248 



F. BORGESEN 



thallus. These different types of the thallus are most certainly adjustments to 

 the very strong surf that continually beats the shores of this extremely exposed 

 island. 



As could be expected from the situation of the island, 27 s. Lat., the 

 algal flora has a subtropical character with a few pronounced tropical forms 

 f. i. Halimeda Opuntia, Valonia ventricosa and Chnoospora fastigiata. No Can- 

 lerpa was collected. 



It is of a special interest to note that some species hitherto known only 

 from the West Indies or adjacent parts of the Atlantic are found at the shores 

 of Easter Island, thus contributing to the remarkable correspondance between 

 the floras of the Pacific and of the West Indies. Regarding this question compare 

 my remarks in »The marine Algae of the Danish West Indies*, vol. II, p. 491 etc. 



Finally I want to express my best thanks to the specialists who kindly 

 assisted me with the determination of certain groups. I am much indebted to 

 Mme. Dr. A. Weber VAN BOSSE and Mme. Paul LEMOINE for having determined 

 respectively the Squamariaceae and the Lithothamniaceae found in the collec- 

 tion, and to Dr. H. E. PETERSEN who took the trouble to name the small 

 fragments found of Ceramium. 



The drawings are for the most part made by mag. scient. O. ROSTRUP 

 under my inspection. 



Chlorophyceae. 

 Fam. Ulvaceae. 



Ulva L. 

 U. Lactuca L. 



Linne, Spec. Plant. II, 1753, p. 1163. 



The specimens are small, some few cm high only, forming low tufts, the 

 thallus being folded, crisped and entangled as is often the case with this species 

 on exposed localities. 



Area of distribution. Seems to occur in all seas. 



Fam. Chaetophoraceae. 

 Endoderma Lagerh. 



E. viride (Reinke) Lagerh. — Fig. 1. 



Lagerheim, G., Bidrag till Sveriges algflora (Ofvers. af K. Vetensk. Akad. Forh., 

 1883, p. 75). I. Huber, Chaetophorees epiphyt. et endophyt. (Ann. Sc. Nat., 7. ser., 

 Bot., torn. 16, 1892, p. 326). BOrgesen, F., The Mar. Alg. of the D. W. I., vol. I, 

 p. io, II, p. 416. — Entocladia viridis Reinke, in Bot. Zeit., 1879, P- 476, tab. 6, figs. 6 — 9. 



In the thick walls of Lanvencia claviformis an Endoderma was present, 

 most likely referable to E. viride, which according to my concepcion of species 



