Ulva (L.). 



1. Ulva Lactuca L. 



LiNNE, Species Plantarum, vol. II, 1753, p. 1163. 



var. rigida (Ag.) Le Jolis. 



Le Jolis, Algiies marines de Cherbourg, 1863, p. 38. 



This species occurs in rather exposed places and also quite 

 sheltered places; it is mostly found in quite shallow water near 

 the shore, but it has once been dredged at about 12 meters. 



It is rather common at the shores of the islands. 



Geogr. Distrib. Extensive. 



2. Ulva fasciata Delile. 



Delile, Flore Egypte, 1813, p. 153, pi. 58, fig. 5. J. Agardh, Till 

 Algernes Systematik, 3die Afd., VI. Ulvaceae, p. 174, 1883. A. Vickers, 

 Phycologia Barbadensis, 1908, PI. II. Collins, Green Algae of North 

 America, 1909, p. 216. 



The few specimens I have collected of this plant are easily 

 distinguishable from Ulva Lactuca. They are characterized by 

 having the thallus divided in many narrow lobes with the mar- 

 gins irregularly dentate or sinuate. In the living plant the lobes 

 are light green in the middle becoming darker towards the mar- 

 gin, this being nicely shown in the figure of Vickers (1. c). 



In cross section the cells are seen to be very high and narrow 

 and their walls in the middle of the thallus are rather thick, much 

 thicker than in Ulva Lactuca. The thickness of the thallus 

 varies about 80 f^. As characteristic of this species J. Agardh 

 has pointed out, that the two layers of cells separate somewhat 

 at the margin, this I have not succeeded in finding in my material. 



I have only once found this species, namely at St. Thomas, in the 

 harbour where it was growing in shallow water and in a rather shel- 

 tered place. 



Geogr. Distrib. All warmer seas. 



Fa/77. 2. CJtcetopJioracece. 

 Blastophysa R< inke. 



1. Blastophysa rhizopiis Rke. 



Reinke, Atlas deutscher Meeresalgen, pi. 23. Huheu, Contributions 

 a la connaisance des Chaetophorees epiphytes et endophytes et de leurs 

 affinites. (Ann. sc. nat., bot., 7. ser., t. XVI, p. 332). Borgesen, in 

 Botanisk Tidsskrift, vol. 31, 1911, p. 131. 



