case to photograph a faint image of a miscroscope through the cells, and Mr Wager hat; .mere- recently obtained photographs of various objects. In many cases these lens-cells may be compared with the corneal facets of an insect's eye, so far as their general appearance and power of causing a convergence of light are concerned. In addition to ordinary methods of photography, it has been found possible to obtain photographs of simple patterns in colors by means of the autochrome plates of Messrs Lumiere. In taking these photographs, whether in the ordinary way or m colors, the images formed by the leaf-cells are magnified by the microscope from 100 to 400 or more diameters, and the photographs are obtained by an ordinary photomicrographic apparatus; but the best results have been "obtained with the Gordon photomicrographic apparatus. It is not suggested', that, .the plant can perceive the images which are thus photographed, but the fact. that.such images can be formed shows that these cells are very efficient lenses, and by xneanj. of them the plant may be enabled to take more advantages of the light which falls upon it than it would otherwise be able to do."