Phylum Rhodophyta L 43 



a moderately large stainable granule; outside the plastid, a single additional granule 

 can usually be found. When a cell is to divide, the granules break up into consid- 

 rable numljers of smaller ones, some of which become organized as a system of strands 

 forming an irregular network on the surface of the plastid. The protoplast, the 

 network, and the plastid undergo constriction; the processes by which the daughter 

 cells return to the original structure were not clearly seen. Interpretation of these 

 observations is difficult. It is possible that the granule outside of the plastid is a 

 nucleus of the type of those which have been observed in Bangia and Porphyra. 



Family 2. Rhodochaetacea [Rhodochaetaceae] Schmitz in Engler and Prantl Nat. 

 Pflanzenfam. I Teil, Abt. 2: 317 (1896). Family Goniotrichaceae Smith Freshw. 

 Algae 121 (1933). Branching filaments, sometimes becoming multiseriate by length- 

 wise division, the vegetative cells capable of escaping and functioning as spores. 

 Sexual reproduction unknown. Asterocystis, uncommon, in fresh water; the remain- 

 ing genera marine, epiphytic on other algae. Goniotrichum. Rhodochaete and Gonio- 

 trichopsis, the cells with numerous plastids. 



Family 3. Porphyrea [Porphyreae] Kutzing (1843). Family Porphyraceae Raben- 

 horst 1868. Family Bangiaceae (Nageli) Schmitz (in Engler and Prantl, 1896). 

 Filaments or thalli of a red or purple color; the cells, in producing spores, may re- 

 lease their protoplasts as wholes or may undergo division into many. Rosenvinge 

 (1927) observed the active motion of these spores. 



The most important genus is Porphyra; the individuals are thalli up to several 

 centimeters in diameter, on rocks or other algae in ocean water along coasts. They 

 are called purple lavers, tsu'ai, amanori; they are used as food, for making soup or in 

 condiments, and are extensively cultivated in Japan (Tseng, 1944). Bangia is either 

 freshwater or marine; in structure it differs from Porphyra in having filementous 

 bodies, uniseriate or pluriseriate. 



During nuclear division in Porphyra tenera as described by Ishikawa (1921), polar 

 appendages form at both ends of the nucleus, which becomes elongate and appears 

 to consist of three strands. The strands break transversely, and each set of three fuses 

 into a mass. Dangeard (1927), dealing with Porphyra umbilicaris and Bangia fusco- 

 purpurea, observed nuclei 5^ in diameter, each consisting of a karyosome, that is, a 

 mass of chromatin, lying in a clear space surrounded by a membrane. In mitosis, the 

 membrane and the unstained matter disappear. Polar appendages grow out from the 

 karyosome, and their tips become cut off as granules which may be regarded as cen- 

 trosomes. The remainder of the karysome becomes organized as two masses, evidently 

 chromosomes, connected to the centrosomes by fibers. Each chromosome divides into 

 two; the daughter chromosomes move to the centrosomes and fuse with them to form 

 karyosomes about which new membranes appear. This description represents a defi- 

 nite, if primitive, process of mitosis. 



Sexual reproduction, here where we first encounter it, involves differentiated ga- 

 metes. Naked sperms, indistinguishable from spores, move to the surface of other 

 cells which function as eggs. A strand of protoplasm grows through the gelatinous 

 wall of the egg from the sperm to the egg protoplast, and the protoplast of the sperm 

 migrates through the passage thus formed. The zygote divides two or three times, 

 producing spores. During the first two divisions, the two masses of chromatin which 

 appear are somewhat different in appearance from the vegetative chromosomes 

 (Dangeard, op. cit.); it may be supposed that these masses are tetrads and diads, and 

 that the divisions are meiotic. Evidently, this is a life cycle of the primitive type, 

 in which all cells except the zygotes are haploid. 



