Phylum Phaeophyta [ 87 



Filamentous or thallose brown algae with haploid and diploid stages equally de- 

 veloped, producing large spores without flagella, solitary or few in the sporangia. 



Here are placed two families, Tilopteridea and Dictyotacea. 



Family Tilopteridea [Tilopterideae] Cohn is a small group, apparently known 

 only from European coasts. They are evidently closely related to the Ectocarpea. 

 They consist of branching filaments which may become pluriseriate. In Haplospora 

 (poorly known; but Tilopteris and other genera are even more so), the haploid stage 

 bears both plurilocular structures, releasing minute swimming cells of the structure 

 usual in brown algae, and unilocular structures which release their contents as single 

 uninucleate protoplasts without flagella. The diploid stage bears only unilocular 

 structures which release their contents as single quadrinucleate non-motile spores. It 

 is inferred that the swimming cells from the plurilocular structures are sperms, and 

 that the protoplasts released from the unilocular structures on haploid bodies are 

 eggs, capable, however, of reproducing the haploid stage if not fertilized; further, 

 that the nuclei of the quadrinucleate spores released by diploid individuals are hap- 

 loid, and become on germination the nuclei of as many cells of the haploid body. 



The Tilopteridea are believed to represent the evolutionary transition between 

 Ectocarpea and the following family. 



Family Dictyotacea [Dictyotaceae] (Hauck) Kjellmann includes about twenty 

 genera, Dictyota, Zonaria, Padina, etc., with about one hundred species which are 

 commonest on the coasts of warmer oceans. They are thalli of moderate size, erect 

 and dichotomously branched or appressed and fan-shaped. They grow by the division 

 of a single apical cell or a row of apical cells in each branch. The cells multiplying 

 behind the apical cells become differentiated into two tissues, superficial small cells 

 rich in plastids and internal larger ones with fewer plastids, forming in different 

 species single or multiple layers of cells. 



The Hfe cycle has been studied by Mottier (1898, 1900), Williams (1898), and 

 Haupt (1932). There are distinct male haploid individuals, female haploid indivi- 

 duals, and diploid individuals, all of the same vegetative structure. The males pro- 

 duce sperms from clusters of densely packed plurilocular antheridia. The females 

 produce eggs solitary in large oogonia solitary or clustered on the thalli. The eggs 

 are without flagella. The diploid individuals produce unilocular sporangia of much 

 the same structure as the oogonia. In Zonaria, each sporangium produces eight non- 

 motile spores; in Dictyota, each one produces four. 



Order 4. Sporochnoidea [Sporochnoideae] Greville Alg. Brit. 36 (1830). 

 Order Chordarieae Greville op. cit. 44. 

 Order Chordariaceae Haeckel Gen. Morph. 2: xxxv (1866). 

 Orders Desmarestiales and Chordariales Setchell and Gardner in Univ. Califor- 

 nia Publ. Bot. 8: 554, 570 (1925). 

 Order Sporochnales Sauvageau in Compt. Rend. 182: 364 (1926). 

 Brown algae producing motile spores, the haploid stage reduced to scant undiffer- 

 entiated filaments, the diploid stage filamentous or thallose, when thallose with apical 

 growth. Ralfsia is an exception to the formal characters of the order: it has a haploid 

 stage of the same structure as the diploid. This is a rather miscellaneous assemblage, 

 rather arbitrarily separated from Phaeozoosporea on the one hand and from Lamin- 

 ariea on the other. 



The haploid body of the form of a short-lived body of a few undifferentiated fila- 

 ments, like a reduced Ectocarpus, bearing gametangia reduced to single cells, has 



