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



Now and then from these cells erect filaments arise penetra- 

 ting through the epidermal layer of the host plant (Fig. 55). The 

 erect filaments reach a length of up to 500 /z. Below they are 

 about 7 — 8,« thick and the length of the cells about 24^. Up- 

 wards they taper gradually and end with long nearly colourless 

 hair-like threads; the cells in these threads may reach a length 

 of up to bO/u or more and are 2 — 3// thick. 



The erect filaments are multilaterally or very seldom oppo- 

 sitely ramified and the branches taper in the same way into hair- 

 like ends. 



The chromatophore (Fig. 55) is parietal with lobed margin 

 and with a lateral pyrenoid often projecting considerably into 

 the interior of the cell. 



The sporangia (Figs. 55, 56 o, b) are placed at the base of 

 the branches or upon branchlets. They are nearly always pedi- 

 cellate, but now and then the uppermost sporangium is sessile. 

 The sporangia are oblong, about 14^ long and 8;z broad. 



Found only once in a sheltered locality in shallow water. 



St. Thomas: The Harbour. 



20. Acrochaethim phacelorhizum nov, spec. 



Thallus cæspitosus ad 1 mm altus et ultra, e filis endophy- 

 ticis et fihs erectis ramosis sporangiferis compositus. 



Fila endophytica inter assimilatores hospitis immersa, sæpe 

 aggregata, in superiori parte ramosa, e cellulis ca. 40// longis et 

 22 — 25, raro 27// latis orta. 



Fila erecta, apicem versus sensim attenuata, a basi ramosa. 

 Rami in superiori parte filorum numerosi, sparsi aut sæpe uni- 

 seriati. 



Chromatophorum parietale pyrenoide laterali instructum. 



Monosporangia sessiha, sparsa aut seriata, oblonga, 12 — 14// 

 lata, 22—24/« longa. 



This plant was found upon Codium elongatum and isthmocladiim 

 among the utricles of which the basal part is immersed while the 

 upper free-growing filaments form tufts about 3 — 4 mm high. 



Some small differences were present in my specimens; I shall 

 first describe those found in Codium elongatum. 



The basal part (Fig. 57) consists of proportionally very thick 

 filaments creeping downwards along the wall of the utricles and 

 between them; in the uppermost end the endophytic filaments 

 are ramified sending downwards from the lower end of the cells 



