October 11, 1912] 



SCIENCE 



479 



tation to the needs of man. " We are now," 

 says Mr. Brooks, " applying science to the 

 affairs of the nation as never before. The old- 

 fashioned publicist with his classical educa- 

 tion, or, at least, traditions, is being shoul- 

 dered out of the way by the man who analyzes 

 the problems of public welfare on scientific 

 principles. . . . Yet there are not a few geolo- 

 gists, though I believe a constantly decreasing 

 number, who seem to view with suspicion any 

 attempt to make the science of geology more 

 useful." We believe comment upon these 

 statements would be altogether superfluous. 

 Wm. H. Hobbs 

 University of Michigan, 

 June 4, 1912 



PREPARATION OF WHOLE POLLEN MOTHER CELLS 



To THE Editor op Science : The brief article 

 by Albert Mann on the preparation of whole 

 pollen mother cells for the examination of 

 mitotic figures, in Science for August 2, sug- 

 gested that others might be interested in some 

 experiments made along the same line by the 

 writer during the winter of 1911-12. The 

 technical difficulties presented by the method 

 worked out at that time are somewhat greater 

 than in that suggested by Mann, but the re- 

 sults were, on the whole, quite satisfactory. 



Whole anthers, which from previous ex- 

 amination were known to represent the stages 

 wanted, were fixed for 30 hours in strong 

 chrome-acetic acid. They were then carefully 

 washed in running water for 24 to 30 hours 

 and gradually run up to 80 per cent, alcohol, 

 in which they were allowed to harden for 

 several weeks. They were then stained for 3 

 to 5 days in a strong cochineal tincture, or 

 in Kleinenberg's hematoxylin. The stains 

 were rinsed off with 80 per cent, alcohol. The 

 specimens were further dehydrated, and after 

 resting in absolute alcohol for 6 to 8 hours 

 were put into a mixture of equal parts of ab- 

 solute alcohol and cedar oil in an open vial or 

 small cylinder. They were allowed to remain 

 in the open vessel on the paraiEn oven until 

 the alcohol had completely evaporated, requir- 

 ing 2 to 3 days. Finally specimens were care- 

 fully dissected or teased apart in a drop of 



oil on a slide, and mounted by the addition of 

 a drop of cedar-oil-balsam and a cover. 



The important points are the hardening of 

 cell walls before staining, the use of 70 per 

 cent, alcoholic stains which do not overstain, 

 and the gradual transfer from dehydrating to 

 clearing and mounting medium, thus avoid- 

 ing shrinkage of delicate cells. To any one 

 acquainted with the two classes of stains the 

 advantage of one which does not overstain to 

 one which must be washed out for differentia- 

 tion is well known, when dealing with mass 

 staining. In trying out Mann's suggestions 

 the writer found difficulty in preventing col- 

 lapse of cells and in getting uniform results 

 from the stains. The triple stain is espe- 

 cially difficult to manage in mass staining, 

 and although a solution of Orange G. in clove 

 oil, which gives the very best results with sec- 

 tions, was used, only a small portion of the 

 material gave really satisfactory results. 



Some of the stains used by the writer are 

 new and the formulse are given here for those 

 who may care to try them. 



Cochineal Tincture, Ammonia-acetate. — 

 Digest 5 g. powdered cochineal with 150 c.e. 

 70 per cent, alcohol and 3 c.c. of glacial acetic 

 acid at a temperature of 60-70° 0. for 5 to 

 8 hours. Add ammonia until solution is neu- 

 tral or but slightly acid and digest for 4 or 5 

 hours as before. Cool and filter until clear. 

 Transfer to stain from 70 per cent, or 80 per 

 cent, alcohol and rinse off excess with the 

 same. 



This solution does not overstain, and with 

 material fixed in chrome-acetic acid stains 

 chromatin lavender to violet and protoplasm 

 a very light pink. In preparing fern prothal- 

 lia for whole mounts the writer has found this 

 to stain sperms and egg cells a violet tint with 

 cell walls rose color. 



For preliminary examination of pollen 

 mother cells the old acetic-methyl green 

 (5 per cent, to 10 per cent, glacial acetic acid 

 added to a half saturated solution of methyl 

 green in water) is the most generally useful, 

 but it is of little value where gelatinous or 

 slimy sap is present. For such cases the 

 writer has found the following solution of 



