462 Wager . — The Perception of Light in Plants . 
Smaller openings in the woodland green would produce a correspondingly 
smaller cone of light and a smaller middle field. 
Cells with a very regular outline, such as occur in Tradescantia fiumi- 
nensis and Zebrina pendula on both sides of the leaf, the upper epidermal 
cells of Ligustrum ovalifolium , various Orchidaceae, &c., may be compared 
to the corneal facets of the compound eyes of insects. They act as very 
efficient lenses, and not only bring the light to a focus but are capable 
of forming clear and distinct images of objects near them. In one case 
Haberlandt (loc. cit., PI. IV, Fig. 2) was able to obtain a somewhat indistinct 
photograph of a microscope stand which was focused upon the basal wall 
of the cell. Guttenberg 1 placed a preparation of the epidermis of Adoxa 
moschatellina firmly under the microscope, and, after removing the mirror 
and diaphragm, directed the instrument towards various objects. He then 
saw the images of the objects quite clearly focused through the cells. 
Similar observations were made with other plants. It is probable that the 
upper epidermal cells of the majority of ordinary foliage leaves will be found 
to possess to a greater or less extent this power. I have examined some 
hundreds of plants, and only in very few has it been absent. Moreover, in 
the great majority the cells of the lower epidermis, although not in all cases 
equal to the upper epidermal cells, function in the same way. 
By appropriate manipulation with the microscope and the Gordon 
photo-micrographic apparatus made by Messrs. Beck, it has been found 
possible to obtain photographs of a variety of objects through cells both of 
the upper and lower epidermis of leaves of many species of plants. Among 
these are portraits from life, reproductions of photographs of various kinds, 
flowers and other objects direct, and it has even been found possible 
to photograph trees, houses, and landscapes, and to reproduce simple 
diagrams in colour on the autochrome plates of Messrs. Lumiere. 
The methods employed are perfectly simple, and do not call for any 
special skill in manipulation. A strip of epidermis is sliced off with a razor 
and floated gently upon a layer of dilute glycerine placed on a thin cover- 
glass. As much of the glycerine as possible is then soaked up with blotting- 
paper. leaving the layer of epidermis adhering closely to the glass. The 
upper surface of the epidermis should be kept dry. The cover-glass is then 
inverted over a damp chamber and placed on the stage of the microscope, 
so that the upper surface of the epidermis will be nearest the mirror. 
Remove the sub-stage condenser but retain the diaphragm ; place the 
object to be photographed at some distance from the microscope ; whether 
this should be two or three feet or several hundred yards depends upon the 
size of the object. Then by means of the plane mirror reflect the image on 
to the epidermal cells, and examine with a i-inch objective. A clear view 
1 Die Lichtsinnesorgane der Laubblatter von Adoxa Moschatellina , L. und Cynocrambe prostrata, 
Gartn. Ber. d. d. bot. Gesell., xxiii, p. 265, 1905. 
