CELLULAR ANATOMY OF THE LEAF 2 1/ 



cells, and by the study of good figures from books. For 

 epidermis the best object is the Tradescantia pilosa or Wan- 

 dering Jew, common in greenhouses, particularly the leaves 

 with a purple color on the under side. By holding these 

 up to the light the stomata (guard cells) may be seen 

 with a lens, showing green against the purple, and the epi- 

 dermis easily strips off; it should be placed in water under 

 a cover glass. 



For the entire internal anatomy, leaves of India Rubber 

 Plant (Ficus elastica} are very good, and are easy to section 

 fairly well with scalpels ; they should be cut across the bundles 

 which run out from the midrib. But prepared and mounted 

 microtome sections are necessary for the full demonstration of 

 cellular anatomy. Such sections show the tissues in great 

 completeness and beauty. The Ficus leaf cannot well be used 

 for the epidermis and stomata, for in it these are far from typical. 



Pedagogics. This exercise is to teach the structure of the 

 plant cell, the use of the microscope, and the nature of the 

 cellular anatomy of the higher plants, and also is for training 

 in observation of minute but definite objects. The subject is 

 difficult for beginners, but is altogether too important to be 

 omitted from a well-proportioned course. 



In teaching the use of the microscope, its proper function 

 as simply an aid to vision, and not as a tool with mysterious 

 properties of its own, should be made plain from the start. 

 This is best done by leading students to see all possible with 

 the naked eye ; when the limit of this is reached, then simple 

 lenses are to be used, - - and when limit of these is reached 

 then low powers of the microscope ; certainly all possible of 

 cellular anatomy should first be brought out without the micro- 

 scope, and they should not take to its use until it is unavoid- 

 able. To learn how to focus, move objects, etc., the low power 



