OLIVE COLORED ALG^. 81 



grow by a discoid hold-fast. The plants grow between 

 tides from six inches to two feet long. It is a peren- 

 nial, and the old fronds will be quite likely to have 

 some species of Ectocarpus growing on them. It is 

 also the favorite and almost the only home of the 

 Polysiphonia fastigiata. It is a rich olive in water, 

 but quite black when dry. 



FUCUS FURCATUS, Ag. 



The forked Fucus resembles the F. vesiculosus in 

 its general habit of growth, but differs from it in 

 several particulars, viz., in having a somewhat wider, 

 shorter ,and more constantly typical frond, in having 

 no air bladders, and in having the terminal forks 

 which bear the seed vessels much longer, more 

 pointed, and less swollen, being two and sometimes 

 three inches long. The whole plant is a foot or 

 more in length, and grows just down at the extreme 

 low-water mark. It may be most easily found and 

 collected, during the time of "spring tides," at new 

 or full , moon. It is common on the rocks at Nahant, 

 Marblehead, and northward. The microscopist dis- 

 tinguishes this species from F. vesiculosus by a differ- 

 ence in the contents of the seed vessels. There are 

 two other species of Fucus recognized in our north 

 eastern flora. F. ceranoides at Marblehead, and F. 



