- 348 - 



mens, which, at all events, must partly rather be regarded as branched 

 than as proliferous, especially towards the apex of the frond. The young- 

 proliferations are in their lower part composed of two cell-rows and above 

 sometimes only of one. The thickness of the frond usually varies from 

 20— 30/i, and the cells are 16— 20/j high and 8 — 12/7. broad in the 

 transverse section. The thickness of the walls amounts [o 1 ju, and the 

 inner wall is frequently somewhat thicker and occasionally considerably 

 thicker than the outer wall, but specimens having both walls equally thick 

 are not rare. The cell-diameter parallel with the longitudinal axis of the 

 frond is the longest and attains a length of 20/<. The cells in the pro- 

 liferations are usually more or less distinctly arranged in rows and I have 

 also, but occasionally, seen the cells of older portions of the frond forming 

 indistinct, longitudinal rows. Specimens with trabecule as described by 

 Rosenvinge (see above under f. genuina p. 344) have been collected by 

 Ostenfeld at IsafjorOur and by me at Reykjavik. My material of this form 

 shows that specimens collected in the beginning of May were furnished 

 with many short proliferations, specimens gathered in the beginning of 

 June had longer proliferations and plants gathered in the later half of 

 June are much larger and furnished with large proliferations of first order 

 and shorter of second order, as described above. Probably the more 

 branched specimens are a summer-form, but, as my material is too scanty, 

 it must be left undecided at present. 



The f. prolifera is undoubtedly closest connected with the f. genuina 

 and must be regarded as a form of Enteromorpha intestinalis. In this 

 connection 1 will call attention to the remarks of G. Agardh (Sp. p. 421) 

 on Ulva compressa /9 prolifera (= Ulva prolifera Fl. Dan.). He writes 

 about it: „Adhuc dubium, anne potius varietas quaedam prolifera Ulvae 

 intestinalis". Specimens showing the transition to f. compressa are fre- 

 quently occurring. 



The f. prolifera grows in the lower part of the litoral zone; I have 

 sometimes found it occurring gregariously. Some specimens collected by 

 Ostenfeld in NW. Iceland, at Myrakciltur, were found floating in the sea 

 far from the coast. Fructiferous specimens have been gathered in June — 

 October. 



Enteromorpha clathrata (Roth) Grev., Kjellm. Arct. Alg. p. 287; Ulva 

 clathrata Le Jol. Liste p. 48 (partim) ; Enteromorpha compressa f. racemosa 

 Stromf. Algveg. p. 53. 



Some specimens, I met with at Djupivogur and Broddanes, are, I 

 think, identic with the var. RothianaLe io\. (I.e. p. 50), and of the forms 

 mentioned by Le Jolis they most resemble the f. prostrata. My plants 

 are up to 30 cm. long and have the cells arranged in rows. The shape 



