PLANT ORGANS AND ORGANISMS 
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plants of the same family. In the cyme the development is centri¬ 
fugal, the central florets opening first, while in the corymb it is 
centripetal, or from margin to center. 
PREFLORATION 
Prefloration. —By prefloration is meant the arrangement of the 
floral envelopes in the bud. It is to the flower bud what vernation is 
to the leaf bud, the same descriptive terms being largely employed, 
as convolute, involute, revolute, plicate, imbricate, etc. 
In addition to those already defined, the following are important. 
Valvate Prefloration , in which the margins meet but do not oyer- 
lap. Of this variety the induplicate has its two margins rolled 
inward as in Clematis. In the reduplicate they are turned outward, 
as the sepals of Althaea. 
Vexillary, the variety shown in the corolla of the Pea, where the 
two lower petals are overlapped by two lateral ones, and the four in 
turn overlapped by the larger upper ones. 
Contorted, where one margin is invariably exterior and the other 
interior, giving the bud a twisted appearance, as in the Oleander and 
Phlox. 
THE FLOWER 
The flower is a shoot which has undergone a series of changes so as 
to serve as a means for the propagation of the individual. 
A Typical or Complete Flower possesses four whorls of floral leaves 
arranged upon a more or less shortened stem axis called a receptacle, 
torus or thalamus. These whorls passing from periphery toward the 
center are: calyx, composed of parts called sepals; corolla, composed 
of parts termed petals; andrcecium, composed of parts called stamens 
or microsporopylls; and gyncecium, composed of one or more parts 
termed carpels or megasporophylls. 
The stamens and carpels constitute the essential organs, and a 
flower is said to be Perfect when these are present and functional. 
A Hermaphrodite flower is one which possesses both stamens and 
carpels which mayor may not be functionally active. In some cases 
the stamens may alone be functional while in others the carpels 
only may function. 
