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 the calyx, 

 the individual leaves 

 being termed sepals 

 (s,k, figs. 1 136, 1 137). 

 Next within this is the 

 corolla, which may or 



, , , FIG. 11-56. An inflorescence of a syringa (Philadelphus). 



may not be made up u . ., ,, , r 



r showing the floral organs of .a hypogynous, monoclmous, poly- 



of Separate leaves, petalous flower; note the calyx with its individual sepals (5) 



known as 'petals (b an< ^ tne corolla with its individual petals (/), the calyx and 



corolla together forming the perianth ; note also the stamens, 



o 3> "37/' 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 (<) and four 

 together form the per- st 'g mas (&) ; ^is inflorescence is a cyme, the terminal flower 

 blossoming first. 



ianth. Next within 



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

 stalk, the filament (f, 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 r&le of gymnosperm and pteridophyte strobili is 

 fundamentally different, in the following pages gymnosperms, but not pteridophytes, wil' 

 be regarded as true flower-producing plants. 



