AGLAOPHENIA MYR1OPHYLLUM. 291 



is formed of several tubes bound together, and exhibits one 

 or two peculiarities. On the back of it, " at nearly equal 

 distances, are formed little regular arch-like risings, which 

 are compressed and hollowed a little in the middle." (Ellis.) 

 This is a very accurate description of these curious promi- 

 nences, which have been supposed to mark the stages of 

 growth. They are formed by the occasional divergence of 

 a portion of the tubes from the ascending line of the stem, 

 and are, in fact, arrested branches. The ramification of 

 A. myriophyllum is very slight and simple, seldom passing 

 beyond a single division of the shoot, which generally takes 

 place not far from the bottom of it. In this way a double 

 plume is formed. The branch rises from one of the knobs, 

 and is a continuation of the divergent fascicle of tubes, 

 which in other cases remains a mere excrescence on the 

 stem. Frequently too, even when the branch is not per- 

 fected, the diverticulum rises into a free spinous point 

 above, which shows its real significance. I have seen a 

 small and imperfect plume springing from one of the 

 knobs on a branch, and it is possible that cases may occur 

 of still further ramification ; but the common habit of A. 

 myriophyllum is undoubtedly simple. 



Another peculiarity of the stem is to be found in the 

 rows of closely set pores, with raised orifices, which occupy 

 the furrows between the tubes and give it a punctate 

 appearance under the lens. 



The pinnae in perfect specimens usually clothe a large 

 proportion of the stem, a small section only towards the 

 base being naked. 



The reproductive bodies, which were first noticed by Dr. 

 Landsborough, whose name is pleasantly associated with 

 this species, differ from those of its British congeners in 

 being protected by a number of detached overarching 

 processes, and not by a closed case or corbula. A. myrio- 



