266 



the figures of Melobesia Corallince Crouan (1. c). These specimens have not been 

 examined by Foslie, but as this author regarded Crouan's species as being only 

 a form of Lithophyllum pustiilatiim, he would 

 probably have referred our plant "as a de- 

 nominated form" to L. macrocarpum, whereas 

 it has disporic sporangia. A closer exami- 

 nation of my specimens, some of which 

 were preserved in alcohol, showed me, 

 however, such differences from the named 

 species that they cannot, in my opinion, 

 be referred to it, but must be regarded as 

 representing a different species bearing 

 Crouan's name. 



The crust is in some cases surround- 

 ing the Cora//zna-frond, being attached to 

 it in its whole extent and fusing together 

 where the borders meet. In other cases it 

 is only attached by its central thicker 

 portion, while the thinner edges of the or- 

 bicular, peltate frond are free (fig. 187, comp. 



A 



Fig. 186. 



Lithophyllum Corallina', from Hirshals. A, vertical 

 section of edge of frond. 560 : 1 B, vertical section 

 of frond near a conceptacle. 350 : 1. C, section of 

 frond with sporangial conceptacle. 65 : 1. 



Fig. 187. 



Lithophiillitm Corallince, from Hanstholm, vertical sec- 

 tions of scutate fronds with free edges. Sporangial 

 conceptacles in A and C, cystocarpic conceptacles in 

 B. Overgrown conceptacles in B and C. 65 : 1. 



Crouan, 1. c. fig. 6, 7). In the first case the 

 frond was up to 105 /i (over 12 cells) thick, 

 in the latter the central part was about 

 250 fj. thick, the inner edge 70— 105 /.< thick. 

 The diameter of the peltate fronds is 2 — 2,5 

 mm. The edge of the frond is thick, poly- 

 stromatic to the very margin or nearly so, 

 the cells cut off from the marginal cell 

 dividing early by transversal walls. The 

 marginal cell is much smaller than in 

 L. macrocarpum (fig. 186 A). The under- 

 most cell in the vertical or ascending cell- 

 rows constituting the frond is not longer 

 than the others, frequently even shorter, 

 being only 1—3 times as long as broad; 

 these cells are usually inclined. The cells 

 of the upper cell-layers are frequently 

 much longer; the transversal pits of these 

 cells are always distinct; they are shown 

 in fig. 186. 



The sporangial conceptacles are only 

 little prominent, forming low warts with 



