CERAMIACEJE. 235 



sparingly and irregularly branched ; branches irregularly 

 divided, jointed, plumulate from every joint ; plumules from 

 half a line to a line long, opposite, or in threes and fours, 

 very crowded at the tips of the branches ; pinnules oppo- 

 site, slender, cylindrical, blunt at the tips. Favellae not 

 known ; tetraspores cruciate, elliptical, borne on the lowest 

 joints of the plumules, either sessile or on very short stalks. 



This plant occurs in many localities, but only in small 

 quantities. The coasts of Devon, Wales, and Ireland 

 are the chief recorded habitats. It grows on mud- 

 covered rocks near low-water mark, and is annual. 



Callithamnion pluma. The feather Calli- 

 thamnion. 



Fronds feather-like, rising from creeping filaments, from 

 a quarter of an inch to about half an inch high, simple or 

 alternately branched ; plumules naked below, clothed above 

 with short, opposite pinnules issuing from each joint; arti- 

 culations of the stem about three times as long as broad, of 

 the plumules' about as long as broad. Tetraspores globose, 

 tripartite, either borne on short, special stems near the base 

 of the pinnules, or at the tip of a shortened pinnule. 



This little plant is rare, probably because it is fre- 

 quently overlooked. It grows parasitically on the stems 

 of Laminaria digitata, on which its upright fronds are 

 set so closely together that the patches w T hich they form 

 resemble crimson velvet. Some of the plumules have 

 pinnules only on one side of the stem. It is annual, 

 and in perfection in summer. 



Callithamnion Turneri. Turner's Callithamnion. 



Fronds rising at right angles from creeping fibres, which 



