REPRODUCTION AND DISPERSAL 



825 



2. FLOWERS 



General characteristics of flowers. The parts of a representative 

 flower. Ecologically speaking, a, flower is an organ whose role is pol- 

 lination, which is the 

 initial process of seed 

 production. Struc- 

 turally, a flower is 

 a shortened shoot 

 with spore-bearing 

 organs, which usually 

 (though not neces- 

 sarily) are subtended 

 by one or more leaf- 

 like structures. 1 In 

 a representative 

 flower the outermost 

 whorl of floral leaves 

 is known as thecalyx, 

 the individual leaves 

 being termed sepals 

 (s,k, figs. 1136,1137). 

 Next within this is the 

 corolla, which may or 



, . FIG. 1136. An inflorescence of a syringa (Philadelphus), 



P showing the floral organs of a hypogynous, monoclinous, poly- 



of Separate leaves, petalous flower; note the calyx with its individual sepals (s) 

 kllOWn as petals (to an< ^ ^ e cor ll a w 'th i* s individual petals (p), the calyx and 

 corolla together forming the perianth; note also the stamens, ' 



C, ngS. 1136, II37)- each composed of a filament (/) and an anther (a), and the 

 The calyx and corolla pistil, of which there are here to be seen the style (0 and four 

 together form the Per- st 'g mas (#) '> ^' s inflorescence is a cyme, the terminal flower 

 blossoming first. 



tanth. Next within 



the corolla are the stamens, each of which consists usually of a slender 

 stalk, the filament (/, fig. 1136), and a spore-bearing body, the anther (a, 

 figs. 1136, 1137) , the spores being known as microspores (fig. 1145). At 



1 The latter statement groups the strobilar organs of many pteridophytes with flowers, 

 there being no sharp line structurally between strobili and certain floral shoots or inflores- 

 cences (see p. 180); however, since the role of gymnosperm and pteridophyte strobili is 

 fundamentally different, in the following pages gymnosperms, but not pteridophytes, will 

 be regarded as true flower-producing plants. 



