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We are still confronted with a situation in which many genera of algae have species that cannot be identified without knowledge of stages in the life cycle which do not lend themselves to preservation as dried herbarium specimens. Corallary to this situation and arising from it is the difficulty in establishing a soundly based nomenclatural type. Such familiar genera as Chlorococcum, Characium, Spirogyra, Stigeoclonium, Trachelomonas, Chlamydomonas, Haematococcus must be present in more than one stage of the life cycle in order to be classified. Many Chlorophyta, such as Stigeoclonium and Cladophora, or Cyanophyta, such as Calothrix and Stigeonema, do not have suitable keys even when sufficient stages are found together in natural habitats. These probably have more species named than actually exist in nature due to the erroneous descriptions of two forms which are actually stages in the life cycle of one species. Our position may be illustrated as similar to that of the Paleobotanist who must describe form genera for stem fossils, seed fossils, and root fossils separately because he finds them separate and cannot be sure, for example, which root fossil belongs with which seed. While the Paleobotanist must await the long chance of finding the seed or sporangial parts attached to the stem and roots for clarification of the problem, Phycologists may, in most instances, cultivate the form in question and obtain specimen material suitable for identification. Through study of ontogeny under culture conditions, criteria useful in the preparation of effective keys to species may be revealed.

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Proceedings of the Iowa Academy of Science





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©1954 Iowa Academy of Science, Inc.



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