184 NATURE STUDY. 



investigate the co-operation of its parts, and their rela- 

 tions to their environment, soil, wind, sun, insects, 

 we are brought into contact with a large part of nature, 

 and study portions of many sciences. The absorption 

 of water and food by the roots leads us into physics, 

 capillarity, and osmosis, though we may not use these 

 terms. The transformation of this absorbed matter into 

 " milk " is a chemical process, although the children 

 may never hear the word chemical. Any observation 

 or study of the insect visitors of the dandelion and of 

 their work leads us into zoology. 



We can emphasize the unity in our physical environ- 

 ment by studying plants and animals as units, and by 

 studying the phenomena of nature in their relations. 

 These relations have been enumerated in Chapter III. 



These relations, so far as they need to be considered 

 here, can be gathered into two general classes, relations 

 of dependence (including causal relations), and rela- 

 tions of similarity and difference ; the first functional, 

 the second structural. As brought out in Chapter I, 

 the dandelion has relations of dependence upon soil, 

 air, wind, and water (rain, dew, clouds, frost, snow), 

 sun, animals, and man; that is, these help or harm it, 

 or are helped or harmed by it. It has a relation of 

 similarity or difference to other plants (more particu- 

 larly composites), more remotely to animals, most re- 

 motely to inorganic nature. It is like or unlike these 

 in form, structure, or plan. 



Which of these relations is most important? In 

 the science of the past, as pursued in most educational 



