FIELDBOOK OF ILLINOIS WILD FLOWERS 



not. If either the pistil or stamens are missing the flower is 

 imperfect. The flower may be incomplete by absence of stamens 

 or pistils and therefore be imperfect, or it may be incomplete 

 by absence of calyx or corolla or both, and remain a perfect 

 flower. A complete flower is necessarily perfect. 



A flower without pistils (incomplete and imperfect), and 

 having stamens, is called a staminate flower; likewise a flower 

 without stamens and having pistils (also incomplete and im- 

 perfect), is called a pistillate flower. A plant which bears the 

 two forms of flowers is monoecious^ plants that bear only pistillate 

 or only staminate flowers are dicoecious. 



Regular and irregular flowers. — ^The majority of flowers 

 are star shaped^ having petals nearly alike in size and shape 

 radiating from the center of the flower. Usually the remaining 

 parts of star-shaped flowers are similarly arranged, and where 

 the members of each set or whorl are alike, the flower is regular 

 or radial. Unlike sepals or petals make the flower irregular or 

 bilateral. 



Five principal types of irregularity will be met among 

 Illinois wild flowers. Perhaps the simplest is that form in 

 which a petal or sepal is deformed, modified or enlarged out 

 of likeness to the others. Orchids, for example, have the lowest 

 petal inflated into a sac and sometimes prolonged backward 

 into a spur. A second form is that of the violets, wherein the 

 two upper petals are alike, the two side petals resemble each 

 other, and the lowest is unequal, swollen or spurred. A third 

 and very pronounced type is illustrated by the pea and bean, 

 whose flowers are butterfly shaped. In them one petal is broad 

 and conspicuous, and in the bud is folded about the others; 

 this is the standard. Two narrower petals, one on either side, are 

 called wings; the two lower and usually smallest petals are loosely 

 united to form the keel^ enclosing stamens and pistil. Five- 

 parted flowers in which the two upper petals unite nearly or 

 entirely their length, the three lower uniting similarly and the 

 two groups thus formed joining below or partly up the sides 

 are called two-lipped^ labiate or bilabiate flowers. The snap- 

 dragon is a good example. The fifth type of irregularity is that 

 of the strap-shaped ray flowers ot the Composites. Here the 

 petals are united into a tube upward a slight distance trom the 

 base, and the rest of the way the tube is as though split open, 

 and the corolla lies flat like a strap. 



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