These branches bear a second and third series; the lesser divisions being 
pinnated with alternate, ovate, patent, stipitate plumules. Plumules simply 
or doubly pinnate, the pinnules long and widely spreading, sometimes re- 
curved. Articulations short in all parts where they are visible. Tetraspores 
numerous, spherical, lining the inner edge of the pinnules, one borne by 
every articulation. Favelle binate, mostly terminal, on less regularly pin- 
nate branches. Colour varying from a full purplish to a brownish red ; 
sometimes pale pink, fading rapidly in fresh water to a dirty white. Swd- 
stance flaccid, adhering to paper, and soon rotting if moistened after having 
been dried. 
A common but very variable species, and yet not difficult to 
understand when a few leading features are kept in view. Its 
most striking characters are the opake stem and branches, the 
short articulations, and the very patent or divaricated ramuli, 
frequently pinnulated above. It verges on the one hand to 
C. roseum, and on the other to C. Borreri and to C. polyspermum, 
but is readily recognized from each of these by some one of its 
characters. 
By the synonyms quoted, it will be seen that at one time I 
made ¢hree species of what I now regard as one: and if I had 
added a fourth (C. affine), I had perhaps acted discreetly—but I 
reserve that species for a future examination. Those who know 
the difficulty attending the determination of these plants, will 
best excuse these and similar mistakes. 
C. Hooker is named in honour of Sir Wm. J. Hooker, by 
whom it was first discovered, and communicated to Dillwyn as 
a new species. 
Fig. 1. CattirHaMNIoN Hooxeri :—the natural size. 2. Base of a smaller 
branch, bearing three plumules. 3. Small branch with a favella. 4. Part 
of a plumule, bearing tetraspores. 5. A tetraspore:—adl more or less 
magnified. 
