Page:The Journal of Indian Botany.djvu/771

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Buller A. H., The Ocellus Function of the Sub-sporangial Swell- ing of Pilobolus — A palmer read before the Linncean Soc. of London- The following is taken from the published minutes.

He stated that the subsporangial swelling of Pilobolus functions, not merely as part of a squirting apparatus, but also as an ocellus, which receives the heliotropic stimulus which causes the stipe to turn the fungus gun toward the light. The swelling is transparent and refracts light, like the bulb of a Florence flask filled with water. Its diameter is always greater than that of the black sporangium which it supports.

The sporangiophore of Pilobolus appears to be the only orthoheliotropic plant organ known which takes up its positively heliotropic position owing to the possession of a special light-perceiving cell-structure.

Pilobohis may well be described as a fungus with an optical sense-organ or simple eye ; and, in using its eye for laying its gun, it appears to be unique in the plant world.

The paper was illustrated with models. A fuller account of the Pilobolus eye is about to appear in the ' Transactions of the British Mycological Society.'

Guilliermond, A. Les constituants morphologiques du cytoplas- me d'apres les recherches recentes de cytologie vegetale. (Morpho- logical constituents of cytoplasm). Bull. Biologique 54 : 465-512. 24 figs. 1921.

This paper is a summary of our present knowledge of the structures in the cell outside the nucleus, to which the author has devoted many years of study. These structures are considered under three heads : (l)thechondriome ; (2) microsomes ; and (3) the vacuole system.

Chondriome is a convenient term for the ensemble of mitochondria in the cell. After proper fixation and staining the mitochondria are revealed as a large number of minute granules, chains of granules, or filaments of varying length, scattered through the cytoplasm. They are found in all cells of all plants (except Cyanophyceae and Bacteria) and animals, and are permanent cell organs, arising always by division of pre-existing mitochondria. They are destroyed by the usual fixing agents containing alcohol and acetic acid, which explains the fact that they were not discovered till as late as 1894 ; chromic acid, osmic acid, and formalin preserve them faith- fully. They stain vividly with iron-haematoxylin, acid fuchsin, and crystal violet. A few cases are known where they may be observed in the living state, as in the epidermal cells of the perianth of white tulip, the leaf cells of Iris germanica, and in the filaments of a species of Saprolegnia.