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New Zealand Journal of Botany abstractsObservations on cell structure and cytology in the genus Durvillaea BoryMargaret RobertsDepartment of Botany, University of Durham, Science Laboratories, South Road, Durham, EnglandAbstract Most of the cells of the four species of Durvillaea examined contain numerous highly refractive physodes, both when examined fresh and also after fixation with many widely used fixatives. These physodes prevent direct observation of all other cell contents under the light microscope and appear as electron-dense bodies in electron micrographs. Two small, basally located chloroplasts can be seen in the meristoderm cells of D. antarctka and D. willana after the removal of the physodes. These chloroplasts divide synchronously with the meristoderm cells so that all cells of the secondary cortex initially contain two chloroplasts; these remain towards the outer ends of the cells and, as the cells of the secondary cortex extend in the anticlinal direction, they also become considerably elongated in this direction. The chloroplasts appear to fragment or disintegrate in the older, more deeply-seated cortical cells. The meristoderm cells divide periclinally and increase the depth of the cortex, whilst characteristic oblique divisions of a type not previously described for this tissue increase the number of cortical files. All newly formed anticlinal walls become mucilaginous and do not develop pits, but the newly formed periclinal walls all remain compact and highly refractive and develop a sieve plate-like structure. The nuclei of the meristoderm cells are spherical and relatively large, but those of all non-meristoderm cells are fusiform, and those of the very elongated cells of the inner primary tissues and of the secondary hyphae may be extremely elongated; spherical nuclei may also occur in cortical cells concerned with the initiation of hyphae, in the hyphal tips, and in the cells lining the conceptacle cavities and ostioles and from which the gametangia and ostiolar hairs respectively originate.
Received 11 July 1978
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