APPARATUS AND SUPPLIES 303 



it best to secure much of the material during the growing season and 

 preserve it until the time for use. Material collected can be prepared 

 by placing it immediately in 95 per cent alcohol and then transferring 

 it after twelve hours into 70 per cent alcohol, in which it may be stored 

 for future use. Material may also be prepared in a 2 or 2^ per cent 

 solution of formalin. Formalin burns the skin. 



Free-hand cutting and mounting. To cut sections, the material 

 may often be held between pieces of pith or smooth cork by the fingers. 

 The material and sections should be kept wet with alcohol during the 

 time of cutting. 



The sections when cut should be wet in water, then stained with 

 Delafield's hematoxylin for a few minutes; drain off the hematoxylin 

 and rinse with water; then use 95 per cent followed by absolute 

 alcohol, to extract all the water from the sections; then pour on xylol 

 for a few minutes. If the section is too heavily stained, some of the 

 stain may be removed by repeated rinsing with water. Mount the 

 section on the slide in a drop of balsam and cover with the thin cover- 

 glass. Mounts so made are permanent. 



Hematoxylin does not mix readily with alcohol, and balsam does 

 not mix with water nor with alcohol. Sections mounted before they 

 are freed from water become cloudy and worthless. 



All materials should be kept covered when not in actual use, and 

 always in order. (Figs. 475, 476.) A good work-table may be made on 

 the side of the school-room. (Fig. 477.) 



Microtome sectioning. The sectioning may be improved by the 

 use of a hand microtome, that may be purchased of a dealer at 

 small cost. A more complicated microtome may be employed, but in 

 this case the material must first be imbedded in a matrix like collodion, 

 paraffine or other substance. This imbedding is a complex process; 

 the material must first be treated with various reagents. The method 

 will not be considered here. The reader should refer to Chamberlain's 

 "Methods in Plant Histology" or to Stevens' "Plant Anatomy" for 

 the methods necessary and for directions for staining. 



476. Box of microscope slides, and a packet of collodion drying in a glass vessel. 



