170 



BOTANY OF THE LIVING PLANT 



cotyledons, followed by decussate leaves of the plumule (Fig. 127 bis, a), 

 which arrangement may be maintained for a time (c) ; but sooner or 



Fig. 127 bis. 

 A-F. Ground-plans of buds of Sunflower of different ages. See Text, (.\fter Cfimxh.) 



later irregularities appear (b), leading to an alternate arrangement (d), 

 which becomes more complex in the upper vegetative region (e), 



and culminates in the very complex struc- 

 ture of the flowering head (Fig. 127 bis. f). 

 It will be unnecessary for us to tiace these 

 successive stages out into detail, though 

 they are found to follow certain definite 

 methods. The point is that from a cyclic 

 beginning a spiral disposition is arrived 

 at. As the individual plant develops and 

 its apex expands, the complexity of the 

 arrangement of its appendages increases. 

 The individual life of the Sunflower illus- 

 trates a relation that is usual, viz. that 

 complex spiral arrangements are found 

 where a widened axis develops with short in- 

 ternodes, and where the crowded primordia 

 of leaves arc nf relatively small size. Such spirals may be seen 

 either in the vegetative or the floral region. A very beautiful example 



Fig. 12S. 

 Transverse section through bud ot 

 Sedum prmnatum. (.After Church.) 



