220 Sargant . — Formation of the Sexual Nuclei 
sections were placed in a small wide-necked bottle half filled with 
distilled water, on the top of which absolute alcohol had been poured 
gently. The alcohol floated for some time on the water, and the 
sections sank down through solutions of gradually increasing density 
until they lay in the pure water at the bottom. Then the alcohol was 
drawn off by a pipette. 
C. STAINING. 
i. Flemming s orange method for material fixed in Flemming'' s 
solution , Hermanns solution , or chromic acid. 
There is little to add to the account given in Part I, p. 474. For 
early stages in the development of the pollen-mother-cell, the potassium 
permanganate was used as a mordant both before and after the 
treatment with safranin. The safranin and gentian violet solutions 
were also of double the usual strength for these stages. For later 
ones — as the first nuclear division in the pollen-mother-cell — the 
ordinary treatment was sufficient. 
2. Mayer's haemalum for chromic material. 
The sections were placed for half an hour in a -5 % solution of 
ferric chloride in water, rinsed and transferred to Mayer’s haemalum, 
nearly full strength. They usually took about two hours to stain 
to the right depth. If the sections were kept alkaline by rinsing 
in hard water and by the use of neutral alcohols, they were of a brilliant 
blue and very permanent. 
3. Mayer's haemalum for absolute alcohol-material. 
The sections were treated as above, but with -i % solution of ferric 
chloride for half an hour, and 10 % solution of Mayers haemalum in 
• 1 % solution of potash alum for about twelve hours. 
4. MI ethyl-green and acid fuchsin for alcohol-material. 
These colours were used in aqueous solution, their proportions 
varied to suit different stages. 
5. Renaut’s haematoxylic eosin for alcohol-material. 
The same treatment as that given in Part I, p. 474, was used. 
