FLOWERS 55 



St-paratc United 



Sepals aposepalous synsepalous 



Petals apopetalous sympetalous 



£,, ,11,1 diadelphous (2 groups) 



Stamens polydelphous < f , , / \ 



[ monodelphous (i group) 



Carpels apocarpous syncarpous 



Incomplete Flowers.- — The representative flower described 

 in a preceding paragraph had all four floral sets of organs 

 present. However, one or more of these sets may be absent, 

 and in this case, the flower is incomplete. Flowers lacking 

 petals are called apetalous (buckwheat). When both sepals 

 and petals are absent, the flower is naked (willows and cotton- 

 woods) . In the majority of flowers, both stamens and pistils, 

 the essential organs of a flower, are present. Such a flower 

 is said to be perfect or hermaphrodite. Some flowers have but 

 one set of essential organs, either stamens, or a pistil. A 

 flower with stamens only, and no pistil, or a flower cluster 

 , (inflorescence) composed of such flowers, is said to be 

 staminate. On the other hand, a flower with a pistil but no 

 stamens, or an inflorescence, composed of such flowers, is 

 said to be pistillate. If staminate and pistillate inflores- 

 cences are on different plants, the species is said to be "dioe- 

 cious." In some dioecious species (hops), the staminate 

 and pistillate inflorescences are very unlike in appearance, 

 while in other dioecious species (salt-grass, Distichlis), the 

 two unisexual inflorescences are very similar. If staminate 

 and pistillate inflorescences are on the same individual plant, 

 it is said to be "monoecious." This is the case in corn, in 

 which the "tassel" (staminate inflorescence) and the "ear" 

 (pistillate inflorescence) are very dissimilar in appearance. 



Inflorescence. — An inflorescence is a flower cluster. Its 

 shape and the arrangement of the flowers in it differ with the 

 kind of plant. There are three general classes of inflores- 



