1917 



Muenscher; Key to Phaeophyceae 



259 



The form D. aculeata f. media has opposite terete branches and is 

 often found with the species. Young specimens of this form have been 

 reported as Desmarestia viridis (Mueller) Lamour. (9), A careful com- 

 parison of both D. viridis and D. aculeata shows that they probably all 

 belong to the latter, at least none of them possess the characteristics of 

 D. viridis. 



Common in the upper sublittoral zone. 



Desmarestia 

 ligulata 



Desmarestia 

 aculeata 



PLATE 50 



Fig. 10. a, Part of a plant of the form herbacea; XO.l. b, Part of 

 plant; X 0.5. c, Cross section of main axis of a plant; X 0-5. 



Fig. 11. a, Cross section of compressed filament; X !• ^^ Sketch 

 of a plant; X 0.05. 



8. AGARUM (Bory) Postels & Ruprecht 



Plant with distinct holdfast, stipe and blade; holdfast composed of 

 branching hapteres ; stipe short, flattened or only flattened above; blade 

 crinkly, perforated, ruifled along tbe edge; midrib broad, like a smooth 

 band running through the middle of the blade. 



