112 THE TEACHING BOTANIST 



places in the outlines in this book. These sets may 

 be bought from various dealers in microscopical sup- 

 plies, but are better made from time to time by the 

 teacher himself, or by the specialists among his pupils. 

 By the addition of a few each year a valuable col- 

 lection will soon result. Proper cases, of many forms 

 and prices, for storing them are supplied by dealers. 



Next in illustrative value after preparations of the 

 plants themselves would come, theoretically, good 

 models of them ; but practically I find good pictures 

 or diagrams better, and shall treat these first. Of 

 pictures, as a rule, photographs are best ; and where 

 comprehensive or complicated things are to be shown, 

 or where the actual living form and surroundings are 

 important, they are indispensable. Their chief draw- 

 back is that when large enough to be shown to a class 

 they are very expensive. This can be overcome by 

 photographing them on glass and projecting them to 

 any desired size on a screen by the well-known stere- 

 opticon method. This, however, is of little use in con- 

 nection with laboratory work and is most useful where 

 lectures are a part of the mode of instruction. Good 

 photographs thus appealing vividly to the mind through 

 the eye seem to me of the greatest value, especially 

 for ecological studies (where, indeed, they are in- 

 valuable), and for representing the natural appear- 

 ance of many important plants from foreign parts 

 which grow badly or not at all in greenhouses, or for 



