F. Børgesen: Rhodophyceæ of the Danish W. Indies. 215 



find the most closely related forms in the group of Spermothamnieæ. 

 In this group, as in the case of our plant, the procarp is termi- 

 nally placed and after the fertilization the cystocarp is more or 

 less covered by fdaments in a similar way as in our plant. Judg- 

 ing by the figure of Ptilothamnion Pluma given by Bornet ') the 

 procarp in this plant seems to be exactly like that in the present 

 one. In other genera, e. g. Spermothamnion we have two auxili- 

 ary cells; but, if we consider the halfpart to the right of the 

 schematic figure of the procarp of this genus given by Oltmanns' 

 in Handbuch, p. 705, it is easily seen that this is exactly like 

 the procarp in our plant. 



As to the antheridial stands these, too, show likeness to those 

 found in the same group; comp., e. g., the figure 2 of Spermo- 

 thamnion flabellatum Born, given by Bornet et Thuret, 1. c, pi. 8. 

 Closely resembling the antheridial stands of our plant are those 

 found in Antithamnion Plumula judging from the figure of 

 BuFFHAM^). Much alike too, are, the antheridial stands of Compso- 

 thamnion gracillimum as represented by the same author^). In 

 Callithamnion, on the other hand, the antheridial stands mostly 

 form small cushions like those I have described and figured for 

 Callithamnion cordatum; for Callithamnion byssoides Buffham has 

 figured (1. c, 1884, pi. X, fig. 5) the antheridial stands of this 

 plant, these showing very great likeness to the present one, but 

 the West Indian specimens of C. hijssoides found by me had the 

 low, cushion-like, antheridial stands commonly found in Calli- 

 thamnion. 



In Engler und Prantl, Die Natiirl. Pflanzenfamihen, I. Teil, 

 Abt. 2 the Fam. Ceramiaceæ is divided in 15 groups; it seems 

 to me on account of the above mentioned facts that our plant 

 must be considered as the representative of a new group : Meso- 

 thamnieæ forming an intermediate link between the groups Calli- 

 thamnieæ and Spermothamnieæ. 



]\|iie Vickers in her "Liste des Algues mar. de la Barbade" 

 (Ann. sc. nat. Bot. 1905, p. 65) mentions a "Callithamnion? sp. 

 nov. ? A des anthéridies cylindriques, comme les Pleonosporiiim, 

 mais les sporanges ne renferment que quatre spores en tetraedres. 



1) Bornet, E. et G. Thuret, Notes algologiques, p. 179, pi. 46, fig. 1. 



2) Buffham, T. H., Notes on the Florideæ and on some newly-found 

 Antheridia (Journ. Queckett Microscop. Club, vol. I, Ser. II, 1884, pi. 

 XI, fig. 2). 



3) Buffham, T. H., Notes on some Florideæ (Journ. Queckett Microscop. 

 Club, vol. VI, ser. II,' 1896, pi. X, fig. 12—13). 



