Killing, Fixing, and Storing Plant Tissues 73 



Picric acid, saturated aqueous solution. 



2% osmic acid. 2 g. crystals in 100 cc. of 1% chronn'c acid, or in 100 cc. of 



water. 

 Ethyl alcohol; commercial 95% grade and anhydrous grade. 

 Bichloride of mercury (HgCL) crystals. 



The use of stock solutions ot 1% and lO^f acetic or propionic 

 acid is advocateci because the error involved in measuring a small 

 volume, say 1 cc, of glacial acetic acid is much greater than in measur- 

 ing 10 cc. of 10% acid. 



Apparatus 



Use specimen bottles that hold a generous cjuantity of killing 

 fluid, especially with bulky or succulent materials that may dilute 

 tlie formula. After washing and partial dehydration, materials may 

 be transferred to smaller bottles or vials for the remainder of the 

 process. 



When the pieces of plant material are dropped into the killing 

 fluid, the hairs, stomates, folds, and other cavities of plant organs 

 retain air bubbles which retard penetration by reagents. If the pieces 

 do not sink at once, attach the bottle to an aspirator, and apply 

 suction for repeated short intervals until the pieces sink, if not to 

 the bottom of the liquid, at least under the surface. Use a safety 

 bottle (Fig. 3.1 A) to keep water from backing into the specimen 



Fig. 3.1— Aspirator setup for pumping specimens in killing fluid: A, safety bottle 

 with finger valve or glass stop clock; B, specimen bottle or large empty bottle into 

 Avhich specimen bottle is placed; C, pint jar used as container for large specimens 



