o;eneral frond tlicrcfore is either simply or doubly, sometimes triply, pinnate. 

 Both the stem and all the lavf^cr and lesser branches are coated with cellules 

 throughout, no articulation being externally visible except near the extre- 

 mities and on the very young branches ; the surface of the larger branches 

 is smooth. All the young and smaller branches are closely set with minute, 

 alternate, many times dichotonious, fastigiate, pellueidly articulate ramuli, 

 which are |-1 line in length. Arliculations of the ramuli 5-3 times as 

 long as broad ; apices spreading, obtuse. Favellce on the ramuli, generally 

 consisting of two divergent lobes, ovate-oblong or acuminate. Tetraspores 

 glol)Ose, lateral or axillary on the forks of the ramuli, sessile. Colour a 

 deep brownish-purple, becoming darker and browner in drying ; the younger 

 ones redder. Substance in the young plant very soft ; in the older firm, 

 not gelatinous. In drying it closely adheres to paper. 



This pretty species has, in its general contour, a great resem- 

 blance to the European Callithamnion tetra(jomim, but in its mi- 

 croscopic characters it comes much nearer to C. grande, in the 

 section distinguished by dichotomous ramuli and scattered tetra- 

 spores. From all known species, however, it is sufficiently distinct 

 in ramification and matters of detail. The form of the favellce 

 is very unusual, and, if constant, as it seems to be, affords an 

 additional mark by which the species may be known. 



The specific name laricinum was chosen, not so much in re- 

 ference to any resemblance to a Larch as to the Moss called 

 Hypnum laricinum, to which, in ramification, this Alga bears 

 some likeness. 



There is a marked difference in luxuriance between specimens 

 from different localities : those from Port Fairy, from which our 

 figure is drawn, are greatly larger than those from Rottnest 

 Island, on which the species was founded. 



Fig. 1. Callithamnion laricinum, — the natural size. 2. Portion of a branch, 

 with dichotomous ramuli. 3. Apex of a ramulus, bearing tetraspores; apex 

 htdixiw^ favellce : — magnified. 



