FLORAL FORMS AND THEIR RELATIONS TO INSECTS 333 



supposed that the carpels of all compound pistils cohere. In the Buttercup, 

 for example, they are free and distinct (fig. 407), whence they are called 

 apocarpous. In Begonia, on the other hand (fig. 404), they are united, 

 or syncarpous. 



We come now to the third subject of variation namely, adhesion, or the 

 union of imlike parts of a flower. A calyx uniting with a corolla, a corolla 

 with stamens, and stamens with pistil, would all be instances of adhesion ; 

 though the first-named manner of union is not common. Very seldom do 



FIG. 405. DOG-ROSE AND FIELD-ROSE. 



Showing urn-shaped (iirceolatK) receptacles, which later turn red and become the " hips 

 The calyx is seen above the receptacle. 



enclosing the fruits. 



sepals unite with petals or, indeed, with members of any other floral whorl. 

 The adhesion of petals and stamens is, however, common enough, and ma}- 

 be looked for as a thing of course ivhenever the petals of a floiver cohere* A 

 well-known example is the Foxglove (Digitalis). On opening one of the 

 flowers the four stamens may be seen adhering to the inner side of the bell- 

 shaped gamopetalous corolla. The anther-lobes and a part of each of the 

 filaments are free, but the lower portions are united to the corolla, upon 

 * Flowers of the Heath family (Ericaceae} are among the few exceptions. 



