Light Sense-Organs in Xerophilous Stems

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IN view of the recent work of Haberlandt on the light sense-organs of leaves, it may be of interest to record the discovery of similar organs in xerophilous stems. Certain of the epidermal cells of the young stems of the Ephedreæ have on their external wall conical structures of the nature of papillæ, the core of the papilla being mucilaginous. This structure acts as a collecting lens focussing the incident rays of light, and a definite area of the cytoplasm of the back wall of the cell is thereby illuminated. Fig. 1, which is a photomicrograph taken in diffuse light of a mounted preparation of epidermis, shows the appearance of these light spots as seen under 1/6 objective.

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