Literature 381 



Tribe 3. Peniese. Cells short or of moderate length, straight, cylindrical, sometimes 

 with a slight median constriction. Cell-wall without pores. Point of division of cell 

 sometimes variable. The cell may arrive at maturity by the development of girdle-bands. 

 Penium Breb., 1844 ; em. Liitkem., 1905. 



Tribe 4. Closterieae. Cells elongate, sometimes very long, generally curved ; sym- 

 metrical in one longitudinal plane only. Cell-wall usually with pores. The cell may 

 arrive at maturity by the development of girdle-bands. At each extremity of the cell is a 

 terminal vacuole with gypsum crystals. Closterium Nitzsch, 1817. 



Tribe 5. Cosmariese. Cells exhibit great variety of form. Cell-wall consists of 

 two thin, firm layers, always furnished with pores. Girdle-bands are never developed, the 

 cell becoming adult very soon after division by growth of the young semicell to maturity. 

 Section a. The point of division, where the new and old parts of the cell-wall are 

 obliquely fitted together, remains plane during division. 



t Cells solitary. Docidium Breb., 1844; em. Lund., 1871 ; Pleurotsenium Nag., 1849; 

 Triploceras Bailey, 1851 ; Ichthyocercus W. & G. S. West, 1897 ; Tetmemorus Ralfs, 1844; 

 Euastridium W. & G. S. West, 1907 ; Euastrum Ehrenb., 1832 ; Micrasterias Agardh, 1827 ; 

 Cosmarium Corda, 1834; Xanthidium Ehrenb., 1834; Arthrodesmus Ehrenb., 1838; 

 Staurastrum Meyen, 1829. 



tt Colonial or filamentous. Cosmocladium Breb., 1856; Oocardium Nag., 1849; 

 Sphserozosma Corda, 1835; Onychonema Wallich, 1860; Spondylosium Breb., 1844; Phy- 

 matodocis Nordst., 1877: Hyalotheca Ehrenb., 1841. 



Section b. The point of division of the cell, where the new and the old parts of the 

 cell-wall are obliquely fitted together, develops a girdle-like thickening or ingrowth, which 

 projects both ways into each of the old semicells during division. 



Streptonema, G. C. Wallich, 1860 ; Desmidium Agardh, 1824 ; Gymnozyga Ehrenb., 

 1840. 



The largest genera are Cosmarium and Staurastrum. A very valuable bibliographical 

 work on the family has been published by Nordstedt ('96 ; '08). 



LITERATURE CITED 



ARCHER, W. ('67). On the conjugation of Spirotxnia condensata (Breb.) and 



truncata (Arch.). Quart. Journ. Micr. Sci. n.s. vii, July, 1867. 

 ARCHER, W. ('75) in Quart. Journ. Micr. Sci. 1875, pp. 414, 415. 

 BERGHS, J. ('06). Le noyau et la cinese chez le Spirogyra. La Cellule, xxiii, 1906. 

 BLACKMAN, F. F. & TANSLEY, A. G. ('02). A Revision of the Classification of the Green 



Algte. New Phytologist, i, 1902. 

 BOLDT, R. ('88). Desmidieer fran Gronland. Bih. till K. Sv. Vet.-Akad. Ilandl. Bd. xiii, 



Afd. 3, no. 5, 1888. 

 BORGE, 0. ('91). Sibiriens Chlorophyllophyce-Flora. Bih. till K. Sv. Vet.-Akad. Handl. 



Bd. xvii, no. 2, 1891. 



BORGE, 0. ('92). Subfossila sotvattensalger fran Gotland. Botaniska Notiser, 189 

 BORGE, 0. ('94). Tiber die Rhizoidenbildung bei einigen fadenformigen Chlorophyceen. 



Upsala, 1894. 



BORGE, 0. ('13). Beitrage zur Algenflora von Schweden. 2. Botaniska Notiser, 1913. 

 BORGESEN, F. ('01) in the Botany of the Fseroes, Copenhagen, 1901, p. 235, t. 8, f, 4. 



