168 SIDNEY F. HAEMEll. 



fig. 11, and ill both the above-cited formulse in which the ovi- 

 cell replaces z^ and z.j respectively. 



The joints of this species are yellow, or more rarely brown. 

 They are never black. Rootlets are very freely developed from 

 the base of the stem, and they may attain a great length. 

 They usually originate rather low on the zocecia and from their 

 lateral edges. As in other species, they become very firmly 

 attached to stones and other objects, and form creeping stolons, 

 from which (as well as from rootlets which are not attached in 

 this way) fresh stems may originate. The colonies do not so 

 often consist of a single main stem as in C. eburnea. It is 

 frequently remarked that the longest and most branched parts 

 of the colony are lateral branches, and not parts of the main 

 stems. 



Ovicells. — In C. ramosa (figs. 10, 11) the ovicells are consi- 

 derably larger than in any of the other species (see figures, all of 

 which are drawn to the same scale, and table of measurements 

 on p. 177). They are regularly pear-shaped, their main axis 

 being straight ; they are much inflated above, their curvature 

 diminishing gradually in all directions from their most pro- 

 minent portion. The aperture is in the form of a distinct 

 funnel-shaped tube, which is considerably smaller at its base 

 than at its mouth ; and the mouth of the funnel, the actual 

 aperture of the ovicell, is more or less circular. In the shape 

 of the aperture this species differs from all the other British 

 forms. 



The tubular aperture is of course not present in incompletely 

 developed ovicells : an account of the development of the ovi- 

 cells will be given in a forthcoming paper. It must also be 

 noted that the aperture is liable to be broken away in old ovi- 

 cells, and that in many cases, where the ovicells or their con- 

 tents are not normally developed, the tube itself is not formed. 

 In normal and completely developed ovicells the shape of the 

 aperture is, however, a perfectly characteristic and constant 

 feature. 



C. aculeata (fig. 4), which in some other respects is so 

 similar to C. ramosa, has a much smaller ovicell than that 



