CHAPTER XVI 

 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 

 indefinitely 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 (Fig. 47). 

 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. 1 Chromo-acetic acid proved to be most satisfactory for 



fixing. For studying fertilization, mounts were made as follows: 



1 Young tips were crushed in water under a cover-glass and on a slide 



i Wolfe, James J., "Cytological Studies in Nemalion," Annals of Botany, 18:607- 

 630. 1904. 



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