THE STEM— ITS GENERAL STRUCTURE 7 1 



sugar-uiaple trees, turpentine from pine, tannin from oak 

 bark, Peruvian bark from cinchona, are all useful products. 



Suggestions. — Parts of a root and stem thro7/ghivhich liquids 

 rise. 49. Pull up a small plant with abundant leaves, cut off the 

 root so as to leave two inches or more on the plant (or cut a leafy 

 shoot of squash or other strong-growing coarse plant), and stand it 

 in a bottle with a little water at tlie bottom which has been coloured 

 with red ink (eosine). After three hours examine the root; make 

 cross sections at several places. Has the water coloured the axis 

 cylinder? The cortex? What is your conclusion? Stand some 

 cut flowers or a leafy plant with cut stem in the same solution and 

 examine as before: conclusion? 50. Girdle a twig of a rapidly 

 growing bush (as willow) in early spring when growth begins {a) 

 by very carefully removing only the bark, and {b) by cutting away 

 also the sapwood. Under which condition do the leaves wilt? 

 Why? 51. Stand twigs of willow in water ; after roots have formed 

 under the water, girdle the twig (in the two ways) above the roots. 

 What happens to the roots, and why? 52. Observe the swellings 

 on trees that have been girdled or very badly injured by wires or 

 otherwise: where are these swellings, and why? 53. Kinds of 

 7vood. Let each pupil determine the kind of wood in the desk, 

 the floor, the door and window casings, the doors themselves, the 

 sash, the shingles, the fence, and in the small implements and 

 furniture in the room ; also what is the cheapest and the most 

 expensive lumber in the community. 54. How many kinds of 

 wood does the pupil know, and what are their chief uses? 



Note to Teacher. — The work in this chapter is intended to be 

 mainly descriptive, for the purpose of giving the pupil a rational 

 conception of the main vital processes associated with the stem, 

 in such a way that he may translate it into his daily thought. It 

 is not intended to give advice for the use of the compound micro- 

 scope. If the pupil is led to make a careful study of the text, draw- 

 ings, and photographs on the preceding and the following pages, 

 he will obtain some of the benefit of studying microscope sections 

 without being forced to spend time in mastering microscope 

 technique. If the school is equipped with compound microscopes, 

 a teacher is probably chosen who has the necessary skill to 

 manipulate them and the knowledge of anatomy and physiology 

 that goes naturally with such work ; and it would be useless to 

 give instruction in such work in a text of this kind. The writer is 

 of the opinion that the introduction of the compound microscope 

 into first courses in botany has been productive of harm. Good 

 and vital teaching demands first that the pupil have a normal, 



