360 



GENERAL BOTANY 



is roofed over by the sporophyll or sporophylls of the pistil 

 proper. The remaining parts of the epigynous flower seem to 

 arise from the upper margin of the ovary, surrounding the style 

 and stigma. 



Flowers are also variously classified on the basis of the pres- 

 ence or absence of certain floral parts and of the form of floral 

 parts, and also on the basis of certain arrangements for insuring 



pollination by wind or 

 insects. The following are 

 the main classes which the 

 student may be expected 

 to meet in an elementary 

 course. 



Complete flowers have all 

 four sets of floral organs 

 (calyx, corolla, stamens, 

 and pistil) represented in 

 one flower, while incomplete 

 flowers have one or more 

 sets lacking. 



Perfect flowers, like the 

 mandrake and marigold, 



a willow (Salix alba) have both sets of essential 



a, staminate catkin; 6, pistillate catkin ; c,stam- Organs (stamens and pis- 

 inate flower ; d, pistillate flower. From Bergen tQ s ^ present, while oper- 

 and Cald well's " Practical Botany " *' i . j 



feet flowers lack one kind 



of essential organs and are thus either wholly staminate or 

 wholly pistillate. Plants which bear imperfect flowers are said 

 to be either monoecious or dioecious, according as they bear imper- 

 fect flowers of both kinds on the same or on different plants. 

 Thus, the willows (Fig. 216) are imperfect and dioecious, since 

 they have only staminate flowers on one tree and only pistillate 

 flowers on another tree of the same species. The oak, on the 

 contrary, is imperfect and monoecious, with both staminate and 

 pistillate flowers on the same tree (Fig. 238). 



Regular flowers have all of the parts of one set of organs 

 alike in form, as in the azalea, while irregular flowers have the 



FIG. 216. Catkins and dioecious flowers of 



