THE MICROSCOPE. 161 



SECTIONING FERN PROTHALLIA AND OTHER 



DELICATE OBJECTS. 



By M. B. THOMAS, 



CRAWFOEDSVILLE, 1ND. 



The material to be sectioned is first hardened by placing it in 

 10 per cent alcohol in a dehydrating apparatus and allowing it 

 to remain for 24 hours. It is then taken out and placed for 1 

 hour in 95 per cent alcohol to insure complete dehydration after 

 hardening. After this the tissue is placed in a li per cent solu- 

 tion of collodion and allowed to remain in a tightly corked vial 

 for 12 hours. (The collodion is be^t made by dissolving li 

 grams of gun cotton in 100 c. c. of equal parts ether and alcohol.) 



The cork is then removed and by slow evaporation of the ether 

 and alcohol the collodion will thicken. When it is of the con- 

 sistency of ordinary glue the tissue is taken out and placed in 

 a paper boat, of the kind used in paraffine imbedding, or an or- 

 dinary watch glass will answer the purpose. The thick collo- 

 dion is then poured over the tissue and it is allowed to harden 

 in the air until a firm film is formed over the surface. 



It is better to pour out the tissue from the vial with the col- 

 lodion and thus prevent it from being broken by handling. 



After the firm film is formed the dish is placed in a jar of 85 

 per cent alcohol and allowed to remain from 5 to 6 hours until 

 the collodion is quite firm. Then with a thin knife cut out a 

 block of the collodion containing the tissue inside. 



The block can be placed in any desired position on the end 

 of a cork and held while thick collodion is poured over it until 

 enough is applied to completely cover it. Each coat as added 

 should be allowed to slightly harden before applying the next 

 until the operation is completed. 



After this is accomplished and the whole allowed to partially 

 solidify in the air, the material is placed in ajar of 85 per cent 

 alcohol where it should remain to harden 6 to 8 hours. 



The cork can be fastened in the jaws of any sliding microtome 

 and serial sections of any desired thickness made in the usual 

 way. 



The knife should be kept wet with alcohol during the opera- 

 tion, and the sections removed from the knife to the slide by 

 means of camel's hair brush. 



