BOTANICAL INFORMATION. 47 
single cellule or little bag of tissue, filled with a colouring 
matter; some are mere strings of such cellules cohering 
by the ends; others, a little more perfect, exhibit the ap- 
pearance of branched threads ; in others, again, the branches 
and stems are compound, consisting of several such threads 
joined together ; and, in others, the tissue expands into broad 
flat fronds. Only the higher tribes show any distinction into 
stems and leaves ; and, even, in these, what appears a stem in 
the old plant, has already served, at an earlier period of 
growth, either as a leaf, as in Sargassum and Cystoseira, or 
as the midrib of a leaf, as in Delesseria. A few exhibit 
leaves or flat fronds formed of a delicate, perforated net-work, 
resembling fine lace, or the skeletons of leaves, a structure 
Which is also found among zoophytes. Of those so con- 
structed the most remarkable are the New Holland genus 
Claudea, the East Indian Dictyurus (Callidictyon, Grev.), and 
a genus, still unnamed, lately discovered at Port Natal, in 
South Africa, by Dr. Krauss, which produces fan-shaped 
fronds, the lower half of which has the structure and colour 
of Nitophyllum, the upper that of the delicate net-work of 
audea. Among British Ale, the only structure analogous 
to these exists in Hydrodictyon, which grows in the form of 
à perfect net, with regular meshes. 
The substance of which the frond consists is as variable as 
the form. Some are mere masses of slime or jelly, so loose 
that they fall to pieces on being removed from the water; 
others resemble, in feel and appearance, threads or silks; 
Some are stiff and horny, others are cartilaginous, or with 
the aspect and elasticity of gristle; others tough and coria- 
ceous, or resembling leather; while the stems of some of the 
larger kinds are almost woody. The leaves of some are 
delicately membranaceous, glossy and transparent ; of others, 
Coarse and thick, and either wholly destitute of nerves, or 
furnished with more or less defined ribs; or beautifully 
veined. Among the most minute kinds, many (comprising 
the family Diatomacee), are cased with organized silez, an 
these cases, which resist the action of fire, are found, in count- 
