EEVISED LIST OF MARINE ALGJE. 



133 



very short branches between which are the 

 sporangia ... ... ... ... Myriotrichia 



Fronds ending in a large, single cell, the cells of 

 the lower part giving off descending filaments, 

 which become interwoven and form a false cortex 41 



41. Ehizoidal filaments few and limited to base of 



plant, branching irregularly pinnate... Sphacelaria 

 Rhizoidal filaments numerous ... ... ... 42 



42. Branches whorled ... ... ... Gladostephus 



Branches not whorled ... ... ... ... 43 



43. Spores formed in the axils of the ultimate ramuli 44 

 Spores on special branches arising from the 



cortical layers of the main axis, branches dis- 

 tichously pinnate ... ... ... Chcetopteris 



44. Lower part of main stem imperfectly corticated 



with rhizoidal filaments, spores solitary in the 

 axils ... ... ... ... ... ... Halopteris 



Lower part of main stems covered with a dense 

 felt of interlaced rhizoidal filaments, spores 

 clustered in the axils ... ... Stijpocaulon 



45. Fronds simple or occasionally proliferous ... 46 

 Fronds branching ... ... ... ... ... 50 



46. Midrib present Alaria 



Midrib wanting 47 



47. Fronds thin, subsessile ... ... ... ... 48 



Fronds thick and coriaceous, distinctly stipitate 49 



48. Sporangia densely covering the surface of the 



frond Phyllitis 



Sporangia immersed or partly immersed in the 

 frond, in scattered spots ... ... ... Punctaria 



49. Cryptostomata present, stem flat, arising from a 



hollow warty base Saccorhiza 



Cryptostomata wanting, stems cylindrical attached 

 by branching rhizoids Laminaria 



