230 



are cylindrical 2 3 times as long as broad. In the basal part 

 of the branchlets the cells are about IQ/j. broad, tapering gradu- 

 ally upwards; the uppermost ones in the end of the filaments are 



often short, conical. The chro- 

 matophores consist of irregularly 

 shaped discs or short plates. 



At the summit of the young 

 branchlets long, thin hairs are 

 generally present (Fig. 218); these 

 hairs are about 3 p thick and 

 about 80 (JL long. Gland-cells did 

 not occur in this plant. 



As mentioned above the plant 

 was quite sterile, neither tetra- 

 sporangia, nor other reproductive 

 organs were found. 



This plant seems to come near 



Fig. 218. Antithamnion spec. Part 

 of an erect filament. (About 140 : 1). 



to A. cruciatum, but the few 

 specimens I have seen were desti- 

 tute of gland-cells, had always 



opposite, not verticillate branchlets, these being alternately, not 



oppositely branched. 



The plant was found epiphytic upon an old specimen of 



Sargassum vulgare washed ashore. 



St. Croix: Near the estate Lt. Princess in the neighbourhood of 

 Christiansted. 



Crouania J. Ag. 



1. Crouania attenuata (Bonnem.) J. Ag. 



AGARDH, J., Alga? mediter., 1842, p. 83; Spec. Alg. vol. II, p. 105; Epi- 

 crisis, p. 84. HARVEY, W. H., Nereis Bor.-Am., p. 226, pi. 31 D; Phycol. 

 Brit., pi. 106. CROUAN in Ann. Sc. Nat., Bot., Ser. Ill, 1848, p. 375, tab. 12, 

 figs. 2425. 



Crouania bispora Crouan in Ann. Sc, Nat., Bot., Ser. III. p. 374, tab. 12, 

 figs. 2123. 



Mesogloia attenuata Ag., Systema, p. 51. 



(For more synonyms comp. also DE TONI, Sylloge Alg., vol. IV, Flori- 

 dese, p. 1417). 



This species occurs in shallow water both in exposed and 

 sheltered places, and in deep water ; as the specimens vary rather 

 much according to the different growing places I shall first give 

 a short description of a plant from an exposed locality and after- 

 wards compare it with a specimen from deep water. 



