Autoradiography 395 



these preparations practical for class study and demonstration. \o dan- 

 ger of breakage is in\ olved, and if the plastic gets marred, the scratches 

 can be polished away. 



apparatus: 



Photo-Seal Kit {Therm Appliance Manujacturing Company, 608 S. 

 First Street, St. Charles, Illinois): consists of an electric sealing press 

 of two 4'' X 5" aluminum platens with a 300W, 1 15V heater cast into 

 the bottom platen, two 4" X 5" nickeloid polished plates and other 

 necessary accessories. 



procedure: 



Root tip preparations: 



1. Fix, hydrolyze, dehydrate and stain. 



2. Arrange root tips in a drop of stain on a sheet of clear \'inylite 

 plastic, I" X 3" and 15 mils thick. 



3. Cover with a second sheet of plastic. 



4. Place preparation between two sheets of bibulous paper, and ap- 

 ply pressure. 



5. When spread, remove papers and top piece of plastic; add identi- 

 fication label if desired, and a third clean piece of plastic. 



6. Place between plates of electric press, tighten wing bolts, and heat 

 for 3 minutes. 



7. Cool imder running water, and remove preparation from bet^veen 

 plates. 



Section mounts: 



1. Mount on plastic in same manner as on glass slide. 



2. Dissolve paraflin in carbon tetrachloride: 20 minutes. 



3. Hydrate, stain, dehydrate and clear. A short stay in xylene will not 

 dissolve the \^inylite. 



4. Place second sheet on top, and laminate. 



comments: 



The nickeloid plates can be protected from tarnishing \vith alimii- 

 num foil sheets. 



Autoradiography 



The use of radioactive isotopes as tracers, localizing in an organ, a 

 tissue, or individtial cell, has pushed autoradiography into a position 

 of considerable importance. The rays and particles of liie isotope in tis- 



