344 The Ohio Naturalist. [Vol, V, No. 7, 



THE AGAR-AGAR AND PARAFFIN METHOD FOR IMBED- 

 DING PLANT TISSUES. 



Harlax H. York. 



In the Journal of Applied Microscopy and Laboratory Meth- 

 ods 6: 2591-2, 1903, the writer gave an account of a method for 

 killing and imbedding plant tissues in a hot solution of agar-agar. 

 While this method is applicable for most histological work, sec- 

 tions cannot always be obtained as thin as are sometimes desired. 

 Recently a method for imbedding and sectioning plant tissues 

 in paraffin after they had been killed and imbedded in a hot 

 agar-agar solution was tried. 



The following are some of the sections made by the agar-agar 

 and paraffin method: Sections of leaf of date palm; sections of 

 leaf of Ficus elastica; sections of stem of Begonia; sections of 

 stem of Equisetum arvense; sections of leaf of beech; sections of 

 a Uromyces on Sparganium eurycarpum; sections of a Phylla- 

 chora on Panicum ; sections of a rust on Scirpus. 



The tissues were first killed and imbedded in a 2 per cent and 

 5 per cent solutions of agar-agar and then imbedded in paraffin 

 in the usual way. 



The 2 per cent solution of agar-agar can be made as follows: 

 Take 10 grams of agar-agar to 500 c. c. of distilled water and boil 

 for two hours. An ordinar}^ oat-meal cooker can be u:ed for 

 boiling this mixture. Filter the agar-agar through a cheese 

 cloth into a glass jar before it is allowed to cool and add for- 

 malin in the proportion of one part of formalin to nine parts by 

 volume of the agar-agar. 



The 5 per cent solution is made in the same way as the 2 per 

 cent solution, only 25 grams of agar-agar to 500 c. c. of distilled 

 water are taken. Formalin should be added in the same manner 

 and proportion as in the 2 per cent solution. Large quantities 

 of the agar-agar solutions can be prepared and preserved in air 

 tight vessels to prevent evaporation. 



The tissues were first put into the 2 per cent agar-agar solu- 

 tion. Put a small quantity of the 2 per cent agar-agar into a 

 test tube or small wide mouth bottle and place with contents 

 into a vessel of boiling water until the agar-agar is melted. After 

 the agar-agar is melted it should be kept at a temperature of 

 70° C. The tissues are placed directly into the hot 2 per cent 

 solution for two hours. Then they are transferred into the 5 

 per cent solution, which has been melted in the same manner as 

 the 2 per cent solution and allowed to remain for an hour or 

 more. The tissues are imbedded in the 5 per cent agar-agar. 

 Take a small wooden block or a plate of glass and with a camel's 

 hair brush put a layer of the hot agar-agar on one end of the 



