. The algae. Algae. EUPHYCOPHYTA 43 groups, and usually lack pyrenoids. The species are not readily determined taxonomically but as many are kept in pure culture they are often given strain numbers. It seems that cells grown in the dark differ from those grown in the Hght. Quiescent dark cells are small and have a photosynthetic quotient (O2/CO2) of i. They give rise to dividing dark cells which in turn give rise to 'Ught' cells in daylight. The light cells are larger, poorer in chloroplast material and less active photosynthetically (photosynthetic quotient = 3). During the course of developm
. The algae. Algae. EUPHYCOPHYTA 43 groups, and usually lack pyrenoids. The species are not readily determined taxonomically but as many are kept in pure culture they are often given strain numbers. It seems that cells grown in the dark differ from those grown in the Hght. Quiescent dark cells are small and have a photosynthetic quotient (O2/CO2) of i. They give rise to dividing dark cells which in turn give rise to 'Ught' cells in daylight. The light cells are larger, poorer in chloroplast material and less active photosynthetically (photosynthetic quotient = 3). During the course of development the amoimt of deoxyribonucleic acid increases. 'Light' cells give rise to a new generation of 'dark' cells in the dark. Reproduction is by means of division into 2, 4, 8 on 6 autospores. Several species form a symbiotic association with lower animals when they are known as Zoochlorella (cf. p. 427). Hydrodictyaceae: P^J/a5/rwm {pedi^ foot; astrum, star). Fig. 19 This alga occurs as a coenobium and it represents a more ad- vanced stage of the simple condition seen in the fresh-water algae. Fig. 19 Pediastrum. A, P. horyanum ( x 333). B, P. simplex yar. duodeniarum ( x 333). Cj P- boryanum var. granulatum showing liberation of zoospores. D, P. duplex with hypnospores. E, P. horyanum gennination of tetrahedron. F, P. horyanum var. granulatum, formation of new plate. (A, B, after Smith; C-F, after Fritsch.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Chapman, V. J. (Valentine Jackson), 1910-. London, Macmillan; New York, St. Martin's Press
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Keywords: ., bo, bookcentury1900, bookcollectionbiodiversity, booksubjectalgae
