228 HALECIID^. 



alternate, one immediately below each 

 joint, the lateral process small and closely appressed to 

 the stem, the cup slender, expanding at the top, and 

 slightly everted; GONOTHEC.E unknown. 



I VENTURE to describe this species, from a specimen in the 

 collection of Trinity College, Dublin, even in the absence 

 of the reproductive capsules. The most marked charac- 

 teristic is the slender, flexible, and feathery habit. The 

 stem, though composed of several tubes, is delicate as 

 compared with that of H. halecinum, and altogether wanting 

 in the rigidity which belongs to that species. The minute 

 structure of the pinnae is also peculiar ; they are divided, 

 by joints which are decidedly oblique (slanting alternately 

 in opposite directions), into numerous very short seg- 

 ments, which are not of equal width throughout, but taper 

 somewhat downwards. The process that supports the hy- 

 drotheca projects but little; and the cup is small, with a 

 slightly everted margin. H. plumosum attains a height of 

 T> inches. 



The H. filiforme* of Alder seems to resemble the present 

 species in its mode of growth, but it is described as having 

 a simple stem and rather long internodes. 



Hab. Ireland. 



* I do not include this form in the present work, as Mr. Alder, I believe, 

 saw reason to change his opinion about it, and to regard it as probably a mere 

 variety or an immature state of some other species. The following is his 

 description: 



" H. FILIFORME, n. sp. Polypary very slender, flexible, simple or consisting 

 of a single tube throughout ; the stem not much branched ; branchlets short, 

 alternate, arising from the side of a cell ; the internodes rather long ; cells 

 rather slender, tubular, with a slightly everted margin. Length 4 } inches.''- 

 Suppl Cat. North. $ Durh. Zooph. 



