175 



CALLITHAMNION HORMOCARPUM. 

 By E. M. Holmes. 



A note having appeared in this journ.il stating- that CaUitham- 

 jiion hormocarpum should be referred to Callithamnion v0r8icolor y it 

 may perhaps be well to poinl oul the difference between Callitham 

 nion hormocarpum and the nearly allied species. 



Through the kindness of Prof. Agarh, who lias sent me au- 

 thentic specimens of C. versicolor, I have been enabled to examine 

 that species, and find that it is entirely distinct from C. hormocarpm/i, 

 which is much more nearly allied to C. roseum, bystoideum, and Sei- 

 rospora Gnfithsiana. 



In C. versicolor the plumules are distinctly and repeatedly forked, 

 the pinnules ending in two short, equal, and nearly parallel cylin- 

 drical cells. In appearance the plumules are truncate and peni- 

 cellate, owing to the densely corymbose branching at the tips. It 

 seems to be merely a variety of C. corymbosum, having a more 

 marked central rachis to each frond. 



In Callithamnion hormocarpum the plumules are not forked, 

 but alternately pinnate, and the tips never end in equal forks, but 

 the pinnae are pinnate, with a slightly flexuous rachis, which 

 gives the pinnules the appearance of being distantly forked, as in 

 Seirospora. 



In appearance the plumules are never truncate or penicillate, but 

 have a lanceolate outline, and are distantly branched. 



C. roseum. — The plumules are much more densely clothed with 

 pinnae, and have a somewhat truncate, but never penicellate, appear- 

 ance ; the pinnules are longer and less branched, and are without 

 the peculiar cells on the joints, and the tufts of seirospores, present 

 in C. hormocarpum. 



C. byssoideum.— The plumules are much more densely tufted 

 than in C. hormocarpum, and the pinnules are corymbose and more 

 slender. 



Seirospora Griffithsiana lias the seirospores always on the tips 

 of the plumules ; C. hormocarpum always on the rachis of the plu- 

 mules, never at the tips, and I have not observed in Seirospora 

 the peculiar cells on the joints which are present in C. hormo- 

 carpum. In some specimens of C. hormocarpum which I have 

 recently examined, these marginal cells appear to have split longi- 

 tudinally into four parts, but not in a tripartite or cruciate manner 

 as is usual with tetraspores. 



British Hepatic^e. — The announcement that the first part of 

 Dr. Carrington's long-promised work is ready, will be gratifying to 

 some of our readers. It is uniform with the last edition of Sowerby's 

 " English Botany," and is issued by the same publisher (Hardwicke). 



