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A TEXTBOOK OF BOTANY [Ch. VI, 10 



foundation, but have still to trace it upward through a 

 remarkable morphological elaboration. 



Typically the flower has sepals, petals, stamens, and carpels 

 (Fig. 225), but these may be absent in various degrees, making 

 the flowers apetalous, asepalous, pistillate, or staminate, all 

 of which terms are self-explanatory. 



Typically all of the whorls have the same number of parts, 

 as in the phyllotaxy of leaf whorls on the stem (page 140, 

 Fig. 94). That number is oftenest five (Fig. 226), no doubt 

 because of the predominance of the § system of phyllotaxy 

 (page 141) ; next most often it is three, connected with the 

 \ system ; while less often it is four, presumably connected 





Fig. 226. — Diagrams of typical flowers, to illustrate the principal 

 numerical plans. Constructed as in Fig. 225. 

 5-plan, Oxalis; 4-plan, Fuchsia; 3-plan, Lily. 



with the | system; and these are the only numbers which 

 prevail through flowers. This relation to phyllotaxy, by 

 the way, shows how purely structural and little adaptational 

 is the numerical feature of floral structure. Any of the four 

 whorls may deviate from the number characteristic of the 

 flower. Thus Poppies have but two sepals, Monkshood has 

 but two petals, Orchids have but one or two stamens, and 

 Peas have but one carpel. As to the stamens, they are some- 

 times fewer, but often are more numerous than the typical 

 number, especially in simple flowers pollinated by many 

 insects, such as Roses and Buttercups. The carpels, on the 

 contrary, rarely exceed the typical number (though they do 

 so in both of the plants last mentioned), but oftener than 



