34 



Dansk Botanisk Arkiv, Bd. 2. Nr. 2. 



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stones and rocks. It has a dark brown colour. In young speci- 

 mens the surface is nearly even and smooth with more or less 

 conspicuous concentric striations, in older ones rather uneven, 



bullate and often somewhat folded. 

 The thallus is rather easily sepa- 

 rated from the substratum. 



The sterile part of the thallus 

 is built in good accordance with 

 that of Ralfsia verrucosa: from a 

 horizontal layer of cells, arch-formed 

 cell-threads grow up turning their 

 convex side against the edge of 

 the thallus, forming in this way a 

 parenchymatical layer in good 

 agreement with Reinke's schematic 

 figure of Ralfsia verrucosa in "Al- 

 genflora" p. 48 ; often the leaf is 

 more or less bilateral as shown in Figs. 20 and 21 being like the 

 figure c of Reinke 1. c, referring to some form from the Chan- 

 nel of Ralfsia verrucosa and in this way showing much likeness 

 to Ralfsia deusta. 



The chromatophore in the material preserved in alcohol was 

 not especially prominent ; it was plate-shaped and a single one 

 was found in each cell. 



Fig. 20. Ralfsia expansa J. Ag. 

 Transverse section of the thallus 

 with unilocular sporangia (40: 1). 



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Fig. 21. Ralfsia expansa J. Ag. 

 Transverse section of the thallus near the edge (40: 1). 



Groups of hairs occur rather abundantly. 



Both unilocular and plurilocular sporangia were met with r 

 occurring on different plants. The unilocular sporangia (Fig. 22 

 a and b) are laterally placed upon the assimilating filaments and 



