The Microscope. 91 



Embedding Plant Tissues. — Dr. E. Schonland, of the University 

 of Oxford, claims to have reached the long-desired process of embed- 

 ding delicate plant-tissues in paraffin, so that nnshrunken serial 

 sections may be cut by the ribbon method. His process is described 

 essentially as follows in the Botanisches Centralhlatt,yo\. xxx, (1887) 

 p. 284: The object should be stained entire in borax-carmine, for 

 which twenty-four hours suffices; then place it in 30 per-cent. alcohol, 

 to which a trace of acetic acid has been added, and then in succes- 

 sively stronger alcohol, up to the strongest commercial, which is 92- 

 95 per cent. ; it is next transferred carefully to a small vial (contain- 

 ing 3-4 cm.) of equal parts of clove-oil and strong alcohol; at first 

 it will float, but when it has sunk to the bottom, which often takes 

 some time, it should be transferred to pure clove- oil, and after an 

 hour into oil of turpentine, in which it must i-emain about six hours. 

 Finally it is placed in melted paraffin for 8-10 hours. The paraffin 

 used must have a melting-point of about 45^ C, and its temperature 

 must never go above 47'^; for keeping the temperature constant, the 

 well-known thermo -regulator must be used. The embedding is done 

 in the usual manner, using either the paper-tray, or the L-shaped 

 pieces of metal. It is generally best to raise the temperature of the 

 paraffin somewhat shortly before pouring it into the mold, to pre- 

 vent the formation of bubbles on cooling. The manipulations for 

 cutting the ribbons of sections with the rocking or sliding microtome 

 are the same as with animal tissues. The sections are fastened to 

 the slide with a mixture of one part of collodion and three parts of 

 clove-oil, or a mixture of filtered white of e^g and glycerine. The 

 first is preferable in case one desires to stain the sections on the 

 slide, while the latter is generally reliable when the fixing only is 

 desired. The slide is then put in a warm place for a short time, or 

 warmed gently over a flame, then plunged into turpentine or flooded 

 with it to dissolve the paraffin. It is then ready for staining or 

 mounting in the usual way. * * * The author adds that the 

 results which can be attained are almost incredible. In serial sec- 

 tions of leaves one can, not infrequently, get four to six sections 

 through the same stoma, and it is easy to get several sections through 

 the apical cell of a fern root, when the embedding is rightly done. 

 * * * — Botanical Gazette. 



