(63) 



we liave seen the stem, oi* the stem and lower branches alone, channeled, 

 the upper segments being plane, whilst in specimens densely fruited, on 

 the other hand, we have seen the stem plane and the segments with the 

 tubercles much incurv^ed. 



EXPLANATION OF PLATE XC. 



Fig. 1. — Gigartina viamillosa, natural size. 

 2. — Portion of a fertile frond. 

 3. — Vertical section of a tubeixle. 

 4. — Spores from same. 

 5. — Vertical semisection of frond. All magnified. 



