VARIATIONS IN STRUCTURE 



289 



FIG. 1 10. Types of anthers, showing various ways 

 in which pollen is discharged. 



definite numbers. 



Sweet peas and clover belong to the same great family 

 (Leguminosa), and this arrangement of stamens occurs in 

 the flowers of very 

 many members of 

 that family. (See 

 Figure 112.} An- 

 other great group of 

 plants is character- 

 ized by the fact that 

 the stamens form a 

 tube which closely 

 surrounds the pistil. 

 From this tube the 

 stamens branch out 

 irregularly and in in- 



The common mallow, the hollyhock, the 

 hibiscus, and the cot- 

 ton plant are members 

 of this group. (See 

 Figure 113.) 



E. Variations of the 

 Gynoecium. The car- 

 pels are usually united, 

 while some flowers, as 

 these of the pea fam- 

 ily, have only one. 

 Many flowers, how- 

 ever, have separate 

 carpels, and this con- 

 dition is known to be 

 more primitive than the united condition. Flowers with 



FIG. in. Flower of morning-glory (Ipomea 

 purpurea), showing a sympetalous corolla and 

 the attachment of the stamens to it. 



