Reagents 23 



possible that the danger of producing artifacts may be increased by 

 the heat. 



After fixing is complete, all reagents containing chromic acid 

 as an ingredient should be washed out with water. Running water 

 is desirable, and where this is not convenient the water must be 

 changed frequently. 



About 8 or 10 hours should be long enough for filamentous algae 

 and fungi, which are immediately penetrated by the water. It is a 

 good plan to start the washing in the morning and let the material 

 wash all day. For fern prothallia, onion root-tips, lily anthers, and 

 any material from such a size up to cubes a centimeter square, let the 

 material wash for 24 hours. Even for delicate algae, 24 hours does 

 no damage, and some of the best cytologists prefer the prolonged 

 washing. 



Many methods have been devised for insuring thorough washing 

 and for facilitating the process. The most obvious method is to 

 allow a gentle stream of water to flow into the Stender dish or bottle 

 containing the material. There is little danger in this method if the 

 material is heavy enough to remain at the bottom : the only objection 

 is that much of the water never reaches the bottom where it is needed. 

 If material is lighter, tie a piece of cheese-cloth over the mouth of the 

 bottle. 



An apparatus for washing several collections at one time may be 

 made as follows : Get a piece of f -inch lead pipe, bore holes about T 5 g 

 or f inch in diameter and about 1| inches apart, put a short rubber 

 tube in each hole and the glass part of a pipette in the end of each 

 rubber tube. Connect the lead tube with the faucet by a large 

 rubber tube. A still better way is to bore T Vmch holes in the lead 

 tube, screw into these holes short brass tubes, and then fasten the 

 pipettes to the brass tubes with thin rubber tubes. 



If there are no facilities for working with metal, take a wooden 

 box about 6 inches wide, 18 inches long, and 4 inches deep; bore 

 f-inch holes in the bottom, and into each hole put a piece of rubber 

 tubing about 4 or 5 inches in length. The pipettes can be fastened 

 in the ends of these rubber tubes. Place the box under the tap. In 

 the botanical laboratory at Woods Hole, Massachusetts, large 



