6 



Methods in Plant Histology 



the condenser ? Why does the mirror bar swing ? Why is one side 

 of the mirror plane and the other concave ? Everyone who uses 

 even a cheap microscope should know the answers to questions like 

 these. All the leading manufacturers furnish, free of charge, booklets 



explaining the construction 

 of the microscope and giving 

 practical directions for its 

 care and use. 



Aside from the micro- 

 scope itself, the microtome 

 is the most important piece 

 of apparatus in the labora- 

 tory. In recent years there 

 has been considerable im- 

 provement in microtomes, 

 but we still have two gen- 

 eral types, the sliding and 

 the rotary. 



The cheapest microtomes 

 which have proved to be 

 efficient for general work are 

 simple forms of the sliding 

 microtome like the one shown 

 in Fig. 2. It should be pro- 

 vided with a clamp which 

 will hold any kind of a knife 

 (Fig. 3). For large or hard 

 objects the weakness of these 

 small instruments is evident 

 from the figures. 

 Where expense is not too great an objection, a larger microtome 

 should be secured. There is great difference of opinion as to the 

 relative merits of the sliding and rotary types. As far as convenience 

 and rapidity are concerned, the rotary microtome is unquestionably 

 superior; further, it will produce good sections with less care and skill, 

 because the movements are automatic. The fact that a ribbon 



FIG. 1. An efficient microscope of moder- 

 ate price. The leading optical companies put 

 the same objectives and oculars upon such in- 

 struments as upon their most expensive stands. 



