The Preparation of Whole Mounts and Smears 105 



3 parts alcohol to 1 part TBA (anhydrous tertiary butyl alcohol) 



2 parts alcohol to 2 parts TBA 



1 part alcohol to 3 parts TBA 



Pure TBA; change twice at 15-min. intervals 



Transfer to a large volume of 5%. solution of balsam or synthetic 

 resin in TBA in a short wide-mouthed bottle. Allow the TBA to 

 evaporate slowly at a temperature of about 35 °C. When' the balsam 

 is slightly more fluid than that used for covering sections, mount the 

 material. Remove a suitable quantity of the plant inaterial with its 

 enveloping balsam, place on a dry, clean slide and lower a dry cover 

 glass carefully so as not to produce bubbles or to push the plants too 

 close to the edges. Dry the finished slides in a horizontal position. 

 (Johansen, 1940.) 



THE DIOXAN-BAISAM METHOD 



This is the most promising of the newer methods of making whole 

 mounts. The method was worked out in almost identical form inde- 

 pendently by McWhorter and AV^eier (1936), Johansen (1937), and 

 the present writer. It is probable that numerous other workers had 

 developed similar schedules. 



Stain filamentous or other delicate materials as in the preceding 

 methods. Pass through a series of aqueous solutions of dioxan, con- 

 taining the following percentages of dioxan: 20, 40, 60, 80. 90, then 

 three or more changes of anhydrous, chemically pure dioxan. The 

 interval in each should be 1 to 2 hr. Examine a few filainents under 

 a microscope, mounted in the last fitiid. If the material is in good 

 condition, transfer to a 10% solution of balsam or resin in dioxan. 

 Use a wide-mouthed bottle and gauge the volume of the liquid so 

 that the material does not become exposed as the dioxan evaporates. 

 Place the uncovered container into an oven or a dust-free place at 

 a temperature of approximately 35 °C. The dioxan evaporates in 

 2 to 8 hr., leaving the material in thick balsam in which it is mounted. 

 Extremely fragile materials, such as Volvox or I'aiicheria, should be 

 started in 5% resin and evaporated very slowly by keeping the con- 

 tainer loosely covered. 



This process is so rapid that it is worth the time to carry small 

 trial lots of the material through the process at different speeds. The 

 condition of the material can be examined at various points in the 

 process. When the optinuim or shortest safe schedule is found, the 

 main batch of material can be carried throiiph. 



