but if once dried, and again moistened, it soon decomposes. Twhercles very 
rare, as large as poppy-seed, irregularly scattered over the branches and 
ramuli. Tetraspores | have not seen. Colour a dull purple red, becoming 
pink in fresh water. 
The genus Gigartina has been peculiarly unfortunate in the 
revolutions which it has undergone according to the views of 
different authors, or of the same authors at different times. As 
originally established by Lamouroux, its limits were very uncer- 
tain indeed, and it included a heterogeneous assemblage of species 
among which Laurencia dasyphylla,.Rhodomela subfusca, Chor- 
daria flagelliformis, and the Chylocladie, with several others were 
associated together. Lyngbye, while he weeded out several 
false species added to the confusion by introducing Desmarestia 
viridis. The first real reformation of the genus was that proposed 
by Dr. Greville in 1830, though he has admitted some species 
of an opposite structure to that of his type, and excluded others 
which coincide with it. I was myself accessory to a step being 
made in the wrong direction in Sir W. J. Hooker's ‘ British 
Flora’, where the Gracilari@ are erroneously combined with the 
Gigarting. That the combination is unnatural will be evident 
by a comparison of the magnified sections of our present plate, 
with those given of Gr. confervoides at Pl. LXV.; the structures 
are widely different. The last revision of the genus, by Professor 
J. Agardh, has at length fixed structural limits, more natural 
than those ascertained by mere outward habit, and from this 
results the rather startling fact, that Jridea radula, Bory, is a 
true species of Gzgartina. Separated from its affinities such a 
connexion would hardly be supposed, but the passage through 
Tridea stiriata, to Gigartina livida, and from that to the subject 
of our present plate is easy and natural. 
Besides G. acicularis, we have two other British species, G. 
pistilata and Teedii, both plants of extreme rarity in this 
country, though abundant in the South of Europe. G. plicata 
and G. Grifithsie, of ‘ British Flora’ have been formed into a 
separate genus; and the remaining species restored to Gracilaria. 
Fig. 1. GIGARTINA ACICULARIS, a barren specimen. 2. A specimen in fruit ; 
both of the natural size. 3. A ramulus with tubercles. 4. A section ofa 
tubercle. 5. Spores. 6. Part of a transverse section of the frond. 7. Part 
of a longitudinal section :—all magnified, the two latter figures highly sc: 
