462 



Dansk Botanisk Arkiv, Bd. 3. Nr. 1. 



From the creeping filaments the 

 erect ones arise. These are mostly 

 simple, bearing now and then — for 

 the most part in their upper end — 

 one or more branches but never many. 

 The erect filaments are nearly cylin- 

 drical; they are 24— 27— Sl/i thick. 

 The length of the cells about 70- 80;i. 



A few tetrasporangia were found 

 (Fig. 422 b). They were sessile, 

 roundish-subreniform in shape with 

 a thick periferal wall, about 45 u 

 broad and 50 /^ long. The spor- 

 angia occurred upon the main fila- 

 ment. 



The plant was gathered near 

 the shore in a rather exposed rocky 

 locality; it had tetrasporangia in 

 the month of January, 



St. Croix: White Bay. 



Griffithsia globifera (Harv.) J, Ag. 



94. Griffithsia tenuis Ag. 



C. Agardh, Spec. Alg., vol. II, p. 131. J. Agardh, Spec. Alg. vol. II, 

 p. 84; Epicrisis, p. 70. Collins and Hervey, Alg. Bermuda, p. 135, pi. VI, 

 figs. 88—39. 



Griffithsia thyrsigera Askenasy, Forschungsreise "Gazelle", IV Theil, 

 Bot., p. 36, pi. IX, figs. 1 and 4. 



Callithamnion tenue Harvey, Nereis Bor.-Am., part III, p. 130. 



Creeping upon some larger algæ I have found some well 

 developed tetrasporic specimens of this plant (Fig. 423). 



As pointed out by Collins and Hervey the Griffithsia 

 thyrsigera Askenasy and Callithamnion tenue of Harvey do be- 

 long to this species.. Regarding Askenasy's description of the 

 tetrasporic plant, some differences are certainly present, but 

 this is, as indicated by Collins and Hervey, most probably 

 due to the more luxuriant development of the West Indian plant. 



Griffithsia tenuis forms very loose tufts composed of the ir- 

 regularly ramified filaments. It is fixed to the host plant by means 

 of vigorous rhizoids breaking out from the decumbent creeping 



Fig. 422. Spermothamnion inve- 

 stiens (Grouan) Vickers, a, part 

 of a plant, b, part of a filament 

 with sporangia, (a, about 70: I; 

 b, about 140:1.) 



93. 



