This species is, as may be seen from the magnified figures in 
our plate, very closely related to the subject of the previous 
plate, and it is for this reason that I have figured them consecu- 
tively. P. formosa differs from P. urceolata chiefly in the much 
greater tenuity of its filaments, and the greater proportional 
length of its joints ; it agrees with that species in its colour, its 
ramification and the peculiar form of its capsules. Were we 
merely to take into consideration the beautifully feathered and 
luxuriant specimens collected by Dr. Greville on the shores of 
Bute, and compare them with the coarse growing state of P. 
urceolata commonly met with, we should probably pronounce 
the two species to be broadly distinguished, and should anticipate 
no difficulty in determining between them. But it must be 
admitted that specimens do occur which show a much greater 
approach both in habit and character; and while I am unwilling 
to erase P. formosa from the list altogether, I am obliged to 
allow that I have seen individual specimens which it has puzzled 
me to say whether they ought to be referred to wrceolata or for- 
mosa. When such perplexities meet us on the shore, one is apt 
to conclude that specific division has been carried too far. In 
the majority of cases, however, the limits are sufficiently marked. 
P. formosa appears to be a plant of bays and estuaries; P. 
urceolata, of the more exposed parts of the coast ; and, whether 
we look on them as different species or as well-marked varieties 
of one species, they appear to be worthy of separate notice. 
Fig. 1. PoLysrpHONIA FORMOSA; tuft :—of the natural size. 2. A branch with 
capsules. 3. A capsule. 4. A branch with tetraspores. 5. Ramulus of 
the same. 6. A tetraspore. 7. Portion of a branch, with ramulus. 8. 
Portion of a main branch. 9. Apex of a young ramulus, with byssoid 
fibres. 10. Cross section of the filament :—all more or less highly magnified. 
