PAPENFUSS: CLASSIFICATION OF THE ALGAE 177 



have emphasized, however, that rehited genera are segi-egated l)y tliis division. 

 In more recent times the division of the Hormogonales into Ileterocysteae and 

 Homocysteae has been followed by Setchell and Gardner (1919) and by Smith 

 (1933) who, however, has since abandoned this classification (Smith, 1950). 



In 1895 ]\Iarchand established the ordinal names Coccogonees and Hormo- 

 gonees (changed to Coceogonales and Hormogonales by Atkinson, 1905, p. 163) 

 for the two tribes of Thuret. The name Hormogonales is still accepted by many 

 phycologists but the designation Coceogonales has been abandoned in favor of 

 Chroococcales, which was proposed by Wettstein (1924). 



Borzi had already in 1878 divided the order Nematogenae of Rabenhorst into 

 the two suborders Hormogoneae and Cystogoneae. The latter suborder included 

 only his new family Chamaesiphonaceae (p. 238) whereas the former received 

 the Nostocaceae, Scytonemataceae, Rivulariaceae, and Oscillatoriaceae. Borzi 

 placed, as others before him had done, the Chroococcaeeae in an order by itself, 

 which he called Gloeogenae. Following up the train of thought of Borzi, Hans- 

 girg (1892, p. 17) divided the bluegreen algae into the three orders Gloeosipheae 

 (= Hormogonales), Chamaesiphonaceae, and Chroococcoideae. The order Cha- 

 maesiphonaceae received attached, unicellular (Chamaesiphon) or filamentous 

 {Clasiidium) forms, which occur as solitary individuals or as colonies, lack hor- 

 mogonia and heterocysts, and multiply by spores (endospores) produced in ba- 

 sipital succession. 



Finally in 1924 Wettstein proposed the currently accepted designation Cha- 

 maesiphonales for the family Chamaesiphonaceae. 



In his treatment of the Schizophyceae in De Toni's Sijlloge algarum, Forti 

 (1907) followed the classification of Kirchner. Borzi, shortly afterward in a 

 series of papers (1914, 1916, 1917), presented a revision of his earlier (1878, 

 1879, 1882) classification of these algae. Some of the new features of this sys- 

 tem were later adopted by Geitler in the development of his system. 



By the year 1925, the Schizophyceae had thus by degrees come to be segregated 

 into three orders and a total of 14 families, including one (Microchaetaceae) w^hich 

 had been erected by Lemmermann in 1907, two (Hyellaceae and Borziaceae) 

 which were established by Borzi in 1914, and three (Nodulariaceae, Lepto- 

 basaceae and Loefgreniaceae) which were created by Elenkin in 1916 and 1917. 



In 1925 (a and b) Geitler published a system which formed a radical depar- 

 ture from previous classifications. He divided the bluegreen algae into seven 

 orders and a total of 19 families. Shortly afterward Geitler (1930-1932) aban- 

 doned in part his sj'stem of 1925 and recognized only the three old orders Chroo- 

 coccales, Chamaesiphonales, and Hormogonales. At this time Geitler regarded 

 the Schizophyceae as comprised of 21 families, the majority of which were the 

 same as those accepted in 1925 but some of the ones recognized in 1925 were 

 reduced and several new ones were added. In 1942 (pp. 37 ff.) Geitler returned 

 in part to his system of 1925 and recognized four orders (Chroococcales, Pleuro- 

 capsales, Dermocarpales, Hormogonales) and 22 families. 



In 1938 and 1949 appeared the first and second fascicles, respectively, of the 

 systematic part of Elenkin 's monumental work on the freshwater and terrestrial 

 Schizophyceae of Russia. Elenkin elaborated upon Geitler's systems of 1925 

 and 1930-1932, and recognized, as far as the groups under consideration by him- 

 self were concerned, no fewer than 12 orders and 47 families. 



