are gradually smaller ; in age the centre becomes more or less hollow. Sub- 

 stance when fresh, cartilaginous, but if kept long, becoming very gelatinous 

 and slippery, giving out in fresh water, considerable quantities of slimy 

 matter. Colour yellowish brown, either drying to an olive, or retaining 

 much of its original hue. 



Hitherto, in British works, the plant here figured has been 

 regarded as a species of Sporochnm. It is now removed, ac- 

 cording to the views of all recent continental authorities, to the 

 Dictyotece, in which family it constitutes the type of a new 

 genus. If we compare its fructification with that of Aspero- 

 coccus, or of Punctaria, we shall be satisfied that its true place 

 in the system cannot be very far apart from these genera. The 

 difference, indeed, is more in the nature of the frond, and the 

 general habit, than in the fructification. From the true Spo- 

 roclini, one of which we have figured at PL LVI. the fructification 

 of the present plant essentially differs, the position of the spores, 

 their form, and the nature of the filaments that accompany them, 

 being quite dissimilar. 



The var. £. of British authors is now regarded by Professor J. 

 Agardh as a distinct species, called by him Stilophora Lyngbyei. 

 I have some hesitation in admitting it to the rank of a species 

 notwithstanding its peculiar character, and the great abundance 

 and uniformity of its production, wherever it occurs ; and it has 

 been found from the south of Ireland to the Orkneys, everywhere 

 preserving the fistular stem, divaricated branches, and attenuated 

 ramuli. It is always found in deeper water than the normal 

 form, and always in land-locked bays, and these modifying causes 

 I have hitherto believed, produce the variations. It is, however, 

 at least a well-marked variety, and, as such, deserving of a figure 

 and description, both which I purpose affording it in a future 

 number of this work. 



Fig. 1. Stilophora riiizodes : — the natural size. 2. Part of a branch. 3. 

 Transverse section of the same. 4. Section of a sorus. 5. Spores: — all 

 or less highly magnified. 



