Z PLANT GROWTH 



The results of discovery are cumulative and no attempt 

 will be made to trace the development of our knowledge of 

 growing plants. The principles involving the chemistry and 

 physics of growth will be explained in terms which will not 

 assume a knowledge of these sciences on the part of the 

 reader. In most cases only the facts pertaining to a particu- 

 lar phenomenon are summarized, but a few brief descriptions 

 are given of some of the more recent discoveries of these 

 facts. 



An attempt has been made to present scientific knowl- 

 edge in a direct and terse manner. If the reader will follow 

 the text illustrations, or better, where possible, study his 

 plants in the light of the text descriptions, he should find this 

 method sufficiently detailed. Considerable thought has been 

 given to presenting clear mental pictures of the structure 

 and the internal work of the plant. 



In order to study or converse about the growing plant 

 it is necessary to know the various parts of the seedling 

 described in the next chapter as well as the whole plant in 

 later chapters. Even that inner structure hidden from view 

 because of the size of cells, as described in Chapter 4, may 

 be studied by the aid of the microscope in order to under- 

 stand its growth and specialization. In fact, it is the influ- 

 ence of the environment of these cell structures which deter- 

 mines their growth and in turn the growth of the whole 

 plant. 



The many different kinds of cells found in plants are 

 shown in the illustrations of plant structure. These cells are 

 all inter-connected and carry on their particular functions 

 through the protoplasm, which is a highly complex chemical 

 containing a large quantity of water. This protoplasmic 

 material is living and can grow or increase in quantity by 

 its synthesis from water and the so-called food-making 

 materials absorbed by the plant from the soil and the air. 



These detailed structures of the parts of typical plants 



