— 15 — 



The plant is not corticated. It is riclily ramified on all sides^ 

 in the uppermost part subdichotomously. 



Both the younger and older cells have only a single nucleus 

 (Fig. 8 J5, F), in accordance with the description of Schmitz^). 

 The parietal chromatophores are thread-like, shorter or longer, and 

 irregularly sinuated (Fig. 8 B, E, F). 



I have found plants with tetraspores, antheridia and cysto- 

 carps, which all occur on separate individuals. 



The tetraspores are sessile on the uppermost and inward-turned 

 side of the mother-cells (Fig. 8 B, C), when young they are oval or 

 obovate, when quite developed nearly spherical; they are commonly 

 tetrahedrally divided more seldom cruciately (Fig. 8 C). 



Fig. 9. Seirospora occidentalis nov. spec, 



A, branch with nearly ripe cystocarp (40:1). B, young cystocarp (150:1). 

 C, U, procarps (150:1). 



The cystocarps are composed of two oppositely-placed gonimo- 

 blasts, which when ripe consist of the ramified moniliform threads 

 of the uniseriated, nearly spherical carpospores (Fig. 0^); the latter 

 are about 40— 42;^ broad. These peculiar seirosporic cystocarps 

 agree very well, apart from the form and size, with those found 

 in Seirospora Griffithsiana Harv. and which Bornet was the first 

 (Notes algologiques, I (1876) p. XIV) to explain as cystocarps in contra- 

 diction to the paraspores (seirospores) also occurring in this plant. 



^) Schmitz, Fr. , Die Gattung Microthamnion J. Ag. = 

 Ber. d. deutschen Ijot. Gesellscli., Bd. XI, 1893, p. 273. 



{Seirospora Harv.) 



