248 ELEMENTS OF BOTANY. 



and the sketch which the pupil is making, — all whUe the work is 

 going on. But if the class unfortunately consists of from twenty- 

 five to forty pupils, in an ordinary recitation room, a good deal of 

 ingenuity will be needed to secure results of any value. 



The microscopes with the prepared objects should be placed upon 

 the desks or tables which are best lighted. 



If there are several instruments it will usually be found preferable 

 to use all of them during any given recitation upon preparations of 

 the same object, but to have some provided with lower and others 

 with higher powers. 



It is important to have a card attached to each microscope stating 

 what object is upon the stage and what magnifying power is given 

 by the combination in use. The class may sometimes be divided and 

 half, or less than half, be allowed to work with the microscope while 

 the rest are engaged in written or oral recitation, or in examining 

 the gross anatomy of the seed, root, stem, etc. Each student should 

 be required to take his note-book to the microscope and draw while at 

 the instrument. 



Several of the best sketches may be put on the board toward the 

 end of the hour, and a composite drawing finally made, embodying 

 the best portions of each. A still better plan is to have posted at the 

 last a drawing which the instructor has prepared beforehand (best 

 with the aid of the camera lucida, or from a photo-micrograph), and 

 if desirable to have this copied by the class. The object sought 

 should be to make the pupils see as much as possible for themselves, 

 but to make sure before leaving the object that they see it as it 

 really is. 



Magnifying Power. — The lowest magnifying power which will 

 show the desired structure is to be preferred, both because this admits 

 of the best illumination and because an average focusing which will 

 suit mo|t of the eyes in the class can be secured with objectives of 

 ^inch or longer focus, but not with higher powers. Constant use 

 should be made of the IJ-inch or 2-inch objective to give general 

 views of the object. A double nose-piece with 2-inch and ^inch, 

 or 1-inch and |-inch objectives attached will save much time and 

 trouble. 



The class may best be made -to understand the meaning of the 



