(170) 



a-half times as long as broad, rendered very indistinct towards the 

 base by numerous longitudinal articulated veins, densest near the base 

 of the branches, where they appear to originate, proceeding spu-ally 

 downwards ; in the upper parts of the branches and ramuli they are free 

 from veins and quite transparent, one to one and a-half times as long as 

 broad. Substance rather flaccid and tender, closely adhering to paper in 

 drying. Colour, a rather bright somewhat brownish red, very deli- 

 quescent in fresh water. Favellte "binate, mostly tei-minal on less 

 regularly pinnate branches." Tetraspores produced on the upper edge 

 of the pinniJse, roundish ovate, sessile, tripartite. 



We are indebted for the discovery of this very pretty species to the 

 acute observation of Sir W. Jackson Hooker. Its most characteristic 

 featm'es are its opaque stem, by which it is readily distinguished from 

 C. 2^oIl/spermicm and C. Borreri, its short articidations and the naked 

 bases of the branches, which will generally separate it fi-om G. roseum; 

 the ramuli or pinnse of that species are also more elongated and more 

 simple. From C. affine it differs in the lengih of the articulations, and 

 the direction and ramification of the branches. 



The species is very generally distributed along our western shores, but 

 appears to be less common on the eastern, occasionally passed over, as 

 we may suppose it to be, for its more common allies C. roseum and 

 C. polyspermum. 



EXPLANATION OF PLATE CXXIV. 



Fig. 1. — Callithamnion Hoolceri, natural size. 

 2. — Pinnule with tetraspores. 

 3. — Tetraspore from same. 

 4. — Favellte. 

 5. —Portion of stem. All magnified. 



