Rural School Leaflet 13 15 



men elderberry is epig^'nous. In the case of hypogynous llovvers the ovary 

 is said to be superior, since it is situated above the other parts. In the 

 case of epigynous flowers the ovary is said to be inferior, because it is sit- 

 uated below the other parts. In case the anthers of the stamens are united, 

 the term syngenesious is used. 



In the foregoing have been given most of the terms used in describing 

 the parts of a single flower. Groups of flowers will now be considered. 

 A flower-bearing part of a plant, or the plan of flower arrangement, is 

 called the inflorescence. The most simple type of inflorescence is the 

 solitary' arrangement (Fig. 4). Here one flower appears in the axil of the 

 leaf and terminates growth in that direction. 



If the flower is borne close to the main stem, and is without a stem, or 

 pedicel, of its own, the flower is said to be sessile. This leads to the next 

 form of inflorescence, the spike. In a spike there is a series of flowers 

 that are sessile, or nearly so, arranged along a more or less elongated 

 common axis (Fig. 5). The common blue vervain shows a good example 

 of a spike. A form of spike that is fairly common is the caikin. A 

 catkin is a flexuous, scaly spike, such as is found in poplars, birches, and 

 the like. A catkin is illustrated in figure 6. 



There is still another form of inflorescence in which the flowers are sessile. 

 This is found in sunflow^ers and daisies and is called a head. The arrange- 

 ment of clover flowers also is called a head. A sunflower head is called 

 a composite head. In it, as is shown in figure 13, there are two kinds 

 of flowers. The center flowers are short and densely massed together, 

 and are called disk flowers. The outer flowers (a) are usually conspicuous 

 and are called ray flowers. Outside of the ray flowers there is a series of 

 green bracts, which apparently bind together the flowers of the head. 

 This series of structures is called the involucre, and its parts are the bracts 

 of the involucre. The broad structure on which the flowers are borne 

 (d) is called the receptacle. A composite head may be composed en- 

 tirely of ray flowers, or the ray flowers may V>c entirely absent. 



The remaining forms of inflorescence have the fl.owers borne on pedicels 

 instead of being sessile. One of the simplest forms is the raceme (Fig. 7). 

 In this case the flowers are borne on pedicels arranged along a common 

 axis, as in a spike, the difference being that here the flowers are not sessile. 

 In a raceme the lower flowers are the older, and usually the larger. Growth 

 continues for an indefinite time and is said to be indeterminate. A cyme 

 differs from a raceme in that the terminal flowers are the older and larger. 

 New flowers appear below the old ones, and growth in length ceases with 

 the first flowers. A growth of this type is called a determinate grow^th. 

 A cyme is shown diagrammatically in figure 8. 



