10 M. FOSLIE. [1902 



Melobesia (Heteroderma) marginata Setch. et Fosl. mscr. 



Thallus forming orbicular crusts, at length extended patches on 

 other algae, 50 — 100 /x thick; conceptacles of sporangia crowded, 

 convex or subconical, 150 — 200 ft in diameter. 



The plant at first forms small orbicular or sometimes råtner 

 irregular, purplish crusts on other algae. These crusts by and by 

 anastomose and at length form extended patches almost covering 

 certain parts of the frond of Oymnogongrus linearis or Laurencia 

 pinnatifida. Steril specimens probably belonging to the same spe- 

 des have also been met with on Odonthalia dentata. The crust 

 is 50 — 100 }J- thick and composed of at least up to 9 layer of 

 cells. The basal cells are almost square or, more frequently, verti- 

 cally elongated, up to 12 \x long and 5—8 li broad. The upper cells 

 on a section are square or somewhat rounded, 6 — 8 p. in diameter, 

 or vertically elongated, up to 10 ft long, occasionally forming short 

 rovvs with the longest diameter in horizontal direction. The cortical 

 cells are smaller. The cellwalls are frequently rather thick. 



The conceptacles of sporangia are densely crowded almost 

 over the whole frond, often so densely that the roofs partly ana- 

 stomose, sometimes however forming small groups as in Melobesia 

 Cymodoceae. They are convex but little prominent, or subconical, 

 150—200 fi in diameter seen from above. The sporangia are four- 

 parted, 50—60 \i long and 25—30 fi broad. 



Dried specimens of this species with emptied conceptacles some- 

 what resemble Lithothamnion corticiforme in habit. On the other 

 hand the species approaches Melob. zostericola and M. Cymodoceae. 



Occurrence. Pacific coast of North America: Bodega Bay, 

 California, on Oymnogongrus and Laurencia ; and Whidbey Island, 

 Wash., on Laurencia pinnatifida, and in the same locality on 

 Odonthalia (steril), Setch ell and Gard ner, Algae of Puget 

 Sound No. 269, 270. 



Melobesia (Eumelobesia) rugulosa Setch. et Fosl. mscr. 



Thallus monostromatic exsept in the neighbourhood of the 

 conceptacles, without cortical cells. Conceptacles of sporangia 

 subconical, 120 — 150 jj- in diameter. 



