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



Most of the branches soon stop their growth and become 

 short spiny branchlets (Fig. 285), a few assume continuous growth 

 hke the main filament. As pointed out by Falkenberg the short 

 branchlets grow somewhat longer than those of Bryothamnion 

 triquetriim; they have generally from four to six side-branches, 

 and the nethermost are again ramified, having three to four 

 spiny ramuli, while the uppermost are reduced to spines. 



At the ends of these spinehke branchlets, in any case in the 

 3^ounger part of the plant, we find a few trichoblasts. These are 

 often considerably developed, being dichotomously ramified seve- 

 ral times. As all the filaments in these trichoblasts are erect and run 

 together, nearly parallel, they form a rather dense bush. One of 

 the largest trichoblasts I have seen had in the basal part cells 

 about 35 // thick. These cells were nearly spherical in shape, being 

 much narrowed at the cross wall ; the cells taper evenly upwards 

 towards the summit of the filaments, the uppermost were only 

 6 — 7 ^ thick. A transverse section of the thallus shows 8—9 peri- 

 central cells with a thick parenchymatic tissue on both sides 

 (Fig. 286). 



The material gathered was quite sterile. 



This plant was dredged in rather deep water about 30 meters. 

 A single specimen was found washed ashore. 



It seems not to be common on the shores of the islands. 



St. Jan: Off Annaberg and off America Hill. St. Thomas: Near 

 Thatch Cay. St. Croix: Sandy Point (washed ashore). 



Geogr. Distrib.: West Indies, Mexico, Brazil; coast of Guinea. 



Subfam. 4. Herposiphonieae. 

 Herposiphonia Nagl. 



1. Herposiphonia tenella (C. Ag.) Nagl. 



Nägeli, c, Herposiphonia (in Schleiden und Nägeli, Zeitschrift für 

 wissenschaftl. Botanik, ^Ia. Heft, Zürich 1846, p. 238, tab. VIII.). Ambronn, 

 H., in Bot. Zeitung, 1880, p. 197, pl. IV. Falkenberg, P., Rhodomelaceen, 

 p. 304. 



Hutchinsia tenella Ag., Spec. Alg., vol. II, p. 105. 



Polysiphonia tenella J. Ag., Algæ Mediter., p. 123; Spec. Alg., vol. II, 

 p. Ill, p. 919. 



In describing the plant I at first refer to specimens collected 

 at St. Croix. These specimens (cfr. Fig. 287) seem in all essentials 

 to agree with the descriptions of Ambronn and Falkenberg. 



