form of that very variable species, from the normal state of which 
its clearly articulate stem affords a ready distinctive character. 
The habit of branching strikingly reminds us of P. elongella, but 
in no other character does it agree with that species. There is 
also an affinity with P. violacea and P. fibrata, and especially 
with P. Grifithsiana; but from all these it differs mm more or 
less degree, and with none, except the last, has it a very strong 
relation. With the view of attracting the attention of collectors 
to the subject, and thereby clearmg up the doubts which I cannot 
help entertaining respecting the validity of the species, I have 
given it an early figure. Nothing is known respecting the manner 
or place of its growth, but very probably it is a parasite on some 
of the smaller Algze; and most likely an annual, and found in 
the summer season. 
Fig. 1. PotystpHonta Ricnarpsoni :—xatural size. 2. Apex of a branch: 
—magnified. 3. Portion of the stem. 4. Portion of an upper branch. 
5. Transverse section of the stem. 6. Capsule or ceramidium :—all more 
or less magnified. 
