WILD FLOWERS OF NEW YORK 



17 



are not opposite; and opposite when the leaves are in pairs opposite each 

 other on the same node. When several leaves are inserted on the same 

 node they are said to be whorled or verticillate. 



Flowers 



The flower of a plant is a group of organs (figure 44) which exist for 

 the purpose of producing seed. The parts of a flower fall into two general 

 groups : those which ac tually function 

 as seed producers (essential organs), 

 and those which act as protective 

 organs or organs for the attraction of 

 insects (floral envelops or perianth). 

 These might also be designated as non- 

 essential organs, since they are lack- 

 ing in certain flowers. 



The essential organs consist of 

 two parts, the pistils (flgure 44 A) and 

 the stamens (figure 44D, E), often 

 designated as the pistillate and stami- 

 nate parts of a flower; and when a 

 flower contains only pistils it is called a pistillate flower, and when it 

 contains only stamens it is called a staminate flower. 



When both stamens and pistils are present in the same flower, it is 

 said to be perfect. If, in addition, the flower possesses the floral envelops, 

 calyx and corolla, it is called a complete flower. Hence a flower which 

 lacks any of these sets of organs is incomplete (that is, if it lacks either 

 calyx or corolla) ; if it lacks either stamens or pistils it is imperfect. 



The perianth or flornl envelopes: 



The ideal flower contains two sets of floral envelops, the calyx 

 (figure 44F) and the corolla. In some flowers the corolla is entirely or 

 partly divided into a certain number of divisions, each of which is called 



