CHAPTER XVII 
RHODOPHYCEAE. RED ALGAE 
The red algae belong almost exclusively to salt water, but a few 
genera are found only in fresh water, usually in running water, and 
a few forms occur both in salt and in fresh water. Nearly all are 
small forms, and for habit work can be floated out and mounted 
on paper. Very few will need glue or gummed paper. 
For more critical habit work and for Venetian turpentine mounts, 
fix in 6 to 10 per cent formalin in sea-water. Material keeps indefi¬ 
nitely in 10 per cent formalin. 
For sections, use the chromo-acetic acid with or without the addi¬ 
tion of a little osmic acid, as recommended for the brown algae. 
The same method of fixing and washing should be used as for the 
brown algae, except that in the case of the few fresh-water forms, fresh 
water should be used in making the fixing agent and in washing it out. 
For Polysiphonia, and doubtless for many other forms, the period 
in the fixing agent should be very much shortened. Picric acid, 
corrosive sublimate, and absolute alcohol have been tried, but the 
results have not been encouraging. 
Batrachospermum.—-This is a green, fresh-water member of the 
red algae. It is not very uncommon in small streams. Fix in 
chromo-acetic acid (in fresh water) and use the Venetian turpentine 
method. Good preparations showing the nuclei may be obtained by 
staining in Mayer’s haem-alum, or Haidenhain’s iron-haematoxylin. 
After the material is ready for mounting, tease out a small portion, 
and still further dissociate the filaments by tapping smartly on the 
cover. 
Nemalion.—Methods for preparing Nemalion have been described 
by Wolfe. Chromo-acetic acid proved to be most satisfactory for 
fixing. For studying fertilization, mounts were made as follows: 
Young tips were crushed in water under a cover-glass and on a slide 
that had previously been treated with fixative; the cover was then removed, 
and the water on the slide ‘allowed to evaporate. The gelatinous nature of 
the wall prevents the contents of the cell from being affected by this treatment, 
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