Journal of Applied Microscopy. 335 



Lily ovaries require one to four hours ; heads of aster at the fertiUzation period, 

 six to twelve hours. Some claim that even delicate objects, like fern prothallia 

 and the filamentous algai and fungi, are not injured by a bath of several days if 

 care be taken not to let the temperature rise above 48 degrees C. to 50 degrees C. 

 7. Imbedding. — Material may be imbedded in paper trays, watch crystals, or 

 in apparatus made for the purpose. Embedding L's 

 consisting of two L-shaped pieces (Fig. 6) of brass, 

 type metal, or lead, are very convenient. We use a 

 pair of L-shaped pieces with arms three inches long. 

 These furnish a box of almost any required size. A 

 piece of glass serves for a bottom. The tray, Minot, 

 or whatever is used should be slightly smeared with 

 glycerine, to prevent sticking. If several objects are to be imbedded in one dish, 

 it is best to have the dish as near the temperature of melted paraffin as possible, 

 otherwise the objects may stick to the bottom and it will be impossible to 

 arrange them properly. Great care should be taken, however, not to have the 

 dish too* hot, since too high a temperature not only injures the material, but 

 also prevents a thorough imbedding. Pour the paraffin with the objects into 

 the imbedding dish and cool as rapidly as possible. If paraffin cools slowly 

 it crystallizes and does not cut well. 



S. Cutting. — Twenty minutes after an object is imbedded it is ready for 

 cutting. Trim the paraffin containing the object into a convenient shape and 

 fasten it upon a block of wood. Blocks of pine three-fourths of an inch long and 

 three-eighths of an inch square are good for general purposes. Put paraffin on 

 the end of the block so as to form a cap about one-eighth pf an inch thick. 

 Warm the cap and the bottom of the piece containing the object and press them 

 lightly together ; then touch the joint with a hot needle, put the whole thing into 

 cold water for a minute, and it is ready for cutting. Cutting can be learned only 

 by experience, but a few hints may not come amiss : a. Keep your knife sharp, 

 b. Keep the microtome well oiled and clean, c. Trim the block so that each 

 section shall be ■a. perfect rectangle. The knife, which should be placed at a right 

 angle to the block and not obliquely, should strike the whole edge of the block at 

 once, and should leave in the same manner, d. Sections will usually come off 

 in neater ribbons if the knife strikes the longer edge of the rectangle so that the 

 sections are united by their longer sides rather than by the shorter. 



9. Fixing Sections to the Slide. — Sections must be firmly fixed to the slide or 

 they will be washed off during the processes involved in staining. Mayer's 

 Albumen Fixative is excellent for this purpose. Formula : 



White of Egg, 50cc. (Active principle.) 



Glycerine, 50cc. (To keep it from drying up.) 



Salycilate of Soda, 1 g. (Antiseptic to keep out bacteria, etc.) 



Shake well and filter. It will keep from two to six months. The fixative may 

 be used alone or in connection with the water method. Put a small drop 

 of fixative on the slide, smear it evenly over the surface and then wipe it off with 

 a clean finger or piece of linen until only a scarcely perceptible film remains ; 



