F. Børgesen: Rbodophyceæ of the Danish W. Indies. 



35 



Fig. 29 b shows a supposed yoimg plant. The germinating 

 spore has given off a single cell, the earliest beginning of the creeping 

 basal filaments, and from this cell an erect filament arises. 



In the full grown plant a great number of erect filaments 

 grow up from the inner part of the basal part ; those in the 

 middle are straight, those in the periphery are bent outwards. 

 In the lower part the filaments are about 9 — 10/^ broad tapering 

 somewhat towards the summit where the diameter of the cells is 

 only about 6 — 7 fi. The cells are about 2 — 3 times as long as 

 broad in the basal part, reaching a length of about 18 — 35//; in 

 the upper part the length is about 30 — ?>b ft. 



The cells contain a parietal chromatophore (Fig. 30) with 

 longer or shorter prolongations along the wall of the cell and a 

 large lateral pyrenoid protruding greatly into 

 the interior of the cell. 



The sporangia are situated upon small 

 secund mostly two-celled branchlets (Fig. 

 29 a) ; they are placed on the upper, inner 

 side of the branches upwards from the 

 axils. They are ovate-oblong (Fig. 30) ; 14 — 

 16// long and 9 — 10 /< broad. 



This species is evidently nearly related 

 to Acrochætiiim Sagræaniim Bornet i). I 

 have compared my specimens with the large 

 plant distributed in Phycotheca Bor.-Am. 

 Nr. 39 under the name of Chantransia 



Fig. 



30. Acrochætium 

 flexuosum Vickers, a, 

 part of a filament with 

 sporangia - bearing 

 virgatula and upon which Bornet has partly branchlet. b, a spor- 



based his description of this species. But ^"^'"JioTt'TOrir""^" 

 the present species is \ much smaller and 



differs among other things by having proportionally shorter cells. 

 This species seems to be common upon Chætomorpha antennina 

 of which the ends of the filaments often are red coloured by the 

 epiphyte. 



St. Croix: Northside. 

 Geogr. Distrib. : Barbados. 



10. Acrochætium unipes nov. spec. 



Thallus usque ad 2 mm altus, a basi ad apicem versus attenuatus. 

 Spora germinans, deorsum prolongationem subsphæricam endo- 



^) Bornet, E., Deux Chantransia corj/mbiferaThuret. Acrochætium et Chan- 

 transia (Bull. Soc. Bot. Fr., t. 51, 19ü4, p. XXI). 



3* 



