F. Borgesen: Phæophyceæ of the Danish W. Indies. 57 



upon both sides of the frond ; their development is quite in 

 accordance with those of Dictyota dichotoma as described by 

 ThuRet *). They are developed from a group of the epidermal 

 cells. The cells in the periphery of such a group are sterile; 

 these cells are lengthened, mostly the innermost, and bent some- 

 what towards the middle forming a kind of 

 involucre round the proper antheridial cells 

 in the middle. When the antherial cells 

 have reached a certain length a small basal 

 cell is cut off at their base and the large 



upper cell is divided verv regularly into a great 



rr ii 11 o * t Fl S- 37 - Dict y° ta re- 



number of quite small cells. Seen trom above nulata J. Ag. Part of 



the antheridia are more or less polygonal by a group of antheridia 



r JO J seen from above. 



mutual pressure (Fig. 37). (About 90 : l). 



The oogonia occur likewise upon both 



sides of the frond and their development is quite in accordance 



with the description and figures of Thuret et Bornet 2 ). Groups 



of epidermal cells become lengthened and when they have reached 



a certain length a small cell is cut off at their base, while the 



upper large cells grow into the oogonia. Individuals with tetra- 



sporangia were not found. 



Found once only, growing upon buoys in the harbour of Christian- 

 sted, S t. Croix. 



Geogr. Distrib. Pacific Ocean at the shores of Mexico, West Indies. 



8. Dictyota dentata Lamx. 



Lamouroux, Exposit. des Caract. du genre Dictyota (Journ. de Bo- 

 tanique, t. II, 1809, p. 42). Kützing, Species Algarum, p. 556; Tab. Phy- 

 cologicæ, vol. IX, pi. 35, fig. I. J. Agardh, Species Alg., vol. I, p. 96. 

 J. Agardh, Till Algernes Systematik, 2dra afdeln., p. 98. J. Agardh, Ana- 

 lecta algologica, Contin. I, 71. F. Hauck, Meeresalgen von Puerto-Rico. 

 (Englers bot. Jahrb., Bd. 9, 1888, p. 466). A. Vickers, Phycologia Barba- 

 densis, pi. XIV. 



All the specimens collected being sterile I cannot give any 

 information as to the organs of reproduction ; but Hauck (1. c.) 

 gives a short description of the tetrasporangia-bearing plants as 

 well as of the oogonia and antheridia which occur in separate 

 plants. 



') Thuret, G., Recherches sur la fécondation des Fucacées et les anthé- 

 ridies des algues, 2. partie, (Ann. des Sciences Nat., 4. serie, t. III, 

 1855, p. 5, pi. 2). 



'-') Thuret, G. et E. Bornet, Etudes phycologiques, 1878, p. 53, pi. 27 — 30. 



