FUNDAMENTAL CONSIDERATIONS 15 



MAKING OF SECTIONS 



Free-hand Sectioning. Free-hand sections are usually satisfactory 

 for the general examination of roots, stems, leaves, barks and many 

 fruits and seeds. Material which is fresh may be sectioned at once, 

 but dry material should be well soaked in warm water before using. 

 Very hard material like heartwoods, the shells of nuts and seeds, 

 may be softened in solution of caustic potash or ammonia water 

 and then washed free of alkali before sectioning. 



The object to be sectioned is held between the thumb and finger 

 of the left hand. If tender and flexible, such as a flat leaf, it must 

 be placed between the two flat surfaces of elder pith before sec- 

 tioning. A segment of pith about an inch long is halved lengthwise 

 with a sharp knife and a portion of the leaf is held between the halves 

 of pith while the section is cut through pith and leaf. The pith 

 is later separated from the leaf section. Sections through other 

 delicate parts of plants may be made in the same way, only a groove 

 should be made in the pith of such size as is necessary to hold the 

 material firmly enough without crushing it. In certain instances, 

 when, because of the smallness of the object and its resistance to 

 cutting, good sections can not readily be made with the aid of pith, 

 a small sized cork stopper can be used with better results. A hole 

 just large enough to prevent the object from slipping is made in the 

 center of the smaller end and the object inserted preparatory to 

 sectioning. The upper surface of the razor is wetted with water or 

 50 per cent, alcohol. The razor, which should be real sharp, is held 

 in the right hand and is drawn across the object with the edge toward 

 the student and the blade sliding on the forefinger of the left hand. 

 The sections should be cut as thin as possible. As soon as a number 

 of sections have been cut, they can be transferred to a vessel of water 

 with a camel's hair brush. 



Sectioning in Paraffine or Celloidin. When it is necessary to study 

 the microscopic structure of very delicate plant parts, superior results 

 can generally be obtained by imbedding the material in paraffine 

 or celloidin, which is subsequently hardened, and sectioned by means 

 of a sliding or rotary microtome. 



