750 



A TEXT-BOOK OF BOTANY. 



material may be placed between pieces of elder or sunflower pith. 

 In some cases the making of sections is facilitated by moistening 

 both the pith and the razor. In the case of seeds and fruits which 

 are very small and at the same time very hard, as colchicum and 

 mustard, it is best to use a velvet or fine grade of cork for holding 

 the material. The cork is indented by means of forceps and the 

 seed or fruit forced into the cavity. 



In the case of very delicate tissues, where the protoplasmic 

 contents of the cells are to be studied, as in the ovaries of flowers, 

 prothalli of ferns and other parts of the plant, where cell division 

 is going on, the material should be embedded in paraffin or celloi- 



FiG. 414. Schematic presentation of the three types of sections: q, cross or transverse sec- 

 tion; /, radial -longitudinal section; /, tangential-longitudinal section. After Meyer. 



din, subsequently hardened, and sectioned by means of a finely 

 adjusted microtome. 



DRIED MATERIAL. Most of the vegetable drugs and some of 

 the vegetable foods occur in commerce in a more or less dried 

 condition, and in order to study them microscopically it is usually 

 necessary to give them some preliminary treatment. With the 

 majority of drugs, soaking in hot or cold water from a few 

 minutes to a few hours will render them sufficiently pliable or 

 soft for sectioning. After this the material is hardened by placing 

 it in alcohol (60 to 70 per cent.) for a few hours or over night. 

 It may then be sectioned and treated with special reagents or 

 stains as desired. Very hard material, as the shells of nuts and 



