8 



METHODS IN PLANT HISTOLOGY 



the construction of the microscope and giving practical directions for 

 its care and use. 



Aside from the microscope itself, the microtome is the most impor- 

 tant piece of apparatus in the laboratory. In recent years there has 



been immense improvement 

 in microtomes, but we still 

 have only two general types 

 — the sliding and the rotary. 

 If there is to be only one 

 microtome, it should be of the 

 sliding type; for all kinds of 

 sectioning can be done with 

 the sliding microtome, while 

 only paraffin ribbons can be 

 cut with the rotary. The ro- 

 tary microtome is convenient, 

 rapid, and, to a large extent, 

 eliminates the necessity for 

 skill; but a good sliding mi- 

 crotome, in the hands of an 

 expert, will yield paraffin sec- 

 tions superior to any which 

 can be cut with a rotary mi- 

 crotome. Paraffin sections of 

 root-tips have been cut as thin 

 as I M with the medium-priced 

 sliding microtome shown in 

 Figure 2. It should be provid- 

 ed with a clamp which will 

 hold any kind of knife ; but we 

 should strongly recommend, 

 in addition, the clamp shown 

 in Figure 3, which will hold 

 any of the thin safety razor blades. For any sections not more than 

 f inch square, the safety razor blade is long enough. Paraffin ribbons 

 f inch wide can be cut with safety razor blades. Celloidin sections, 

 up to f inch square, can be cut with the safety razor blade; but larger 

 sections must be cut with a microtome knife. 



Fig. 1. — An efficient microscope of moderate price. 

 The leading optical companies put the same objec- 

 tives and oculars upon such instruments as upon their 

 most expensive stands. 



