SPECIAL METHODS 
133 
the edges. Such preparations may be used directly as lantern slides. 
Large sections of the stem of a tree fern make good mounts without 
any staining. Large sections of cornstalk are rather hard to cut, 
because the rigid bundles tear through the soft parenchyma. Flood¬ 
ing with 95 per cent alcohol facilitates the process. A slight harden¬ 
ing is sufficient, so that about 4 or 5 sections can be cut in a minute. 
The corn stem, and similar structures, can be cut in paraffin by Miss 
Langdon’s method, described on page 93. 
STONY TISSUES 
Sections of the stony tissues of hickory nuts, walnuts, peach 
stones, and similar refractory substances cannot be cut by ordinary 
methods. 
With a fine saw, saw sections about 1 mm. in thickness. Rub 
a section between 2 pieces of fine sandpaper until it is not more 
than half a millimeter in thickness. Then rub it between 2 smooth 
hones, keeping the hones wet with water. When the section is thin 
enough, wash it thoroughly in water, using a pipette to rinse off any 
particles of dirt. Dehydrate in absolute alcohol, clear in clove oil, 
and mount in balsam. The long, narrow pores show better without 
any clearing. In this case, dry the section thoroughly, heat a few 
drops of balsam on the slide to drive off the solvent, put the section 
into the balsam, and add a cover. The air caught in the long, narrow 
pores will make them appear as black lines. Sections of most nuts 
show excellent detail without any staining. Thin sections, however, 
may be stained in the usual way. 
PETRIFACTIONS 
Paleobotany has made such rapid progress during the last ten 
years that scarcely any problem involving the anatomy of living 
vascular plants can be investigated intelligently without some knowl¬ 
edge of Mesozoic and Paleozoic forms. Material, especially that of 
Paleozoic Pteridophytes and Gymnosperms, is becoming available, 
and consequently it is increasingly necessary for laboratories to have 
apparatus and technic for cutting rock-sections. 
The outline of the process of cutting a rock-section is very simple: 
1. Saw the rock into two pieces. 
2. Polish the cut surface. 
3. Fasten the cut surface to a piece of glass with hot shellac. 
