INTRODUCTION. 



27 



term is also applied to the small bracts surrounding the separate florets in 

 compound flowers. 



Flower buds open' in a definite order ; in some plants the upper and central 

 flowers expand first, and then the lower or outer ones in regular succession. 

 This is termed centrifugal. In cases where the lower and outer buds open 

 first, and afterwards the upper and central, it is termed centripetal. 



The Flower. 



A complete flower consists of two series of leaves of a peculiar character, 

 called floral envelopes; of stamens, or fertilising organs; and one or more 

 pistils or seed-bearing organs. The outer envelope is called the calyx, and 

 its leaves are termed sepals. The inner is called corolla, and its leaves 

 petals. These two envelopes collectively are called a perianth / when both 

 are present, the plant is said to be dichlamydeous ; where only one, what- 

 ever may be its form or appearance, it receives the name of calyx, and 

 the plant is said to be monochlamydeous ; when neither are present, the plant 

 is called achlamydeous. 



Calyx. When the sepals are united so as to form a more or less perfect 

 tube, it is said to be monosepalous or gamosepalous. The lower part is called 

 the tube, and upper and expanded portions, the limb. When the sepals are 

 separate and distinct, it is polysepalous. When it adheres to the ovary and 

 invests it, it is said to be superior, and when no such combination takes place, 

 to be inferior. 



Corolla. When the petals unite at base into a tube, it is said to be mo- 

 nopetalous or gamopetalous ; when not united to be polypetalous. A mono- 

 petalous corolla may be regular or irre- 

 gular. It is regular when its figure is 

 uniform, and its incisions equal. The 

 regular monopetalous corolla may be 

 campanulate or bell-shaped ; tubular, 

 having the tube long and cylindrical ; 

 funnel-shaped, having the tube narrow 

 below and widening towards the limb ; 

 salver -shaped, with the tube long and 

 narrow, and suddenly dilating into a 

 broad horizontal limb ; rotate, 

 last, but with a short tube ; ventricose or 

 urceolate or pitcher-shaped, contracted at the orifice. It is irregular when the 

 incisions are not uniform, and the opposite sides are not arranged on the 

 same axis. It may be ringent or bilabiate, gaping like the mouth of an ani- 

 mal, the tube widening above, and the limb divided transversely into two 

 unequal parts ; personate, when the tube is expanded, and the orifice nar- 



Fig. 20. 



like the Monopetalous corolla 



strous 



a Regular, b Mon- 



Fig. 21. 



rowed by the approximation of the two 

 lips. A polypetalous corolla also may 

 be regular or irregular. The lower part 

 of the petals is called the claiv, and where 

 this is well marked, they are said to be un- 

 guiculate ; the upper and spreading por- 

 tion is termed the lamina or border. 

 The regular polypetalous corolla is cru- 

 ciform, when there are four petals ar- 

 ranged in the form of a cross ; rosaceous 

 when the petals, with little or no claw, 

 spread out as in the rose ; caryophyllaceous when the petals have long claws, 



Papilionaceous flowers. 



