BRIEFER ARTICLES 



MANIPULATING MICROSCOPIC ORGANISMS IN STAINING 1 



Perhaps the chief limiting factor in the successful preparation of 

 permanent microscopic mounts of unicellular and colonial organisms is 

 the difficulty of manipulation during the staining, with the incidental 

 loss of the material in the necessary changing of the staining and washing 

 solutions. The small size of such forms as Sphaerella, Pandorina, 

 Volvox, Pediastrum, and the desmids renders these organisms especially 

 liable to loss in these parts of the process. When handling the very small 

 forms, the usual precautions taken in staining filamentous algae are 

 generally wholly inadequate to prevent the loss of the material. 



The difficulties in the way of success, however, may be overcome by 

 using a funnel, filter paper, and a wash bottle, and combining the careful 

 manipulations of quantitative chemistry, to prevent loss of valuable 

 material, with the dehydration and staining methods of the Venetian 

 turpentine method of mounting algae. 2 After the organisms have been 

 killed in the usual i : 1 1400 chromacetic acid solution, the entire contents 

 of the vessel can be filtered, leaving the material to be stained on the 

 filter paper in the funnel. Complete washing to remove the killing 

 fluid can be secured by the use of the wash bottle. Should it be desirable 

 to let the material stand in water for a few hours, the filter paper may 

 be punctured and the material washed out into a beaker (this will save 

 the work of washing). Refiltering later will leave the material on the 

 filter paper and, with a little washing with water from the wash bottle, 

 ready for the staining. 



This manipulation is especially adapted to use with the iron-alum 

 haematoxylin stain. The staining method itself may be greatly short- 

 ened, and in the modified form gives splendid results with these lower 

 forms. The iron-alum should be dissolved in distilled water and all 

 water treatments of material should be made with distilled water to 

 avoid precipitates. Weak solutions of iron-alum should be used, o 1 

 per cent solution at most. Frequently a few drops of a 1 per cent 



Col- 



1 Contribution from the Department of Botany, Pennsylvania State 

 lege, no. 8. ' 



2 Chamberlain, Chas. J., Methods in plant histology, 3d ed. Chicago, 1915 



Botanical Gazette, voL 63] 



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