Sy 
TYPES OF CRYPTOGAMS; THALLOPHYTES 255 
302. Other Floridez.— Nemalion represents one of the simplest 
modes of fruiting in the red alge. In others there is great variety in 
structure and great complication in the mode of fruiting. Some 
species of Polysiphonia (or Dasya) may well be studied in compari- 
son with Nemalion and in further illustration of this important 
group.! Understanding that a siphon, in alge, is a row of cells, end 
to end, study the structure of a plant of Poly- 
siphonia as illustrating its name. How many 
siphons are there? Do the main branches 
have any other cells covering the surface (cor- 
ticating cells) ? 
Note the tufts of repeatedly forking, one- 
siphoned filaments. 
303. Fruiting of Polysiphonia. — The anther- 
idia are to be sought on the branching fila- 
ments just mentioned. Note how they differ 
from those of Nemalion. The clustered fruits 
or cystocarps will be recognized as ovoid- G6 
globose or urn-shaped bodies attached 
externally to the frond. Note whether ® 
the group of spores is naked or otherwise, ‘9 
whether the spores are produced singly 
or in chains; how attached; shape. 
Many Floridee have another kind of 
fruiting bodies, spores produced without Wealden 
fertilization, codrdinate with the asexual 4 spores of Nemalion (greatly 
spores of black mould (see Sect. 308). magnified); B, portion of 
In Floridee such spores are usually rare af 3 tet es 
isia, with tetraspores, f¢. 
found in fours and are called ¢etraspores. 
Are tetraspores usually found on separate plants ? 
In Polysiphonia the tetraspores appear to be formed in threes 
(tripartite), the fourth being underneath the three. When found, 
describe their position and arrangement. 
304. Alge.— Diatom, Oscillatoria, Pleurococcus, Spt- 
rogyra, Vaucheria, Nitella, Fucus, Nemalion, these eight 
1 It is desirable also to exhibit fresh or pressed specimens of various genera 
to show their general aspect. 
