206 THE TEACHING BOTANIST 



Pedagogics. This is one of the most valuable of all exer- 

 cises. It is one of the very best for training the morphological 

 instinct and also for giving knowledge of ecology. 



The students should be able in nearly all cases, using 

 relative position as the main guide, to work out with certainty 

 the exact morphological origin of each part, whether from 

 root, stipule, etc. It will be impressed upon them how little 

 the shape, size, color, etc., of organs has to do with their 

 morphology. Of course a complete knowledge of the mor- 

 phology involves an understanding of the exact steps by which 

 the new organ has been formed, i.e. in the case of a pitcher, 

 whether the leaf has infolded and united its edges to form the 

 cup, or (as is actually the case) whether it has grown up as 

 a cup from the start. It will be well for the teacher to have 

 some one or two series of specimens illustrating all the inter- 

 mediate stages of a particular structure, such, for example, as 

 a Barberry spine. In some cases the student will be able to 

 see what the intermediate steps must have been ; but in others 

 this is impossible without a study of embryology, and here 

 (as in the case of pitchers, for instance) it will be necessary 

 for the teacher to supply hints and some information, which 

 students will be prepared to appreciate and utilize after their 

 minds have been once at work upon the problem. It should 

 be made plain to them that the root, leaf, stem, etc., back 

 to which they reduce everything, are not in themselves irre- 

 solvable elements, but simply adaptive structures traceable 

 back to still simpler origins, i.e. back to the thallus. 



On ecology of the structures they can do little better than 

 guess at uses ; for, removed from their native homes, the plants 

 can give no idea of their habits. Here is where the outdoor 

 study of native plants through field excursions is most valuable. 

 In ordinary temperate climates the ecological adaptations are 



