. The algae. Algae. Ix CUTLERIA 11 >o V UD w ASPEROCOCCUS. Ix LAMINARIA Fig. 188 Types of life cycle in the Phaeophyceae and their pos- sible inter-relationships. RD = position of reduction division in the life cycle. A Study ofthe life cycles (Fig. i88) of representative genera in the Phaeophyceae is of some interest. It will be noted that in the dia- gram the arrows indicating suggested evolutionary progression in the Hfe cycles in general conform to evolutionary morphological progression. In most of the types the Hfe cycle is not simple, be- cause each generation is capable of repeating
. The algae. Algae. Ix CUTLERIA 11 >o V UD w ASPEROCOCCUS. Ix LAMINARIA Fig. 188 Types of life cycle in the Phaeophyceae and their pos- sible inter-relationships. RD = position of reduction division in the life cycle. A Study ofthe life cycles (Fig. i88) of representative genera in the Phaeophyceae is of some interest. It will be noted that in the dia- gram the arrows indicating suggested evolutionary progression in the Hfe cycles in general conform to evolutionary morphological progression. In most of the types the Hfe cycle is not simple, be- cause each generation is capable of repeating itself. Lying behind the life cycle, however, is the fundamental nuclear cycle, but despite this there is no real regular alternation of generations ex- cept in the Dictyotales, Laminariales and some members of the Chordariales and Sphacelariales. This diagram leads to the con- clusion that the primitive Phaeophycean was either a plant with only a haploid generation in the Hfe cycle, or one in which there was isomorphic alternation. The first alternative would involve the interpolation of a sporophytic generation through a delay in meiosis, and the subsequent loss of the gametophyte. The second hypo- 319. 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
