MORPHOLOGY OF REPRODUCTIVE ORGANS 141 



In some cases such degeneration is accompanied by an 

 increase in the number of the members of other whorls. In 

 cultivated semi-double flowers we frequently find both stamens 

 and carpels partially transformed into petals, and the number of 

 the latter considerably increased. 



4. Displacement. — This results in the superposition of ap- 

 parently successive whorls which in the typical flower are 

 alternate with each other. In some cases it is only apparent, 

 and is due to multiplioation of the whorls, as in the Barberry 

 already described. The result of the multiplioation in the latter 

 is that each petal has a stamen before and a sepal behind it 

 (fig. 249). 



In the Lily-of-the-valley there is a six-parted perianth, each 

 lobe of which has a stamen in front of it. This is not due, 

 however, to displacement. The perianth is the representative 

 of two whorls of leaves which alternate with each other, and 

 there are two whorls of stamens within the perianth, also 

 regularly alternating. The flower being very small, the bases 

 of all these leaves are crowded closely together, the two whorls 

 of the perianth become completely fused into one, and the true 

 relation of the parts can only be detected by cai'eful examina- 

 tion and comparison with the flowers of other members of the 

 same natural order. 



In many oases, however, particularly in the corolla and 

 androecium, the members of two succeeding whorls are super- 

 posed. Allusion has been made to such displacement in the 

 case of the stamens of obdiplostemonous flowers, the outer whorl 

 of which is superposed upon the petals, while the inner one 

 stands opposite to the sepals. In several natm-al orders — Plum- 

 baginacese, Primulaoeae, and Rhamnaoese, for example —the 

 stamens, which are isostemonous, stand each in front of a petal 

 (figs. 251 and 263). 



The anteposition is generally explained by the suppression 

 of an external whorl of stamens between those remaining and 

 the petals. Traces of these missing stamens are seen in some 

 flowers ; thus in some Primulacese, there is found in this position 

 in the flower a whorl of staminodes. 



5. Cohesion of Parts, or the Coalescence of the Members of 

 the same Whorl. — We have seen that in the typical flower the 

 members of each whorl of floral leaves are distinct from each 

 other. This is, however, very frequently not the case; the 

 calyx, instead of being evidently formed of a number of sepals, 

 appears like a more or less cup-shaped body with a number of 



