40i SYSTEMATIC BOTANT. 



Order 4. Heptandria, with seven stamens, as in Pelargonium. 



Order 5. Octandria, with eight stamens, as in Polygala. 



Order 6. Decandria, with ten stamens, as in the Pea, Vetch, 



and many other Papilionaceous flowers. {Fig. 538.) 

 Order 7. JDodecandria, with twelve to nineteen stamens, as in 



the Orange. {Fig. 539.) 

 Order 8. ToJyandria, with twenty or more stamens, as in the 



Mallow and St. Johu's-wort. {Fig. 540.) 



In the 19th Class, Syngenesia, we have five orders. The 

 flowers in all are compound. By Linnaeus a sixth order was in- 

 cluded in this class, iinder the name of Monogamia, which em- 

 braced all solitary flowers that had united anthers, as Lobelia 

 and Violet; but this order was afterwards abolished, so that the 

 class Syngenesia, as it now stands, is essentially a natural one, 

 and corresponds to the order Compositge of the Natural Systems. 

 The names and characters of the orders are as follows : — 



Order 1. Polygamia aqualis. This includes all plants in which 

 the flowers or florets of the capitula are all perfect 

 or hermaphrodite, as in Lettuce, Chicory, and Dan- 

 delion. 



Order 2. Polygamia superflua, where the florets of the disk or 

 centre of the capitula are hermaphrodite, and those 

 of the ray or of the margin are pistillate, as in the 

 Daisy, Elecampane, and Chamomile. 



Order 3. Polygamia frustranea, where the florets of the disk are 

 hermaphrodite, while those of the ray are neuter, 

 as in Centaurca, the only British genus which 

 presents this structure. 



Order 4. Polygamia nccessaria, where the florets of the disk 

 are staminate and sterile, while those of the ray 

 are pistillate and fertile, as in the Marigold {Calen- 

 dida). 



Order 5. Polygamia segregata, where each flower or floret of the 



capitulum has an involucre of its own, as in the 



Globe-thistle {Echinops). The last two orders do 



not include any British Plants. 



The Orders in the 20th, 21st, and 22nd Classes are founded 



on the number and union of the stamens; as such characters 



are not taken into consideration in the definition of these Classes. 



Thus :— 



Order 1. ^jonandria, with one stamen, as in the genus Orchis, 

 and many other Orchidaceous Plants. 



Order 2. Diandria, with two stamens, as in the Venus' Slipper 

 ( Cypripedium) . 



Order 3. Triandria, with three stamens, as in the plants of the 

 genus Carcx and Typha, 



