GROWTH 241 



of the whole growing region of a shoot or root, for the latter 

 is merely composed of a number of active cells. 



Although it is not possible to define in a single sentence the 

 exact meaning or connotation of the terra growth, it may 

 generally be taken to imply a permanent change in the form 

 of a living organism or some of its members, and that the region 

 which is growing is also increasing in weight. 



The actual growing regions of the shoots developed in the 

 dark from a potato tuber not only change their form but also, 

 while they are growing, increase in weight at the expense of 

 the water and reserve-food drawn from the tuber. It will be 

 found, however, that the total weight of the tuber (which does 

 not grow) and its growing shoots decreases in consequence of 

 the loss of water by transpiration and by loss of carbon dioxide 

 in the respiration process. 



During the early stages of its life when a plant emerges from 

 the seed, growth takes place in all parts of its body. After a 

 time, however, growth is confined to certain special localised 

 portions, or growing points, and to the cylindrical cambium- 

 tissue which brings about secondary growth in thickness of 

 dicotyledonous stems. 



The growing-points in the case of stems and roots are generally 

 terminal, or situated near the ends of these members : in such 

 cases the youngest part is nearest, and the oldest part farthest 

 away from the apex of the shoot or root. 



In the stems of grasses their increase in length is due to the 

 activity of growing-points which are situated at the base of the 

 internodes ; moreover the growth in length of the long leaves of 

 onions and rushes, and that of many peduncles of flowers goes on 

 at the base of the structures, their tips being the oldest parts : 

 growing-points of this character are described as intercalary. 



When a cell or a plant member begins to grow its rate of 

 growth is at first slow; afterwards it grows more and more 

 rapidly until a maximum rate is attained, after which the growth 



Q 



