100 DKSCRIPTIVE BOTANY. PAHT I. 



tals and stamens. The disk, therefore, is not properly 

 a distinct organ ; but merely a modification of one 

 or other of these. As connected with the develop- 

 ment and modification of the torus itself, we may here 

 describe three conditions of the flower, which are con- 

 sidered of the greatest importance in systematic botany, 

 and which we will explain by referring to the annexed 

 diagram (fig. 102.). When that part of the torus from 



which the petals and stamens originate, is limited to the 

 space immediately between the calyx and pistil : the 

 corolla and stamens are necessarily seated below the 

 ovarium, and are in consequence termed " hypogy- 

 nous" (a). But when the torus is so developed, that it 

 becomes partially extended over the inner surface of the 

 calyx, the corolla and stamens appear to arise from, and 

 are seated upon, this organ, and they are then termed 

 ' perigynous" (6). When the torus, modified as in the 

 last case, also extends up the sides of the ovarium, the 

 pistil is closely united with the calyx ; and the corolla 

 and stamens are placed near the summit of the ovarium, 

 and are then styled " epigynous" (c). In this case, the 

 ovarium is also said to be " inferior," with respect to 

 the other parts of the flower, and these again are called 

 " superior," with respect to it. In the perigynous and 

 hypogynous corollae, the reverse is the case, the ovarium 

 being superior and the other parts inferior. There are 

 a few other modifications which cannot exactly be re- 

 ferred to either of these three. In the white Water-lily 

 (Nymphtfa allxi), the petals and stamens are attached to 

 the sides of the ovarium, though the calyx is perfectly 



