central portion of the frond is filled with a watery mucus, through which 
run longitudinal jointed fibres, with a narrow, coloured endrochrome and a 
wide pellucid limbus, anastomosing together into a lax net-work, with large, 
oblong, subhexagonal meshes; these constitute the axis: the periphery or 
outer wall of the frond is formed of very delicate, closely packed, horizontal 
dichotomous, moniliform filaments, which spring from the most exterior of 
the fibres of the net-work, and their apices, closely glued together, unite into 
the membranous coat of the frond. _ Fructification ; 1, spherical masses of 
spores or favellidia contained in ovate capsules, furnished with a terminal pore, 
their walls formed of moniliform filaments. The mass of spores appears to be 
formed by a transformation of the internal net-work. 2. Oblong éetraspores 
divided at maturity by three transverse lines, formed from the filaments of 
the periphery, and scattered at intervals among them. Colour a dull purple. 
RAPD ems 
This curious little plant appears to have been first noticed by 
Dillenius, in whose Herbarium specimens are preserved, ac- 
cording to Mr. Turner; and was next excellently described by 
Lightfoot, who remarks that its branches resemble “the jomted 
leaves of the Cactus opuntia,” a resemblance which has suggested 
the specific name, by which it has smce been universally distin- 
guished. Lightfoot’s trivial name “eyes” has, however, the 
priority: though no one has adopted it. 
Its generic relations were, as appears by the numerous syno- 
nymes, long imperfectly understood, and few Algz have been more 
tossed about from one group to another, until, in 1830, Dr. 
Greville proposed it as the type of a new genus, in which step 
he has since been gladly followed by every succeeding author. 
His judgment was formed solely from consideration of the struc- 
ture of the frond; the fructification bemg unknown to him. The 
tetraspores were first described, so far as I am aware, by Prof. 
J. Agardh, in his ‘ Algze Mediterranez,’ his specimens having 
been received from Professor Meneghini, and they have been 
excellently figured by Kiitzing, in his great work. In this 
country both kinds of fruit were discovered by Mrs. Griffiths, to 
whose kindness I am indebted for all the specimens I have seen. 
C. opuntia can only be confounded with a dwarf state of 
Chylocladia articulata, which is about the same size. But, not 
to speak of difference of structure, the brighter colour, cylindrical 
joints, delicate substance, acute angles, and forked fronds of the 
latter, sufficiently distinguish it. 
Fig. 1. CATENELLA OPUNTIA :—of the natural size. 2. Fronds. 3. A joint bearing 
a ceramidium. 4. Ceramidium cut open. 5. Spores, from the same. 6. 
Longitudinal section of the frond. 7. Transverse semi-section, with tetras- 
pores iz situ. 8. A tetraspore :—all more or less highly magnified. 
