Classification of Green Algce. 
1 1 7 
3. Rhipocephalus. Kiitzing. 
Thallus consisting of a cylindrical encrusted stipe, bearing 
above several flat fronds consisting of closely inter¬ 
woven threads. 
4. Callipsygma. J. Agardh, 1887. 
Characters of Rhipocephalus, but stipe flattened. The 
edges bear ridges, from the summit of each of which 
a flat frond arises ; all the fronds lie in the same plane. 
5. Udotea. Lamouroux, 1816. 
Thallus of a cylindrical or flattened, creeping or erect 
stipe, simple or branched, and bearing one or more 
simple flat fronds, which shew concentric zones of 
growth. Stipe with differentiation of pith and cortex ; 
frond with or without such differentiation. Incrustation 
present or absent. Zoosporangia (?) round, on short 
side-branches of the frond-threads. 
6. Halimeda. Lamouroux, 1812. 
Thallus usually strongly incrusted, composed of branched 
series of wedge-shaped or reniform flattened segments, 
often all lying in one plane. Marked differentiation 
of pith and cortex. Cortical branches hexagonal by 
mutual presure. Zoosporangia (?) round or club- 
shaped, aggregated in botryoidal clusters on the edges 
of the thallus-segments. Swarmers observed. 
7. Pseudocodium. Weber van Bosse, 1895. 
Habit of Codium, but the cortical branches adhering 
very closely together, and hexagonal by mutual 
pressure as in Halimeda. 
8. Codium. Stackhouse, 1795-1801. 
Thallus of various shapes, crustaceous, spherical, or 
cylindrical and branched. No external differentiation 
of parts, but a well marked central pith, consisting of 
longitudinally running, parallel threads, from which 
arise club-shaped branches arranged perpendicularly 
to the surface, forming the cortex. No incrustation. 
Gametangia obovoid branches of the cortical threads, 
containing anisoplanogametes of which the male are 
small and yellow, the female large and green. Plants 
dioecious. 
Fam. VI. Verticillaive. 
Thallus consisting of a long, cylindrical, typically unbranched t 
undivided, upright stem, fixed below by branched unseptate rhizoids, 
and hearing above acropetal whorls of typically branched segmented 
appendages (leaves), delimited from the stem by closed or perforated 
septa, which are also found between the leaf-segments. Chloroplasts 
small, disc-shaped, with pyrenoids. 
Reproduction by the formation in certain specialised fertile 
portions of the leaves, or in a special category of fertile leaves only, of 
isoplanogametes directly, or of aplanospores which may become 
gametangia or themselves germinate. Zoospores unknown. 
