grown plant average from :^ to f of an incli in diameter, 

 narrower at the base and swelling out somewhat at the 

 apex. Tlie apices of the branches are obtuse and much 

 darker in colour than the rest of the plant. Occasionally 

 the fronds are somewhat compressed. In length they 

 vary greatly. We have found, after examination of a large 

 number, that a well grown plant (in this district) is on an 

 average from 8 to 10 inches long, but Harvey speaks of 

 them as sometimes reaching a length of 2 feet. The plant 

 he figures, however (PJiyc. Brit., PI. XCIII.), is under 

 8 inches in length, so that our plants may be taken as of 

 normal size for the British Islands. 



In colour Codium tomentosum is a rich dark green, 

 intensely so near the apices of the branches — so dark, 

 indeed, as to appear almost black. This will be found to 

 be due to, first, the closer packing of the superficial palisade 

 "cells" in these localities, and secondly, to the aggrega- 

 tion of the chloroplastids in the apices of the palisade 

 " cells " themselves. The green is not so intense nearer 

 the base. In substance the plant, when fresh, is fairly 

 firm and rigid, and, externally, soft and slippery to the 

 touch ; but after preservation in alcohol it becomes soft 

 and flaccid. 



Anatomy. 

 A. Vegetative Organs. 



The thallus consists essentially of densely woven 

 branched hyphoe, forming a central core or medulla, fi'om 

 which arise very ninnerous short and thick branches, 

 standing at right angles to the long axis of the branch and 

 closely packed so as to form a velvety pile covering the 

 entire surface. 



The plant is attached to the substratum, as already 

 stated, l^y numerous rhiz()ids. Th(> rlii/oiils arc branched 



