Phylum Rhodophyta [ 49 



This order, in all recent literature called Gigartinales, is a numerous and varied 

 one. The bodies are generally erect; they may be cylindrical or flattened, unbranched 

 or branched. In some examples, Haliarachnion, Rhodophyllis, Sebdenia, the zygote 

 sends out extensive filaments, which make contact with unspecialized cells scattered 

 in the body. In other examples, the zygote makes contact with a lower cell of the 

 carpogonial filament. In either case, the cells with which contact is made are auxiliary 

 cells and give rise to cystocarps; these produce carpospores, and the carpospores pro- 

 duce tetrasporic individuals. Certain species of Phyllophora, Gymnogongrus, and 

 Ahnfeldtia are exceptional in producing tetraspores in the place of carpospores; these 

 species have no free-Uving tetrasporic generation. In these organisms, as contrasted 

 with Liagora tetrasporifera, it is believed that this type of Ufe cycle has been estab- 

 lished by reduction of a longer one. 



Kylin (1932) assigned twenty families to this order. Gracilaria is a minor source 

 of agar agar. Gigartina mammilosa and Chondrus crispus (Irish moss or carageen) 

 are well known as yielding a jelly, carageenin, resembling but distinct from agar agar 

 (Tseng, 1945). 



Various abnormal growths on red algae have been found to be parasitic red algae, 

 almost always on hosts closely related to themselves (Setchell, 1914). To the present 

 order belong Gardneriella and its host Agardhiella; Plocamiocolax and its host Plo- 

 camium; Gracilariophila and its host Gracilaria (Wilson, 1910). 



Order 3. Gelidialea [Gelidiales] Kylin in Kgl. Svensk. Vetensk.-Akad. Handl. 

 63, no. 11: 132 (1923). 

 Family Gelidieae Kiitzing (1843). 

 Order Gelidieae J. Agardh Sp. Alg. 2: 464 (1851). 

 Heterocarpea in which the zygote sends out a single elongate filament which makes 

 contact successively with several chains of nurse cells and gives rise to carpospores; 

 bodies consisting of branched filaments, the ultimate tips of the lateral branches 

 compacted into a firm layer covering a branching body, cylindrical or flattened; the 

 surface adjacent to the masses of carpospores pushed out and punctured by pores 

 through which the spores escape. 



There is a single family Gelidiea [Gelidieae] Kiitzing ( Family Gelidiaceae Schmitz 

 and Hauptfleisch). Such economic importance as the red algae possess lies chiefly in 



Fig. 7 — a, Thallus of Nemalion multifidum x 1. b, c, d^ production of sperms; 

 beginning of production of carpospores; and cluster of carpospores of Nemalion 

 multifidum after Bornet and Thuret (1867). e, Thallus of Chondrus crispus x 1. 

 {, Reproduction of Dudresnaya purpurifera (order Furcellariea or Cryptonemiales) 

 after Bornet and Thuret, op. cit. The trichogyne, whose free end with attached 

 sperms is seen above, is irregularly twisted below; it leads to the egg (carpogonium); 

 connecting filaments, growing from cells below the egg, make contact with auxiliary 

 cells at the summits of specialized filaments; each auxiliary cell gives rise to a cluster 

 of carpospores. g, Thallus of Delesseria sinuosa x 1. h^ Longitudinal section of 

 conceptacle of Polysiphonia nigrescens x 500, after KyUn (1923). The zygote z is 

 the fourth and terminal cell of the carpogonial filament whose connection with the 

 supporting cell b is not shown; the auxiliary cell a has grown from the supporting 

 cell after fertilization. 



