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TAXONOMIC CHARACTERISTICS ii
VI. Vegetative cells with i to i6 parietal, more or less spirally arranged
ribbonlike chromatophores, each with several or many pyrenoids
arranged in a single median line; nuclei centrally located and sup-
ported by cytoplasmic strands; zygospores ellipsoid, ovoid, or lenticular,
always formed in one of the gametangia
1. With conjugating tubes formed by one or both gametangia
before conjugation; outer layer of vegetative cell walls of pectic
compounds, which usually disappears during conjugation
12. Spirogyra
2. Without conjugating tubes, conjugation directly through an
opening where the reflexed gametangia are in contact; this area
of contact becomes encircled by a ring of pectic compound;
vegetative cells without a pectic sheath, chromatophores only
slightly curved 13, Sirogonium
Other Summaries of the Zygnemataceae
Vaucher, J. P. 1803. Conjuguees. Histoire des Conjerves d'eau douce.
Geneva, pp. 37-81.
Agardh, C. A. 1824. Systerna Algarum. Lund.
Hassall, A. H. 1845. History of British Freshwater Algae. London.
Bary, A. de. 1858. U titersuchungen iiber die Familie der Conjugaten.
Leipzig.
Palla, E. 1894. "Ueber eine pyrenoidlose Art und Gattung der Con-
jugaten." Berichte deutsch. hot. Gesells. 12, p. 228.
West, G. S. 1916. "Zygnemaceae." Algae. Cambridge Botanical
Handboohj. i, pp. 331-53.
Oltmanns, Fr. 1922. "Zygnemaceae." Morphologic der Algen. Jena, i,
pp. 87-106.
Skuja, H. 1929. "Siisswasser Algen von den westestnischen Inseln."
Acta Horti Bot. Univ. Latviensis. 4, pp. 38-49.
Czurda, V. 1932. Zygnemales. Siisswasserflora Mitteleuropa. 9.
Smith, G. M. "Zygnemataceae." Freshwater Algae of the United
States, pp. 536-57.
Transeau, E. N. 1934. "Genera of the Zygnemataceae." Trans. Amer.
Micros. Soc. 53, pp. 201-7.
Fritsch, F. E. 1935. "Zygnemoideae." Structure and Reproduction of
the Algae, pp. 316-37.
Czurda, V. 1937. Conjugatae. Handbuch der Pflanzenanatomie. 6.
Kolkwitz, R., and Krieger, W. 1941-44. Zygnemales. Rabenhorst's
Kryptogam enflora von Deutschland und der Schweiz. 13, abt. II.
(Keys to genera and species. Contains most complete bibliography,
lists of obsolete names, and alleged synonyms.)