3 



INTRODUCTION 



In seeking the answer to any one of these questions you 

 are sure to meet facts which help supply the answers to 

 the others. So it is well to have a number of questions in 

 mind even when you are giving particular attention to 

 one. You will not solve your problems one at a time. 

 You will solve them together. That is because everything 

 in life depends so much on everything else. All the parts 

 of living things work together. They do not work inde- 

 pendently. They help each other. Thus all plant work, 

 as you have seen, may be divided into nutrition and re- 

 production. Roots, stems, and leaves are sure to be work- 

 ing together to accomplish these great common tasks. So 

 in finding out what share a particular part has in the whole 

 work, you are sure to have light thrown on what the other 

 parts are doing. Similarly, for example, you may have 

 studied an automobile engine. In studying one part, you 

 learned something also about the other parts. 



In trying to explain facts you have observed about 

 plants, you will need advice on several points, and one 

 principal point is this avoid haste. Hasty thought may 

 be worse than no thought at all, but clear thought is the 

 secret of wisdom. You cannot think clearly of these 

 matters and think in a hurry. Don't let the idea bother 

 you that some one else may find an explanation before you 

 do. What you want to do is to forget everything but the 

 problem. Forget even yourself. You are a true scientist 

 only when you put yourself and your feelings entirely out 

 of mind and consider the question only in the light of the 

 facts. 



Here is the plant body which grows. How do the ma- 

 terials which are added to it get into it? Certainly not 

 through a mouth, as in animals. How then ? Your own 



