IP s t e I s i a 261 



of that of the present species and only a few 

 features need be considered. As far as it goes 

 the histology bears out the gross anatomy in 

 indicating a primitive position for the present 

 species. 



Stipe. The pith-web is much simpler than 

 that of most of the kelps. It is made up of 

 anastomosing hyphae as is usual; but they are 

 shorter, composed of shorter cells, with less 

 mucilasfinous matrix between them than most 

 species, e. g. Laminaria bongardiana which 

 was studied for comparison. These hyphae are 

 sometimes so poorly developed that in both 

 cross and longitudinal sections (Plate II.) of 

 the stipe the pith appears to be composed of 

 small spherical cells with only a few longer 

 hyphae, contrasting strongly with Laminaria 

 whose stipes show very many long hyphae and 

 but few round openings where others have 

 been cut across. The development of thick 

 walled supporting tissue (sclerenchyma) from 

 the cortex is also less marked in Renfrewia 

 than in most kelps though there is some varia- 

 tion in this respect. Sometimes there is no 



