136 BRITISH SEA-WEEDS. 



the margin of the lamina, and themselves connected by 

 pellucid striae. Spores in spherical conceptacles immersed 

 in the midrib towards the tips of the branches ; tetraspores 

 in sori disposed on each side of the midrib, or in proper 

 leaflets, near the tips of the branches. 



This is the most common of the Delesseria, and is 

 found on almost all parts of the British coast. Its 

 colour is generally a bright red, becoming darker in 

 drying. It grows on Algse, and on the sides of per- 

 pendicular rocks facing the sea, near low- water mark. 

 In drying it does not adhere to paper. 



Delesseria angiistissima. The very slender 

 Delesseria. 



Frond four to eight inches high, nearly cylindrical below, 

 compressed above, much and irregularly branched ; branches 

 alternate, much divided above, and furnished with forked 

 branchlets. Spores in spherical conceptacles, which are 

 either immersed in the tips of the frond, or in small 

 branchlets, springing from the axils of the upper branches ; 

 tetraspores cruciate, in sori on the inflated tips of the 

 branches, or in axillary branchlets. 



This plant was first discovered by Mr. Brodie, more 

 than half a century since, and at that time Mr. Turner 

 considered it to be only a variety of D. alata. Many 

 years afterwards, Dr. Harvey, " in deference to the re- 

 peated protests of Mrs. Griffiths," inserted it in his 

 f ManuaP as a distinct species, "under the temporary 

 name of Gelidium ? rostratum, recommending it to the 

 notice of observers, and adding that ( my own opinion 

 on this puzzling matter was not very decided/ " The 

 character in dispute is the membranous wing on either 



