208 
METHODS IN PLANT HISTOLOGY 
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 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 (Fig. 52). This short stain in safranin 
gives a faint rosy tinge to mucilaginous structures, but does not obscure 
the fine nuclear detail. In the nucleus of the sperm, the chromosomes 
remain distinct, so that the number, 20, can be counted from the 
time the sperm is formed (Fig. 52C) up to fertilization. 
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. 
Fix 24 hours, changing the fixing agent 2 or 3 times. Wash 24 
hours in sea-water. 
If carefully applied, the following is a good method: Put the 
material into 5 per cent glacial acetic acid (in sea-water) and watch 
it. As soon as the vigorous effervescence begins to subside, rinse 
in sea-water and transfer to Flemming’s weaker solution, and fix 
24 hours. Iron-haematoxylin is best for figures, but for general 
structure the safranin, gentian-violet, orange combination gives 
beautiful results. 
