190 



Methods in Plant Histology 



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. 



FIG. 48. Polysiphonia fibrillosa: from a preparation fixed in chromo-acetic acid, 

 stained in eosin, and mounted in glycerin; X255; A, an antheridium ; B, a cystocarp. 

 with carpospores; C, a tetrasporic branch with tetraspores. 



The time should be very short, 5 to 40 minutes being sufficient. If 

 material is left too long, it goes to pieces. Wash in a gentle stream of 

 sea-water for 24 hours. Stain in iron-haematoxylin. and then for 

 2 to 3 minutes in safranin (Figs. 48 and 49). 



With very delicate forms, like Callithamnion and Griffithsia, the 

 washing may be in part or even wholly omitted, and the chromic acid 

 extracted by the lower alcohols, the material being kept in the dark. 



Corallina. Corallina and other forms whose surface is incrusted 

 with lime need special treatment. The following solution is good: 



Chromic acid 1 g. 



Glacial acetic acid 1 c.c. 



Sea-water. 100 c.c. 



