810 Transactions. — Botany. 



Distinguished from the last by having three to five small tubercles at the 

 extremities of the segments. 



D. baculimi, Brebisson. (E. XXXIII.) 



Doubtful. 



I am by no means sure that I have really seen this plant here. 



D. truncatum, Brebisson. (E. XXVI.) 



Not common. 



A fine large species, not unlike D. clavatuni, but broader and more 

 tapering towards the ends ; indeed, generally a larger plant. 



D. dilataturn, sp. nov. 



Figs. 11-14. 



The frond is large, stout, cylindrical, distinctly constricted at the middle, 

 and the suture forms a thickened ring projecting at each side. The 

 segments are not very broad at the base, but widen considerably imme- 

 diately after, and at about half then- length begin to taper to within a short 

 distance from the end, when they again slightly dilate. At the extreme 

 end there is a minute globular tubercle at each side, and along the edge 

 three to five others, giving it a crenate appearance. 



End view circular. 



The empty frond is distinctly punctate, and I have seen specimens 

 almost granulate. 



In the process of division, the new segments commence as minute 

 orbicular hyaline globules between the original segments ; the globules 

 gradually enlarge, becoming after a while elliptical, then slightly tapering ; 

 the terminal dilation, visible in the old segment, is not seen until the 

 separation takes place (and, indeed, for a short time after) ; the terminal 

 edge is rounded, and the coronet of tubercles is absent. It is not uncom- 

 mon to find fronds apparently almost symmetrical, except that one segment 

 is rounder or more ovate than the other. This is the new segment formed 

 in division. 



The endochrome is bright green, the vesicles numerous, scattered, and 

 conspicuous, and at the extremities are seen the moving granules in a 

 circular globule characteristic of the genera Docidium and Closterium, but 

 this globule is not always clearly visible. I have seen once or twice also a 

 kind of circulation in the endochrome similar to that observed in Closterium 

 lunula. In these cases the particles travelled from the middle towards the 

 end along the edge, and a return current (as it might be called) from the 

 end towards the middle was visible nearer the axis of the frond. 

 Length of frond, -^ inch ; greatest breadth, -^^ inch. 

 Bather common in spring. 



