4 PEACTICAL BOTANY. 



Cutting Sections. A sharp razor is the best 

 cutting instrument. Care must be taken to keep the 

 object and the razor wet during the process of cutting, 

 in order to avoid the entrance of air into the tissue, and 

 to prevent adhesion of the section to the razor. When 

 fresh material is cut, water or very dilute alcohol may 

 be used for this purpose, but if material which has been 

 hardened is cut, it is advisable to use alcohol of the 

 same strength as that in which the material has been 

 preserved. 



When a successive series of sections of an object is 

 required, a microtome may be used. 



Imbedding. The objects are frequently so large 

 that they may be held in the hand whilst they are 

 being cut. If they are too small for this it is convenient 

 to imbed them in some substance. 



The simplest method is to fix the object into a slit in 

 a piece of pith. Elder-pith is the best. 



When the sections are to be made with a microtome, 

 it is more convenient to imbed in some easily fusible 

 substance ; by this means also the position of the object 

 is less likely to be distorted in the process of cutting. 

 Many mixtures of waxy and fatty substances are used 

 for this purpose, of which the following is perhaps the 

 best : 



Solid paraffin (melting-point about 58 C.) : 2 parts. 



Yaselin : 1 part. 



These must be melted together and well stirred. The 

 resulting substance is sufficiently transparent to enable 

 the exact position of the object to be ascertained ; it is 

 easy to cut, and it is readily soluble in carbolic acid and 

 turpentine. The relative proportions of paraffin and 



