200 - APPENDIX 



7. The classification of flowering plants is largely based on the 

 structure of the flowers. The flowers are consequently referred to 

 In the keys more frequently than other parts of the plant. 



8. A typical flower has four kinds of organs, pistils, stamens, 

 petals and sepals. In the lower groups of both monocotyledons and 

 dicotyledons the pistils and stamens are numerous and all the parts 

 of the flower are separately attached to the enlarged end of the 

 flower-stalk called the receptacle. 



9. The pistils are at the center of the flow^er. In the lower 

 part of the pistil, called the ovary, is a cavity or cell which contains 

 the ovules. From the ovules the seeds are developed. The part 

 of the walls of this cavity to which the ovules and seeds are at- 

 tached is called the placenta. The stigma is the part of the pistil 

 on which the pollen must fall in order to germinate and fertilize the 

 ovules. It is usually borne on the end of a stalk called the style, 

 but this may be short or wanting. The stigma is then sessile. 



10. The stamens are borne around the pistils. Each consists of 

 a stalk, called the filament, bearing anthers at the tip. In the cavi- 

 ties or cells of the anthers the pollen grains are produced. 



11. Outside of the stamens are two series of leaf-like organs mak- 

 ing up the perianth. The inner whorl, known as the corolla, consists 

 of petals which are usually some other color than green. These are 

 usuall ythe organs which make flowers attractive. The outer whorl 

 is made up of sepals. These are usually green. When they 

 resemble petals in color the calyx is said to be corolloid. In the 

 bud they protect the inner more delicate organs. 



12. This type of flow^er has been modified in various ways in the 

 higher groups. One of these is by the omission of some of the 

 organs. Thus one or both of the perianth whorls may be lacking. 

 If the corolla is wanting the flower is apetalous, if the calyx is also 

 wanting it is asepalous or achlamydeous. 



13. Frequently some of the flowers lack stamens and the rest 

 lack pistils. Such flowers are called imperfect while those having 

 both are perfect. A flower with stamens and lacking pistils is 

 staminate. one with pistils and larking stamens is pistillate. Stamin- 

 ate flowers often have rudimentary pistils and pistillate flowers rudi- 

 ments of stamens. A rudimentary stamen is known as a stamin- 

 odium. A flower lacking both pistils and stamens is neutral. 



14. If the staminate and pistillate flowers are produced on the 

 same individual plant it is monoecious. Indian corn in which the 

 staminate flowers are borne in the tassel and the pistillate in the 

 ear is a good example. In dioecious plants the staminate and pistil- 

 late flowers are on separate plants. This is the case in the cotton- 

 wood and boxelder. If some of the flowers are staminate and the 

 rest perfect the plant is polygamous. If the staminate occur on 

 separate plants it is polygamous-diodecious. This is the case in 

 some grapes. 



15. Modifications of the flowers is often brought about by the 

 union of organs of the same kind. Thus the sepals may unite and 

 the flower becomes gamosepalous, or the petals unite and it is gamo- 

 petalous. The stamen filaments may unite as is generally the case 

 in the pea family. If they are united into one group they are mona- 

 delphous, if in two groups they are diadelphous. In most of the 

 composites the anthers unite to form a tube around the style, i. e., 

 they are syngenesious. 



