60 BRITISH SEA-WEEDS. 



British coasts and in the Channel Islands, but seldom 

 in great abundance. It is annual, and is in perfection 

 about July. 



Genus XIX. DICTYOTA. 



Root coated with woolly fibres. Frond flat, ribless, mem- 

 branous, forked, networked ; the surface cellules minute, 

 equidistant, converging at the tips of the frond, which end 

 in a single cell. Fructification, roundish clusters of spores 

 scattered over the whole frond beneath the cuticle, through 

 which they burst at maturity. — Dictyota, from the Greek 

 dihtuon, a net, in allusion to the network on the surface of the 

 fronds. 



This genus contains several species, which are dis- 

 tributed over very various latitudes, from the tropics to 

 the North Sea. 



Dictyota dichotoma. Forked Dictyota. 



Frond regularly forked, from four inches to a foot long, 

 and from an eighth of an inch to half an inch wide, wedge- 

 shaped at the base then linear. Fructification in dots scat- 

 tered over the frond, but not extending quite to either 

 margin. 



This species is very common, and varies much accord- 

 ing to the conditions under which it grows. In still, 

 deep water, the fronds become broad and robust, and 

 vice versa, in shallow water and exposed positions, they 

 are small and narrow. 



Dictyota, dichotoma var. intricata. — This form, 

 which has been described by some authors as a distinct 

 species, has fronds of a dark-brown colour, thick sub- 

 stance, very narrow, elongated, spirally twisted and 

 tangled. 



