NO. 8 DAWSON : A REVIEW OF THE GENUS RHODYMENIA 131 



Harvey. Both this and the preceding species are said to have acute, at- 

 tenuated apices which distinguish them from all others. 



Distribution. — The type specimen from Port Cooper, Bank's Penin- 

 sula, New Zealand. 



(7) RHODYMENIA ERYTHRAEA Zanard., Plant. Mar. Ruhr, 

 enum. (1858), p. 276; Piccone, Algol. Eritrea (1884), p. 328; 

 Rhodymenia palmata Mont., Pugill. Alg. Yemens, p. 8 (excl. 

 synon.) non aliorum. 



Of this species we have only a description. The best we can do is to 

 interpret it according to the two suggestive statements it contains : "Ap- 

 pearance wholly like R. palmata. Tetraspores scattered over the whole 

 surface." More material from the Red Sea may eventually establish this 

 species as a definite entity. 



Distribution. — The tj^pe specimen from the Red Sea at Hodeida; 

 also on the coast of Yemen. 



Section 2. Palmatae J. Ag. p. p. (Epicr., 329 (1876) ; Palmaria 

 Stackh., Tent. mar. crypt., 69 (1809)) 

 Of this section the tetrasporic material available of R. palmata and 

 the descriptions and illustrations of fertile specimens of other species 

 within the group establish fairly well certain morphological relationships 

 among the 7 species at present included. Two features of tetrasporic 

 plants are distinctive: the sorus, present as an irregular, cloudlike, dis- 

 connected, or convoluted body, definitely limited and distinct from the 

 portions of the frond in which tetraspores are not being produced ; the 

 frond, somewhat thickened in the soral regions because of extra cell 

 division and growth stimulated by the tetrasporic development in the 

 cortical layers. At the maturity of spores, their enlargement and conse- 

 quent displacement of the surrounding cells cause an irregularity in the 

 otherwise smooth outline of the frond-surface. The cortical layer, which 

 in sterile fronds may be only 2 or 3 cells thick, increases by periclinal 

 divisions to from 4 to 7 in tetrasporic fronds. This increase in the cortex 

 causes the cells to appear more or less in strings or anticlinal rows, but the 

 displacement or pushing aside of these by the enlarging spores destroys 

 much of the regularity. The appearance of the spore, however, imbedded 

 in the thickened cortex, surrounded by these rows or strings of cells gives 

 the impression of a nemathecium (plate 18, figs. 3-4), and in both section 

 Palmatae and section Clinophora the term "nemathecial" will be used to 

 describe this condition. 



