UNISEXUAL FLOWERS 



13 



s- 



P- 



FIG. 7. Section 

 through a flower of the 



Flowers having the four sets of organs, as shown in Figure 2, 

 are called complete flowers to distinguish them from incomplete 

 flowers, that is, flowers in which some of the 

 organs are lacking. The organs are gener- 

 ally arranged in a circular fashion around 

 the receptacle, and are characterized as be- 

 ing in cycles or whorls. In some flowers a 

 part or all of the perianth is lacking. In 

 the Buckwheat, as shown in Figure 3, only 

 one whorl surrounds the stamens and pistil, 

 and it is evident that this flower does not 

 have both calyx and corolla. In such cases, 

 the petals are considered missing and the 

 flower is said to be apetalous (" without 

 petals"). Often instead of being composed 

 of entirely separate petals (polypetalous), u ig but 

 the corolla is a tube or funnel-shaped struc- O ne pistil (p), but many 

 ture, which appears to be composed of united stamens (s). Much en- 

 petals (gamopetalous) , separate only at the lar s e(i - 

 top. (Fig. 4.) The flowers of the Tobacco Plant, Pumpkins, 



Squashes, and Water- 

 melons are examples of 

 gamopetalous flowers. 

 In some cases, as in the 

 Tobacco, Clover, and 

 some other plants, the 

 sepals seem to have 

 joined into one structure 

 (gamosepalous), forming 

 a tube- or cup-like calyx. 

 (Fig. 4 and 5.) Flowers 

 also differ in the essential 

 organs contained. 

 FIG. 8. Section through an Apple flower Unisexual Flowers. 

 showing the compound pistil composed of five Flowers having both sta- 

 carpels. The five carpels, (a) are free above mens and pistils are 

 but joined below, -c, corolla; s, stamens; i, k nown as per f ec t or bisex- 

 ual flowers. In some 



plants, the stamens and pistils occur in different flowers, in which 

 case the flower having stamens only is called a staminate flower, 



