PAPENFUSS: CLASSIFICATION OF THE ALGAE 183 



pistils. But we do not know wliether any process similar to fertilization takes place with 

 the spores of these algae. 



Niigeli (1847) divided the algae into two classes: (1) "Algae," which lack 

 sexual reproduction, and (2) "Floridcae," which reproduce sexually. He re- 

 garded the tetrasporangia of the Florideae as female sex organs which produce 

 four spores, the antheridia of C. Agardh and others he considered male sex or- 

 gans wliich produce sperms, and the cystocarps he regarded, in agreement with 

 Decaisne, as structures of vegetative reproduction. Ruprecht (1851, pp. 205- 

 206), on the other hand, thought the tetraspores corresponded to the pollen and 

 the carpospores ("Samen") to the seeds of phanerogams. He thought the an- 

 theridia produced sperm cells, which were lacking in phanerogams, although 

 this had not yet been established. It is evident that Ruprecht, like earlier botan- 

 ists and those of the following fifty years, did not understand tlic role of the 

 tetrasporangia in the life history of these algae. 



Thuret (1851) illustrated and described in unqualified terms as antheridia, 

 structures which he studied in several red algae and their contents as anthero- 

 zooids (a term proposed by Derbes and Solier, 1850, p. 263), although he was 

 unable actually to determine their role inasmuch as he found that both the car- 

 pospores and the tetraspores would germinate without having been in contact 

 with the "antherozooids." Thuret 's observations were confirmed by Pringsheim 

 (1855). 



Finally, Bornet and Thuret in 1866 and 1867 for the first time clearly de- 

 scribed sexual reproduction in a number of red algae. They determined the na- 

 ture of the female apparatus, which Nageli (1861) had observed but had misin- 

 terpreted, and saw the spermatia attached to and coalescing with the trichogyne. 

 Bornet and Thuret's discovery that the female gamete is produced in the ter- 

 minal cell of a special filament, the carpogonial branch, and that tliis gamete is 

 not liberated from the gametangium explained in large part why sexuality had 

 eluded the various earlier investigators. From what was known about sexual 

 reproduction in other groups, it was thought the female gamete would be an 

 individualized protoplast like the egg of Fucus or of Volvox. 



The observations by Bornet and Thuret were extended by themselves (1876, 

 1878, 1880), Solms-Laubach (1867), Janczewski (1876), Schmitz (1879b, 1883) 

 and others. Schmitz (1883) w^as the first to observe that in certain red algae 

 the fertilized carpogonium produces filaments that fuse with a neighboring cell, 

 which he (p. 229) termed the auxiliary cell, and that the gonimoblast develops 

 from this cell. He thought that a second fusion of nuclei occurred in the auxil- 

 iary- cell and that red algae consequently showed a double fertilization. He 

 anticipated the skepticism that his interpretation of this phenomenon would 

 generate, for he wrote (p. 246) : 



Einen zweimaligen Befruchtungsact im Entwickelungskreis einer einzelnen Species 

 anziinehmen, dagegen straubt sich jedoch zur Zelt die botanische Anschauung voUstandig, 

 das widerspricht aller Tradition. 



Oltmanns (1898) later showed that no fusion of nuclei occurs in the auxiliary 

 cell, which receives a fusion (diploid) nucleus from the connecting filament but 

 whose own (haploid) nucleus migrates to one side of the cell and plays no part 

 in the ensuing development. 



