254 THE TEACHING BOTANIST 



vividly as possible, and with all available illustrations, just 

 where and under what conditions they grow. 



The compound microscope is, of course, necessary from 

 the start. 



The representation of the living plant, no matter how small, 

 called for under Exercise 70, a, seems to me most important. 

 Even in Pleurococcus, where a single plant cannot be distin- 

 guished with the naked eye at all, the student gains far more 

 accurate knowledge of the exact place of the organism in 

 nature if he has to draw and describe the appearance of the 

 colonies or masses of it, than if, after a hasty glance at the 

 living form, he confines his studies to magnified images of it. 

 Throughout this study of natural history of plants I regard this 

 representation of the appearance of the entire organism, as it 

 looks alive, as one of the most important of all exercises. 

 Colored drawings are the best, and the fullest scope should 

 be given the artistic talents of students ; but a black and 

 white drawing, with colors, etc., explained in notes, is better 

 than a coarsely or badly colored picture. 



Exercise 70, b, is also important ; it may be brought out by 

 shading, but also, and for most students better, by imaginary 

 cross-sections. These are of great value for testing the stu- 

 dents' knowledge. 



Exercise 70, c, is necessary ; they should acquire the habit 

 of seeking for the reproductive parts. 



Exercise 70, </, can best be answered in a concise paragraph. 

 Of course, for Pleurococcus, this is most simple, as the plant 

 is unicellular, and all functions are performed by one cell ; 

 substances are absorbed anywhere over the surface. Spirogyra 

 and other floating forms are but little more complex ; such 

 simple forms hardly have any " ecology." In the more com- 

 plex forms, however, adaptations become more pronounced, 



