y. Sectioning Unembedded Tissues 



Materials that have sufficient rigidity to withstand the impact of 

 the sectioning knife can be sectioned without embedding. The most 

 rapid and simple method consists of grasping a piece of fresh or 

 preserved plant material in the fingers and slicing with a razor or a 

 razor blade. Extremely thin sections can be cut in this way by a skilled 

 and experienced worker. These methods receive entirely too little 

 attention in teaching and research. These seemingly crude methods 

 can yield excellent preparations for teaching. The student who 

 collects his own materials and makes his own preparations, even 

 though crude ones, gains an understanding of plant structure that 

 cannot be imparted solely by thrusting a neatly labeled finished slide 

 before him. Much wasted effort could be spared in research by 

 adecjuate preliminary survey work conducted by freehand sectioning. 



Written directions are of little instructional value for this work. 

 Patience, experience, and perhaps inherent skill are the chief require- 

 ments. Sectioning can be aided by enclosing the material between 

 pieces of pith or cork. Split a cylinder of pith lengthwise and cut a 

 longitudinal groove or a recess in the pith of appropriate size and 

 shape to receive the specimen. Wrap the two pieces of pith together 

 with thread, and soak in water. The pith expands and encloses the 

 material firmly enough to be sliced with a sharp blade. The tissues 

 and the knife should be kept wet with water and the sections floated 

 in water. The subsec^uent handling of the sections is described at the 

 end of the discussion of sectioning. A drip siphon is a useful device 

 when doing extensive freehand sectioning. Place a 2- to 5-liter bottle of 

 distilled water above the work table, and install a siphon that 

 terminates in a glass tube drawn to a fine aperture. Adjust the siphon 

 with a screw clamp so that a drop of water is released every 2 or 3 sec. 

 and drops into a waste container. The worker can have both hands 

 occupied with the sectioning, and a drop of water for wetting the 

 material or floating a section is instantly available at any time. 



[91] 



