204 



MONOSTROMA, ULVA, LAMINARIA, &c. LESS. 



which may be as much as 2-3 metres long and 70-80 cm. 

 wide. 



Other genera of tangles attain even greater dimensions. 

 A common New Zealand genus, Lessonia (Fig. 44, B) is a 

 gigantic tree-like weed, the trunk of which is sometimes 

 more than three metres (9-10 ft.) long, and as thick as a 



FIG. 44. A, Laminaria claustoni, a young plant, showing stem with 

 branched root-like organ of attachment, and deeply-cleft leaves (about 

 th natural size). 



B, Lessonia fascescens, showing tree-like form (about -faih natural 

 size). 



(A after Sachs : B after Le Maout and Decaisne. ) 



man's thigh, while the graceful Macrocystis, another southern 

 genus, is believed to attain a length of over 200 metres 

 (700 ft.), and is known to grow as much as 5 J metres (over 

 1 8 ft.) in six months. 



But in spite of their immense size these olive sea-weeds 

 are comparatively simple solid aggregates of cells. Ex- 

 amined with the naked eye the difference between them 



