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 len- 

 ticular, 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. Sy sterna Algarum. Lund. 

 Hassall, A. H. 1845. History of British Freshwater Algae. London. 

 Bary, A. de. 1858. U titer suchun gen 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 



Krypto gam en flora von Deutschland und der Schweiz. 13, abt. II. 



(Keys to genera and species. Contains most complete bibliography, 



lists of obsolete names, and alleged synonyms.) 



