34 



in others it is reduced to an often narrow belt 

 lying a little above the middle of the cell. 



The sporangia are monosporous, oblong- 

 ovate, 9 11 13 fj. long, 69, mostly 7 8// 

 broad. They are as a rule sessile and usually 

 secundly seriated in long rows placed on the 

 inner (upper) side of the branches from the 

 base upwards (Fig. 25 a); but more scattered 

 sporangia also occur (Fig. 27) just as pedicellate 

 sporangia are by no means rare. 



The present plant has a great likeness to 

 Chantransia Hypnese but this differs in having 

 Fig. 28. Acrochse- endophytic basal filaments. Further it is also 



sp^'pirtTffiil- related to Acrochsetium flexuosum Vickers. But 



merits with spor- in this plant the monospores are secund upon 



ang 450 1) short ramuli, while in the present the ramuli are 



wanting, the monospores being placed in long 



series upon the branches. 



This species has been found mostly 

 in more sheltered localities. It seems 

 to be common. 



St. Croix: Coakley Bay, Christians- 

 sted, Lt. Princess, Sandy Point; St. Tho- 

 mas: The Harbour. 



9. Acrochsetium flexuosum Vickers. 



VICKERS, A., Liste des Algues de la 

 Barbade. (Ann. sciences nat. IX S6r., Bot. 

 1905, vol 1, p. 60). 



A quite certain determination 

 derived from the somewhat imperfect 

 diagnosis of M Ue VICKERS seems impos- 

 sible, and had the plant I now suppose 

 to be this species not grown upon 

 Chastomorpha antennina it had perhaps 

 not occurred to me to refer it to this 

 species. 



The plant found forms dense tufts 

 about 700 // high; it has a large base Fig. 29. Acrochxtium flexuosum 



composed of creeping filaments more Vickers. a, part of a filament 



showing branchlets with spor- 



or less fusing together in the inner an gia. b, a young plant. 

 part, (a, about 125:1. &, about 160 :1). 



