253 



of the thallus (Fig. 244), not in the older, the thallus here consisting 

 of roundish, relatively large and thin-walled cells in the middle, 

 smaller ones towards the periphery. Larger and smaller intercellular 

 openings are often present. The peripheric cells are, when seen 

 from above, irregularly polygonal, about 40 //. broad in the young 

 parts of the thallus, in the older subcylindrical or barrelshaped, 

 about 140 n long and 35 p broad (Fig. 245). Upon a transverse 

 section they are nearly subquadratic. 



The tetrasporangia are formed in the summit of the ramuli 

 (Fig. 246); in the specimens found, however, not in any great 

 number; they are about 80 // in diameter. 



Fig. 245. Laurencia chondrioides n. spec. 



Surface cells of young (to the right) and 



older (to the left) parts of the thallus. 



(About 35:1). 



Fig. 246. Laurencia chondrioides 

 n. spec. Part of tetrasporic thallus. 

 (About 6:1). . 



The specific name alludes to the appearance of the dried 

 specimens, the beautiful rosy colour and whole habit of which 

 forcibly recalls some forms of Chondria dasyphylla. When com- 

 pared in more detail several striking differences are noticeable, 

 for instance in Chondria the large central cells are clearly seen 

 through the cortical layer, while this is not the case in Laurencia. 

 Moreover, transverse sections show the same difference. 



This plant has been dredged only in relatively deep water, 

 in a depth of about 30 meter. 



Only found once: St. Jan: off America Hill. 



6. Laurencia cervicornis Harv. 



HARVEY, W. H., Nereis Bor. Am., II, p. 73, tab. 18 C. 

 COLLINS, FR. S., The Algae of Bermuda. (Proceed, of the Amer. Aca- 

 demy, vol. LI 1 1, No. 1, 1917, p. 118.) 



