105 



the upper thickening layers are after decalcifying easily separated 

 by pressure. 



Remark on the synonomy. According to kindly communica- 

 tion of Prof. Far low he considers his L. polymorphum to be 

 most nearly related to L. compactum. On the same substratum 

 as a specimen of his L. fasciculatum, mentioned under L. colli- 

 culosum, I found a small crust with sporangia in development, 

 which belongs to the present species, and the named plant most 

 probably at least in the main includes L. compactum. Besides, I 

 got a well developed, sporangia-bearing specimen from Mr. Collins, 

 which also is identic with this species. PL 19, fig. 4. Collins' 

 coll. 2136. „ Eagle Island, Maine. Apparently thrown up from 

 deep water". 



I cannot agree with Kolderup Rosen vinge, that his L. 

 circumscriptum [i validum belongs to the species, to which it is 

 referred by him. He had the kindness to send me specimens of 

 this form, and, in my opinion, it is not a form of L. circumscriptum, 

 but accords well with L. compactum. He remarks that it is not 

 impossible, that the plant may be identic with the latter 1 ), but has 

 on the other hand seen every transition to L. circumscriptum, 

 and, therefore, he thinks it referable to this. However, if it may 

 be considered a specific character whether the conceptacles of 

 sporangia grow down into the frond, or not, L. circumscriptum 

 must only with regard to this character be regarded a species 

 different from the older L. compactum. In the former the concep- 

 tacles never grow down into the frond according to Stromfelt. 2 ) 

 I have, too, collected rather numerous specimens of this species 

 fully coinciding with Stromfelt's description, and the immersed 

 conceptacles do not become overgrown. On the other hand, in 

 L. circumscriptum ft validum, as Rosenvinge remarks 1. c. „af- 

 kastes kun Laaget, men ikke hele Konceptakiets Loft, og idet dette 

 og de mellem Konceptaklerne liggende Partier fortsaette Vsexten, 

 bliver Konceptaklerne overvoxede". The conceptacles of sporangia 



v ) „Det er ikke umuligt, at denne form kan vsere identisk med L. compactum 



Kjellm." 

 2, i Algveg. Isl. p. 20. 



