CHAPTER V. 



DEVELOPMENT. 



4 



Progressive changes during growth. Morphological, physical, and physio- 

 logical. Influence of inheritance. Variation. Selection. Reserve- 

 materials : their formation and transport. Germination. Matura- 

 tion. Ripening of fruits and seeds. 



DEVELOPMENT as here understood includes those progres- 

 sive changes of form and appearance which accompany the 

 growth of a plant from an infantile to an adult state. It 

 forms no part of our present plan to pursue this part of the 

 subject here, as any elementary text-hook contains sufficient 

 details as to the progressive organisation of flowering 

 plants. Growth considered separately results in increase 

 of hulk only, but development includes the whole cycle 

 of changes which convert an atom of homogeneous proto- 

 plasm into a tree laden with fruit or into a wheat plant 

 heavy with golden ears. A mangel or a turnip which, 

 under favourable circumstances, gets bigger and bigger, 

 may be said to grow. It increases in size and weight, but 

 neither its outward appearance nor its internal construc- 

 tion is otherwise much affected. The giant mangels exhi- 

 bited at root shows illustrate growth rather than develop- 

 ment. They are very big, but their nutritive power is by 

 no means in proportion to their size, as the quantity of 

 nutritive matter developed is small indeed as compared 



