686 PLANT CHROMOSOMES 



the mid-prophase stages (pachytene) in pollen mother-cells of 

 Zea Mays, recommends that the slides be gently heated after the 

 coverslip has been applied. The pollen mother-cells flatten, the 

 nuclear membrane disappears and the long thread-like para- 

 synapsed chromosomes are mostly spread out in a horizontal 

 plane. 



Sax and Sax (J. Arnold Arboretum, xiv, 1933, p. 356) dissect out 

 entire endosperms from female cones of Coniferales and fix them 

 in 70 parts absolute alcohol mixed with 30 parts acetic acid. Fix 

 several hours and store in 80 per cent, alcohol. They make 

 aceto-carmine smears from the fixed material. This haploid tissue 

 is very useful for study. 



HusKiNS (Journ. Genet, xviii, 1927, p. 315) fixed material in 

 Carnoy, stored it in 70 per cent, alcohol and later prepared slides 

 by Belling's second method. 



By smearing a single anther, immediately flooding with Belling's 

 aceto-carmine and heating over a spirit flame for a second, the slide 

 is ready for immediate examination to determine the stage of 

 meiosis. Thereafter the rest of the anthers can be rejected or used 

 for further treatment by this or any other method. The worker is 

 thereby saved endless labour, since only material at the correct 

 (or approximately correct) stage is subjected to lengthy teclmiques. 



See also Belling, " The Use of the Microscope ; Belling, 

 Journ. Roy. Micr. Soc, 1925, p. 445 ; de Meyere, Zool. Anzeig., 

 Ixxxviii, 1930, p. 209. 



1370. Permanent Iron-Aceto-carmine Preparations in Canada 

 Balsam. First designed by Belling {Biol. Bull. Marine Biol. 

 Lab., 1, 1926, p. 160). See also Longley {J. Agr. Res., xxxv, 

 1927, p. 769). 



McClintock {Genetics, xiv, 1929, p. 180) dried smears slowly 

 and mounted them in balsam. She has also described {Stain 

 Tech., iv, 1929, p. 53) a highly satisfactory method of making 

 permanent aceto-carmine smears. Anthers are collected and put 

 into a mixture of 1 part acetic acid to 3 parts absolute alcohol. 

 Fix twelve to twenty-four hours. The contents of an anther are 

 squeezed out on a slide into a drop of Belling's iron aceto-carmine 

 solution (Belling's second procedure above) and a cover-glass is 

 placed over the drop. Care should be taken to remove all anther 

 walls and other flower parts. Then heat the slide over a spirit 

 flame for a second, repeating four to five times. Next, place the 

 slide in a Petri dish filled with 10 per cent, acetic acid. When the 

 cover-glass has risen away from the slide remove it and place both 

 it and the slide in a Coplin jar containing equal parts of alcohol 

 and acetic acid. Some pollen mother-cells stick to the slide and 

 some to the cover. Run both coverslip and slide through the 

 following solutions : 1 part acetic acid to 3 parts of absolute 

 alcohol, 1 part acetic acid to 9 parts absolute alcohol, absolute 



