556 PAPENFUSS 



outside the order Oedogoniales that is known to possess swarmers with a 

 subterminal collar of flagella, the apparent existence of an intimate relation- 

 ship between it and Halicystis (which forms terminally bifiagellate gametes) 

 is a matter of far-reaching significance. In fact, Feldmann (1954) recently 

 removed Derbesia (and its gametophytic stage, Halicystis) from the Sipho- 

 nales and erected for it the order Derbesiales. 



Among the interesting discoveries of recent times are those showing that 

 even the Volvocales include forms with two photosynthetic and alternating 

 phases. Thus it has been shown by Strehlow (1929) and Behlau (1935) that 

 the unicellular quadriflagellate Chlorobrachis gracillima is the diploid stage 

 of the colonial Pyrobotrys gracilis. Behlau (1939) has also shown that 

 Carteria ovata is the diploid stage of Chlamydomonas variabilis. 



PHAEOPHYCOPHYTA 



By 1906 the details of sexual reproduction had been studied in only six 

 genera of brown algae: Fucus, Zanardinia, Cutleria, Ectocarpus, Giffordia, 

 and Dictyota. Fucus had been shown by Strasburger (1897) to be diploid, and 

 Yamanouchi in 1909a established that meiosis occurs during the first two 

 divisions of the primary nucleus of the oogonium and antheridium. Fucus 

 thus was shown to have a life history analogous to that of animals, and this 

 appears to be true of all Fucales. 



Reinke (1877, 1878) had obtained evidence indicating that Zanardinia 

 shows an alternation of isomorphic generations, and he (1878) and Falken- 

 berg (1879) were of the opinion that Cutleria showed an alternation of hetero- 

 morphic generations, with Cutleria representing the gametophytic generation 

 and another brown alga, long known by the generic name Aglaozonia, rep- 

 resenting the sporophytic generation. Yamanouchi (1909b, 1911, 1912, 1913) 

 furnished cytological proof of the correctness of Reinke and Falkenberg's 

 interpretations of the life histories of Zanardinia and Cutleria. 



In consequence of the observations of Reinke (1877, 1878), Falkenberg 

 (1879), Berthold (1881), Sauvageau (1896), and others concerning the 

 gametic role of the zooids from the plurilocular reproductive organs of Zanar- 

 dinia, Cutleria, Ectocarpus, and Giffordia, a firm conviction developed among 

 botanists (and was adhered to for almost half a century) that the plurilocu- 

 lar organs of brown algae were always gametangia and the unilocular organs 

 sporangia. Frequently it was observed that the zooids from the plurilocular 

 organs germinated directly. To explain this asexual behavior it was assumed 

 that the gametes had lost their sexual power and germinated parthenogeneti- 

 cally. 



Studying Pylaiella and the related Ectocarpus, Knight (1923, 1929) showed 

 that this explanation was incorrect. She demonstrated that brown algae have 

 two kinds of plurilocular organs — some occurring on haploid plants and func- 



