Abstract
THE observations by Cottam1 on reproduction and growth of the sea-grass, Zostera marina, are of considerable biological interest. He suggests that perhaps the length of the growing season may be an important factor in determining the breadth of the leaves in any habitat, and paints out that Setchell has shown that reproduction in the species occurs between 15° and 20° C. and growth in the range 10°–20° C. In recent work on increase in shell-area in the oyster2, I found that there is large spring as well as autumn growth in the Fal Estuary, but only a trace of growth in spring, with a large summer or autumn growth in the River Blackwater. Now in the Fal Estuary the temperature rises slowly from about 10° in winter, whereas in the more insular Blackwater oyster beds the rise is very rapid. Breeding begins in the oyster3 at about 15°–16° C., and increase in shell-area ceases at the onset of the breeding season. There is thus a longer spring growing period in such hydrographical situations as the Fal Estuary than in localities like the Blackwater.
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References
Cottam, C., NATURE, 135, 306, Feb. 23, 1935.
Orton, J. H., J. Mar. Biol. Assoc., 15, 384, 419; 1928.
Orton, J. H., ibid., 12, 339; 1920.
Orton, J. H., Johnstone Memorial Volume, p. 97; 1934.
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ORTON, J. Biology of Growth and Breeding. Nature 135, 509 (1935). https://doi.org/10.1038/135509c0
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DOI: https://doi.org/10.1038/135509c0
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