THE PLANT BODY 



17 



Axillary flowering branc/i 



are secured by the spiral as by the cyclic leaf arrangement. The 

 spiral arrangement of leaves is often distorted by growth and is 

 therefore difficult to trace on mature shoots. It is consequently 

 more clearly evident at 

 the apex of a branch, 

 where the twisting 

 effects of growth are 

 less evident. 



Since the buds and 

 lateral branches arise 

 from the axils of the 

 leaves of the season, 

 it is evident that the 

 entire branch system 

 must follow either the 

 spiral or the cyclic 

 plan upon which the 

 leaves are arranged 

 (Fig. 8). The general 

 form and leaf exposure 

 of an adult plant will 

 therefore be largely de- 

 termined by the above 

 body plans and by the 

 manner in which they 

 are worked out through 



Axillary leafy branch- 



-^Secondary roots 



-Primary taproot 



FIG. 8. Body plan and arrangement of organs in 

 the buckwheat (Fagopyrum) 



Note that the branches spring from the angle (axil 

 of the leaf) between the leaf and stem, and are there- 

 fore disposed spirally on the stem, like the leaves. 

 The adjustment of leaves and roots to light and soil 

 is evident 



growth as the plant 

 matures. 



The root systems of 

 plants are less definite 

 in their arrangement 

 than the branch sys- 

 tems, probably owing to the fact that their soil environment is 

 more uniform and less exacting than the forces and elements to 



o 



which the aerial portions of the plant body are subjected. Thus, 

 there may or there may not be a primary central taproot cor- 

 responding to the central stem axis aboveground. The secondary 



