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



But unfortunately I have not been successful and therefore 

 I am forced to adhere to my former position. As there men- 

 tioned this species was found upon Acanthophora spicifera (Vahl) 

 Børgs. From the basal cell which to begin with is roundish and 

 thickwalled (Fig. 41 E) short creeping fdaments grow out ; some 

 of these are epiphytic creeping upon the surface of the Acantho- 

 phora, others penetrate into the tissue of the host-plant (Figs. 41 

 F, G, H, I) but it sometimes happens that young plants occur 

 which are not at all parasitic. From the basal layer several 

 erect fdaments gradually arise. The cells are usually a little 

 constricted at the cross-walls; they contain a well-developed 

 parietal chromatophore with a large lateral pyrenoid. The cells 

 are about 8^ broad and about 20// long and mostly 21/, times 

 as long as broad with some variations. The filaments are usually 

 only slightly branched in the lower part, more so higher up; the 

 side-branches grow out at an acute angle from the mother-branch 

 and in well-developed plants the branches are again multilaterally 



ramified. 



Most of the specimens had monosporangia ; these are ovate- 

 oblong, 6/z broad and 10// long, as a rule sessile, more rarely 

 pedicellate, serially arranged upon the upper side of the branches. 

 Sporangia divided into two spores were only found in few plants ; 

 these are larger than the monosporangia, oval, about 9/< broad 

 and 14// long; they are mostly sessile, sometimes pedicellate 

 or placed upon short branchlets. In my former description I 

 remarked that a single sporangium was found in which the 

 upper half was again divided by a vertical wall. How far this 

 suggests that the plant in reality has tetraspores, the specimens 

 found representing only a young state of development, can only 

 be settled by means of more material. 



Acrochætium bisporwn has been found only once, in the Harbour of 

 St. Thomas. 



Geogr. Distrib., Danish West Indies. 



14. Acrochætium occidentale nov. spec. 



Thallus usque ad 1 — 2 mm altus, e fdis erectis ramosis spor- 

 angiferis et filis endophyticis constructus. 



Spora in filamentis assimilatoricis hospitis germinans, magna, 

 ovata — globularia, e parte basah fila circum filamenta hospitis 

 repentia, e parte superiori filum erectum singulum gignit. 



Filum erectum inferne nudum media parte ramosum, ramis 

 sparsis ad apicem versus attenuatis instructum. 



