250 



METHODS IN PLANT HISTOLOGY 



the mount may be sealed with balsam, but we prefer to leave the 

 mounts for a day or two before sealing. Such mounts would probably 

 keep for a year or two without sealing (Fig. 62). 



We have mounted Nemalion in Venetian turpentine; but by this 

 method the material becomes hard and behaves like cartilage, so that 

 it cannot be crushed under a cover. However, it can be crushed on a 

 piece of glass with a scalpel. 



Fig. 63. — Pohjxiphonia fihrillosa: A, nearly mature cystocarp, showing the large cell formed by 

 the fusion of .several auxiliary cells with the pericentral cell — the carpospores are large and elongated; 

 B, an antheridium — the term "antheridium" is more correctly applied to the structure shown in C, 

 a, which cuts off one or more sperms, s; D, young tetraspores. Fixed in Flemming's weaker solution, 

 cut 3 II, and stained in iron-alum haematoxylin. A and B X240; C and D X780. 



Nemalion, stained in eosin, makes beautiful mounts, but they al- 

 ways fade. 



Polysiphonia. — This is a very difficult form to handle, but Dr. 

 Yamanouchi has developed an adequate method, and, by following 

 it, anyone should be able to get good preparations. 



For mounting in glycerin, glycerin jelly, or in Venetian turpentine, 

 fix in 10 per cent formalin and stain in iron-haematoxylin. 



For sections, fix in Flemming's weaker solution, but omit the osmic 

 acid for spermatogenesis and germination of carpospores. The time 

 should be very short, 5-40 seconds being sufficient. If material is left 

 too long, it goes to pieces. The chromo-acetic-osmic solution, men- 

 tioned at the beginning of this chapter, may be used. 



