Chapter 3 



THE FLOWER 



The flower is often considered characteristic of angiosperms; yet no 

 one character can be used to set these plants apart from other seed- 

 bearing plants. Moreover, the flower cannot be so defined as to separate 

 it from similar reproductive structures in the gymnosperms. The mor- 

 phological basis of the flower is rarely emphasized in definitions; often 

 the flower is "the reproductive structure of the angiosperms." Mor- 



Fig. 41. Diagrams showing primitive structure of flowers of Magnolia acuminata, 

 A to C, and Liriodcndron tulipifcra, D to F. C and F, longitudinal sections; A and 

 E, cross sections through peduncle; B, longitudinal section showing vascular supply 

 to appendages; D, cross section through ^mdroecial region of receptacle showing 

 origin of stamen traces. /;' 



phologically, it is a determinate stem tip bearing sporophylls and, com- 

 monly, other appendages that are sterile (Fig. 41). But this definition 

 applies equally well to many cones, those of the gymnosperms and 

 even of some of the lower vascular plants. The cone is a characteristic 

 reproductive structure in most vascular plants. If the term flower is to 

 be restricted to the fertile stem tip of the angiosperms and its ap- 

 pendages, it is necessary to compare these structures and their 

 sporangia with those of other groups. 



86 



