266 



ORGANOGRAPHY, 



or thalamus which is situated between the calyx and the 

 pistil, and which forms a support to the corolla and stamens ; 

 while others, again, define the disk as the portion of the torus 

 situated between the calyx and pistil, when that part assumes 

 an enlarged or irregular appearance. Here the term torus is 

 used in the sense in which we apply it in that volume, i.e., 

 synonymous with thalamus and receptacle, but the application 

 of the term disk is more extended than in our definition. 



The disk is not to be considered as an essential organ, al- 

 though it is properly treated of in this place, as it comes next in 

 order to the stamens as we proceed with our examination of the 

 parts of the flower. The disk seems, in many cases at least, to 

 be merely a modification of the stamens, which appears to be 

 proved, not only from its parts occasionally alternating with 

 them, as in Gesnera, &c , but also from the circumstance of 

 portions of it when highly developed becoming occasionally 

 changed into stamens. It is frequently of a nectariferous nature, 

 and hence was treated of by Linmeus and many succeeding 

 botanists, under the head Of nectaries. 



Fig. 564. 



Fig. 563. Flower of the Fennel {FoeniailumX The ovary is surmounted hy 

 a disk, (i Fig. ^ii\. Flower of tlie Rue (7iM/rt gravcohm). The pis- 

 til is surrounded by a disk in the form of a fleshy ring, on the outside of 

 which the stamens are inserted. 



Fig. 565. 



Fifh SW. Pistil of the Tree 

 Paeony invested by a 

 large cup-shaped disk. 



The disk is developed in a variety 

 of forms ; thus in the Orange and 

 Rue {fig 564) it forms a fleshy ring 

 surrounding the base of the pistil ; in 

 the Tree Pticony {fig 565), a dark 

 red cup-shai)cd expansion covering 

 nearly the Avholc of the pistil except 

 the stigmas ; in the Rose and Cherry, 

 a sort of waxy lining to the tube of 

 the calyx ; in Umbelliferous Plants, a 

 swelling on tlic toj) of the ovaries 

 adhering to the styles {fig. 563, </), 

 this form of disk has been termed 

 the styJopodium. In other cases, the 



