INTRODUCTION 3 



are stressed In various chapters to give the reader a clear 

 understanding of the plant, necessary as a basis for the obser- 

 vation and study of the growing plant. These parts should 

 be compared and contrasted in different plants and in many 

 cases described in brief notes for future comparisons. All 

 experiments should be studied carefully and compared with 

 normal or untreated plants. Often important differences 

 may seem doubtful differences until such comparisons can 

 be made. Such careful observation and checking are the 

 final constructive steps necessary for the most successful 

 improvement in methods or in plants. 



As the fundamentals of plant life are learned it becomes 

 easier to understand fertilizer requirements, as described in 

 Chapter 22, and to diagnose the plant's lack of certain food- 

 making materials and of water for its absorbing roots. 

 Water and fertilizers applied by gardeners using that knowl- 

 edge have paid pleasing dividends in many "Victory" 

 gardens. 



The soil, as outlined in Chapters 7 and 21, is such a com- 

 mon material that it is usually thought of as only a source 

 of water and of fertilizers for the plant. If that were the 

 case, the use of water solutions or water gardening would be 

 simplified. We speak of a good or of a poor soil, because of 

 the plant's response not only to the water and the minerals, 

 but to the many other components of a good soil, such as 

 air, soil structure, and the life of the soil. 



Plants are often compared to factories in their activities. 

 They take their raw materials from the earth and the at- 

 mosphere and by using the sun's energy for power, convert 

 them into many useful products. Sugars and starches are 

 the first products, but these can be reconverted into any 

 number of substances found in the plant, most of which are 

 useful to man. The cell walls become wood, the proteins are 

 useful for food or to make the parts of the seed, the coloring 

 matters make the leaves green and give color to the flowers 



