black ; but in this refpect is liable to confiderable variation. From C. rivularis 

 it may at once be diftinguifhed, not only by its different mode of growth above 

 noticed, but equally by its gloffy hue and far greater lubricity; from bipunctata and 

 genuflexa by its darker colour; and from all thefe, by its curious internal ftruclure; 

 in which refpect however under the microfcope it approaches nearly to C. fpiralis, 

 but differs in its larger fize, and in its granules not being difpofed in a fingle fpiral 

 tube; to C. jugalis it is ftill more nearly allied, but has a lefs flaccid appearance to 

 the naked eye, and is eafily diftinguifhed when magnified, by its want of connecting 

 proceffes. It would be a fortunate circumftance for the arrangement of this tribe, 

 if more dependance could be placed on the relative proportions of the length and 

 thicknefs of the joints; but it frequently happens that the former is twice or thrice, 

 or even more, greater in fome fpecimens than in others. This circumftance may 

 account for the difference of the fpecific characters given to die prefent plant in the 

 Flora Danica, and Catale&a Botanica ; the former describing it ' articulis longis,' 

 the latter, ' brevibus.' I have frequently feen filaments in the fame fpecimens that 

 agreed with either; but have, confiftently with its moft general appearance, adopt- 

 ed a term between thefe two extremes. Muller's defcription, which is otherwife 

 both curious and accurate, is on this account not always applicable ; he fays that 

 every joint contains four Roman X's, and thence derives the name that he has given 

 it. The granules appear to be confined in fpiral tubes, and vary confiderably in 

 fize as well as in the difbnce of the tubes; being fome times much crowded, 

 and fometimes at a confiderable diftance from each other. In order to determine 

 with more certainty than was otherwife poffible the nature of thefe granules, my 

 friend D. Turner and I placed fome in a folar microfcope, and found them 

 perfectly pellucid, of a homogenous nature, with no appearance of their being 

 filled by any granular fubftance; which confirmed, in fome degree, an opinion be- 

 fore entertained, that thefe are not feed veffels, but the true fructification of the 

 plant. 



A. B.C. C. nitida. magnified i. 



