PAPENFUSS: CLASSIFICATION OF THE ALGAE 131 



For a long time a great deal of misunderstanding existed regarding the na- 

 ture of the reproductive organs of these plants and this more than anything 

 else was responsible for the differences of opinion among early botanists as re- 

 gards the systematic position of the group. Some authors, as for example De 

 Jussieu (1789), regarded the antheridium as an anther and the oogonium as a 

 pistil and consequently placed these plants among the phanerogams. The first 

 to disagree with such an interpretation of the reproductive organs were Wallroth 

 (1815) and Bischoff (1828) , although neither of them understood their true nature. 



Vaucher (1821), Kaulfuss (1825), and Bischoff (1828) studied the germi- 

 nation of the zygospore and thereby threw light on one phase of the reproduc- 

 tion of these plants. The function of the antheridium remained doubtful until 

 Thuret in 1840 (see also his paper of 1851) discovered that flagellated sperms 

 were produced in it. Braun (1852, 1853), Pringsheim (18G3a, 1863b), Sachs 

 (1874) and De Bary (1875) contributed further to the knowledge of the struc- 

 ture of the thallus, the development of the reproductive organs, and the germi- 

 nation of the zygospore, and De Bary (1872) studied in detail the process of 

 fertilization. Oehlkers in 1916 produced convincing evidence that the thallus 

 is haploid, meiosis occurring at the germination of the zygospore. (The belief 

 of Tuttle [1926] that the plants are diploid, with meiosis occurring during the 

 early development of the sex organs, appears to be based upon inaccurate 

 observation. ) 



In addition to contributing a great deal to knowledge of the structure of 

 the thallus and the reproductive organs, Braun in a long series of publications, 

 especially those from 1849 onward, laid the foundation upon which the present 

 classification of the Charophycophyta is based. At the time of his death he had 

 in an advanced stage of preparation a monograph of the species of the world, 

 which was completed by Nordstedt (see Braun and Nordstedt, 1883). In more 

 recent times important contributions to the taxonomy of the group have been 

 made especially by Migula (1890-1897, 1925), Groves and Bullock- Webster 

 (1920, 1924) and Zaneveld (1940). Wood (1952) has given a list of the described 

 species. In addition to the family Characeae, to which are referred all the liv- 

 ing species as well as certain fossils. Peck (1946) recognizes three fossil fami- 

 lies— Clavatoraceae, Trochiliscaceae, and Sycidiaceae. Miidler (1953) divides 

 the fossil charophytes into three orders and a total of six families as follows : 

 Sycidiales, with the family Sycidiaceae ; Trochiliscales, with the family Trochilis- 

 caceae; Charales with the families Palaeocharaceae, Clavatoraceae, Lagynopho- 

 raceae, and Characeae. 



Although knowledge of the Charophyceae has progressed far beyond the stage 

 when there was disagreement as to whether these very ancient plants were flow- 

 ering plants, vascular crytogams, or nonvascular crytogams, a great deal of un- 

 certainty still exists as to the exact phylogenetic position of the group. Cohn 

 (1872a, 1872b, 1880) placed them as an order, Phycobryae, in the Bryophyta, 

 to which phylum they were also referred by Bennett (1878, 1879), who appar- 

 ently was not aware of Cohn's classification, and by various other botanists of 

 the last century and by Hy as recently as 1913. 



Current opinion is divided on whether the Charoj)hyceae belong with the green 

 algae or constitute an autonomous pliylum, and, if so, whether this phylum be- 

 longs in the algae or occupies a position higher than the thallophytes. 



