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 figwer 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~Séparately “attached to the enlarged end of the 
flower-stalk called the receptacle. 
9. The pistils are at the center of the flower. 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 
usually the 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 
pud they protect the inner more delicate organs. 
12. This type of flower 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 polygamo-dioecious. 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. 
