The Montgomery advertiser., 1906-04-13
THE EYES OF PLANTS.
Their Sensitiveness to Light Investl-
 gated by Men of Science.

Literary Digest.
 The sensitiveness of plants to light. including the wellknown phenomenon of 'heliotropism." or turning toward light; have often ,Sesn been studied, studied by Professor Haberlandt of the University of Gratz. Germany. has set himself the task of determining in just what part tiveness resides, and he has succeeded, as he believes. in locating what he calls the light perceiving organs of plants, which he describes in recent book Nature" (London) we quote the fol- lowing paragraphs:
 By covering the blade of the lead shows that the principaf and most deli cate sensitiveness resides in the blade. although a coarser and secondary sen- in the stalk, It results from this part of the inquiry that the lamina of the leaf must contain the organs for light perception. if such organs exist. Any may be expected to be on the surface, although in such translucent organ as a leaf this does not necessarily fol Haberlandt is amply justified in look. ing for what he calls the ocelli of plants in the, epidermis covering the upper surface of the leaf We may. by light striking it obliquely from above at 45 degrees; such leaf Is not
 in the sht Postobs fSsanes ana w fact, until 1t receives light at right angles to it's surface. Then curvature ceases and the leaf remains in a state qf equilibrium satisfied as it were with
 But how does the leaf differentiate between oblique and perpendicular il. finda-hu rnfprngp0nic examination that there is a bright spot of light on the inner walls of the epidermic cells which changes position when the specimen is obliquely illuminated. He believes that the leaf is stimulated to curvature by the fact that the spots of light are not central in the cells, and that cur lumination is once more central: The membrane of the basal wall of each cell. therefore. must act as sort Of on bs whsn paaton T w vi the most light. The reviewer goes on: .'Haberlandt shows that the epidermic cell is we'll fitted to concentrate light. It is very commonly lenslike in form, it's outer wall being convex. its inner wall either plane or curved. Haber- landt shows by geometrical construc- the cell sap as equal to that. of water the focus is usually. at point either within the cell or below it in the other tissues. In either case central illum-
  zone are produced on the basal cell wall. It must not be sup posed that all leaves have lens-shaped epidermic cells; some leaves. known as aphotometric, are indifferent to the direction of incident light, and even in photometric leaves Haberlandt shows that discrimination is possible without the epidermis playing the part of a lens. Where the outer wall of the epi- dermis is fiat, 1t often occurs that the inner wall bulges into the sub1acent tis- lens effect we get stronger iliumination in the central region of the basal walls of the epidermis."
 If the epidermic cells are eyes" each having "retina" and a lens to con centrate light thereon. 1t is clear that immersion in fluid of the same refrac- tive index as the cell sap must inter fere with the plants power of light perception. This fact appears to be es- tablished by Haberlandt's experiments with the hop and other plants. He even believes that he has proved that the effect of the waxy bloom on certain leaves is to prevent the "blinding" of the plants in this way by a shower of rain The reviewer concludes:
 'The author has once more earned the gratitude of his fellows by his sug- gestive discoveries and speculations. He must be allowed to have made out strong case for his theory. but he would be among the first to grant that more work is needed before it can be considered as completely established