24 Methods in Plant Histology 



quantities of material are washed at one time by using an ordinary 

 washtub with the bottom arranged as just described for the box. 

 If one is using such a large box or tub and does not need all the 

 streams of water, the tubes not in use may be closed by means of 

 clamps. 



The following is a simple and effective method : Cut f - or J-inch 

 glass tubing in pieces about 2 inches long, make flanges on both ends 

 by heating in a Bunsen flame and pressing against a flat piece of 

 iron or stone, and then fasten cheese-cloth over the ends. A dozen 

 or more may be washed at one time by placing them in a pan and 

 allowing water from the tap to flow into the pan. There should be 

 holes in the bottom of the pan so that about half the water will flow 

 through the holes rather than over the rim of the pan. Some use 

 little bags of cheese-cloth instead of the glass tubes. 



If running water is not available, put the material into a rather 

 large bottle or dish; a 200 c.c. bottle is not too large for half a 

 dozen J-inch cubes. Change frequently, especially at first. Nothing 

 is safe with less than 24 hours of this sort of washing. 



If the washing has not been thorough, the subsequent staining 

 is likely to be unsatisfactory. 



Some of the chromic-acid formulae are as follows : 



a) Stock Chromo-Acetic Solution.- 



Chromic acid 1 g. 



Glacial acetic acid 1 c.c. 



Water 100 c.c. 



This solution has been used quite extensively in embryological 

 work upon the higher plants. It fixes thoroughly, but often causes 

 plasmolysis in cells with large vacuoles. 



6) Weak Chromo-Acetic Solution (Shaffner's formula). - 



Chromic acid . 3 g. 



Acetic acid . 7 g. 



Water 99.0 c.c. 



This has also been used in embryological work. It causes little 

 or no plasmolysis. Difficult material, like Aster heads and ripe 



